Author Topic: SpaceX Falcon Landing legs - General Discussion Thread  (Read 200057 times)

Offline Avron

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Just wanted to move this off the poll thread..

CRS-3 is coming up and we have this quote from Elon via
http://shitelonsays.com/files/SpaceX_Press_Conference_September_29_2013.mp3

[Question about landing on land and FAA licensing for landing] We have actually been working with Air Force range safety and the FAA to identify landing locations at Cape Canaveral and we have identified a few. I don't think that we are quite ready to say what those locations are but they are kind of out on the tip of Cape Canaveral, on the eastern most tip of Cape Canaveral. It's great working with both Air Force range safety and the FAA. They have actually been quite supportive of the whole thing. You need a (FAA) license and we expect to get it.


Would they need to file a flight plan for the stage/vehicle to RTLS? i.e would it be public before the event?

Yes to the first; I wouldn't bet on the latter.

They will require launch and reentry licenses; IIRC those may be combined and in any case include (among other things) flight plan and safety analysis.  That said, the vast majority of information is not public AFAICT (the licenses published by the FAA are perfunctory and do not provide details).

To do an RTLS, the operator would have to show a combined Ec below the allowable threshold.  Flight path, IIP, and dwell time over populated areas are considerations, not to mention vehicle history.  (In the original rule making considerations that was explicitly mentioned, e.g., experimental aircraft restrictions until a certain number of flight hours.)

I would be amazed if the FAA approved return anywhere near a populated area (or overflight during terminal phase) without significant flight history.  To Jon's point, that probably means waiting on more GH2 tests, and likely quite a few water "landings", before the FAA approves RTLS.

Joek, has some great docs on FAA requirements..

If they get to use LC-36 . there is not overflight .. I guess they just have to do the math on risk to the public... the range always has the button ..

Normally I would agree with Jon.. but we are talking Elon thinking here, so thats a whole new ballgame..
« Last Edit: 11/25/2014 08:16 PM by Chris Bergin »

Offline Avron

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #1 on: 01/11/2014 09:46 PM »
Anyone know that flight  this booster belongs ?  It has the mounts of legs, I think..

http://www.spacex.com/sites/spacex/files/careers/cycle_large5.jpg

Offline Lars_J

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #2 on: 01/11/2014 09:49 PM »
Anyone know that flight  this booster belongs ?  It has the mounts of legs, I think..

http://www.spacex.com/sites/spacex/files/careers/cycle_large5.jpg

That was CASSIOPE 1st stage, the first v1.1 core. All three v1.1 vehicles flown appear to have had the lower leg joint attachments installed.
« Last Edit: 01/11/2014 09:49 PM by Lars_J »

Offline Avron

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #3 on: 01/11/2014 10:10 PM »
also from the poll thread..

So they might put legs on it even if they're intending to do a water splashdown.

That's what Elon said, yeah.

Remotely more on-topic: they do have three CRS flights scheduled for 2014, and I wouldn't be surprised if they started making recovery attempts on non-CRS flights too, so subtract one from whatever you voted, for an estimates of how many recovery attempts they'll be making in 2014!

Musk said that they would attempt recovery on pretty much all flights after Thaicom-6 (not just CRS flights).

Looking for the quote on what was on the critical path for CRS-3 .. think it was Dragon vs legs..

Offline Barrie

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #4 on: 01/11/2014 10:12 PM »
Thanks for starting the thread, Avron. 

I'd agree with Jon, too, but it does seem from Elon's comments that he would be quite happy for 'testing in production' (ie trying to land the 1st stage after every operational flight) to obviate some Grasshopper testing.   It's like a multi-threaded approach, and it doesn't matter which approach gets them there first.

Online QuantumG

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #5 on: 01/11/2014 10:18 PM »
Looking for the quote on what was on the critical path for CRS-3 .. think it was Dragon vs legs..

I've been pasting that quote a lot lately :)

Talking about CRS-3 he said:

Quote from: Elon Musk
We are not going hold up that flight for landing legs. So if landing legs end up being delayed for any reason then we won't hold up the flight for that. But the full plan is to have landing legs on that mission. The schedule for that mission is mostly governed by upgrades to the Dragon spacecraft. We have an upgraded avionics system and we are able to provide a lot more power to NASA for powered cargo. It essentially triples, I think, the amount of powered cargo that NASA can have. So I think that's what is driving that schedule. It's a high priority for us to get that mission launched as soon as we can. It looks like probably sometime in February most likely.

Quote from: Elon Musk
We have actually been working with Air Force range safety and the FAA to identify landing locations at Cape Canaveral and we have identified a few. I don't think that we are quite ready to say what those locations are but they are kind of out on the tip of Cape Canaveral, on the eastern most tip of Cape Canaveral. It's great working with both Air Force range safety and the FAA. They have actually been quite supportive of the whole thing. You need a (FAA) license and we expect to get it.

Quote from: Elon Musk
Our goal is to recover the first stage on all CRS flights and really on most flights. The next two flights are somewhat of an exception. When we negotiated these deals, we didn't have much bargaining power. It was before we obviously flown this version of the Falcon 9 successfully. So we kind of agreed to give up all performance on the rocket and not reserve anything for reusability. But going into the future, with future contracts, with a few exceptions, we have reserved enough performance to recover the stage. It's not just the CRS flights, it should be most flights after these next two (flights). In terms when we actually re-fly the stage, it's going to depend on what condition the stage is in and obviously getting customers comfortable with that. So it's difficult to say when would actually re-fly it. If things go super well then we would be able to re-fly a Falcon 9 stage before the end of next year and that's our aspiration.

all via http://shitelonsays.com/transcript/spacex-press-conference-september-29-2013-2013-09-29

Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline Lars_J

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #6 on: 01/11/2014 10:37 PM »
Anyone know that flight  this booster belongs ?  It has the mounts of legs, I think..

http://www.spacex.com/sites/spacex/files/careers/cycle_large5.jpg

That was CASSIOPE 1st stage, the first v1.1 core. All three v1.1 vehicles flown appear to have had the lower leg joint attachments installed.

Here is a picture of the leg attachment points on the CASSIOPE flight, where the points are circled in red. Those points appear to serve no other purpose, and they are in the right place, but I could be wrong.
« Last Edit: 01/11/2014 10:37 PM by Lars_J »

Offline joek

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #7 on: 01/11/2014 11:02 PM »
If they get to use LC-36 . there is not overflight .. I guess they just have to do the math on risk to the public... the range always has the button ..

Then again, for RTLS the IIP and potential debris field are in front of and downrange of the returning stage.  There is still a lot of important stuff within a few kilometers of LC-36, including personnel classified as "public" (i.e., those not directly involved in the licensed activity); and a bit further downrange (with respect to the returning vehicle) are a lot of civilians.

Hitting the button early may mitigate some risks.  But what if a problem shows up late?  Can or will the debris field and risk be sufficiently constrained to yield an acceptable Ec?  I don't know, and I doubt anyone else can provide a credible analysis at this time.  In short, it will likely be a few years (and many tests) until the FAA grants permission for RTLS to anywhere near a populated site.

Offline Comga

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #8 on: 01/11/2014 11:28 PM »
If they get to use LC-36 . there is no overflight .. I guess they just have to do the math on risk to the public... the range always has the button ..

Then again, for RTLS the IIP and potential debris field are in front of and downrange of the returning stage.  There is still a lot of important stuff within a few kilometers of LC-36, including personnel classified as "public" (i.e., those not directly involved in the licensed activity); and a bit further downrange (with respect to the returning vehicle) are a lot of civilians.

Hitting the button early may mitigate some risks.  But what if a problem shows up late?  Can or will the debris field and risk be sufficiently constrained to yield an acceptable Ec?  I don't know, and I doubt anyone else can provide a credible analysis at this time.  In short, it will likely be a few years (and many tests) until the FAA grants permission for RTLS to anywhere near a populated site.

Jim talked about the FTS not demolishing the stage and spewing debris all around.  Rather he said that it would terminate the operation, while leaving the stage basically intact.  If the IIP only comes ashore in the last few seconds, with the engine burning, essentially replicating the 100m lateral Grasshopper flight, they will have mitigated the risk to a great degree.

It would still surprise me if they aimed for land before two or so first stages had been brought back to off-shore targets and demonstrated precision navigation.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline Lars_J

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #9 on: 01/11/2014 11:32 PM »
Yes, they might do RTLS but with a target in the ocean a few miles out from the shore - before going for a land landing.
« Last Edit: 01/11/2014 11:32 PM by Lars_J »

Offline Lar

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #10 on: 01/11/2014 11:38 PM »
Yes, they might do RTLS but with a target in the ocean a few miles out from the shore - before going for a land landing.
Perhaps, but Musk was quoted saying they were seeking permission to land back at the Cape for CRS-3.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Lars_J

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #11 on: 01/11/2014 11:46 PM »
Yes, they might do RTLS but with a target in the ocean a few miles out from the shore - before going for a land landing.
Perhaps, but Musk was quoted saying they were seeking permission to land back at the Cape for CRS-3.

He was saying that a few months ago, yes. But without any GH2/F9R-1 test flights in McGregor or NM, I think that is a very remote possibility at this point. A couple of GH2 hops will of course change that if they happen.

Online TrevorMonty

If they get to use LC-36 . there is no overflight .. I guess they just have to do the math on risk to the public... the range always has the button ..

Then again, for RTLS the IIP and potential debris field are in front of and downrange of the returning stage.  There is still a lot of important stuff within a few kilometers of LC-36, including personnel classified as "public" (i.e., those not directly involved in the licensed activity); and a bit further downrange (with respect to the returning vehicle) are a lot of civilians.

Hitting the button early may mitigate some risks.  But what if a problem shows up late?  Can or will the debris field and risk be sufficiently constrained to yield an acceptable Ec?  I don't know, and I doubt anyone else can provide a credible analysis at this time.  In short, it will likely be a few years (and many tests) until the FAA grants permission for RTLS to anywhere near a populated site.

Jim talked about the FTS not demolishing the stage and spewing debris all around.  Rather he said that it would terminate the operation, while leaving the stage basically intact.  If the IIP only comes ashore in the last few seconds, with the engine burning, essentially replicating the 100m lateral Grasshopper flight, they will have mitigated the risk to a great degree.

It would still surprise me if they aimed for land before two or so first stages had been brought back to off-shore targets and demonstrated precision navigation.

The targeting of landing site a few 100metres off shore then lateral flight to landing pad makes sense

Offline jongoff

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #13 on: 01/12/2014 12:58 AM »
It would still surprise me if they aimed for land before two or so first stages had been brought back to off-shore targets and demonstrated precision navigation.

This is my thinking too. I think that people *may* be reading more into Elon's comments about first stage recovery on future flights with an actual land landing that might be gas-and-go refuelable. Recovering the first stage could include a water splashdown that resulted in an un-refliable but useful-for-post-flight-inspection stage. A botched land landing would likely result in a decent fireball/explosion where it hits (though most of the prop will be gone by this point, not all will), which I would think would make it harder for them to get FAA approvals in the future. As one of my SpaceX friends says, they do tend to be more ballsy than your traditional aerospace company, but I doubt even SpaceX would be that ballsy. But who knows, this is Tony Sta^H^H^H^H er... I mean Elon Musk we're talking about, so you never know. :-)

~Jon
« Last Edit: 01/12/2014 01:12 AM by jongoff »

Offline aero

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #14 on: 01/12/2014 01:28 AM »
Boy you're quick. I deleted that post almost as soon as I hit the post button!
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Offline Kabloona

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #15 on: 01/12/2014 03:51 AM »


Hitting the button early may mitigate some risks.  But what if a problem shows up late?  Can or will the debris field and risk be sufficiently constrained to yield an acceptable Ec?  I don't know, and I doubt anyone else can provide a credible analysis at this time.  In short, it will likely be a few years (and many tests) until the FAA grants permission for RTLS to anywhere near a populated site.

I'm more optimistic/hopeful about the time frame. The stage will have less than a 10% propellant load when it's anywhere near the landing site. As for the credibility of Ec analysis, the range already does Ec calcs for a fully loaded stage. Why is it any harder to do the calcs with, say, a 10% prop load vs. a 100% load? The model already exists, it's just plug and chug.

The long pole will be proving the reliability/accuracy of terminal guidance, but with the past successes of GH and the upcoming tests of F9R I could see SpaceX having all the data they need for satisfying FAA for an LC-36 RTLS within a year if all goes well.
« Last Edit: 01/12/2014 04:37 AM by Kabloona »

Offline Lars_J

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #16 on: 01/12/2014 05:07 AM »
The targeting of landing site a few 100metres off shore then lateral flight to landing pad makes sense

The problem with that is that the stage has virtually no hover capability... the 'divert to landing point' manuever has to happen pretty far up, as the stage is coming in at terminal velocity.

Offline meekGee

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #17 on: 01/12/2014 05:25 AM »
The targeting of landing site a few 100metres off shore then lateral flight to landing pad makes sense

The problem with that is that the stage has virtually no hover capability... the 'divert to landing point' manuever has to happen pretty far up, as the stage is coming in at terminal velocity.

... and that's a good thing, since it reduces the uncertainty in estimating the IIP.

It comes down towards the "crash pit" in the water, extends legs, fires up, and only if all is well, it performs the divert maneuver.   Even after the IIP starts moving, it still only moves from the crash pit to the landing pad. (and depending on the exact maneuver, might overshoot it by a few tens of meters momentarily, still within the landing pad safe area though.)

If there is any deviation from the prescribed course after the divert maneuver begins, the red button gets pushed, and the rocket crashes somewhere between the crash pit and the landing pad.

This is what they've been telling the range, I'm sure.  Whether GH2 flies first or not - it only affects SpaceX odds of landing safely and avoiding an embarrassment.  The range's job is to protect the public.

That said, timing wise, I think GH2 will fly in TX by then, but might not have a chance to test leg deployment.
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Offline guckyfan

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #18 on: 01/12/2014 07:54 AM »
Two points that have been covered before.

Elon Musk said they need less than 1 ton of fuel for landing. That's just a few hundred kg of RP-1, as much as a small truck would carry. Or a small plane which is allowed over populated areas.

About the landing itself. The point was made that the landing trajectory will be naturally short of the landing point. If the landing burn is vertical that by itself will extend the landing trajectory to the landing point, because it comes down more slowly and can travel farther than without that burn. So there is a built in safety factor in the landing process.


Offline Lar

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Re: SpaceX Falcon Landing legs - General Discussion Thread
« Reply #19 on: 01/12/2014 08:40 AM »
Yes, they might do RTLS but with a target in the ocean a few miles out from the shore - before going for a land landing.
Perhaps, but Musk was quoted saying they were seeking permission to land back at the Cape for CRS-3.

He was saying that a few months ago, yes. But without any GH2/F9R-1 test flights in McGregor or NM, I think that is a very remote possibility at this point. A couple of GH2 hops will of course change that if they happen.

Yes, we are not very far away from CRS3 and not one GH2 hop at all yet. I find that surprising, I was SURE they would want to test a few things so every day without a GH2 makes CRS3 landing on land a bit less likely, IMHO.

Did you change your Avatar to the LEGO classic space logo? :)
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