Author Topic: SpaceX Falcon 9 v1.1 DISCUSSION AND UPDATES (THREAD 1)  (Read 361280 times)

Offline R7

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Re: SpaceX Falcon 9 v1.1
« Reply #1220 on: 03/09/2013 04:01 PM »
Finally, anyone have a good speculation about what contact with cold water will do to the engines?
It is a safe guess that the working engine will be ruined, for everything else it depends on actual temperature. I passed my metallurgy exam long ago, but still remember that quenching makes steel harder but more brittle. So may be the thrust structure wont be reusable after such quench-splash...

You forget that nothing in a running regen rocket engine gets very hot, except the combustion products. CC is mostly copper anyway. Hottest part would be the GG and the turbine. Shutdown purging would help cooling it.

Robert Truax studied water effects on rocket engines a lot, fired pressure fed engines underwater etc.

See http://neverworld.net/truax/

I'd speculate the most dramatic effect on recently running engine being immersed in water would be that surfaces get wet  ;D
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Online meekGee

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Re: SpaceX Falcon 9 v1.1
« Reply #1221 on: 03/09/2013 04:03 PM »
It's not supposed to reused after the water landing, just prove that it can impact the ocean in one piece (something v1.0 never did). The killer is side loads, so they have to prove they can orient the vehicle tail first before the rest of the recovery sequence can work. If they do a relight and softly land in the water, great, but that's nothing Grasshopper can't do.
I was thinking more in terms of how much damage a water landing would do vs a grasshopper style dirt landing. At a minimum I would expect the center nozzle to implode once the bottom is sealed by water and chilling begins. But, that still leaves lots of forensic knowledge to be obtained about the flight hardware if they get it back. The physical landing environments are different enough that I don't have a good feeling for what will happen on water. Ergo the question.

oooh,  that might be loud.

They already have GH.  For the purpose of reuse, the key step here is the reentry interface.  If the stage can get to subsonic flight, they've got it made, whether it then breaks on impact or not.

So I am not sure how much they'll play around with the last 10' of landing.  The only significance there is if they want to ensure that the stage floats (so they can post-mortem), and then maybe they should add a float to it, since it is not that heavy. (instead of relying on both tanks remaining sealed).
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Online Okie_Steve

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Re: SpaceX Falcon 9 v1.1
« Reply #1222 on: 03/09/2013 04:06 PM »
Robert Truax studied water effects on rocket engines a lot, fired pressure fed engines underwater etc.

See http://neverworld.net/truax/

I'd speculate the most dramatic effect on recently running engine being immersed in water would be that surfaces get wet  ;D

Wow! Thanks for the link. I'll go study it.

Online arnezami

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Re: SpaceX Falcon 9 v1.1
« Reply #1223 on: 03/09/2013 04:10 PM »
I wonder if they would add a camera on the first stage to record the water landing, which we could watch afterwards... :)

That would be epic.

Offline ugordan

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Re: SpaceX Falcon 9 v1.1
« Reply #1224 on: 03/09/2013 04:15 PM »
ugordan, thanks for remembering me. 

You're welcome. It's only fair to give you credit seeing as how you've provided us with various bits of info on their plans over time when other sources were usually nowhere to be found.

Offline Zed_Noir

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Re: SpaceX Falcon 9 v1.1
« Reply #1225 on: 03/09/2013 04:26 PM »

I've been told that the v1.1 will become SpaceX's "workhorse" launch vehicle.  SpaceX has told NASA they plan on producing up to 40 v1.1 cores/boosters a year for the F9 and F-H vehicles.

That was a given

I bet you are meaning the first sentence, because there's no way that SpaceX has the launch demand needed to produce 40 cores/boosters per year (currently the most produced almost-completely-same core stages must be the Soyuz rockets, and they are only flying up to 20 flights per year).  ::)

I recall SpaceX planned to eventually launch 20 LVs annually evenly between F9 & FH. So 40 F9 V1.1 cores annually seems about right.

Offline butters

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Re: SpaceX Falcon 9 v1.1
« Reply #1226 on: 03/09/2013 04:29 PM »
SpaceX can't be thinking about recovering the first several F9v1.1 boosters for reuse, and who knows how much (if any) forensic value they might derive from hauling them out of the ocean for analysis. Maybe... maybe they reuse the primary thrust structure.

The purpose of this exercise is progress incrementally toward RTLS. First test if they can flip retrograde, null the horizontal velocity, and execute a controlled vertical powered descent. Then on future flights they can introduce an uprange horizontal velocity and target a "landing" point closer to shore. Demonstrate that they can hit these targets with accuracy, ideally on missions with different launch azimuths and (if supported) from both LEO/SSO and GTO staging velocities.

It probably won't be entirely straightforward for SpaceX to get FAA approval for RTLS. The FAA hasn't regulated anything like this before. The potential risks to life and property are much greater than for launches or reentries over water. So I think they'll have to do quite a few of these RTLS simulations over water before they are authorized to attempt an actual landing.

Offline rickl

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Re: SpaceX Falcon 9 v1.1
« Reply #1227 on: 03/09/2013 04:41 PM »
I agree, butters.  Right now they just want to try out the concept.

I was very surprised to learn that they are going to do this so soon.  I figured on a couple years of Grasshopper tests, at least. 

It's remarkable that they are even thinking about doing this, after 50+ years of simply dumping boosters in the ocean, or on the steppes of Central Asia.
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Offline Lars_J

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Re: SpaceX Falcon 9 v1.1
« Reply #1228 on: 03/09/2013 04:47 PM »
I wonder if they would add a camera on the first stage to record the water landing, which we could watch afterwards... :)

That would be epic.

The first stages already have cameras (at least two), and do broadcast for a little while after stage separation. But I assume that they would add more cameras and equipment to ensure broadcast of video & telemetry all the way down.

EDIT: If you look at this re-broadcast of the SpaceX launch coverage, you can see the longest view yet from the 1st stage after stage separation - quite neat view from the interstage as the 1st stage starts to tumble - Go to minute 43:
« Last Edit: 03/09/2013 08:31 PM by Lars_J »

Offline ArbitraryConstant

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Re: SpaceX Falcon 9 v1.1
« Reply #1229 on: 03/09/2013 04:52 PM »
I was thinking more in terms of how much damage a water landing would do vs a grasshopper style dirt landing. At a minimum I would expect the center nozzle to implode once the bottom is sealed by water and chilling begins. But, that still leaves lots of forensic knowledge to be obtained about the flight hardware if they get it back. The physical landing environments are different enough that I don't have a good feeling for what will happen on water. Ergo the question.
If the idea is to come to a speed of ~0 at low altitude and then cut thrust, seems like it would be a mostly survivable fall followed by bobbing around like a cork because it's almost entirely helium by volume. Almost like a parachute landing except for the freshly fired engine.

If they do a relight and softly land in the water, great, but that's nothing Grasshopper can't do.
I think the main thing is surviving reentry.

Offline R.Simko

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Re: SpaceX Falcon 9 v1.1
« Reply #1230 on: 03/09/2013 04:56 PM »
Any chance they can do the water landing in shallow water, in case the rocket breaks up or sinks?  Makes it a lot easier to retrieve.

Offline Jason1701

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Re: SpaceX Falcon 9 v1.1
« Reply #1231 on: 03/09/2013 05:04 PM »
So if the center engine creates a bowl wider than 3.3 m, the rocket could descend into the bowl, which would then get deeper. I wonder how deep it could descend before the top of the bowl collapses and swallows the booster!

Sounds like an xkcd what-if topic.

Offline joek

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Re: SpaceX Falcon 9 v1.1
« Reply #1232 on: 03/09/2013 05:10 PM »
Right now, SpaceX views their manifest is basically a self-funding technology development program (not something that customers love, I'm sure) but so far it seems to have a good chance of working out for both sides.

Unless the development is seen as beneficial by customers, especially if they see that the costs and risks are spread across many.

edit: To clarify... Agree; I think that's something that most customers find attractive and will work to the benefit of both SpaceX and their customers.
« Last Edit: 03/09/2013 05:51 PM by joek »

Offline go4mars

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Re: SpaceX Falcon 9 v1.1
« Reply #1233 on: 03/09/2013 05:32 PM »
So if the center engine creates a bowl wider than 3.3 m, the rocket could descend into the bowl, which would then get deeper. I wonder how deep it could descend before the top of the bowl collapses and swallows the booster!
Interesting question.  Old footage of Sea Bee and Sea Horse implies to me, not very deep, but if I'm wrong, and if the stage could handle it, a "brown pants ocean landing" would be interesting. 

If needed, to make a big enough "bowl", perhaps a 5 engine (9 is probably not survivable for the stage at that point) very high-g puddle dimpler maneuver would save fuel and allow them to arrive at the ocean surface with a fair bit of speed (actually landing in a highly agitated water tube filled with a steam cushion).   Thrust transient could be the denouement.

The difference in fuel use between that, and doing a dry land brown pants landing might be negligible, now that I think about it a little more. 

A new name for brown pants landing:  Shedoudami Landing. 
As in "That scared the shedoudami!"        Say it out loud...
« Last Edit: 03/11/2013 11:38 AM by go4mars »
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Offline kch

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Re: SpaceX Falcon 9 v1.1
« Reply #1234 on: 03/09/2013 07:56 PM »
So if the center engine creates a bowl wider than 3.3 m, the rocket could descend into the bowl, which would then get deeper. I wonder how deep it could descend before the top of the bowl collapses and swallows the booster!

Sounds like an xkcd what-if topic.

Well, the exhaust gases would flow up the sides of the booster, possibly keeping the water away.  It might just keep right on going, descending into the "bowls" of the Earth ... :D

Offline Prober

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Re: SpaceX Falcon 9 v1.1
« Reply #1235 on: 03/11/2013 11:32 AM »
It will displace some water - proportionally to the engine thrust, but not 100%. So, just before "touchdown" there should be a bowl of about several dozens cubic meters volume, I'd love to see that :)

Hmmm, maybe they will try to "touchdown" at a negative altitude of a couple of meters for this test then, depending on how deep the "bowl" is, the effects of the bowl collapsing on engine shutdown, and the floating stability of the stage. Falling over and buckling can't be good for recovery prospects.

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don't focus on the water landing or miss the real test.
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Online Okie_Steve

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Re: SpaceX Falcon 9 v1.1
« Reply #1236 on: 03/11/2013 08:35 PM »
don't focus on the water landing or miss the real test.
Yep, totally agree. It's just that Spacex seems to like to have a long string of possible tests if everything works, or until something goes wrong so they get the most for their testing $$. Think of COT2+ for example. It would not surprise me if the much discussed rotation of the 1st stage after separation was preliminary testing for the V1.1 flip maneuver for example. So for the V1.1 flight there are a bunch of probably objectives as I see it.

1 - Does it fly norminally
2 - Can the 1st stage be flipped and stabilized with cg thrusters to orient for reentry.
3 - Can the 1st stage avionics settle fuel and restart the engine properly
4 - Can they maintain stable attitude and trajectory down to subsonic speeds
5 - Can they do a hoverslam to the ocean surface
6 - Can they recover the stage and engines
7 - What does forensic analysis tell them about their design assumptions
8 - etc.

Obviously number 1 is the biggie for the V1.1 vehicle and launching for paying customers, but the further down the list they get on any given flight the more they learn towards F9R and future projects. I was just curious about the water landing and recovery since I'd not really thought in those terms before but it's certainly not "that important" in the near term compared to things higher up the list. Feel free to add or reorder as you see fit.

Offline modemeagle

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Re: SpaceX Falcon 9 v1.1
« Reply #1237 on: 03/11/2013 11:03 PM »
I did some simulations and came up with a preliminary figure with the following:
If SI is shut down with ~ 3km/s delta-v residual prop (this is with the upper stage mass removed) then the vehicle could be 24km down range, 85 km altitude and with a apogee of 168km. This could land ~100km down range after removing all horizontal velocity at apogee (~523m/s).  This is just one simulation run I ran and it still gave just over 700 m/s residual prop on SII at MECO.  I am not saying this is what they are doing, just that the payload for CASSIOPE is small enough that they should have a lot of room for reserve propellant.

Offline oiorionsbelt

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Re: SpaceX Falcon 9 v1.1
« Reply #1238 on: 03/12/2013 03:46 PM »
That's interesting modemeagle.
Did anyone figure out how SpaceX will resolve the over the horizon telemetry acquisition for this flight?
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Offline Jim

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Re: SpaceX Falcon 9 v1.1
« Reply #1239 on: 03/12/2013 04:30 PM »
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