Author Topic: SpaceX: Advanced Launch Abort System (LAS)  (Read 220663 times)

Offline neilh

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #20 on: 04/28/2011 08:46 PM »
OK, B$ detector going off big time on the Mars landing aspect. The only way to make that work is with a parachute to get you subsonic first, and then turn on the engines (rockets cannot fire into a supersonic flow)....
That's not true at all. Rockets can, in fact, fire into a supersonic flow. For supersonic retropropulsion with just a single engine, there is a marked reduction in drag, but for canted side-mounted rocket engines like this, there wouldn't be a reduction in drag.

Indeed, supersonic retropropulsion is actually one of the main research areas of Robert Braun, the NASA Chief Technologist.

http://www.ssdl.gatech.edu/papers/conferencePapers/AIAA-2009-5613.pdf
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Online hop

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #21 on: 04/28/2011 08:56 PM »
If that center J-2 on Apollo 13 ripped out from its mount and torpedoed through the entire S-II stage (as some speculated could have happened had it not shut down first), I wonder if the gentle SPS acceleration would have done the trick.
Right, escape being possible doesn't mean it's guaranteed to save you in every scenario. This is true whether you have high power escape motors or not.

I'm not saying that SpaceX system couldn't be better than what Apollo had, I'm just disappointed by the needless conflation of an *escape tower* with an *escape system*. SpaceX should know better.

Online ugordan

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #22 on: 04/28/2011 09:03 PM »
Right, escape being possible doesn't mean it's guaranteed to save you in every scenario. This is true whether you have high power escape motors or not.

I agree and I'm not saying having a LAS would necessarily have worked in that case, either.

Quote
I'm not saying that SpaceX system couldn't be better than what Apollo had, I'm just disappointed by the needless conflation of an *escape tower* with an *escape system*. SpaceX should know better.

Maybe there's a fine distinction between "escape" and "abort" to be made? SPS could have aborted away from let's say a gracefully shut down stage, but it probably wouldn't have worked that well if the vehicle executed a RUD.

In the end, this is all spin and I don't personally get too excited over it.

Offline 2552

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #23 on: 04/28/2011 09:06 PM »
Looks like the vision is for Martian powered landing. What really interests me is at 1:18 you get a view of a Spacex "space barge" holding cargo and another Dragon spacecraft for accent. Are those engines underneath the Dragon for the martian accent phase?

Screencap (cropped) from the 720p HD version at 1:17, taken in fullscreen mode.


Offline Downix

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #24 on: 04/28/2011 09:08 PM »
because after that escape was possible without the tower.

If that center J-2 on Apollo 13 ripped out from its mount and torpedoed through the entire S-II stage (as some speculated could have happened had it not shut down first), I wonder if the gentle SPS acceleration would have done the trick.
Gentle?  The AJ-10-137 was overpowered for it's job as SPS, by 200% according to estimates, and wasn't used at full power during the Apollo flights.  The reason why is due to it's design beginnings were on the original Moon-direct landing Apollo, and was carried over when the mission profile was changed to LOR. (it would have enabled the SM+CM to lift off from the Moon, leaving the S-IVB on the surface of the moon)  While it would not yank it away as fast as the tower would, once out of the atmosphere it would get the crew away from an emergency.

You know, looking this up answered another question I'd had since the ESAS study came out, what the LR-85 mentioned as a possible US engine for Ares was. 
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Offline 2552

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #25 on: 04/28/2011 09:11 PM »
Attached is the SpaceX press kit.

And the actual press kit... http://www.spacex.com/downloads/20110428-spacex-sts134.pdf

Link doesn't seem to work, goes to a 404 for me. Can someone attach it here?

Online ugordan

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #26 on: 04/28/2011 09:14 PM »
Gentle? 

Gentle compared to the LES acceleration. Not when used as normal main propulsion.

Link doesn't seem to work, goes to a 404 for me. Can someone attach it here?

Hmm. Still works for me. Have you tried copying the URL text manually into the address bar?

Offline Cog_in_the_machine

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #27 on: 04/28/2011 09:15 PM »
Here.
^^ Warning! Contains opinions. ^^ 

Offline 2552

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #28 on: 04/28/2011 09:18 PM »
Gentle? 

Gentle compared to the LES acceleration. Not when used as normal main propulsion.

Link doesn't seem to work, goes to a 404 for me. Can someone attach it here?

Hmm. Still works for me. Have you tried copying the URL text manually into the address bar?

Yes, didn't work. Maybe SpaceX took it down but it's still in your browser cache, so the link still "works" for you?

Here.

Thanks.
« Last Edit: 04/28/2011 09:18 PM by 2552 »

Online ugordan

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #29 on: 04/28/2011 09:21 PM »
Maybe SpaceX took it down but it's still in your browser cache, so the link still "works" for you?

Nope, the PDF definitely downloads every time plus I tried it in another browser where it wasn't cached. Curious.

Oh, well.

Offline Ben the Space Brit

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #30 on: 04/28/2011 09:33 PM »
Yep, definitely looks like a separate MAV; Possibly 4 x Merlin-1 as the propulsion system.  Likely the Dragons would be only descent and ascent vehicles, there would be a separate (Bigelow-designed?) orbital transfer vehicle.

Talk is cheap and even CGI is cheaper than rocket engineering.  However, I do suspect that this is SpaceX metaphorically throwing down the gauntlet: "If you won't, we will."
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Offline Nathan

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #31 on: 04/28/2011 09:35 PM »
Looks like the vision is for Martian powered landing. What really interests me is at 1:18 you get a view of a Spacex "space barge" holding cargo and another Dragon spacecraft for accent. Are those engines underneath the Dragon for the martian accent phase?

Screencap (cropped) from the 720p HD version at 1:17, taken in fullscreen mode.



Well this is exciting. One would expect that the payload to surface would be limited though. perhaps limited to astronauts, suits and a small 100kg open rover to transport one to the habitat. This would imply a transit hab launched along with the dragon to get the astronauts there.

On the other hand, if payload can be 5tonnes then one can take consumables along for 2 astronauts for a cramped but direct journey. A second Dragon could land an inflatable hab and some supplies. Other dragon's could drop greenhouses etc. All on a direct launch to mars. No other spacecraft required to be developed (even though image shows other spacecraft)

So interesting. What payload could Dragon land using supersonic retro-propulsion? The answer could prove interesting.
Given finite cash, if we want to go to Mars then we should go to Mars.

Offline HMXHMX

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #32 on: 04/28/2011 09:42 PM »
And to be honest, I agree with the CCDev2 reviewer that using a hybrid rocket is risky for abort. Dreamchaser is cool, but is more difficult to develop.
I don't see it as risky, it depends on the particulars of the hybrid system doesn't it?  I made one, once, which was Hypergolic, so no concern over ignition there.

*edit* Come to think of it, my particular design would not be smart for the Dream Chaser in any case, as I used a 5% formula of Chlorine TriFlouride as the oxidizer.  That stuff is dangerous in the highest degree, so falls under the "Don't do this at home kids" category.

In my view, the problem with a hybrid for abort is start up time.  You really want something that can deliver 100 ms or less to full thrust, and all hybrids I've seen are more like 1500 ms.

Offline Rocket Science

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #33 on: 04/28/2011 09:43 PM »
Anyone hear of any "Dead Man Zone" using the propulsive landing planned?
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Offline Downix

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #34 on: 04/28/2011 09:48 PM »
And to be honest, I agree with the CCDev2 reviewer that using a hybrid rocket is risky for abort. Dreamchaser is cool, but is more difficult to develop.
I don't see it as risky, it depends on the particulars of the hybrid system doesn't it?  I made one, once, which was Hypergolic, so no concern over ignition there.

*edit* Come to think of it, my particular design would not be smart for the Dream Chaser in any case, as I used a 5% formula of Chlorine TriFlouride as the oxidizer.  That stuff is dangerous in the highest degree, so falls under the "Don't do this at home kids" category.

In my view, the problem with a hybrid for abort is start up time.  You really want something that can deliver 100 ms or less to full thrust, and all hybrids I've seen are more like 1500 ms.
You've never worked with Chlorine TriFlouride then.  That stuff is insta-on. (I did not have a fine enough fidelity camera when testing it, so all I can say is that it was faster than 200ms.
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Online Robotbeat

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #35 on: 04/28/2011 10:10 PM »
And to be honest, I agree with the CCDev2 reviewer that using a hybrid rocket is risky for abort. Dreamchaser is cool, but is more difficult to develop.
I don't see it as risky, it depends on the particulars of the hybrid system doesn't it?  I made one, once, which was Hypergolic, so no concern over ignition there.

*edit* Come to think of it, my particular design would not be smart for the Dream Chaser in any case, as I used a 5% formula of Chlorine TriFlouride as the oxidizer.  That stuff is dangerous in the highest degree, so falls under the "Don't do this at home kids" category.

In my view, the problem with a hybrid for abort is start up time.  You really want something that can deliver 100 ms or less to full thrust, and all hybrids I've seen are more like 1500 ms.
You've never worked with Chlorine TriFlouride then.  That stuff is insta-on. (I did not have a fine enough fidelity camera when testing it, so all I can say is that it was faster than 200ms.
I am pretty sure DreamChaser doesn't use anything that sounds like "Chlorine TriFlouride." They use nitrous.
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Offline Lobo

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #36 on: 04/28/2011 10:10 PM »
OK, B$ detector going off big time on the Mars landing aspect. The only way to make that work is with a parachute to get you subsonic first, and then turn on the engines (rockets cannot fire into a supersonic flow). Not impossible, but ends up with a completely redesigned vehicle. Plus (of course), you still need to get back up, which means a entirely separate vehicle. And there's no way you're landing on the Moon with it without a crasher stage to brake from LLO.

There's also no way you are getting back off the lunar surface without an ascent stage you can then jettison after LOR or TEI.

Dragon -could- land on Mars, but like you said, it'd need a lot of help.  If it had a modified "top trunk" with an inflatable hypercone, that could be one way. 
But in a Mars Mission, it'd probably end up being far more practical to have a purpose build Mars lander and ascender.  The Dragon capsule could be used as the Crew Return Module for the final descent back to Earth.  You'll need one of those no matter what you do. 

If you were able to equip Dragon with a hypercone that could slow it sufficiently, or maybe supersonic parachutes, which could then give way to parachutes for slowing to subsonic speeds, then possibly Dragon could be used as a common cargo lander to land supplies ahead of a manned mission.  It wouldn't need to get off the ground then.  Land a few of those with food, equipment, and tools, then land a habitat module, then land your crew vehicle would would be used for descent and ascent.

Don't know how practical that would really be though.  Again, some purpose built equipment would probably work better.  Dragon itself is a purpose built capsule.  Built for the purpose of launching humans from -Earth- and returning them to -Earth-.  Probably make the most sense to land on MArs with a vehicle built for that purpose.

Offline Jim

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #37 on: 04/28/2011 10:11 PM »
Right, escape being possible doesn't mean it's guaranteed to save you in every scenario. This is true whether you have high power escape motors or not.

I agree and I'm not saying having a LAS would necessarily have worked in that case, either.

Quote
I'm not saying that SpaceX system couldn't be better than what Apollo had, I'm just disappointed by the needless conflation of an *escape tower* with an *escape system*. SpaceX should know better.

Maybe there's a fine distinction between "escape" and "abort" to be made? SPS could have aborted away from let's say a gracefully shut down stage, but it probably wouldn't have worked that well if the vehicle executed a RUD.

In the end, this is all spin and I don't personally get too excited over it.

at those altitudes, an S-II explosion would not be a "big" deal , no shock wave due to low density of the atmosphere

Offline Lobo

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #38 on: 04/28/2011 10:21 PM »
Yep, definitely looks like a separate MAV; Possibly 4 x Merlin-1 as the propulsion system.  Likely the Dragons would be only descent and ascent vehicles, there would be a separate (Bigelow-designed?) orbital transfer vehicle.

Talk is cheap and even CGI is cheaper than rocket engineering.  However, I do suspect that this is SpaceX metaphorically throwing down the gauntlet: "If you won't, we will."

I think there was a picture of a similar horizontal lander with vertical ascent capsule in some of the picturs I've seen for NASA's Mars DRA 5.0.  It's probably be a good way for SpaceX to go as they'll have some diameter constraints with FH, and they dont' want their lander to be too tall and skinny.

Offline go4mars

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Re: SpaceX: Advanced Launch Abort System (LAS)
« Reply #39 on: 04/29/2011 02:28 AM »
Are those engines underneath the Dragon for the martian accent phase?

Probably.  Maybe it doubles as a methane powered surface hopper for exploring different locations on Mars also.  Could refuel at base from the atmosphere, go suborbital somewhere far away, then fly back with some rocks, photos, measurements, and leave behind an array of sensors.  Then fuel up again and go somewhere else. 
« Last Edit: 04/29/2011 03:14 AM by go4mars »
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