SpaceX Grasshopper Flies High(universetoday.com)
universetoday.com
SpaceX Grasshopper Flies High
http://www.universetoday.com/101627/spacex-grasshopper-flies-high/
206 comments
I am not that much of a space buff....but for some reason...when I see this video and the one posted by the OP - I get SOOO excited.
Perhaps it is the innovation of never seeing a rocket do a full-blown take-off and then land vertically and then seeing what the long-term result will be - which is orders of magnitude better and more efficient than how it is today....that just gets me excited.
But I am truly glad to be alive today and glad Elon Musk is who he is....and doing what he is doing.
In 40 years, if he continues on his current trajectory, my kids will find it weird that space travel was "novel" in my generation.
That's VERY exciting.
Perhaps it is the innovation of never seeing a rocket do a full-blown take-off and then land vertically and then seeing what the long-term result will be - which is orders of magnitude better and more efficient than how it is today....that just gets me excited.
But I am truly glad to be alive today and glad Elon Musk is who he is....and doing what he is doing.
In 40 years, if he continues on his current trajectory, my kids will find it weird that space travel was "novel" in my generation.
That's VERY exciting.
thats what got me excited, when I watched Elon Musk talking about this project on TEd, since then I am following this project of SpaceX.
Absolutely. This is literally "rocket science" - the cutting edge of space transportation research.
I find this confusing. It's awesome, that's for sure. But it seems like lifting all the fuel needed to do a soft landing is inherently a tradeoff for less payload capacity. What is the benefit, then? Is it just so much cheaper to be able to re-use the first two stages?
Almost the entirety of the cost of an orbital launch is in manufacturing and operational costs. Cost of fuel is basically just noise. If you can reduce operational turnaround time and operational complexity, even at a cost of payload, then you'll save so much money it'll be worth it in the long term. SpaceX is aiming for a re-assemble, gas up and go workflow. If they can pull it off it might reduce their per flight launch costs by a factor of 10 in the short term and perhaps as much as 100 if they get really good at it (although that's likely several generations of hardware down the line, at best). With that sort of thing on offer a reduction in payload is easily justifiable.
Imagine if somebody replaced your car with a version that had twice the carrying capacity, but would only run for one tank of gas. It wouldn't be a worthwhile trade would it?
Imagine if somebody replaced your car with a version that had twice the carrying capacity, but would only run for one tank of gas. It wouldn't be a worthwhile trade would it?
To put it in perspective, the fuel used to launch a Space Shuttle cost in the neighborhood of $1 million, while the cost of the entire launch was somewhere around $500 million to $1 billion.
Another perspective is that the Falcon9 carries about as much kerosene as a 747.
I decided to fact check you. 57,285 U.S. gallons in a fully loaded 747. Jet-A is 6.84 lb/US gal. That's about 196 tons. Looks like stage 1 of the Falcon 9 is estimated to use 239 tons of RP-1 and stage 2 49 tons.
http://www.boeing.com/boeing/commercial/747family/pf/pf_400_...
http://www.spacelaunchreport.com/falcon9.html
http://www.boeing.com/boeing/commercial/747family/pf/pf_400_...
http://www.spacelaunchreport.com/falcon9.html
Cool, so they're well within an order of magnitude of each other.
For the Falcon 9, it costs about $200k for propellant per launch (Kerosene is cheaper than LH2 and the F9 puts about 1/10th as much mass in orbit) while the price of the launch is about $50 million.
Could and real or kerbal rocket scientists here explain why SpaceX isn't doing something like the curiosity rover landing? Sure there's 3 extra steps, deploy parachute, cut parachute, and evasive maneuver, but the fuel saving would massive.
I'm not sure the savings would be as massive as you think (and would be offset by other costs).
Parachutes (and associated equipment) are heavy, so you'll burn fuel lifting that extra weight.
Parachutes are complicated, and would be an extra system to develop, test, and validate.
Parachutes are annoying to repack/replace (increasing turnaround time).
Parachutes put odd stresses on large objects when they deploy (increasing the amount of inspection you would have to do after each flight).
All that hassle to reduce the terminal velocity by a couple hundred miles an hour. That's not that big a win for a pretty high cost.
Parachutes (and associated equipment) are heavy, so you'll burn fuel lifting that extra weight.
Parachutes are complicated, and would be an extra system to develop, test, and validate.
Parachutes are annoying to repack/replace (increasing turnaround time).
Parachutes put odd stresses on large objects when they deploy (increasing the amount of inspection you would have to do after each flight).
All that hassle to reduce the terminal velocity by a couple hundred miles an hour. That's not that big a win for a pretty high cost.
> All that hassle to reduce the terminal velocity by a couple hundred miles an hour.
That's the TLDR. The delta-vee from the parachute is not worth the trouble.
That's the TLDR. The delta-vee from the parachute is not worth the trouble.
Or put it another way, parachutes are generally less effective than using a system you already have for other purposes. A parachute probably beats a rocket engine if your only task is landing, but when you already have the rocket engine, you're better off using it for landing than building a completely separate landing system.
In short, same basic reason why we use wings and wheels to land airplanes rather than dropping them from a parachute when they reach their destination.
In short, same basic reason why we use wings and wheels to land airplanes rather than dropping them from a parachute when they reach their destination.
Not "massive". The empty stage is very light, so a little propellant goes a long way. It's less than 10% of the fuel for the entire descent phase (and the optimal upper stage length goes up to compensate somewhat).
Well, one reason is that parachutes at this scale aren't that simple. For instance, check out the ones on the Shuttle SRBs: http://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Boos...
Also, the first stage put up the second and third stage units.
What if you have a payload container that was the size and weight limits of the second and third stage, which was put up into LEO by the first stage. The payload would then be picked up by vehicles already in orbit, and the first stage unit returns to earth.
Assuming that the payloads are simply building materials, to be assembled by bots in orbit....
What if you have a payload container that was the size and weight limits of the second and third stage, which was put up into LEO by the first stage. The payload would then be picked up by vehicles already in orbit, and the first stage unit returns to earth.
Assuming that the payloads are simply building materials, to be assembled by bots in orbit....
The first sage alone won't take your payload to LEO - you'd still need a second stage. However, orbital tugs with electric engines could take your payload from LEO to other orbits with less reaction mass than a chemical rocket could.
You'd still have to refuel their reaction mass, unless we are talking solar or magnetic sails.
You'd still have to refuel their reaction mass, unless we are talking solar or magnetic sails.
It's also extra weight to lift.
I imagine there's a lot less fuel required to land than is required to take off. That is, on launch, the rocket is probably (eventually) reaching speeds of several thousand miles per hour.
Upon landing, the atmosphere does most of the slowing-down for you, so you only need enough fuel to reduce the speed from terminal velocity (not sure what this would be for a rocket, probably several hundred miles an hour, at least) to 0. So, I'm sure it's not an insubstantial amount of fuel, but maybe less than you'd think?
Upon landing, the atmosphere does most of the slowing-down for you, so you only need enough fuel to reduce the speed from terminal velocity (not sure what this would be for a rocket, probably several hundred miles an hour, at least) to 0. So, I'm sure it's not an insubstantial amount of fuel, but maybe less than you'd think?
Not to mention that the giant flying fuel tank (er... 'rocket') is _substantially_ lighter now that you've burned most of the fuel off.
And separated from the 2nd stage and the payload, of course.
Two other points to consider:
Atmosphere is slowing you down as you go up as well, so lift off requires fighting that as well. Therefore the energy you've expended is not entirely stored in potential energy. (Fun fact: If it weren't for the atmosphere, rockets would actually take off almost horizontally. They go up at first to get out of the thickest air before going sideways.)
The craft is much lighter, because it no longer has the payload, and also has used almost all of its fuel.
Atmosphere is slowing you down as you go up as well, so lift off requires fighting that as well. Therefore the energy you've expended is not entirely stored in potential energy. (Fun fact: If it weren't for the atmosphere, rockets would actually take off almost horizontally. They go up at first to get out of the thickest air before going sideways.)
The craft is much lighter, because it no longer has the payload, and also has used almost all of its fuel.
> I imagine there's a lot less fuel required to land than is required to take off.
Right.
At take off, the delta vee is the escape velocity PLUS all the losses due to friction, which are tremendous.
At landing, the delta vee is only equal to terminal velocity. EDIT: Okay, plus some flying time on top of the landing point.
Right.
At take off, the delta vee is the escape velocity PLUS all the losses due to friction, which are tremendous.
At landing, the delta vee is only equal to terminal velocity. EDIT: Okay, plus some flying time on top of the landing point.
Another way to state this: at launch, air resistance is your enemy. When landing, it's your friend.
"With an advanced rocket you can do maybe two to three percent of your lift-off mass to orbit, typically. And then reusability subtracts two to three percent. So then you've got nothing toward or negative and that's also not helpful. So, the trick is to try to shift that from two to three percent in the expendable configuration, to make the rocket mass efficiency, engines efficiency, and so forth so much better so that it moves to around three and half to four percent in the expendable configuration and then try to get clever about the reusablility elements and try to drop that to around the the one and a half to two percent level so that you have a net payload of about two percent."
http://youtu.be/vDwzmJpI4io?t=27m
(Watch from 27m for about 50 seconds.)
http://youtu.be/vDwzmJpI4io?t=27m
(Watch from 27m for about 50 seconds.)
According to http://www.popularmechanics.com/science/space/rockets/elon-m... :
> "The payload penalty for full and fast reusability versus an expendable version is roughly 40 percent," Musk says. "[But] propellant cost is less than 0.4 percent of the total flight cost. Even taking into account the payload reduction for reusability, the improvement is therefore theoretically over a hundred times."
> "The payload penalty for full and fast reusability versus an expendable version is roughly 40 percent," Musk says. "[But] propellant cost is less than 0.4 percent of the total flight cost. Even taking into account the payload reduction for reusability, the improvement is therefore theoretically over a hundred times."
As Elon Musk put it, it's the difference between filling up your car at the end of a trip, and then going on another trip immediately, versus having to build a whole new car almost from scratch at the end of each trip.
Fuel cost is only 2-3% of the mission's cost, according to Elon Musk.
There is an estimated 40% reduction in payload to become reusable but since the fuel is only less than 1% of the cost in launching the rocket it is pretty acceptable.
Fuel is very inexpensive (~2% the cost of a rocket launch), rockets are very expensive. If you can trade off fuel for not having to build a new rocket you drop the cost to orbit by orders of magnitude.
Additionally you can build more expensive rockets that are more efficient since rocket creation becomes a capital rather than a reoccurring cost.
Additionally you can build more expensive rockets that are more efficient since rocket creation becomes a capital rather than a reoccurring cost.
But why not just use a parachute and airbags? They're going to be a vast amount lighter than the fuel you'd need for a rocket landing.
Parachutes are a pain in the ass to replace. But more than that taking a dunk in the ocean isn't so good for rockets, and spending the better part of a day with a search and recovery team and all the relevant equipment necessary out looking for the rocket and hauling it back home isn't cheap, it also adds a lot of delay to the whole workflow. Compare that to a propulsive landing on the launch pad next to the assembly facilities. You don't have to have a whole special team of folks on hand. The first stage is back in your hands in a matter of hours, where it can be transported back to the assembly building using a simple crane or other specialized equipment. And it can be inserted into the processing workflow much faster than if it had been out in the ocean, and with less overhead of having to clean it, refurbish it, inspect it, etc.
But why everybody compares landing solely on parachutes in ocean with landing solely on engines on land? For example, Soyuz use multiple parachutes for slowing down and engines for guiding and final soft landing on land.
The Soyuz does not "soft land" anywhere. It basically crash lands at a speed which doesn't cause any injury. For a first stage rocket the advantages of coming down on land via just parachutes are pretty much non-existent to negative.
First off, if the goal is to save fuel from having to do a propulsive return to the launch site then that's not going to happen (except for the 2nd stage and capsule). The US has a lot of sparsely inhabited land but it doesn't have the same huge swathes of uncared for steppe that Russia/Kazakhstan have where they can just dump spent rocket stages everywhere with nary a care. There are range safety issues there that can't easily be avoided. Second, a giant rocket stage coming down on just parachutes is going to be damaged more on land than at sea. If you're trying to avoid the weight of landing gear you're just going to end up with the rocket engines crunching into the ground, which isn't going to be good at any speed. OK, so you can't save RTLS fuel, and you can't avoid having landing gear, at that point the only difference is a tiny little dribble of fuel to bring the stage in for a controlled powered landing. So you might as well just do that and be done with it.
First off, if the goal is to save fuel from having to do a propulsive return to the launch site then that's not going to happen (except for the 2nd stage and capsule). The US has a lot of sparsely inhabited land but it doesn't have the same huge swathes of uncared for steppe that Russia/Kazakhstan have where they can just dump spent rocket stages everywhere with nary a care. There are range safety issues there that can't easily be avoided. Second, a giant rocket stage coming down on just parachutes is going to be damaged more on land than at sea. If you're trying to avoid the weight of landing gear you're just going to end up with the rocket engines crunching into the ground, which isn't going to be good at any speed. OK, so you can't save RTLS fuel, and you can't avoid having landing gear, at that point the only difference is a tiny little dribble of fuel to bring the stage in for a controlled powered landing. So you might as well just do that and be done with it.
The Soyouz lands 'somewhere' in a fairly large target area. The recovery overhead is still non-trivial.
Something as big and 'light' as the F9 first stage will be slowed down tremendously by the atmosphere. No need to add all the extra complexity and weight of parachutes.
Something as big and 'light' as the F9 first stage will be slowed down tremendously by the atmosphere. No need to add all the extra complexity and weight of parachutes.
You can't direct where the rocket ends up, highly likely that the rocket will get damaged or much less likely that the rocket will damage something else (This is why NASA dumps it's rockets over the ocean). Then you have find a way to get the rocket home, which involves time and money. Why not just burn fuel (rocket fuel is only a few times more expensive that burning water) and bring the rocket home?
If you need more payload build a bigger rocket.
You could also add wings to the rocket and fly it home which has it's own set of trade-offs and benefits(see space shuttle).
If you need more payload build a bigger rocket.
You could also add wings to the rocket and fly it home which has it's own set of trade-offs and benefits(see space shuttle).
> highly likely that the rocket will get damaged
And because you don't know whether it is damaged or not (sometimes the damage may not be obvious), it's likely that the rocket will have to get a long post-flight inspection to check if it is suitable for another flight. It's something you can almost completely avoid if you land the rocket gently.
I read somewhere, that the costs of recovering SRBs of Space Shuttle from the ocean and then inspecting and fixing them were many times greater than building another pair of boosters.
And because you don't know whether it is damaged or not (sometimes the damage may not be obvious), it's likely that the rocket will have to get a long post-flight inspection to check if it is suitable for another flight. It's something you can almost completely avoid if you land the rocket gently.
I read somewhere, that the costs of recovering SRBs of Space Shuttle from the ocean and then inspecting and fixing them were many times greater than building another pair of boosters.
The SRB thing isn't true. The costs ended up being pretty much the same for new vs. refurbed. The thing is, with solid boosters the "rocket engine" tends to just be giant aluminum cylinders, almost all the complexity of the job is in casting the fuel and putting the segments together, which is completely orthogonal to the reusability aspects.
Also, part of the allure of SRBs is that they are cheap to manufacture, comparatively (this is a false savings, due to increased operational complexity, but it's still very tempting), so even if a significant amount of money could be saved per SRB through reuse it wouldn't have affected the cost a launch much.
Also, part of the allure of SRBs is that they are cheap to manufacture, comparatively (this is a false savings, due to increased operational complexity, but it's still very tempting), so even if a significant amount of money could be saved per SRB through reuse it wouldn't have affected the cost a launch much.
The SRBs don't just impose higher operational complexity, but also far higher acoustic load that requires much higher structural strength and therefore weight on everything else.
They also complicate the range safety situation and make on-pad aborts after they've been lit impossible. Once they've been lit you're going wherever they're going, whether you like it or not.
Yet, NASA plans to use them on the new Space Launch System (SLS). Lobbyism?
Pretty much, yes. They want to keep the people making those engines employed. I think there might be some talk about eventually going to a renewed F-1 engine with a much reduced complexity and greater thrust than the original. There is a reason why the SLS is also known as the Senate Launch System.
> They want to keep the people making those engines employed.
It's more like wanting the companies that make them more profitable by requiring no retooling. I don't buy the "it's about the workers" thing.
It's more like wanting the companies that make them more profitable by requiring no retooling. I don't buy the "it's about the workers" thing.
Maybe you are thinking of the costs of "re-using" the Space Shuttle. $250 Million to refurb it each time. But we do it for cost savings!
Fun fact, the cost of building a Shuttle orbiter from scratch was about $1.7 billion.
The cost of launching a Shuttle including the amortized development costs ended up being $1.5 billion per launch.
The cost of launching a Shuttle including the amortized development costs ended up being $1.5 billion per launch.
Parachutes were the first thing they tried, on the first stages of the first Falcon 9 launches. It didn't work; the stages broke up on re-entry before they slowed down enough to deploy the parachutes. The response was to try active control to keep them intact --- and I guess they figure they might as well keep it all the way down.
Parachute and/or airbags are not necessarily lighter than fuel on a rocket as big as falcon. Parachutes don't scale linearly with the weight of the cargo. Plus they introduce an additional complexity and a point of failure.
On large heavy objects they also impose significant stress on it's structure.
I don't think a parachute would give them the amount of control they want over where it lands. Maybe the idea is to eventually have many of these things docking in the same area, like an airport. If you have a fleet of multi-million dollar rockets, you want to be in as much control of them as possible.
You cannot land a large payload on Mars with a parachute due to the very thin atmosphere.
When I first read this I thought you were missing the point, then I remembered Musk's ambition to live on mars and the planned landing sequence for the Red Dragon. Good point!
Parachutes are really hard. Ask Carmack at Armadillo, but make sure he's in a good mood first. It's not because he's an idiot or anything.
Plus, parachutes create a new failure mode: parachute deploying when it shouldn't.
Plus, parachutes create a new failure mode: parachute deploying when it shouldn't.
…or not deploying when it should.
Think like systems administrator. They've gotta have a rocket engine and a nav system or its not much of a 1st stage. However adding parachutes, airbags, etc, is new systems. Which means much lower reliability and higher expense.
Elon wants rapid (think aircraft), turn around times. That's what's driving the decisions.
Basically, yes. Fuel costs make up a marginal part of the rocket's cost. One reason the Space Shuttle was such a massive failure was because it was supposed to be "re-usable", yet it really wasn't. It threw away most of its volume every time it launched, yet it still had to carry more fuel into space for the soft landing. It had downsides from both sides of the equation.
I thought the same thing. One of the Youtube commentswas pretty insightful in that it mentioned that when you do a parachute landing into the ocean, it's landing in salt water. Therefore the craft has to be taken apart inspected, cleaned, and put back together. So I'm assuming they've done the cost benefits and figured it's cheaper this way.
I wonder if a combination parachute/thruster landing would be more feasible though? Sort of like the Mars Science Lab without the sky-crane.
I wonder if a combination parachute/thruster landing would be more feasible though? Sort of like the Mars Science Lab without the sky-crane.
Perhaps on Mars, unlikely on Earth. With our dense atmosphere a vehicle like a mostly empty Falcon 9 first stage is going to have a fairly low terminal velocity, in the low hundreds of km/s range. Slowing down from that speed to a controlled hover/landing is pretty easy. The cost/benefit on Mars might be different though, since the atmosphere is thinner.
> in the low hundreds of km/s range
I think you might mean m/s? low hundreds of km/s is very supersonic. ;)
I think you might mean m/s? low hundreds of km/s is very supersonic. ;)
What am I, a physicist? Jeez, boffing a few orders of magnitude like that is pretty bad, and it's too late to edit.
I meant kph, which was HOPEFULLY obvious from context.
I'll just leave this here: http://www.smbc-comics.com/?id=2679
I meant kph, which was HOPEFULLY obvious from context.
I'll just leave this here: http://www.smbc-comics.com/?id=2679
Not to mention the operational costs of a small navy to recover the rocket and transport it to a launch site.
I believe the "small navy" was a political and technological requirement and not something you'd need today. A single ship ought to do now.
Political, because it was the Space Race, and a lot of it was about shows of force. And hey, why not? You have a bunch of carrier battle groups just waiting around for a hot war, and you need to have them out training anyway, so why not use them to pick up spacecraft from time to time?
Technological, because guidance wasn't necessarily very accurate. It's interesting to look at the miss distances here:
http://en.wikipedia.org/wiki/Splashdown_(spacecraft_landing)...
Some of these landed hundreds of miles from their target. However, by the time Apollo came around, they were all very close. You definitely want a big recovery fleet to cover a lot of area when you can't be sure it'll land on target, but that's not so much of an issue these days.
Political, because it was the Space Race, and a lot of it was about shows of force. And hey, why not? You have a bunch of carrier battle groups just waiting around for a hot war, and you need to have them out training anyway, so why not use them to pick up spacecraft from time to time?
Technological, because guidance wasn't necessarily very accurate. It's interesting to look at the miss distances here:
http://en.wikipedia.org/wiki/Splashdown_(spacecraft_landing)...
Some of these landed hundreds of miles from their target. However, by the time Apollo came around, they were all very close. You definitely want a big recovery fleet to cover a lot of area when you can't be sure it'll land on target, but that's not so much of an issue these days.
I remember reading about the issue in a book called "This New Ocean"
apparently by the time Apollo was on the go NASA had to ask the military to position the ships off to the side of the splashdown zone - the guidance improved so dramatically they were afraid of hitting the carrier directly
Weird bit of trivia... The pad the the rockets are landing on is a helipad (green perimeter lights). I suppose that makes sense for the video, since there isn't, AFAIK, an FAA spec for rocketpad lighting...
I don't understand the need for the intermediary stages, couldn't the main rocket just deliver the payload and then land?
As it is in that video, it's having to carry engines and fuel for 3 separate stages, for no apparent reason.
As it is in that video, it's having to carry engines and fuel for 3 separate stages, for no apparent reason.
It would be more convenient and cost effective to do so, if we could. But we lack the technology.
The rocket equation is a harsh mistress, it demands exponential amounts of fuel the faster you want to accelerate a given stage (specifically, as a ratio to the exhaust velocity of the rocket). Given that orbital velocity is quite high (about 8.5 km/s) relative to the exhaust velocity of the best chemical propellants (about 3 km/s for LOX/Kerosene) this results in impractical mass fractions to contend with (17:1 to get to orbit, and that's with no payload). But you can cheat. If you use staging and drop away the dead weight of empty fuel tanks and no longer needed engines from lower stages then you can make an end run around the rocket equation. You make a rocket that can accelerate a payload up to a certain velocity, then you make an even bigger rocket which can deliver the entire other rocket as a payload to a different velocity, and so on, until the sum total of all the velocities is the necessary total speed you require to get to orbit.
We're actually fairly close to being able to make single-stage-to-orbit (or SSTO) launchers workable, but it's a difficult problem. We can just about make a single stage with a high enough mass fraction to do it, but then there is almost no payload remaining. And the only way to make a vehicle with such a tiny payload cost effective would be to make it reusable, but enabling reusability would add additional weight which would destroy any payload whatsoever and probably prevent it from even reaching orbit, catch-22. Potentially we could use advanced engines, rocket fuels, and lightweight materials (like carbon fiber) to build a reusable SSTO which would have a reasonable payload, but such designs are hugely untested and very risky. So for now the best hope for reusability seems to be to incrementally advance the design of existing multi-stage rockets.
The rocket equation is a harsh mistress, it demands exponential amounts of fuel the faster you want to accelerate a given stage (specifically, as a ratio to the exhaust velocity of the rocket). Given that orbital velocity is quite high (about 8.5 km/s) relative to the exhaust velocity of the best chemical propellants (about 3 km/s for LOX/Kerosene) this results in impractical mass fractions to contend with (17:1 to get to orbit, and that's with no payload). But you can cheat. If you use staging and drop away the dead weight of empty fuel tanks and no longer needed engines from lower stages then you can make an end run around the rocket equation. You make a rocket that can accelerate a payload up to a certain velocity, then you make an even bigger rocket which can deliver the entire other rocket as a payload to a different velocity, and so on, until the sum total of all the velocities is the necessary total speed you require to get to orbit.
We're actually fairly close to being able to make single-stage-to-orbit (or SSTO) launchers workable, but it's a difficult problem. We can just about make a single stage with a high enough mass fraction to do it, but then there is almost no payload remaining. And the only way to make a vehicle with such a tiny payload cost effective would be to make it reusable, but enabling reusability would add additional weight which would destroy any payload whatsoever and probably prevent it from even reaching orbit, catch-22. Potentially we could use advanced engines, rocket fuels, and lightweight materials (like carbon fiber) to build a reusable SSTO which would have a reasonable payload, but such designs are hugely untested and very risky. So for now the best hope for reusability seems to be to incrementally advance the design of existing multi-stage rockets.
> The rocket equation is a harsh mistress
Love this, totally making it mine ;) Also, there is the problem of efficiency loss due to over/underexpansion as you switch from atmospheric to vacuum conditions, and I have never heard of a rocket engine with variable nozzle geometry to compensate for it.
Love this, totally making it mine ;) Also, there is the problem of efficiency loss due to over/underexpansion as you switch from atmospheric to vacuum conditions, and I have never heard of a rocket engine with variable nozzle geometry to compensate for it.
That was the promise of aerospike engines, but they have their own problems.
https://en.wikipedia.org/wiki/Aerospike_engine
https://en.wikipedia.org/wiki/Aerospike_engine
I'd really love to see a spreadsheet with all this calculations. (Or better, an online html5 virtual rocket calculator tm.) With some default data (usual payload weight, fuel price, orbit speed, ...) and you can choose how many stages and haw much fuel each stage has and the spreadsheet calculate the total price of the mission.
You have a lot of information, but I understand that putting all of this in a xls would be a lot of work.
You have a lot of information, but I understand that putting all of this in a xls would be a lot of work.
What you need is a transporter that can teleport you from a space-bound craft to a surface location and back without all of this rocket launching business to deal with.
That would be quite convenient... A little too convenient?
> Potentially we could use advanced engines
Nuclear rockets would be so awesome if they weren't so nasty.
Nuclear rockets would be so awesome if they weren't so nasty.
The video actually shows two stages and the Dragon capsule, which is payload. As to the use of staging, there are several reasons:
1) During the late stages of the boost, the one second stage engine is pushing only its single engine, fuel and tankage. You're no longer dragging around the nine engines of the first stage and their tanks. That weight saving means you get a lot more delta-V for each unit of expended fuel.
2) The engines themselves are also different. Rocket nozzles designed for optimal performance at sea level aren't optimal for high-altitude or vacuum conditions; those optimal for vacuum won't work at sea level (their exit pressure is so low that the exhaust has trouble pushing air out of the way). And compromise designs aren't optimal in either environment.
3) In the proposed SpaceX reuse architecture, they don't need to protect that long, thin first-stage tank from re-entry at orbital velocity. It's not clear how they could.
1) During the late stages of the boost, the one second stage engine is pushing only its single engine, fuel and tankage. You're no longer dragging around the nine engines of the first stage and their tanks. That weight saving means you get a lot more delta-V for each unit of expended fuel.
2) The engines themselves are also different. Rocket nozzles designed for optimal performance at sea level aren't optimal for high-altitude or vacuum conditions; those optimal for vacuum won't work at sea level (their exit pressure is so low that the exhaust has trouble pushing air out of the way). And compromise designs aren't optimal in either environment.
3) In the proposed SpaceX reuse architecture, they don't need to protect that long, thin first-stage tank from re-entry at orbital velocity. It's not clear how they could.
Good answer, thanks.
I've been playing too much Kerbal Space Program, I assumed the first stage had already reached orbital velocity.
I've been playing too much Kerbal Space Program, I assumed the first stage had already reached orbital velocity.
KSP is great fun and extremely educational, but it makes things way easier than they are in real life, presumably for the sake of fun.
One way this is done is by making Kerbin a lot smaller than Earth. Specifically, over ten times smaller. This reduces the speed needed for low Kerbin orbit to around 2000m/s, while low Earth orbit needs around 8000m/s.
A factor of four in speed probably already sounds bad, but it's much worse than one might naively expect. The amount of fuel needed to accelerate a given payload to a particular speed grows exponentially with the target speed. A typical rocket engine exhaust velocity, both in KSP and real life, might be 4000m/s. When the target velocity is half the exhaust velocity, as is the roughly the case with Kerbin, then you need about 40% of your rocket's mass to be fuel. In other words, you can orbit about 60% of your total mass. When the target velocity is double the exhaust velocity, as is roughly the case with Earth, you need 86% of the initial mass to be fuel, so you can only orbit about 14% of the rocket.
In other words, if you're putting 1000kg into orbit, then in KSP you need about 700kg of fuel, while on Earth you need over 6000kg of fuel. For a single stage rocket, that 1000kg that you're putting into orbit includes fuel tanks and engines. You need much bigger engines and fuel tanks to lift 7000kg than you do to lift 1700kg, so a lot of that 1000kg you get into orbit is going to be empty fuel tanks and spent engines, not actually useful stuff.
Staging lets you work around this problem by letting you reduce the amount of useless junk you put into orbit. By dropping large amounts of empty fuel tank and spent engine early on, you no longer have to lift it all the way up, and you have more orbited mass left over for actually useful widgets.
A single stage that goes from ground to orbit isn't too hard in KSP. On Earth, it's right at the limits of technology. Nobody has operated a rocket as a single stage to orbit, but a couple of pieces of larger rockets are theoretically capable of reaching orbit from the ground on their own if flown by themselves. It's possible, but the amount of useful payload that such a thing can put into orbit is so small that it's not cost effective.
One way this is done is by making Kerbin a lot smaller than Earth. Specifically, over ten times smaller. This reduces the speed needed for low Kerbin orbit to around 2000m/s, while low Earth orbit needs around 8000m/s.
A factor of four in speed probably already sounds bad, but it's much worse than one might naively expect. The amount of fuel needed to accelerate a given payload to a particular speed grows exponentially with the target speed. A typical rocket engine exhaust velocity, both in KSP and real life, might be 4000m/s. When the target velocity is half the exhaust velocity, as is the roughly the case with Kerbin, then you need about 40% of your rocket's mass to be fuel. In other words, you can orbit about 60% of your total mass. When the target velocity is double the exhaust velocity, as is roughly the case with Earth, you need 86% of the initial mass to be fuel, so you can only orbit about 14% of the rocket.
In other words, if you're putting 1000kg into orbit, then in KSP you need about 700kg of fuel, while on Earth you need over 6000kg of fuel. For a single stage rocket, that 1000kg that you're putting into orbit includes fuel tanks and engines. You need much bigger engines and fuel tanks to lift 7000kg than you do to lift 1700kg, so a lot of that 1000kg you get into orbit is going to be empty fuel tanks and spent engines, not actually useful stuff.
Staging lets you work around this problem by letting you reduce the amount of useless junk you put into orbit. By dropping large amounts of empty fuel tank and spent engine early on, you no longer have to lift it all the way up, and you have more orbited mass left over for actually useful widgets.
A single stage that goes from ground to orbit isn't too hard in KSP. On Earth, it's right at the limits of technology. Nobody has operated a rocket as a single stage to orbit, but a couple of pieces of larger rockets are theoretically capable of reaching orbit from the ground on their own if flown by themselves. It's possible, but the amount of useful payload that such a thing can put into orbit is so small that it's not cost effective.
"A multistage (or multi-stage) rocket is a rocket that uses two or more stages, each of which contains its own engines and propellant. A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or attached next to each other. Taken together these are sometimes called a launch vehicle. Two stage rockets are quite common, but rockets with as many as five separate stages have been successfully launched. By jettisoning stages when they run out of propellant, the mass of the remaining rocket is decreased. This staging allows the thrust of the remaining stages to more easily accelerate the rocket to its final speed and height."
https://en.wikipedia.org/wiki/Multistage_rocket
https://en.wikipedia.org/wiki/Multistage_rocket
Right, excellent.
Except the first stage doesn't run out of propellant does it, because it has to LAND again. Hence my puzzlement.
I know why multi-stage rockets are used... I'm asking why this rocket needs them, since they solve a problem it doesn't have by design.
Except the first stage doesn't run out of propellant does it, because it has to LAND again. Hence my puzzlement.
I know why multi-stage rockets are used... I'm asking why this rocket needs them, since they solve a problem it doesn't have by design.
Rockets don't have stages because they run out of propellant, they have stages so that you don't spend 99% percent of your fuel pushing engines and tanks into orbit which you don't need once you get there.
> "they have stages so that you don't spend 99% percent of your fuel pushing engines and tanks into orbit"
In fact you can kinda make a rocket that can reach orbit that doesn't have "stages" but rather jettisons engines themselves. Early Atlas rockets did this: they had one set of fuel tanks but two engines. About two minutes into the flight they would jettison one of the engines.
In fact you can kinda make a rocket that can reach orbit that doesn't have "stages" but rather jettisons engines themselves. Early Atlas rockets did this: they had one set of fuel tanks but two engines. About two minutes into the flight they would jettison one of the engines.
Are you saying it should be single-stage-to-orbit? That's currently technologically nearly impossible, even if the rocket doesn't need to land back to Earth.
Not as technologically impossible as you might think: http://www.reactionengines.co.uk/space_skylon.html
I really don't understand why Skylon isn't getting more coverage.
>they solve a problem it doesn't have by design.
This is where you're incorrect. Not having to accelerate the empty first stage to orbital speed (and back!) is a huge fuel savings.
This is where you're incorrect. Not having to accelerate the empty first stage to orbital speed (and back!) is a huge fuel savings.
A single stage rocket is desirable from a technological point of view since it sheds a lot of complexity: you don't have to deal with multiple engines, separation mechanisms, structural considerations, etc. However, multi-stage rockets can deliver more real payload to orbit, since they maximize the amount of fuel that is spent on taking the actual payload up there.
Single-stage rockets need to carry a lot of dead mass (empty tanks and engines) all the time, and that is a lot of wasted fuel. A multi-stage rocket can dispose the big first stage engines once it's cleared out most of the Earth's gravitational pull and use smaller engines to continue.
Another important consideration is that rocket engines don't run optimally during the whole burn. The first stages are optimized for atmospheric conditions, whereas later stages are optimized for vacuum conditions. Therefore having one big engine propel you up all the way incurs in an even grater loss of fuel due to the inefficiency at high altitudes. You could probably have a rocket engine capable of having a variable geometry to compensate for this but AFAIK is almost impossible to do it.
See the following for more details:
[1] http://en.wikipedia.org/wiki/Staging_(rocketry)#Advantages [2] http://en.wikipedia.org/wiki/Rocket_engine_nozzle
Single-stage rockets need to carry a lot of dead mass (empty tanks and engines) all the time, and that is a lot of wasted fuel. A multi-stage rocket can dispose the big first stage engines once it's cleared out most of the Earth's gravitational pull and use smaller engines to continue.
Another important consideration is that rocket engines don't run optimally during the whole burn. The first stages are optimized for atmospheric conditions, whereas later stages are optimized for vacuum conditions. Therefore having one big engine propel you up all the way incurs in an even grater loss of fuel due to the inefficiency at high altitudes. You could probably have a rocket engine capable of having a variable geometry to compensate for this but AFAIK is almost impossible to do it.
See the following for more details:
[1] http://en.wikipedia.org/wiki/Staging_(rocketry)#Advantages [2] http://en.wikipedia.org/wiki/Rocket_engine_nozzle
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How does the first stage not get damaged by the backblast from the second stage seperating?
SpaceX uses pneumatic 'pushers' to separate the stage. After a few seconds the two stages are far enough apart that igniting the second stage won't cause any real damage to the first stage.
Check out the video on this page for a good view of what that process looks like: http://www.extremetech.com/extreme/149741-spacex-falcon-9-la...
Check out the video on this page for a good view of what that process looks like: http://www.extremetech.com/extreme/149741-spacex-falcon-9-la...
I can't even begin to describe how psyched I get when I see demos like this. The advances that SpaceX and their competitors are making in terms of making access to space cheaper are what will eventually lead to the human species settling on other planets.
It also reminds me that when it comes to science, and who knows, maybe other things as well, it's not just public sector vs private sector. SpaceX wouldn't be driving us forward like this if NASA hadn't put in a whole heap of groundwork first, but similarly NASA have other goals to worry about besides keeping costs down. It's that combination of NASA's huge ambition and private enterprise's drive to make efficiency savings that will eventually get us colonizing places that aren't the Earth.
I hope it happens in my life time,
It also reminds me that when it comes to science, and who knows, maybe other things as well, it's not just public sector vs private sector. SpaceX wouldn't be driving us forward like this if NASA hadn't put in a whole heap of groundwork first, but similarly NASA have other goals to worry about besides keeping costs down. It's that combination of NASA's huge ambition and private enterprise's drive to make efficiency savings that will eventually get us colonizing places that aren't the Earth.
I hope it happens in my life time,
It's like the Internet.
First, you need a massive government program to get the technology from the pie in the sky stage to something usable - a multi-decade, arduous process that produces no short-term profits, if any. Once that's done, it's time for the private sector to step in.
First, you need a massive government program to get the technology from the pie in the sky stage to something usable - a multi-decade, arduous process that produces no short-term profits, if any. Once that's done, it's time for the private sector to step in.
Something something Eternal September of Rocketry.
"Unfortunately, this video is not available in Germany because it may contain music for which GEMA has not granted the respective music rights."
Here's a short link to bypass: http://www.ssyoutube.com/watch?v=sWFFiubtC3c
Here's a short link to bypass: http://www.ssyoutube.com/watch?v=sWFFiubtC3c
SpaceX uploaded a version without music: http://www.youtube.com/watch?v=xUvbh-Z8Abk
This is probably a good place to point out: The SpaceX flight software team is looking for skilled software engineers! There are openings from anything from front-end RoR stuff to flight software and simulations infrastructure. If you want to help making stuff like this video run, check out some of these:
https://jobs.github.com/positions/bd54ba2a-a930-11e2-9c0e-5c...
http://www.spacex.com/careers.php?jvi=oarEWfwV,Job
http://www.spacex.com/careers.php?jvi=odfMWfwU,Job
https://jobs.github.com/positions/bd54ba2a-a930-11e2-9c0e-5c...
http://www.spacex.com/careers.php?jvi=oarEWfwV,Job
http://www.spacex.com/careers.php?jvi=odfMWfwU,Job
What are the upsides to living in LA?
Depends on where you live now, I guess. Let's just say living in LA is not the reason I work here... though it isn't nearly as bad as I had feared.
Can someone share some details on how the rocket is stabilized? There are a few different ways to do it -- how does this one work?
I assume it's some sort of gimbal control/vectoring of the thrust (since I don't see any 'extra' exhaust further up the rocket)
It gimbals the engine for pitch and yaw, and uses cold-gas thrusters for roll (around the vertical axis).
Yeah I think that's what it is unless told otherwise. Quite impressive stuff!
Its likely that full-fledged Space Travel with reusable rockets will be possible in the coming years
The pace of progress seems to have been faster than even SpaceX anticipated. Within the next year we'll see very significant tests of core components of the system and flight profile (for the first stage at least).
The very next Falcon 9 flight (out of Vandenberg) will use the performance overhead provided by the v1.1 upgrade to do a controlled reentry of the 1st stage and then after it has reached terminal velocity it will slow down to a hover out over some remote part of the ocean, then splash down. This is a good and cheap test of a huge part of the flight profile. Meanwhile, the Grasshopper 2 will be more of a full-up Falcon 9 (v1.1) first stage, with 9 engines and will include retractable landing gear. Instead of testing controlled hovering and precision landing it'll go up to supersonic speeds and potentially up to 90km altitude. Essentially testing the return to launch site flight profile in a more realistic setting with more realistic hardware.
And then if that proves fruitful they will essentially just stick that hardware into the Falcon 9 stack and do a full up orbital launch with a flyback 1st stage. Possibly within the next few years even. If that works it'll be rather amazing, since much of the cost of a launch is in the manufacture of those 9 engines on that first stage. Even if a reusable stage costs 3x as much as a regular stage and halves the payload capacity if they can get just 6 flights out of each one it'll break even, and if the numbers are more favorable they'll drop the floor out of the orbital launch market and then own it, to the tune of tens of billions of dollars a year in revenue (a feat they are already on their way to doing with their current lineup of rockets). Perhaps more profoundly it'll hasten the day when it will be conceivable to use kickstarter to fund an interplanetary science mission.
The very next Falcon 9 flight (out of Vandenberg) will use the performance overhead provided by the v1.1 upgrade to do a controlled reentry of the 1st stage and then after it has reached terminal velocity it will slow down to a hover out over some remote part of the ocean, then splash down. This is a good and cheap test of a huge part of the flight profile. Meanwhile, the Grasshopper 2 will be more of a full-up Falcon 9 (v1.1) first stage, with 9 engines and will include retractable landing gear. Instead of testing controlled hovering and precision landing it'll go up to supersonic speeds and potentially up to 90km altitude. Essentially testing the return to launch site flight profile in a more realistic setting with more realistic hardware.
And then if that proves fruitful they will essentially just stick that hardware into the Falcon 9 stack and do a full up orbital launch with a flyback 1st stage. Possibly within the next few years even. If that works it'll be rather amazing, since much of the cost of a launch is in the manufacture of those 9 engines on that first stage. Even if a reusable stage costs 3x as much as a regular stage and halves the payload capacity if they can get just 6 flights out of each one it'll break even, and if the numbers are more favorable they'll drop the floor out of the orbital launch market and then own it, to the tune of tens of billions of dollars a year in revenue (a feat they are already on their way to doing with their current lineup of rockets). Perhaps more profoundly it'll hasten the day when it will be conceivable to use kickstarter to fund an interplanetary science mission.
Thanks for the detailed rundown!
If you don't mind me asking - where did you find all this out? I've been looking for a good source of SpaceX news. The official website/g+/facebook/etc just posts short updates whenever a mission occurs. I'm looking for news about what is on the horizon and more detailed analysis.
If you don't mind me asking - where did you find all this out? I've been looking for a good source of SpaceX news. The official website/g+/facebook/etc just posts short updates whenever a mission occurs. I'm looking for news about what is on the horizon and more detailed analysis.
NewSpaceWatch focuses specifically on commercial companies trying to innovate in space travel: Armadillo, SpaceX, Bigelow, etc.
http://www.newspacewatch.com/
http://www.newspacewatch.com/
I second that recommendation. This is the successor to a site called "Hobbyspace" which was the best clearinghouse for all commercial space news since the mid-1990s. Although it was just a hobbyist's website, I have reason to believe that its comprehensive reporting and very clear-headed analysis actually bears some of the credit for catalysing the entire Newspace movement (eg., Elon Musk was a following and commenting there since before he founded SpaceX...).
Oh wow - is there any way to find his old posts. It would be really interesting to see some of his comments and thoughts given everything that has happened since.
Yeah if somebody digs up his comments I'll be REALLY interested to read them :)
I am also interested in this. I know where I can get detailed news and analysis in the Tech industry, but I haven't come across too many good resources for the space industry. If I could find great news sites or podcasts or similar I'd consume them like you wouldn't believe.
http://www.nasaspaceflight.com/
That is where you will find the best info for the space industry more than likely. A lot of the info is in the forums though and you will have to kind of hunt it down. They also have a private section of the site that you can pay to gain access that has a lot of insider info.
That is where you will find the best info for the space industry more than likely. A lot of the info is in the forums though and you will have to kind of hunt it down. They also have a private section of the site that you can pay to gain access that has a lot of insider info.
Thanks for the link
newspacewatch.com is probably the best overall resource. spaceflightnow.com is decent for news of what's happening right now in space. Otherwise there isn't any single source for everything. It helps to run to wikipedia for any new thing you read about and then spend time poking around any other websites you run across.
Do you have more information on the "water landing" planned for the next Falcon 9 flight? Why won't the SpaceX team attempt to land it on some sort of floating platform?
Seems to me that this would yield an even better test "for free" and even provide the possibility of recovering the first stage for analysis.
Seems to me that this would yield an even better test "for free" and even provide the possibility of recovering the first stage for analysis.
The current Falcon 9 first stage doesn't have landing gear. That would make landing it on anything solid... problematic.
They'd have to add flight worthy landing gear, which hasn't been tested yet and would add weight. This test just uses a straight up stock Falcon 9 v1.1 first stage, so it's super low overhead. Also, they're not sure it'll work. But if it doesn't it just means they end up with what they were expecting, broken up first stage bits in the ocean.
They do plan on retrieving the stage if possible, it should float.
They do plan on retrieving the stage if possible, it should float.
And I haven't been this excited (nay, giddy) since I was about 6 and reading Space Colonies For Kids or whatever.
I'm a bit worried about the bimodality of the future but man the good parts are going to be good.
I'm a bit worried about the bimodality of the future but man the good parts are going to be good.
I'm pretty optimistic about the future. The information age is young yet and only recently starting to come into its first full stage of maturity. And there are a ton of very hopeful signs out there, especially in terms of long term trends. I think the chances that things will turn out well are actually higher than not doing so.
Don't get me wrong, I'm optimistic myself. I'm just a bit concerned about how some poorly defined cohort of 'people who don't read HN' are going to fare; not all of those trends are looking super rosy.
Oh, certainly. There are a lot of scary trends right now, but there are also a lot of very positive trends. Personally I think the forces behind the latter are more powerful, but it's not exactly a sure thing necessarily. If someone told me that in 2070 the developed world was basically neo-feudalist with strong class divisions amidst an effectively world-wide police state I could easily believe it.
I think there are a few major, mostly technological, developments which haven't happened yet but are essentially inevitable which will tend to tip things even stronger toward the "good" side. I should probably write about that at some point.
I think there are a few major, mostly technological, developments which haven't happened yet but are essentially inevitable which will tend to tip things even stronger toward the "good" side. I should probably write about that at some point.
Hopefully the bad parts will be okay too!
We already have many of the bad parts from cyberpunk books.
> The very next Falcon 9 flight (out of Vandenberg) will use the performance overhead provided by the v1.1 upgrade to do a controlled reentry of the 1st stage and then after it has reached terminal velocity it will slow down to a hover out over some remote part of the ocean, then splash down. This is a good and cheap test of a huge part of the flight profile.
Could you explain the first part a bit more, or point me somewhere? How was is the first stage going? Does it need a heat shield?
EDIT: Ha, looks like a lot of people had the same question at the same time.
Could you explain the first part a bit more, or point me somewhere? How was is the first stage going? Does it need a heat shield?
EDIT: Ha, looks like a lot of people had the same question at the same time.
The first stage of almost any launch system wouldn't need a heat shield for reentry. The second stage absolutely would.
Any idea how fast it's going when the first stage separates?
I believe same thing was done by NASA in the 70s. So not really big step forward in this particular regard.
edit: Can't find it at the moment. So far I've found http://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X which did what grasshopper and more almost 20 years back. I still believe I've read something earlier though. Will edit when/if I find it.
edit: Can't find it at the moment. So far I've found http://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X which did what grasshopper and more almost 20 years back. I still believe I've read something earlier though. Will edit when/if I find it.
Nope, aside from the Lunar Excursion Module and its simulators, NASA did nothing like this until the 1990s, with the Delta Clipper. And that wasn't really NASA - it was a BMDO project which later got taken over by NASA. (NASA then crashed the Delta Clipper on their first flight with it, and promptly went back to their preferred innovation strategy: very large contracts which result in absolutely nothing).
>very large contracts which result in absolutely nothing
That's a moderately ironic statement, given the fact that SpaceX wouldn't be doing anything remotely close to what they're doing today without the very large contract they got from NASA.
That's a moderately ironic statement, given the fact that SpaceX wouldn't be doing anything remotely close to what they're doing today without the very large contract they got from NASA.
Actually, no irony at all here. The large contract that SpaceX (and Orbital Sciences) received were for shipping cargo to the space station -- cash-on-delivery. No delivery, no cash. This is profoundly different from the business-as-usual NASA contract which is: give a contractor a billion dollars. Contractor produces a bunch of powerpoint slides. Give the contractor another billion dollars. Contractor goes a further billion dollars over budget, and produces a bunch of powerpoint slides. Rinse & Repeat.
This is how NASA was able to spend over 30 years and $30B trying and failing to develop a new orbital vehicle, where SpaceX was able to do it for under $400M.
This is how NASA was able to spend over 30 years and $30B trying and failing to develop a new orbital vehicle, where SpaceX was able to do it for under $400M.
Without NASA contracts (to be noted: fixed price contracts predicated on delivery of goods, for the most part) SpaceX would have much less cash on hand and their pace of R&D would be much slowed. But they would still exist and still be pushing the state of the art, just at a slightly slower pace. They have one of the most competitive orbital launchers on the market, they have a ton of commercial business already on the docket, and the next 3 SpaceX launches are, in fact, non-NASA commercial flights (a Canadian weather satellite, a commsat for servicing East Asia and Oceania, and several Orbcomm commsats).
That's essentially what I meant... They'd still be making progress, they just got to make progress much faster thanks to some big contracts from NASA.
Actually not true, but I suspect if you've been researching this you've discovered that. NASA has of course researched vertical landing techniques from the beginning, both with manned missions (Apollo) and robotic. However, it was "on the list" prior to the great de-funding and generally sat in the 'to be looked at' drawer from then on.
The DC-X program, and others like it were spawned by private industry who were betting on a huge 'single stage to orbit' (or SSTO) model for satellite launches that would be needed for the Reagan 'Star Wars' missile defense program. They died when Star Wars died and NASA briefly assumed control of DC-X when its private backers pulled out but was stretched too thin to give it any real push.
That said, Elon and others will tell you that the current crop of rockets would not be possible without the work that NASA did and has shared. SpaceX also has benefited from computer systems that are 10,000X more powerful than the ones that NASA had available for their use, and materials that are 1/3 to 1/2 the weight and yet stronger than their NASA counterparts. Sensors that are 100x more sensitive and 1/1000th the cost. A six degree of freedom inertial unit was $125,000 in 1970 and resolved differences of .1G. A 9 degree of freedom unit from Sparkfun Electronics [1] is now $125, and reliably resolves 1/4096'th of a G. So I don't doubt that the same engineers at NASA could build what SpaceX is building today, today, but I assure you they didn't have the tools to build it back in the 70's or even in the 90's.
[1] https://www.sparkfun.com/products/10736
The DC-X program, and others like it were spawned by private industry who were betting on a huge 'single stage to orbit' (or SSTO) model for satellite launches that would be needed for the Reagan 'Star Wars' missile defense program. They died when Star Wars died and NASA briefly assumed control of DC-X when its private backers pulled out but was stretched too thin to give it any real push.
That said, Elon and others will tell you that the current crop of rockets would not be possible without the work that NASA did and has shared. SpaceX also has benefited from computer systems that are 10,000X more powerful than the ones that NASA had available for their use, and materials that are 1/3 to 1/2 the weight and yet stronger than their NASA counterparts. Sensors that are 100x more sensitive and 1/1000th the cost. A six degree of freedom inertial unit was $125,000 in 1970 and resolved differences of .1G. A 9 degree of freedom unit from Sparkfun Electronics [1] is now $125, and reliably resolves 1/4096'th of a G. So I don't doubt that the same engineers at NASA could build what SpaceX is building today, today, but I assure you they didn't have the tools to build it back in the 70's or even in the 90's.
[1] https://www.sparkfun.com/products/10736
>A six degree of freedom inertial unit was $125,000 in 1970 and resolved differences of .1G. A 9 degree of freedom unit from Sparkfun Electronics [1] is now $125, and reliably resolves 1/4096'th of a G.
And the 1970s one weighed a lot more than 3.52 oz!
http://i.imgur.com/nrm2fUb.jpg
And the 1970s one weighed a lot more than 3.52 oz!
http://i.imgur.com/nrm2fUb.jpg
That's still peanuts in rocket money and scale.
All these things could have been done earlier if the politics was different.
DC-X used F-15 gyros / guidance with some software tweaks for example.
All these things could have been done earlier if the politics was different.
DC-X used F-15 gyros / guidance with some software tweaks for example.
So true, so true.
No. It was a stated goal of the Space Shuttle project, but it failed. Had the Space Shuttle been a commercial venture it would have been abandoned decades ago; other than the fact that it generally worked (which, to be clear, is saying something, that's not guaranteed), it was an awful design.
Can't edit the parent post anymore, indeed I was wrong, but only about the year. The project I've added however is around 20 years old, so I still don't find Grasshopper revolutionary in this one aspect - reusable VTVL rocket.
Yeah, I was going to mention the DC-X. The video you link below shows what is probably a future grasshopper test, where they take the vehicle off of vertical to show it can really reorient itself.
Are you referring to that neat trick they pulled a half dozen times, where they landed a rocket on its tail in an airless environment with 1/6 gravity? That was still pretty impressive on a bunch of other levels.
No, I'm referring to on-earth tests, such as this http://www.youtube.com/watch?v=wv9n9Casp1o However I can't find the exact one I had in mind, or perhaps I was off with the date.
[citation needed]
Anyone have experience working at, or with, SpaceX that can shed some light on what it's like to work there?
I've been on the Flight Software team at SpaceX for a little over three years. It feels a lot like a startup. The team is still relatively small and people are pretty passionate about what they are working on. The project variety is wide as well. Personally, I've gotten to work on low-level drivers and OS stuff, application code that runs on the vehicles and ground systems, Dragon's fault-tolerant platform, internal web-based tools, and operations in Mission Control during the Dragon missions. Can't really give details about any of this stuff but I do love working here.
There was an AMA with several of the software teams a little while back:
http://www.reddit.com/r/IAmA/comments/1853ap/we_are_spacex_s...
There are several openings right now for software engineers, including people with web experience (people usually don't think we're looking for those skills):
https://jobs.github.com/positions/bd54ba2a-a930-11e2-9c0e-5c...
There was an AMA with several of the software teams a little while back:
http://www.reddit.com/r/IAmA/comments/1853ap/we_are_spacex_s...
There are several openings right now for software engineers, including people with web experience (people usually don't think we're looking for those skills):
https://jobs.github.com/positions/bd54ba2a-a930-11e2-9c0e-5c...
Hey! Can you spare some career advice for an aspiring aero engineer that wants to work on the software side of the rocket? If you could share what you would consider is a good path to follow to get to where you are right now, I would really appreciate it. I am a programmer at heart but even that could not pull me away from my love of space ;) so I decided to study aerospace engineering first.
It's hard to say what works best since we have so many different backgrounds on the team. I think having an interesting portfolio of projects (professional or side / hobby type stuff) is important - make sure you've done some awesome stuff that you can map onto what you might do here. Also, hone your communication skills. A big part of success at SpaceX is being able to work with others in a team and quickly get ideas across. Getting an internship is definitely a good way to go - we usually give interns pretty meaty projects that are a good taste of what full-time work might be like. Good luck!
Thanks! I am already working on some robotics projects for both personal and university research purposes. I am trying to build a strong portfolio, just like you advice, and trying to figure out exactly what fits me best. Once again, thanks for your advice!
My recommendation would be to consider adding CS as minor or double major. Then try and get some internship and/or on campus lab experience doing software or robotics work (robotics software is pretty close to flight software). Another great way to get experience is to get involved with extra-curricular group doing some kind of robotic or aerospace challenge. Think DARPA grand challenge, NASA Sample Return Robot challenge, or one of AUVSI's robotics competitions.
SpaceX has an intership program, that might be a good thing to look into.
Would you guys consider remote work? I would love to work for SpaceX but I can't really justify uprooting my family and moving to the other side of the world for it :-\
Get in line, buster :( Woe betide Australia's near-nonexistent aerospace engineering field. It's why I play with trains instead.
I think the general rule is not, but there exist exceptions. Foreigners (without greencards), however, are extremely difficult to hire due to export regulations (http://pmddtc.state.gov/regulations_laws/itar_official.html)
You will probably have a really hard time getting to work on essential parts of the rocket due to ITAR regulations [0].
[0] http://en.wikipedia.org/wiki/International_Traffic_in_Arms_R...
[0] http://en.wikipedia.org/wiki/International_Traffic_in_Arms_R...
Are that engines reusable in a short time? or must they go through a mayor refurbishment after each flight?
Basically it is just refuel. The entire rocket is reusable. Musk mentioned in some interview it would take a couple of days.
Impressively, he actually said "single digit hours" between flights for the lower stages. See "turnaround time": http://www.popularmechanics.com/science/space/rockets/elon-m...
"Like re-fueling your car" - he uses that analogy a lot. It's probably not exactly like that, but it gives an idea what the real goal is.
That aerial shot they have in the video is pretty neat... I wonder if they are using a UAV for that, or just some ballsy helicopter pilot?
Hexacopter so yes a UAV.
It was "SpaceX’s hexacopter."
".from SpaceX’s hexacopter."
They have all the nicest toys!
I'm building a quadcopter with my kids. With parts sourced from China - http://hobbyking.com/ - it's ridiculously cheap.
I'm sure SpaceX's hex is big, powerful, and carries all sorts of nice toys, including having enough lift to carry an HD camera and stabilizer - but still, it's not that complicated to make one. I could probably make an HD-camera-carrying hex myself if someone was willing to sponsor the parts - including stabilization for the camera, onboard controller for extra smooth flight, etc. And I'm not a rocket scientist. :)
You want a hex for this sort of job because you can lose one rotor without crash-landing your sensitive HD gear. With a quad, you lose a rotor, the whole vehicle crashes.
I'm sure SpaceX's hex is big, powerful, and carries all sorts of nice toys, including having enough lift to carry an HD camera and stabilizer - but still, it's not that complicated to make one. I could probably make an HD-camera-carrying hex myself if someone was willing to sponsor the parts - including stabilization for the camera, onboard controller for extra smooth flight, etc. And I'm not a rocket scientist. :)
You want a hex for this sort of job because you can lose one rotor without crash-landing your sensitive HD gear. With a quad, you lose a rotor, the whole vehicle crashes.
Even buying something off the shelf, that's not an absurdly expensive 'toy' (<$2k, certainly... so, not 'cheap' but certainly well within the 'hobby' range for a lot of folks). The camera is a few hundred more, but it's amazing how cheap HD-capable cameras have gotten recently.
If you build it yourself, you could put together a video platform like that for under $1k (including the gyro stabilized camera gimbal).
If you build it yourself, you could put together a video platform like that for under $1k (including the gyro stabilized camera gimbal).
Hey JshWright, I recently got very interested in creating one of these and you seem to be pretty knowledgeable about this. Can you please give me advice on where a newbie can start with this? I would like to learn how to build one on my own from scratch.
Thank you.
Thank you.
I'm not much past the newbie stage myself...
The RCModelReviews youtube channel has a number of good videos on basic RC concepts (not multirotor specific, but the RC stuff still applies).
One tip I'll give you is to look into getting a Eurgle/FlySky/Imax/Turnigy 9x Transmitter (different brand names, same basic Chinese knockoff..). It's a solid radio with a lousy stock firmware, but there are a number of good open soruce firmwares out there that are very easy to flash onto the controller (especially if you use something like the SmartieParts programming board). For ~$100 (for the radio plus the programmer) you end up with something that rivals radios costing an order of magnitude more (or so I've heard... I've never touched a high end radio).
I'm approaching the hobby in stages:
1) Buy a Blade mQX (which comes with a cheap transmitter) and learn the basics of flying a multirotor
2) Get a 9x transmitter, mod it, and learn how it works
3) Get a 'JR compatible' OrangeRX DSM2/DSMX module for the 9x, so you can bind it with the mQX and get used to flying with the full size 'real' tranmsmitter
4) Get an 'ARF' (almost ready to fly) kit (this should include the frame, ESCs, motors, props, etc), and a flight control board (I'll probably start with something cheap like the Kk 2.0). This is a good time to learn things like "What is an ESC?".
5) Start modding your ARF quad (replace the ESCs, add a camera, get a more capable flight controller (like the Arducopter), etc)
6) Build something from scratch
I'm currently on step 3, researching step 4.
The RCModelReviews youtube channel has a number of good videos on basic RC concepts (not multirotor specific, but the RC stuff still applies).
One tip I'll give you is to look into getting a Eurgle/FlySky/Imax/Turnigy 9x Transmitter (different brand names, same basic Chinese knockoff..). It's a solid radio with a lousy stock firmware, but there are a number of good open soruce firmwares out there that are very easy to flash onto the controller (especially if you use something like the SmartieParts programming board). For ~$100 (for the radio plus the programmer) you end up with something that rivals radios costing an order of magnitude more (or so I've heard... I've never touched a high end radio).
I'm approaching the hobby in stages:
1) Buy a Blade mQX (which comes with a cheap transmitter) and learn the basics of flying a multirotor
2) Get a 9x transmitter, mod it, and learn how it works
3) Get a 'JR compatible' OrangeRX DSM2/DSMX module for the 9x, so you can bind it with the mQX and get used to flying with the full size 'real' tranmsmitter
4) Get an 'ARF' (almost ready to fly) kit (this should include the frame, ESCs, motors, props, etc), and a flight control board (I'll probably start with something cheap like the Kk 2.0). This is a good time to learn things like "What is an ESC?".
5) Start modding your ARF quad (replace the ESCs, add a camera, get a more capable flight controller (like the Arducopter), etc)
6) Build something from scratch
I'm currently on step 3, researching step 4.
I recommend checking out forums like RCGroups, there's loads of information there.
There are many ways to start into the hobby. You can get yourself a radio and a simulator and learn to fly on the computer first. You could go for an off-the-shelf solution like the DJI Phantom that will fly very well without much tuning or fiddling (but it'll cost the part). Or you can go the DIY way - a good keyword is "MultiWii", it's a fairly cheap but rather labor-intensive way of getting your first copter to the skies.
There are many ways to start into the hobby. You can get yourself a radio and a simulator and learn to fly on the computer first. You could go for an off-the-shelf solution like the DJI Phantom that will fly very well without much tuning or fiddling (but it'll cost the part). Or you can go the DIY way - a good keyword is "MultiWii", it's a fairly cheap but rather labor-intensive way of getting your first copter to the skies.
Hobby King for parts. RCGroups for info.
http://www.hobbyking.com/
http://www.rcgroups.com/forums/
http://www.hobbyking.com/
http://www.rcgroups.com/forums/
That's what I was thinking... certainly much cheaper than chartering a helicopter.
Haven't heard much from Armadillo Aerospace in a while. Are they still active?
Yeah they're still active.
http://www.armadilloaerospace.com/n.x/Armadillo/Home/News?ne...
http://www.armadilloaerospace.com/n.x/Armadillo/Home/News?ne...
They've always seemed more like a hobby company than the competitors. Their small scale has really seemed to slow them down, like lots of manufacturing and sourcing issues that a bigger company can just throw money at.
Even smaller than Armadillo - I really like Copenhagen Suborbitals. They are basically your friendly hackers next door, looking to launch a person into space.
http://www.copenhagensuborbitals.com/
http://www.copenhagensuborbitals.com/
Can't watch this in Germany of course.
Likely because of the soundtrack used. The music added is Ring of Fire by Johnny Cash which limits distribution of the video to certain countries and probably to non-mobile devices. Adding music you don't own the copyright to is probably not a good idea for achieving maximum viewership and distribution. In this case the music is distracting and doesn't add any value, although I like the song.
http://youtube.googleapis.com/v/se7_JpbtPwA&rel=1
Version with different music. Heard it works in other countries.
Version with different music. Heard it works in other countries.
VPN? Regional limitations is a ridiculous idiocy in the age of the Internet.
Of course, because ... no? Why? It works great in Sweden, for instance so it can't be "side of the Atlantic" that decides. Some DRM/rights issue?
The video has a music soundtrack ("Ring of Fire") which gets it blocked in Germany.
Wikipedia have an article about it:
http://en.wikipedia.org/wiki/Blocking_of_YouTube_videos_in_G...
Wikipedia have an article about it:
http://en.wikipedia.org/wiki/Blocking_of_YouTube_videos_in_G...
ProxTube to the rescue.
I watched the videos (no sound - at work) and it seems like from the discussion that they are thinking of returning to the launch site. I looked at the Saturn V data and the first stage came down 350 miles down range and the second stage 2300 or so miles down range. Are the SpaceX launches going to have little downrange component for the first stage?
Yep, Elon Musk has publicly mentioned that it will light up the engine to boost back to the launch site.
>So, I think, there's a number of improvements across the board, in structures, avionics, engines and then, as I said, this version [the Falcon 9 1.1] is really designed to be able to have the first stage come back - boost back – to launch site, deploy landing gear and actually land propulsively.[1]
With a flyback stage the optimal separation altitude and velocity drops, and the second stage gets even larger to compensate. But yes, the engine will cancel the downrange component of velocity and reverse it. Since the stage is empty the fuel requirements are actually quite modest.
[1] http://shitelonsays.com/transcript/crs-2-post-landing-teleco...
>So, I think, there's a number of improvements across the board, in structures, avionics, engines and then, as I said, this version [the Falcon 9 1.1] is really designed to be able to have the first stage come back - boost back – to launch site, deploy landing gear and actually land propulsively.[1]
With a flyback stage the optimal separation altitude and velocity drops, and the second stage gets even larger to compensate. But yes, the engine will cancel the downrange component of velocity and reverse it. Since the stage is empty the fuel requirements are actually quite modest.
[1] http://shitelonsays.com/transcript/crs-2-post-landing-teleco...
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Would have loved to see what happened to the dummy cowboy. The final fews frames are not very clear due to the smoke and dust.
Did they have another cowboy? It makes me think it's the same test from a few months ago.
Most of the Grasshopper tests have had a cowboy on the landing gear frame.
The test few months ago was a 40 feet climb I think
Yeah, you can see him in the first few frames.
So what's the big water tower for in the background?
Probably stores water for their deluge system for rocket engine testing. From http://en.wikipedia.org/wiki/Rocket_engine_test_facility
"The rocket exhaust is directed into a flame bucket or trench. The flame trench is designed to redirect the hot exhaust to a safe direction and is protected by a water deluge system that both cools the exhaust and also reduces the sound pressure level (loudness). The sound pressure level of large rocket engines has been measured at greater than 200 decibels — one of the loudest man-made sounds on earth."
"The rocket exhaust is directed into a flame bucket or trench. The flame trench is designed to redirect the hot exhaust to a safe direction and is protected by a water deluge system that both cools the exhaust and also reduces the sound pressure level (loudness). The sound pressure level of large rocket engines has been measured at greater than 200 decibels — one of the loudest man-made sounds on earth."
Probably water. ;)
Maybe for fire-fighting? Seems a little close for that though, if something went wrong it could be in the middle of it. I can't think of anything else though.
Edit: Maybe it feeds some sort of un-manned fire suppression system? That would be pretty smart.
Maybe for fire-fighting? Seems a little close for that though, if something went wrong it could be in the middle of it. I can't think of anything else though.
Edit: Maybe it feeds some sort of un-manned fire suppression system? That would be pretty smart.
A flying Segway! How cool is that?
Poor bird gets killed in the video as it tries to fly away as the rocket takes off
The bird is way closer to the camera than the rocket. Check the video again when the bird starts to land it is approximately the size of half the width of the rocket. That would make the bird be positioned halfway between the camera and the rocket and well clear of the blast.
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The saddest part is that I would have been willing to capitalize SpaceX voluntarily, as an investor. Instead, Elon Musk steals from me through NASA.
On the bright side, SpaceX is so economical compared to NASA's past methods, that if it succeeds, we will all benefit. So what might be characterized as theft at one point in time, might eventually be seen as a great investment.
Only time will tell.
Only time will tell.
For all Elon Musk's libertarian rhetoric, he sure disregards it whenever expedient.
I actually think he's pretty moderate. His views are not mainstream, but I would expect someone like him to think in those terms.
OTOH, his pal Peter Thiel is pretty extreme. That's someone I'm not comfortable with.
OTOH, his pal Peter Thiel is pretty extreme. That's someone I'm not comfortable with.
Most libertarians do. It's called making money and all's fair in love and business.
http://www.youtube.com/watch?v=sWFFiubtC3c
This will give you an idea of how grasshopper fits into the full flight plan.