Orbcomm satellite in wrong orbit after Falcon 9 launch(spaceflightnow.com)
spaceflightnow.com
Orbcomm satellite in wrong orbit after Falcon 9 launch
http://spaceflightnow.com/falcon9/004/121008orbcomm/
7 comments
I found the article misleading as well ... if an engine was shut down, you'd assume (with some margin of error) that the remaining 8 engines would fire 9/8th as long to provide the same total thrust and would therefore burn about as much propellant as the original 9 engines.
Orbital rendezvous with the ISS has a very tight window (2.5-10 minutes), since on-orbit propellant is very limited. They could add more, and make the window a bit bigger, but that subtracts directly from cargo, which is already small: just 1000 lbs.
The launcher has to drop Dragon basically right underneath the ISS; it approaches by raising altitude just several km. (In orbit, speeding up or slowing down means a change in altitude as well, so catching up or slowing down requires a lot more fuel.)
Since the second stage drops off Dragon just below and a little behind the ISS, a second burn to raise the orbit would necessarily take it past the ISS. NASA is, understandably, very cautious around the ISS. I'm a bit surprised the even allowed a secondary payload boost. It was probably on very, very tight conditions.
Making up for the lost engine probably got them to about the right place, but the different flight profile meant it wasn't the perfect place. Presumably it was inside Dragon's maneuver window, but outside the parameters NASA set for the secondary payload. This could happen if the second stage got too far "ahead" of the ISS due to a longer, lower burn, putting the second stage stack immediately below the ISS instead of below and behind it. Dragon, being in a lower (slower) orbit, can just wait a bit and get in the right position, but the booster could not proceed immediately as it would go too close to the ISS and could not wait as it is battery powered. Thus: secondary payload doesn't get its orbit.
Missing the secondary's orbit is unfortunate, but that is the nature of the secondary payload. You take a gamble in return for a discounted ride. It's appropriate for a prototype, as this is, and they'll probably still get their primary mission done--testing that it functions properly in orbit. Probably won't get to use it in their constellation if it works, which would have been gravy.
The launcher has to drop Dragon basically right underneath the ISS; it approaches by raising altitude just several km. (In orbit, speeding up or slowing down means a change in altitude as well, so catching up or slowing down requires a lot more fuel.)
Since the second stage drops off Dragon just below and a little behind the ISS, a second burn to raise the orbit would necessarily take it past the ISS. NASA is, understandably, very cautious around the ISS. I'm a bit surprised the even allowed a secondary payload boost. It was probably on very, very tight conditions.
Making up for the lost engine probably got them to about the right place, but the different flight profile meant it wasn't the perfect place. Presumably it was inside Dragon's maneuver window, but outside the parameters NASA set for the secondary payload. This could happen if the second stage got too far "ahead" of the ISS due to a longer, lower burn, putting the second stage stack immediately below the ISS instead of below and behind it. Dragon, being in a lower (slower) orbit, can just wait a bit and get in the right position, but the booster could not proceed immediately as it would go too close to the ISS and could not wait as it is battery powered. Thus: secondary payload doesn't get its orbit.
Missing the secondary's orbit is unfortunate, but that is the nature of the secondary payload. You take a gamble in return for a discounted ride. It's appropriate for a prototype, as this is, and they'll probably still get their primary mission done--testing that it functions properly in orbit. Probably won't get to use it in their constellation if it works, which would have been gravy.
Actually, rocket math isn't quite as easy as that and they burn quite a bit more, but yes that's a simplistic explanation of what happened.
Longer thrust would not be equivalent to bigger thrusts for non vertical paths, neither the arrival time or vectors once there. That's probably related.
I can also imagine that even the weight profile will change, thus leading to different paths...
I can also imagine that even the weight profile will change, thus leading to different paths...
Depends on where in the flight the engine stopped providing thrust too.
Based on the wording of the article, it seems that the satellite is in the wrong orbit not because of the fault with the first stage but because the second stage wasn't allowed to make a correction burn due to NASA rules.
I'm not that well informed here, but my guess is it was a combination of both. They mention
> the extra burn time [of the first stage] left the rocket with insufficient propellant to safely place the Orbcomm satellite into a higher orbit.
I take that to mean that at the time when the first stage ran out of fuel, they were still within the "no-space-junk" threshold where they weren't allowed to separate/jettison the first stage (if that's how it works).
If the first stage had gone smoothly and left them with enough propellant, they would have used that propellant to climb out of ISS danger zone, and then fire the second stage safely.
> the extra burn time [of the first stage] left the rocket with insufficient propellant to safely place the Orbcomm satellite into a higher orbit.
I take that to mean that at the time when the first stage ran out of fuel, they were still within the "no-space-junk" threshold where they weren't allowed to separate/jettison the first stage (if that's how it works).
If the first stage had gone smoothly and left them with enough propellant, they would have used that propellant to climb out of ISS danger zone, and then fire the second stage safely.
The fault in the first stage led directly to rocket being in wrong place, too close to ISS, thus prohibited from firing.
Makes me wonder why they omitted that sentence from the quote. It certainly made the hacker news linker misunderstand it!
Another good article: http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce3...
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Does this mean that the SpaceX statement yesterday along the lines of "it worked as designed" was false, or did they just lie by omission of the fact that they didn't launch it high enough?
Basically everything in the rocket launch is automated, there was a primary and secondary mission on board the rocket. When a problem happened with one of the engines it was shut down and still was able to complete the primary mission which was the dragon capsule but it had to consume extra fuel in order to do so and that left the secondary mission without enough fuel to deliver the orbcomm satellite within the required safety margins of the ISS. So in that aspect the rocket did exactly what it was supposed to do, it saw a problem and dealt with it completing its primary mission at a sacrifice of its secondary mission.
Edit: It could also be the case that it did have the required fuel but part of the agreement with NASA was that if any anomaly should happen that the secondary mission is aborted or that it had a specific time window where it was allowed to start its engines back up to deliver the second payload and it missed that window because it took longer to get to orbit.
Edit: It could also be the case that it did have the required fuel but part of the agreement with NASA was that if any anomaly should happen that the secondary mission is aborted or that it had a specific time window where it was allowed to start its engines back up to deliver the second payload and it missed that window because it took longer to get to orbit.
I don't think they have addressed this issue yet. When they said things like "Falcon 9 did exactly what it was designed to do", all of that is 100% true. Additionally, all comments SpaceX have made so far, I think, are written about the ISS mission. They have not said anything about success or failure of other aspects of the launch, like this satellite. I assume we'll hear something eventually, but given that everything might be fine (the Orbcomm people are working to get it in the right orbit, it sounds like) they're probably just sitting tight for now.
Even if the satellite can propel itself to the correct orbit, it may burn a lot of fuel which can take years off the operational life of the satellite. Those years are worth a lot of money.
You have to take the subjective statements out of the equation. AFAIK the mission had two objectives:
1. Loft Dragon into an orbit from which it can chase and catch the ISS.
2. Loft the Orbcomm test/demo payload into some orbit specified by the customer.
During the launch they lost an engine. They still achieved objective 1. They did not achieve objective 2. The most interesting thing to know will be why they didn't achieve objective 2.
1. Loft Dragon into an orbit from which it can chase and catch the ISS.
2. Loft the Orbcomm test/demo payload into some orbit specified by the customer.
During the launch they lost an engine. They still achieved objective 1. They did not achieve objective 2. The most interesting thing to know will be why they didn't achieve objective 2.
Sounds like they needed a second stage to get the Orbcomm payload to the correct orbit, but they were too close to ISS to detach the first stage rockets. This is because, after compensating for the loss of one of the engines, they didn't have enough fuel to get to the minimum-safe distance to detach the stage 1 boosters.
The rocket system worked as designed in that it recovered from a failure. The mission was a partial success (or partial failure, depending on one's outlook). No need to dramatize it.
Target orbit was 192x203 miles, actual orbit was 122 x 202 miles. These are very different numbers.
Does anyone know why the Orbcomm needs such a specific orbit? If it's in orbit at all can't it do most of whatever it is supposed to do?
(Sorry probably a dumb question, huh)
(Sorry probably a dumb question, huh)
It's got to suck working on making a satellite, with precision engineering and the highest quality materials, to just have it go nowhere.
Most space hardware is made from very ordinary materials, for what it's worth. Lots of aluminum.
I was thinking of some of the fancy aluminium-lithium alloys, but I guess they are mainly used on the rocket bodies, not the satellites. But even if it's just aluminium, that's a lot of high-spec machining and welding to just burn up.
This was just a test satellite. It's very likely they'll be able to get it into a 'good enough' orbit to complete their testing.
Sure, but at the same time the article said there are 11 more of the same ones ready to go up.
It is a loss, but looks like the cost of being on the first wave of a new space startup.
It is a loss, but looks like the cost of being on the first wave of a new space startup.
Luckily this was a test satellite with a planned short lifetime (from what I can understand).
They're going to use the propellant on the satellite to get as close as possible to their planned orbit, which would normally be more of a problem as it drastically shortens the lifetime of a LEO satellite which needs that propellant to keep altitude.
They're going to use the propellant on the satellite to get as close as possible to their planned orbit, which would normally be more of a problem as it drastically shortens the lifetime of a LEO satellite which needs that propellant to keep altitude.
So can the orbit be corrected, or is this satellite just lost?
It can be corrected, but only to the extent of how much fuel/propellant is available on the satellite's on-board propulsion system... And when I mean "available", I mean "available within the new amount of distance the orbit has to be raised". From the article:
"It's possible but unlikely that the satellite has enough spare propellant to complete its mission," McDowell wrote in an email to Spaceflight Now.
"It's possible but unlikely that the satellite has enough spare propellant to complete its mission," McDowell wrote in an email to Spaceflight Now.
It may be able to move into another orbit which they can use for testing, but there's no way they have enough fuel to reach their planned orbit.
"The OG2 prototype satellite, flying as a secondary payload on this mission, was separated from the Falcon 9 launch vehicle at approximately 9:00 pm EST. However, due to an anomaly on one of the Falcon 9’s first stage engines, the rocket did not comply with a pre-planned International Space Station (ISS) safety gate to allow it to execute the second burn. For this reason, the OG2 prototype satellite was deployed into an orbit that was lower than intended. ORBCOMM and Sierra Nevada Corporation engineers have been in contact with the satellite and are working to determine if and the extent to which the orbit can be raised to an operational orbit using the satellite’s on-board propulsion system"
http://www.orbcomm.com/Collateral/Documents/English-US/ORBCO...