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SpaceX Vehicles and Missions => SpaceX General Section => Topic started by: Chris Bergin on 04/28/2011 05:13 pm

Title: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris Bergin on 04/28/2011 05:13 pm
Today, SpaceX released a new video on our plans for an advanced launch abort system.

A bit of time travel - here's an article from Feb, 2012:
http://www.nasaspaceflight.com/2012/02/spacex-dragon-advancing-launch-abort-system-new-heights/

Then Doctor Who back to when I posted this thread....

;D

WATCH THE VIDEO:

http://www.youtube.com/watch?v=6p6EruPdoXY
 

The video was unveiled by Garrett Reisman, SpaceX Commercial Crew Development Program Manager, during a NASA press conference on Commercial Crew Development.

 

Attached is the SpaceX press kit.

Below is the SpaceX press release on Commercial Crew Development.

 

 

Kirstin Brost | Communications Director | SpaceX | 202-649-2716

 

Twitter: http://twitter.com/SpaceXer

Facebook: http://www.facebook.com/SpaceX

 



 

Tuesday, April 19, 2011

Contact: Kirstin Brost, SpaceX

202-649-2716

 

SpaceX Wins NASA Contract to Complete Development of Successor to the Space Shuttle

First Astronaut Mission Expected in Three Years

 

WASHINGTON D.C. - NASA has awarded Space Exploration Technologies (SpaceX) $75 million to develop a revolutionary launch escape system that will enable the company’s Dragon spacecraft to carry astronauts.  The Congressionally mandated award is part of the agency's Commercial Crew Development (CCDev) initiative that started in 2009 to help private companies mature concepts and technologies for human spaceflight.

 

"This award will accelerate our efforts to develop the next-generation rockets and spacecraft for human transportation," said Elon Musk, SpaceX CEO and Chief Designer.  "With NASA’s support, SpaceX will be ready to fly its first manned mission in 2014."

 

Musk said the flight-proven Falcon 9 launch vehicle and Dragon spacecraft represent the safest and fastest path to American crew transportation capability.  With their historic successful flight on December 8th, 2010, many Falcon 9 and Dragon components that are needed to transport humans to low-Earth orbit have already been demonstrated in flight. Both vehicles were designed from the outset to fly people.

 

The announcement comes at a time when the United States has a critical need for American commercial human spaceflight. After the Space Shuttle retires in a few months, NASA will be totally dependent on the Russian Soyuz to ferry astronauts to and from the International Space Station (ISS) at a cost of more than $753 million a year -- about $63 million per seat.

 

Musk said Dragon – designed to carry seven astronauts at a time to the space station at a cost of $20 million a seat – offers a far better deal for the U.S. taxpayer.  While considerable flight testing remains, the critical-path technology Dragon needs for carrying humans to orbit is the launch escape system.

 

New Launch Abort System

 

SpaceX's integrated escape system will be superior to traditional solid rocket tractor escape towers used by other vehicles in the past.  Due to their extreme weight, tractor systems must be jettisoned within minutes of liftoff, but the SpaceX innovative design builds the escape engines into the side walls of Dragon, eliminating the danger of releasing a heavy solid rocket escape tower after launch.

 

The SpaceX design also provides crew with emergency escape capability throughout the entire flight, whereas the Space Shuttle has no escape system and even the Apollo moon program allowed escape only during the first few minutes of flight.  The result is that astronauts flying on Dragon will be considerably safer. 

 

Furthermore, the integrated escape system returns with the spacecraft, allowing for easy reuse and radical reductions in the cost of space transport.  Over time, the same escape thrusters will also provide the capability for Dragon to land almost anywhere on Earth or another planet with pinpoint accuracy, overcoming the limitation of a winged architecture that works only in Earth's atmosphere.

 

Under the award, SpaceX will modify Dragon to accommodate crew, with specific hardware milestones that will provide NASA with regular, demonstrated progress including:

 

·         Static fire testing of the launch escape system engines

·         Initial design of abort engine and crew accommodations

·         Prototype evaluations by NASA crew for seats, control panels and cabin

 

The December 8th, 2010, demonstration flight of Falcon 9 and Dragon was the first flight under NASA’s Commercial Orbital Transportation Services (COTS) program, which was initiated to develop commercial cargo services to the International Space Station.  After the Space Shuttle retires, SpaceX will fly at least 12 missions to carry cargo to and from the International Space Station as part of the Commercial Resupply Services (CRS) contract for NASA.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lee Jay on 04/28/2011 05:18 pm
So, they really do want to land Dragon on Mars.

Does anyone but me think this is an exaggeration?

"SpaceX Wins NASA Contract to Complete Development of Successor to the Space Shuttle"

The contact won't cover the development to completion and it's not really the successor to the Space Shuttle, it's a new and different manned launch capability designed mostly for an entirely different purpose.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 04/28/2011 05:20 pm
Attached is the SpaceX press kit.

And the actual press kit... http://www.spacex.com/downloads/20110428-spacex-sts134.pdf
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: mr. mark on 04/28/2011 05:21 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?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: agman25 on 04/28/2011 05:29 pm
Chief Designer Musk does have a talent for the dramatic.

"Over time, the same escape thrusters will also provide the capability for Dragon to land almost anywhere on Earth or another planet with pinpoint accuracy, overcoming the limitation of a winged architecture that works only in Earth's atmosphere."
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: mr. mark on 04/28/2011 05:31 pm
And the actual press kit... http://www.spacex.com/downloads/20110428-spacex-sts134.pdf

IMPRESSIVE! and one great presentation. You got to admit having ex NASA astronauts on the team is a huge plus.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris Bergin on 04/28/2011 05:32 pm
Attached is the SpaceX press kit.

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

Opps, thanks! I didn't notice the pdf on the e-mail :)

I like how their pdf respects Shuttle....which is more than we can say about Virgin.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lurker Steve on 04/28/2011 05:53 pm
·         Static fire testing of the launch escape system engines

·         Initial design of abort engine and crew accommodations

·         Prototype evaluations by NASA crew for seats, control panels and cabin


Looking at these milestones, they will still have significant work to do to finish up a crewed-ready vehicle.

Are they developing their own engines for the LAS ? I think the other vendors have already had static fires of the LAS engines on a test stand. SpaceX looks to be behind here.

There is only an "initial" design of abort engine milestone. Does this mean only a token effort for actual integration into the crewed capsule is performed ? Is final integration part of the next phase ?

I imagine the current cargo Dragon will not include flight controls, the LAS, and a bunch of other new features (like Windows) that are only necessary for transporting passengers.

I know they are trying to push the fact that the 2 vehicles have the same basic design, but in reality, the crewed vehicle needs a new name.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: mr. mark on 04/28/2011 05:57 pm
They plan having a full up test of LAS at ground level next summer. Not sure how to read that as far as integration with the Dragon spacecraft.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 04/28/2011 05:59 pm
·         Static fire testing of the launch escape system engines

·         Initial design of abort engine and crew accommodations

·         Prototype evaluations by NASA crew for seats, control panels and cabin


Looking at these milestones, they will still have significant work to do to finish up a crewed-ready vehicle.

Are they developing their own engines for the LAS ? I think the other vendors have already had static fires of the LAS engines on a test stand. SpaceX looks to be behind here.

There is only an "initial" design of abort engine milestone. Does this mean only a token effort for actual integration into the crewed capsule is performed ? Is final integration part of the next phase ?

I imagine the current cargo Dragon will not include flight controls, the LAS, and a bunch of other new features (like Windows) that are only necessary for transporting passengers.

I know they are trying to push the fact that the 2 vehicles have the same basic design, but in reality, the crewed vehicle needs a new name.

The current cargo Dragon (that already flew) does and did include windows.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 04/28/2011 06:04 pm
Dragon is behind in LAS, but with other systems it is ahead, so all in all I'd classify the Dragon as on-level with other CCDev vehicles development wise.  So no going "well, this company has tested it's LAS" and such, because none of the companies are truly ahead in this scenario.  SpaceX has a functional capsule, which puts it ahead in many areas, but it lacks the crew safety systems which the other vendors have already gotten a jump on in developing.  This, from my viewpoint, says nothing about them being ahead, or behind, just that they are following a different path.  And their path may prove itself to be the better one in the end, we don't know.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 04/28/2011 06:14 pm
Now, this is largely my opinion, but...
SpaceX has orbited, reentered, and recovered a capsule. They've proven everything (except life support and seats) that's absolutely required for sending crew (controls are also desired and will be on the final craft before any crew are launched, but are not strictly required). A LAS is something that you'd rather never ever use, and was never used in the US manned space program. Taking that into consideration, they are far ahead of anyone else, though developing the LAS may take time. (However, other CCDev2 spacecraft have the advantage that they are using the existing and well-demonstrated Atlas V, while the Falcon 9 is newer and has yet to really hit its stride when it comes to launch tempo.)

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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: AS-503 on 04/28/2011 06:19 pm
And the actual press kit... http://www.spacex.com/downloads/20110428-spacex-sts134.pdf

IMPRESSIVE! and one great presentation. You got to admit having ex NASA astronauts on the team is a huge plus.


I think ATK has more ex-NASA brass than anybody.

Bravo to SpaceX. I sure hope they can develop the abort system the way they are spinning it.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 04/28/2011 06:40 pm
You got to admit having ex NASA astronauts on the team is a huge plus.

Not really, see Spacehab.  There are just as many minuses as pluses.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 04/28/2011 06:53 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: space nut on 04/28/2011 07:16 pm
If one was to pre-position supplies and return modules (moon,Mars Moon, Mars, Etc.) and have ready made Bigelow habs , I would assume yes we
can go to Mars in 10 to 15 years.

This is what we need,

What NASA needs is lunar , mars landing modules and EDS, Tugs,Fuel depot
and put back the moon and mars plan that was taken away.
Need the Plan !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I love the Direct plan and SDHLV but yes it can wait some, but only
some to enable a healthy list of providers.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: simonbp on 04/28/2011 07:58 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 04/28/2011 08:02 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: hop on 04/28/2011 08:36 pm
Quote
The SpaceX design also provides crew with emergency escape capability throughout the entire flight, whereas the Space Shuttle has no escape system and even the Apollo moon program allowed escape only during the first few minutes of flight.
This is misleading. Apollo only had the *escape tower* for the first few minutes of flight, because after that escape was possible without the tower. Same applies to Soyuz (and in that case, crew lives have been saved by this)

Sigh. SpaceX is doing genuinely cool things, and doing them well. Do they really need to spin half truths like this ?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 04/28/2011 08:43 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: neilh 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
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: hop 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: 2552 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.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix 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. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: 2552 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?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan 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?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Cog_in_the_machine on 04/28/2011 09:15 pm
Here.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: 2552 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Ben the Space Brit 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."
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Nathan 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: HMXHMX 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Rocket Science on 04/28/2011 09:43 pm
Anyone hear of any "Dead Man Zone" using the propulsive landing planned?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lobo 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim 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
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lobo 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.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars 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. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Zed_Noir on 04/29/2011 02:39 am
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.

SpaceX  change the URL. A "-" character is inserted between STS and 134 near the end of the URL. The current URL link to the press kit follows.

http://www.spacex.com/downloads/20110428-spacex-sts-134.pdf (http://www.spacex.com/downloads/20110428-spacex-sts-134.pdf)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 04/29/2011 02:58 am
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.
Then it's darn easy to get such a reaction started.  Have inside the solid fuel combustion chamber a pellet of EPDC rubber filled with Monomethylhydrazine, use a plug holding red fuming Nitric acid in the feed line, and BAM, you have start in under 100ms.  You turn on the engine, the pump forces the plug into the engine, where the RFNA meets the EPDC, immediately dissolving it and exposing it to the MMH producing a hypergolic reaction, kicking the hybrid engine into starting for the LAS.  Once you no longer need it for a LAS, drop the EPDC rubber pellet, as RFNA does not intact with the HTPD and would just be expelled out the back harmlessly.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Proponent on 04/29/2011 03:01 am
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.

I agree it's not a huge deal, but SpaceX does have a habit of presenting the ordinary as extraordinary, and it's good to be aware of that.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: jak Kennedy on 04/29/2011 03:08 am
Just saw what I believe is a new article from Elon in Business Week.

"We're entering the era of commercial space flight, which will advance dramatically faster than in the past. But I made the decision to patent almost nothing: Our competition is the Chinese and Russian governments, against whom patents are unenforceable and can simply be used as a recipe. It's much better for our technology to be trade secrets. I'd rather keep the information to myself. There could be a Chinese spy or a cyber attack, but my CIO is from PayPal, which never got cracked."

http://www.businessweek.com/magazine/content/11_19/b4227076914379.htm
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: QuantumG on 04/29/2011 03:46 am
Means you can move a lot faster too..
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: wally on 04/29/2011 05:26 am
Isn't Dragon to cramped for a trip to Mars?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Proponent on 04/29/2011 05:40 am
You wouldn't have to make the whole trip in the Dragon; there would probably be a hab module as well, and Dragon would be used just during descent to the martian surface.

On the other hand, I'm sure you could find volunteers who would be willing to make the whole trip in the Dragon.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Zed_Noir on 04/29/2011 01:21 pm
Isn't Dragon to cramped for a trip to Mars?

That depends on how many crew members you got on a Mars Dragon. It's likely a Mars Dragon mission will have 3 crew like Apollo.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: yg1968 on 04/29/2011 03:17 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.

Isn't the risk more related to the fact that Dream Chaser can't land in water?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 04/29/2011 05:51 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.

Isn't the risk more related to the fact that Dream Chaser can't land in water?
The HL-20 could land in water as a ditch landing.  I do not know if the DC kept this capability.  But that would be better discussed on the DC thread. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: sanman on 04/29/2011 06:33 pm
You wouldn't have to make the whole trip in the Dragon; there would probably be a hab module as well, and Dragon would be used just during descent to the martian surface.

On the other hand, I'm sure you could find volunteers who would be willing to make the whole trip in the Dragon.

How long would that trip be again? Everybody seems to have different trip plans, and it's unclear to me whether a SpaceX manned trip would be identical to what's specified in Mars Direct.

What's the shortest possible trip that could be made in a manned vehicle/hab?

How much would this cost? (under SpaceX everyday low prices, as opposed to rug bazaar prices)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: spacetraveler on 04/29/2011 06:42 pm
What NASA needs is lunar , mars landing modules and EDS, Tugs,Fuel depot
and put back the moon and mars plan that was taken away.

I agree, if NASA could spend $11.5 billion on this stuff instead of a BFR, we would be much further ahead in exportation.

Multiple EELV or FH launches could lift it.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Michael Bloxham on 05/22/2011 02:22 am
I have a question. How much propellant would the LAS on Dragon be expected to hold?

Thanks,

- Mike
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: strangequark on 05/22/2011 01:26 pm

How long would that trip be again? Everybody seems to have different trip plans, and it's unclear to me whether a SpaceX manned trip would be identical to what's specified in Mars Direct.

What's the shortest possible trip that could be made in a manned vehicle/hab?

How much would this cost? (under SpaceX everyday low prices, as opposed to rug bazaar prices)

Tough questions to answer well, but I'll take the first part, at least. I'm assuming you mean shortest practical trip, as what's possible depends on how many gigatonnes of propellant you're willing to launch. Duration depends on the type of trajectory. Mars Direct recommended a conjunction class mission. That is, you launch when Mars and Earth are on opposite sides of the sun from one another. This is the lowest energy path, and results in a longer surface stay (a year or more). Conjunction transfers are between about six and nine months, depending on the amount of energy you want to sink into it, and the year you are launching.

If I costed it, I'm afraid it would only be a step above a WAG.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Nomadd on 05/22/2011 03:05 pm
I have a question. How much propellant would the LAS on Dragon be expected to hold?

Thanks,

- Mike

 A huge advantage of this LAS is that it wouldn't need any extra fuel mass. It will use the 1200kg or so manuevering fuel that the capsule already carries.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jason1701 on 05/22/2011 07:55 pm
I have a question. How much propellant would the LAS on Dragon be expected to hold?

Thanks,

- Mike

 A huge advantage of this LAS is that it wouldn't need any extra fuel mass. It will use the 1200kg or so manuevering fuel that the capsule already carries.

If they didn't carry any extra fuel, they couldn't do a propulsive landing. Also, there were some rumors that the LAS might be monopropellant, whereas Draco is bipropellant. Both of these provide reasons for them to carry extra fuel.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 06/22/2011 03:16 am
On the Lunar Lander thread we got onto a tangent about the Dragon LAS, and if the Draco thruster system or a derivative of it could be part of the LAS. 

So I dug up what information I could, the Draco thruster as it is now has a chamber pressure of ~6 bar/~100 psia.  The chamber itself, however, based on what I can observe should be able to handle 30 bar/~500 psia.  This level of chamber pressure difference is not unknown, the RS-36 handled a pressure differential of almost twice this and had a very similar chamber design and an almost identical fuel mixture. 

So, calculating out the thrust of a 500 psia in this chamber, by changing the pressure going in (not a difficult thing to do in my experience if you design for it with a pintle system) and you would wind up with a 2.6klbf thruster, at the cost of your isp dropping like a rock, to ~250.  8 x 2.6k == 20.8 klbf, a little over 90kN, more than the Soyuz abort system.  This would require other changes to the system, of course, and is likely not the solution they would use, but it was an interesting academic exercise.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 06/22/2011 05:42 am
On the Lunar Lander thread we got onto a tangent about the Dragon LAS, and if the Draco thruster system or a derivative of it could be part of the LAS. 

So I dug up what information I could, the Draco thruster as it is now has a chamber pressure of ~6 bar/~100 psia.  The chamber itself, however, based on what I can observe should be able to handle 30 bar/~500 psia.  This level of chamber pressure difference is not unknown, the RS-36 handled a pressure differential of almost twice this and had a very similar chamber design and an almost identical fuel mixture. 

So, calculating out the thrust of a 500 psia in this chamber, by changing the pressure going in (not a difficult thing to do in my experience if you design for it with a pintle system) and you would wind up with a 2.6klbf thruster, at the cost of your isp dropping like a rock, to ~250.  8 x 2.6k == 20.8 klbf, a little over 90kN, more than the Soyuz abort system.  This would require other changes to the system, of course, and is likely not the solution they would use, but it was an interesting academic exercise.
If the throat is the same size, then to a first order estimate, having five times the chamber pressure will get you five times the thrust. So, not 2.6klbf but 450lbf (original Draco is 90lbf).

Except it will likely be worse than that since the 90lbf is in vacuum with the vacuum-optimized nozzle (alleviated a bit by the higher pressure...).

Also, you generally don't want to design an engine with a Factor of Safety of 1... you'll kill it with just the start-up transient, most likely.

Also, with higher chamber pressure comes higher thermal loads, thus higher temperatures and lower material strengths...

...and, since we're being pressure-fed, here... much heavier tanks and valves... with the same factor of safety, the tanks just got about 5 times heavier for the same amount of propellant

And after all this, we're still a good ten times less thrust than is needed per abort engine.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris-A on 06/22/2011 06:00 am
Pretty much "Rockets and Spacecraft are not Lego blocks" apply here.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 06/22/2011 06:25 am
On the Lunar Lander thread we got onto a tangent about the Dragon LAS, and if the Draco thruster system or a derivative of it could be part of the LAS. 

So I dug up what information I could, the Draco thruster as it is now has a chamber pressure of ~6 bar/~100 psia.  The chamber itself, however, based on what I can observe should be able to handle 30 bar/~500 psia.  This level of chamber pressure difference is not unknown, the RS-36 handled a pressure differential of almost twice this and had a very similar chamber design and an almost identical fuel mixture. 

So, calculating out the thrust of a 500 psia in this chamber, by changing the pressure going in (not a difficult thing to do in my experience if you design for it with a pintle system) and you would wind up with a 2.6klbf thruster, at the cost of your isp dropping like a rock, to ~250.  8 x 2.6k == 20.8 klbf, a little over 90kN, more than the Soyuz abort system.  This would require other changes to the system, of course, and is likely not the solution they would use, but it was an interesting academic exercise.
If the throat is the same size, then to a first order estimate, having five times the chamber pressure will get you five times the thrust. So, not 2.6klbf but 450lbf (original Draco is 90lbf).

Except it will likely be worse than that since the 90lbf is in vacuum with the vacuum-optimized nozzle (alleviated a bit by the higher pressure...).

Also, you generally don't want to design an engine with a Factor of Safety of 1... you'll kill it with just the start-up transient, most likely.

Also, with higher chamber pressure comes higher thermal loads, thus higher temperatures and lower material strengths...

...and, since we're being pressure-fed, here... much heavier tanks and valves... with the same factor of safety, the tanks just got about 5 times heavier for the same amount of propellant

And after all this, we're still a good ten times less thrust than is needed per abort engine.
If everything else were the the same, you would be correct.  However, I was focusing on the various bits TRW developed for the LCPE, to enable that engine to throttle so widely without a dramatic pressure change.  By changing the pintle arrangement, they produced differing thrust envelopes at the same pressure within the chamber itself.  SpaceX uses a similar pintle design, so logic says that they too can take advantage of these differing thrust envelopes.

As for heavier tanks, only if they are to hold the load.  If instead it was to be a forced emergency pressurization, that is the extra pressure was not added until needed, you could get by with the existing tankage.  Old trick I used to use for my step-brothers dragster, to enable him to utilize the same fuel tank as other racers but gain the advantage of a pressurized system when he needed it. I strapped a bottle of Nitrogen gas, which would be forced into the tank body, putting pressure on the outside of the bladder, pushing the fuel up the pipe, pressurizing it to ensure that the system regulated the fuel flow, and not the fuel-flow regulating the system.  So long as the duration of the added pressure was not overly long (which a LAS situation should not be), it would not be an issue.

And why would someone do all this when they could introduce their own LAS motors?  Weight, by dual-purpose, they could save a lot of weight.  They may be going about their own custom LAS motors, who knows.  But it is an interesting thought to see how one could accomplish the job.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lampyridae on 06/22/2011 09:45 am

How long would that trip be again? Everybody seems to have different trip plans, and it's unclear to me whether a SpaceX manned trip would be identical to what's specified in Mars Direct.

What's the shortest possible trip that could be made in a manned vehicle/hab?

How much would this cost? (under SpaceX everyday low prices, as opposed to rug bazaar prices)

Tough questions to answer well, but I'll take the first part, at least. I'm assuming you mean shortest practical trip, as what's possible depends on how many gigatonnes of propellant you're willing to launch. Duration depends on the type of trajectory. Mars Direct recommended a conjunction class mission. That is, you launch when Mars and Earth are on opposite sides of the sun from one another. This is the lowest energy path, and results in a longer surface stay (a year or more). Conjunction transfers are between about six and nine months, depending on the amount of energy you want to sink into it, and the year you are launching.

If I costed it, I'm afraid it would only be a step above a WAG.

Also depends what technical hurdles one is trying to avoid.

An opposition class mission means only a 4 to 6 week stay on Mars, longer trip times but as a bonus you could get a flyby of Venus. Higher re-entry g-load is much rougher on deconditioned astronauts so much better zero-g countermeasures are needed.


Conunction class missions require a lot more stuff to be landed on the surface (bigger hab, bigger rover, more food etc) and increases the chances that something that can go wrong there. I think EDL is a fairly large problem, and I would guess that, although the pic suggests otherwise, SpaceX would gradually step things up (in the crazy world where it does land on Mars).

As Dragon being actual design for landing on Mars - forget it. For a start, you'll probably need a much wider aeroshell, or a biconic, even to put just four people down. The retro engines also have cosine losses, as a side effect of being abort motors. But a lot of the technologies developed for Dragon will make it easier to make a Mars lander, which is sort of the "spirit" of the Mars image (if you'll excuse the pun).

By the time we actually get to Mars (like 40 or 50 years away if HEFT is any guide), the whole NASA procurement model may have changed. NASA develops the cutting edge tech, private companies build the hardware to fixed-price contracts.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: dunderwood on 06/22/2011 03:41 pm
So I dug up what information I could, the Draco thruster as it is now has a chamber pressure of ~6 bar/~100 psia.  The chamber itself, however, based on what I can observe should be able to handle 30 bar/~500 psia. 

I'm curious what information you found that would suggest such a pressure bump is manageable.  I would think that a spacecraft thruster would be highly weight optimized.  A thruster that could handle 5 times more pressure than it is going to run at (and still maintain 'man-rated' safety factors) sounds like a thruster that is far too heavy in its current state.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 06/22/2011 04:19 pm
So I dug up what information I could, the Draco thruster as it is now has a chamber pressure of ~6 bar/~100 psia.  The chamber itself, however, based on what I can observe should be able to handle 30 bar/~500 psia. 

I'm curious what information you found that would suggest such a pressure bump is manageable.  I would think that a spacecraft thruster would be highly weight optimized.  A thruster that could handle 5 times more pressure than it is going to run at (and still maintain 'man-rated' safety factors) sounds like a thruster that is far too heavy in its current state.
Based on the testing reports and the images of the engines. That is why they don't make sense to me, the information has them as at least three times heavier than I would expect. However this robustness would simplify servicing dramatically, so while a mass penalty, you would reduce the system cost. The high thrust mode theorized here would wear it out, however. So long life in normal operation, or one time use for emergency.

Alternatively, if the LAS is tied instead to the landing thrusters being used for non-water landings, you'd still need a dual-mode chamber, but could use a less severe case of one.  But then you would have to LAS over water.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kkattula on 06/22/2011 05:26 pm
If everything else were the the same, you would be correct.  However, I was focusing on the various bits TRW developed for the LCPE, to enable that engine to throttle so widely without a dramatic pressure change.  By changing the pintle arrangement, they produced differing thrust envelopes at the same pressure within the chamber itself.  SpaceX uses a similar pintle design, so logic says that they too can take advantage of these differing thrust envelopes.

As for heavier tanks, only if they are to hold the load.  If instead it was to be a forced emergency pressurization, that is the extra pressure was not added until needed, you could get by with the existing tankage.  Old trick I used to use for my step-brothers dragster, to enable him to utilize the same fuel tank as other racers but gain the advantage of a pressurized system when he needed it. I strapped a bottle of Nitrogen gas, which would be forced into the tank body, putting pressure on the outside of the bladder, pushing the fuel up the pipe, pressurizing it to ensure that the system regulated the fuel flow, and not the fuel-flow regulating the system.  So long as the duration of the added pressure was not overly long (which a LAS situation should not be), it would not be an issue.
...

Has someone repealed the laws of physics?  I didn't get the memo...  :)

Subjecting a dragster fuel tank to a few psi is nothing like subjecting a tank designed for 100 psi with a 1.4 safety factor to 500 psi.  The burst pressure is likely less than 200. These are not DOT tanks, over-designed to handle years of abuse, they're custom aerospace tanks designed to do a specific job with adequate but not excessive margin.

And, as previously stated, you can't get 29 x the thrust out of a fixed chamber & nozzle by increasing the pressure 5 x. Rocket engines just don't work that way. It's absolute nonsense.

Simply put, in choked flow the mass flow rate increases linearly with upstream pressure. Rockets work by throwing that mass out the back at the exhaust velocity. (which equals Isp * g). So 5 times the chamber pressure = 5 times the mdot = 5 times the thrust, at best. In practice, there are other factors, but they only make a few % difference.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 06/22/2011 06:03 pm
If everything else were the the same, you would be correct.  However, I was focusing on the various bits TRW developed for the LCPE, to enable that engine to throttle so widely without a dramatic pressure change.  By changing the pintle arrangement, they produced differing thrust envelopes at the same pressure within the chamber itself.  SpaceX uses a similar pintle design, so logic says that they too can take advantage of these differing thrust envelopes.

As for heavier tanks, only if they are to hold the load.  If instead it was to be a forced emergency pressurization, that is the extra pressure was not added until needed, you could get by with the existing tankage.  Old trick I used to use for my step-brothers dragster, to enable him to utilize the same fuel tank as other racers but gain the advantage of a pressurized system when he needed it. I strapped a bottle of Nitrogen gas, which would be forced into the tank body, putting pressure on the outside of the bladder, pushing the fuel up the pipe, pressurizing it to ensure that the system regulated the fuel flow, and not the fuel-flow regulating the system.  So long as the duration of the added pressure was not overly long (which a LAS situation should not be), it would not be an issue.
...

Has someone repealed the laws of physics?  I didn't get the memo...  :)

Subjecting a dragster fuel tank to a few psi is nothing like subjecting a tank designed for 100 psi with a 1.4 safety factor to 500 psi.  The burst pressure is likely less than 200. These are not DOT tanks, over-designed to handle years of abuse, they're custom aerospace tanks designed to do a specific job with adequate but not excessive margin.

And, as previously stated, you can't get 29 x the thrust out of a fixed chamber & nozzle by increasing the pressure 5 x. Rocket engines just don't work that way. It's absolute nonsense.

Simply put, in choked flow the mass flow rate increases linearly with upstream pressure. Rockets work by throwing that mass out the back at the exhaust velocity. (which equals Isp * g). So 5 times the chamber pressure = 5 times the mdot = 5 times the thrust, at best. In practice, there are other factors, but they only make a few % difference.
That's not, however, what I discussed. 

You're saying increase it's pressure to 500 psi.  How pressurized systems work is by letting the pressure out, reducing it's pressure level.  The solution I mentioned was to add more pressure back in *as* it's releasing it's pressure.

Let us use for example, you have an outgoing port from the tank of 4 inches square, but you only *need* 0.5 inches square.  You put a simple poppet valve, which reduces the port availability to 0.5.  But now you need to increase flow, you raise the valve so that the full 4 inches now are available, bleeding the pressure off faster.  Combine with adding pressure as you empty, and you can empty your tanks very very fast.  Alternatively, you can have a separate, larger, fuel feed line which is normally closed which you can open instead, resulting in faster drain that way.

A reminder, the force exerted by a rocket engine is equal to the mass flow rate of the rocket engine times the velocity of the exhaust gases (the stuff coming out of the rocket).

F = mdot * Ve

Anything which changes this, will change the force coming out, yes?

One of the papers (can't get on NTRS atm or else I'd post the link) discussed the use of a pintle design where you can change your throat diameter, through a long pintle.  Normal operation, the pintle is full-length, which means it is sitting inside of the throat.  You need to use to use regen cooling of the pintle for this to work, of course, but that is not a major challenge.  High-thrust, you pull the pintle in, out of the throat.  Depending on the size of your pintle, you can dramatically increase your throat area.  Alternatively, you can also have a nozzle-injection of oxidizer out the center of the pintle, and run fuel-rich, resulting in a primitive form on TAN.

There is more than one way to skin a cat.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 06/22/2011 06:06 pm
Downix, do yourself a favor and buy this book (any edition after the first, which is really old and probably hard to find):
http://www.amazon.com/Rocket-Propulsion-Elements-George-Sutton/dp/0471326429
You should be able to pick it up for less than $30 if you get like the 6th edition used.

Thrust = Cf*throatarea*chamberpressure. Cf ("thrust coefficient) varies between 1.2 and 2 at most. For our pressure ratios (i.e. 100-500 psi at sea level), it really varies only between 1.2 and 1.5 no matter what fuel. So, for our purposes, thrust is proportional to chamber pressure. You can't get really more than 5x the thrust by increasing chamber pressure by 5x.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 06/22/2011 06:10 pm
Downix, do yourself a favor and buy this book (any edition after the first, which is really old and probably hard to find):
http://www.amazon.com/Rocket-Propulsion-Elements-George-Sutton/dp/0471326429
Hey, found an image of the TRW throat-modifying pintle design.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kkattula on 06/22/2011 06:14 pm
...
So I dug up what information I could, the Draco thruster as it is now has a chamber pressure of ~6 bar/~100 psia.  The chamber itself, however, based on what I can observe should be able to handle 30 bar/~500 psia.  This level of chamber pressure difference is not unknown, the RS-36 handled a pressure differential of almost twice this and had a very similar chamber design and an almost identical fuel mixture. 

So, calculating out the thrust of a 500 psia in this chamber, by changing the pressure going in (not a difficult thing to do in my experience if you design for it with a pintle system) and you would wind up with a 2.6klbf thruster, at the cost of your isp dropping like a rock, to ~250.  8 x 2.6k == 20.8 klbf, a little over 90kN, more than the Soyuz abort system.  This would require other changes to the system, of course, and is likely not the solution they would use, but it was an interesting academic exercise.

No mention here of variable throat area.  Just increased chamber pressure which requires
increased tank pressure.

Variable throat area wouldn't work to the scale you suggest anyway.  Massive increase of throat area would kill L*, leading to insufficient combustion. Not much point in just flowing unburned propellant out the nozzle...


And many pressure-fed rockets systems already replenish pressure in the tanks as they empty. Usually with helium. IIRC, Draco doesn't use blow down tanks.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 06/22/2011 06:18 pm
Downix, do yourself a favor and buy this book (any edition after the first, which is really old and probably hard to find):
http://www.amazon.com/Rocket-Propulsion-Elements-George-Sutton/dp/0471326429
Hey, found an image of the TRW throat-modifying pintle design.
That's orthogonal to the discussion, here. I never even mentioned injector design.... I assumed you could use any kind of injector. Throat area and chamber pressure are the only things that matter to a first (or maybe zeroth) order estimate of thrust.

EDIT: Dracos don't use a plug-nozzle. Neither do Merlin or Kestrel.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kkattula on 06/22/2011 06:21 pm
Downix, do yourself a favor and buy this book (any edition after the first, which is really old and probably hard to find):
http://www.amazon.com/Rocket-Propulsion-Elements-George-Sutton/dp/0471326429
You should be able to pick it up for less than $30 if you get like the 6th edition used.


Second.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 06/22/2011 06:30 pm
...
So I dug up what information I could, the Draco thruster as it is now has a chamber pressure of ~6 bar/~100 psia.  The chamber itself, however, based on what I can observe should be able to handle 30 bar/~500 psia.  This level of chamber pressure difference is not unknown, the RS-36 handled a pressure differential of almost twice this and had a very similar chamber design and an almost identical fuel mixture. 

So, calculating out the thrust of a 500 psia in this chamber, by changing the pressure going in (not a difficult thing to do in my experience if you design for it with a pintle system) and you would wind up with a 2.6klbf thruster, at the cost of your isp dropping like a rock, to ~250.  8 x 2.6k == 20.8 klbf, a little over 90kN, more than the Soyuz abort system.  This would require other changes to the system, of course, and is likely not the solution they would use, but it was an interesting academic exercise.

No mention here of variable throat area.  Just increased chamber pressure which requires
increased tank pressure.

Variable throat area wouldn't work to the scale you suggest anyway.  Massive increase of throat area would kill L*, leading to insufficient combustion. Not much point in just flowing unburned propellant out the nozzle...

And many pressure-fed rockets systems already replenish pressure in the tanks as they empty. Usually with helium. IIRC, Draco doesn't use blow down tanks.


If it was the only thing done, you'd be right.  There are other options to further improve the concept.  But it is clear at this point that by the point you get done, you'd have an engine far too heavy, breaking the whole point.  (but still not certain why the Draco is so much larger than comparable RCS systems)

And, as I did point out above, I hadn't considered the engines to be used for soft-landing, assuming the manned Dragon would be an ocean-recovered vehicle.  If instead it is the soft-landing engines, changes the needs, and the base thrust, accordingly, yes?

Switching gears, what would the landing engine performance need to be?  There's no information on that at all.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 06/22/2011 06:31 pm
Downix, do yourself a favor and buy this book (any edition after the first, which is really old and probably hard to find):
http://www.amazon.com/Rocket-Propulsion-Elements-George-Sutton/dp/0471326429
You should be able to pick it up for less than $30 if you get like the 6th edition used.


Second.
I actually have it on my wish list and the birthday is coming up.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: tnphysics on 06/29/2011 12:50 am
Could the LAS also be used for Moon takeoff?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kkattula on 06/29/2011 03:43 am
Could the LAS also be used for Moon takeoff?

Yes.  If you don't mind running out of fuel before you get even halfway to lunar orbit.  :)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 06/29/2011 04:05 am
FWIW the artwork shows 2 rows of seats with the lower 3 in the base of the cabin and 4 in the top row.

Eliminate the lower seats, reduce the top row to 3 seats, add a new Al-Li bulkhead and fuel tanks. If it's to be just a lander/LLO return vehicle lose the TPS and external panels.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 06/29/2011 04:11 am
2 rows of seats with the lower ones in the base of the cabin. Eliminate the lower ones and add a new bulkhead and fuel tanks.
Then you'd lack the thrust to lift off, due to the weight of the fuel.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 06/29/2011 04:27 am
Half of the fuel will have been used by then, so you have the new mass of the empty tanks and a thin bulkhead, but you're absent the mass of the external panels, TPS and 60% of the normal crew mass.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Dave G on 06/29/2011 04:39 am
Let's take a step back.  Why would you want to use Dragon to land on the Moon?  My assumption is that you would want to do a manned lunar surface misson with the current hardware (FH/Dragon). 

OK, so that isn't possible, but you might be able to do it with a highly modified Dragon.  Why bother?  At that point, it would make more sense to design a purpose built lander.  No need for a heat shield.  One big engine on the bottom.  2 FH launches for an EOR/LOR mission.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kkattula on 06/29/2011 06:19 am
Let's take a step back.  Why would you want to use Dragon to land on the Moon?  My assumption is that you would want to do a manned lunar surface misson with the current hardware (FH/Dragon). 

OK, so that isn't possible, but you might be able to do it with a highly modified Dragon.  Why bother?  At that point, it would make more sense to design a purpose built lander.  No need for a heat shield.  One big engine on the bottom.  2 FH launches for an EOR/LOR mission.

Getting a bit OT, but check out this ESA reference arcitecture:

http://esamultimedia.esa.int/docs/exploration/ReferenceArchitecture/Final%20ReviewJan09/04_Human_moon_mission_version9esa120109.pdf

The FH would fit nicely as the 50 tonne launcher, in a SpaceX (plus?) version of this.

Dragon should just stay in Lunar Orbit.

No reason the Draco's and the bigger LAS thrusters couldn't be used on similar landers, though/
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Dave G on 06/29/2011 10:37 am
Let's take a step back.  Why would you want to use Dragon to land on the Moon?  My assumption is that you would want to do a manned lunar surface misson with the current hardware (FH/Dragon). 

OK, so that isn't possible, but you might be able to do it with a highly modified Dragon.  Why bother?  At that point, it would make more sense to design a purpose built lander.  No need for a heat shield.  One big engine on the bottom.  2 FH launches for an EOR/LOR mission.

Getting a bit OT, but check out this ESA reference arcitecture:

http://esamultimedia.esa.int/docs/exploration/ReferenceArchitecture/Final%20ReviewJan09/04_Human_moon_mission_version9esa120109.pdf

The FH would fit nicely as the 50 tonne launcher, in a SpaceX (plus?) version of this.

Dragon should just stay in Lunar Orbit.

No reason the Draco's and the bigger LAS thrusters couldn't be used on similar landers, though/

Yes, exactly.

I do think this is on topic, since SpaceX advertises that thier new LAS will have the ability to land on solid ground.  So it's quite natural for people to speculate how far you could take that new feature.

BTW, thanks for the link!
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: RocketEconomist327 on 06/29/2011 03:34 pm
Didn't see this posted.

http://www.nasa.gov/pdf/563409main_201106_Commercial_60day_Report_508.pdf

VR
RE327
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 06/29/2011 04:48 pm
From NASA CCDev-2 First Bi-Monthly Report, SpaceX page

"Durring CCDev 2, SpaceX plans to continue to mature their crew transportation system, with emphasis on Launch Abort System (LAS).  SpaceX's crew transportation system features the existing and flight-proven Falcon 9 launch vehicle and Dragon spacecraft which have been designed since inception for crew carriage.  Thus, the system on which SpaceX will focus during CCDev 2 is the safety-critical LAS.  SpaceX also plans to mature their crew systems design and perform crew cabin trials during CCDev 2.

SpaceX successfully completed its initial milestone, a CCDev 2 Kickoff Meeting, in May.  During the Kickoff Meeting, SpaceX reviewd NASA certification requirements, and the company presented to NASA officials the design status of all systems along with risks and potential mitigations.  The next SpaceX milestone is the LAS Propulsion Conceptual Design Review, planned for July, where SpaceX will present design data, documentation, risk assesments, and schedule data along with analysis and verification plans to show that their concept is technically sound and accomodates human factors requirements."

The attached CG image, which I have not seen before, has a few new features, like structural members behind the front four seats, with the outer two seats forward of the center two and what must be air supply cylinders. 

Not really that much at all.  Perhaps we will be shown some details in the next bi-monthly report.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 06/29/2011 05:06 pm
Dragon should just stay in Lunar Orbit.

No reason the Draco's and the bigger LAS thrusters couldn't be used on similar landers, though/

On the SpaceX CCDEV video at 1:15, http://www.spacex.com/multimedia/videos.php?id=58&cat=recent

Don't they already show dragons nest (lander) in the background at 1:15?  I imagine dragon comes down riding on it, then ISRU refills its tanks.  Dragon can fly around separately nearby, but for hopping to a faraway part of Mars or back to mars orbit would get back on the nest.  Can even be used without dragon to move base supplies far distances on Mars.  Could be useful for exploring areas of the planet that are seasonably inaccessible. 

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 07/02/2011 06:44 pm
Downix, do yourself a favor and buy this book (any edition after the first, which is really old and probably hard to find):
http://www.amazon.com/Rocket-Propulsion-Elements-George-Sutton/dp/0471326429
You should be able to pick it up for less than $30 if you get like the 6th edition used.

Thrust = Cf*throatarea*chamberpressure. Cf ("thrust coefficient) varies between 1.2 and 2 at most. For our pressure ratios (i.e. 100-500 psi at sea level), it really varies only between 1.2 and 1.5 no matter what fuel. So, for our purposes, thrust is proportional to chamber pressure. You can't get really more than 5x the thrust by increasing chamber pressure by 5x.
While waiting the five days to my birthday, ran into this at the library. Interesting bit was the various methods inside discussing how flow rates can change without greater pressure nor nozzle changes.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 07/07/2011 09:15 pm
Downix, do yourself a favor and buy this book (any edition after the first, which is really old and probably hard to find):
http://www.amazon.com/Rocket-Propulsion-Elements-George-Sutton/dp/0471326429
You should be able to pick it up for less than $30 if you get like the 6th edition used.

Thrust = Cf*throatarea*chamberpressure. Cf ("thrust coefficient) varies between 1.2 and 2 at most. For our pressure ratios (i.e. 100-500 psi at sea level), it really varies only between 1.2 and 1.5 no matter what fuel. So, for our purposes, thrust is proportional to chamber pressure. You can't get really more than 5x the thrust by increasing chamber pressure by 5x.
While waiting the five days to my birthday, ran into this at the library. Interesting bit was the various methods inside discussing how flow rates can change without greater pressure nor nozzle changes.
Well, congratulations! You have Sutton!

You're looking for thrust. Once you become sonically choked, you only can increase flowrate by increasing the throat area or increasing pressure.

Anyways, it's all moot. Except for Sutton, that's good!
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: bluedack on 07/11/2011 06:27 pm
Nice to meet you.
You've mentioned soyuz's LAS thrust.
How much is that ?
And where is the resource ?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 07/11/2011 06:33 pm
Downix, do yourself a favor and buy this book (any edition after the first, which is really old and probably hard to find):
http://www.amazon.com/Rocket-Propulsion-Elements-George-Sutton/dp/0471326429
You should be able to pick it up for less than $30 if you get like the 6th edition used.

Thrust = Cf*throatarea*chamberpressure. Cf ("thrust coefficient) varies between 1.2 and 2 at most. For our pressure ratios (i.e. 100-500 psi at sea level), it really varies only between 1.2 and 1.5 no matter what fuel. So, for our purposes, thrust is proportional to chamber pressure. You can't get really more than 5x the thrust by increasing chamber pressure by 5x.
While waiting the five days to my birthday, ran into this at the library. Interesting bit was the various methods inside discussing how flow rates can change without greater pressure nor nozzle changes.
Well, congratulations! You have Sutton!

You're looking for thrust. Once you become sonically choked, you only can increase flowrate by increasing the throat area or increasing pressure.

Anyways, it's all moot. Except for Sutton, that's good!
Which can be done, you can even do both.  SpaceX's Pintle injector lends itself to both very easily.

But that is neither the case, as the information coming out of SpaceX looks to be a very interesting arrangement.

And, the day after I found the book in the library, my grandparents sent me an Amazon.com gift card, which I then ordered myself a copy *and* a slide rule.  (always wanted my own slide rule, my grandfather still uses his)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Downix on 07/11/2011 06:37 pm
Nice to meet you.
You've mentioned soyuz's LAS thrust.
How much is that ?
And where is the resource ?


http://www.russianspaceweb.com/soyuz_sas.html

From this, it lists the Soyuz escape systems thrust as 76 metric tons, which would be 167551 lbf, more than Apollo, less than CST-100 or Dream Chaser.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: mrhuggy on 07/28/2011 06:18 pm
Garret Reisman talking at the Newspace 2011 conference has talked a little about the launch abort system. It has passed its system design review 2 days ago and is due to complete its primary design review in september and the Super Dracos are dur to be tested soon in Texas.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 07/28/2011 06:21 pm
Garret Reisman talking at the Newspace 2011 conference has talked a little about the launch abort system. It has passed its system design review 2 days ago and is due to complete its primary design review in september and the Super Dracos are dur to be tested soon in Texas.
So he called them Super Dracos?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 07/28/2011 06:25 pm
Apparently, Clark Lindsey reported (http://hobbyspace.com/nucleus/index.php?itemid=31266) the same.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: corrodedNut on 07/28/2011 06:29 pm
Garret Reisman talking at the Newspace 2011 conference has talked a little about the launch abort system. It has passed its system design review 2 days ago and is due to complete its primary design review in september and the Super Dracos are dur to be tested soon in Texas.
So he called them Super Dracos?

Yes he did...welcome to the family, "Super Draco".
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Halidon on 07/29/2011 04:06 am
A new entry in the SpaceX Lexicon is born. Hope they're prompt about posting a video of Super Draco firing.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: manboy on 07/29/2011 06:48 am
Garret Reisman talking at the Newspace 2011 conference has talked a little about the launch abort system. It has passed its system design review 2 days ago and is due to complete its primary design review in september and the Super Dracos are dur to be tested soon in Texas.
So he called them Super Dracos?

Yes he did...welcome to the family, "Super Draco".


From twitter

"Reisman: passed system design review for escape system 2 days ago; PDR in Sept. Soon testing "Super Draco" thrusters in TX."

EDIT: I see I was beaten to the punch.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: balan h20 on 07/30/2011 03:31 am
These new super Draco's , what amount of total thrust would the require to launch a Dragon from Mars or the moon. Why do I always give the planets a capital letter and the moon a lower case is this a sign of disrespect or learned behavior from school. Should I be giving the Mood a capital letter is it because it has no roman god or greek god name like the planets. I have gotten off track sorry it is just that I noticed this and it bugged me.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 07/30/2011 04:03 am
These new super Draco's , what amount of total thrust would the require to launch a Dragon from Mars or the moon.

In the case of Mars (which is what SpaceX is interested in), I suspect there will be a ISRU methane ascent stage to assist with getting dragon off the planet (and which could also double as a surface freight mover, taking raw materials to bases, moving bases to other parts of the planet, providing transportation between bases, exploring remote locations, etc.).  http://authors.library.caltech.edu/21127/

I would love to be wrong, but I'm pretty sure dragon will never be able to get from Mars surface to orbit by itself. 

I don't know if "super draco" runs on methane or not, but I suspect that at this iteration, it does not.   
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: hop on 07/30/2011 04:11 am
These new super Draco's , what amount of total thrust would the require to launch a Dragon from Mars or the moon.
The relevant question is total dV, not thrust. Any LAS will have plenty of thrust by definition.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 07/30/2011 04:15 am
These new super Draco's , what amount of total thrust would the require to launch a Dragon from Mars or the moon.
The relevant question is total dV, not thrust. Any LAS will have plenty of thrust by definition.

I think the dragons lungs are too tiny to sustain that high note for so long. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: SpacemanInSPACE on 07/30/2011 07:03 am
What is needed for Dragon to be able to make a powered landing on the moon, and then later launch back into lunar orbit to Rendezvous with the second stage?. Can these Super Dracos which are designed for crew capsule escape system, also achieve this?

I'm also assuming the second stage would need to be modified for mating with the dragon.

Help me out guys i'm confused!!!
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: hop on 07/30/2011 07:19 am
What is needed for Dragon to be able to make a powered landing on the moon, and then later launch back into lunar orbit to Rendezvous with the second stage?
Magic ?

An LAS only needs a few hundred m/s. LLO is a couple thousand. Look at the Apollo LM (http://en.wikipedia.org/wiki/Apollo_Lunar_Module). If you want to land on the moon and get back to orbit, you will need something like that.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Halidon on 07/30/2011 07:33 pm
What is needed for Dragon to be able to make a powered landing on the moon, and then later launch back into lunar orbit to Rendezvous with the second stage?. Can these Super Dracos which are designed for crew capsule escape system, also achieve this?

I'm also assuming the second stage would need to be modified for mating with the dragon.

Help me out guys i'm confused!!!
Unfortunately that's well beyond the practical. The current second stage is not a service module, and there's no way you could pack enough propellant into Dragon to both land and take off from Luna while still carrying, well, anything.

SpaceX could do something along the lines of the ACES-based vehicles in ULA's "Master Plan" presentation, using Raptor or whatever is the current plan for missions beyond Merlin Vac as SM/LM/Depot. But it's asking too much to want Dragon to do everything on its own.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 07/30/2011 07:45 pm
This is what happens t these forums when there is no real news.  A discussion of the LAS, where the big new is that the engines have a name, devolved into talking about landing on the Moon and taking off from Mars.  Dragon is meant for neither, and this topic at least started as a discussion of a totally separate and announced capability of near term Dragon capsules.

OTOH, I do like hop's answer to what Dragon would need.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: SpacemanInSPACE on 07/30/2011 08:27 pm
What is needed for Dragon to be able to make a powered landing on the moon, and then later launch back into lunar orbit to Rendezvous with the second stage?
Magic ?

An LAS only needs a few hundred m/s. LLO is a couple thousand. Look at the Apollo LM (http://en.wikipedia.org/wiki/Apollo_Lunar_Module). If you want to land on the moon and get back to orbit, you will need something like that.



Ok, thankyou for giving me a realistic vision of its capabilities.

I don't feel any harm in asking questions, now I understand that the leap from these super dracos to the advanced landing engines is greater than I thought.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 08/01/2011 05:01 pm
Ok, thankyou for giving me a realistic vision of its capabilities.

I don't feel any harm in asking questions, now I understand that the leap from these super dracos to the advanced landing engines is greater than I thought.

It's not a question of engines per se; dragon was not designed to hold enough fuel.   
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 08/01/2011 08:40 pm
Reviewing the NOFBx pdf I see that they had a proposal for a ~10,000 lb-f LAS engine using their fuel, and had presented it to CCDev participants. That seemed smallish, but if you use 8 of them (the number depicted in crew Dragon videos & stills) that gives ~80,000 lb-f. Enough?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 08/01/2011 10:30 pm
Reviewing the NOFBx pdf I see that they had a proposal for a ~10,000 lb-f LAS engine using their fuel, and had presented it to CCDev participants. That seemed smallish, but if you use 8 of them (the number depicted in crew Dragon videos & stills) that gives ~80,000 lb-f. Enough?
Orion's LAS has something like 500klbf. The Orion's 23tn are with or without the LAS (which weights som 6tn). Because if the Dragon weights 6tn when crewed, and considering that the F9 is "easier" to run away than a solid, it's in the ballpark.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: john smith 19 on 08/03/2011 12:02 pm
I'd say getting to a PDR by Sept of this year is pretty impressive from an April ATP.

I'll note that Spacex have been talking about this idea since at *least* 2009. A presentation of theirs discusses what's needed to turn a "Cargo" Dragon into a "Crew" Dragon. Key items were CO2 scrubbing, tighter temperature control and and the LES. It also lists *which* crew rating standards Dragon was designed to. There are a *lot* of them. Upgrading a design which had not been designed from day 1 this way looks to be a PITA.

Looking at Sutton 4ed lists the Apollo LES and the Apollo attitude thrusters. The tower thrust is roughly 10x the attitude thrusters.

People have said Boeing's CST-100 will use 2 *different* designs and just swallow the mass hit.

However there are precedents for a "unified" design. The Lance propulsion system (Hypergolic but pressurized with a solid fuel gas generator) used a nozzle-within-nozzle system to generate c55 000 lb on T/O & 5000 lb at cruise. Both were cast Aluminum and ablatively cooled.

Aerojet have demonstrated 20:1 turn down with a solid rocket as part of the US Joint Common Missile programme. This used a pintle in the throat, which has been used in engines going back to c1960.

*Both* were (are) primary propulsion systems, running a boost/cruise cycle. "Super Draco" will normally run in "cruise" with occasional runs at "emergency" thrust levels. 

This suggests *one* way it could be done would be a 2 position pintle in the throat and some kind of 2 position valve. Pintle in throat with valve on "normal" setting give low thrust pulses. Setting 2 (or "11" for admirers of Spinal Tap) moves the pintle out of the throat and cranks up the propellant flow, maybe to continuous thrust. Hard setting the flows on different valves *could* give the same kind of differential thrust steering as Apollo used with under and over-nominal sized throats on the steering rocket nozzles.

Rocketdyne also demonstrated their LEAP thruster with about an 8:1 thrust ratio if you can generate 1100psi of chamber pressure. I'm sure there are others.

Given the Moons 1/6g I *think* it could handle landing. Lunar escape is listed as 7700fps so (presumably) that would be about what it'd take to go from a transfer trajectory *directly* into a landing. Depending on landing mass it would probably need re-fueling which would beg the question "from what?"
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: yamato on 08/03/2011 01:45 pm

Given the Moons 1/6g I *think* it could handle landing. Lunar escape is listed as 7700fps so (presumably) that would be about what it'd take to go from a transfer trajectory *directly* into a landing. Depending on landing mass it would probably need re-fueling which would beg the question "from what?"

from additional external tank? Dragon could land with an additional tanks palette berthed on top. After refueling, it throws empty tanks away and takes off :)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: A_M_Swallow on 08/03/2011 09:34 pm
{snip}

Given the Moons 1/6g I *think* it could handle landing. Lunar escape is listed as 7700fps so (presumably) that would be about what it'd take to go from a transfer trajectory *directly* into a landing. Depending on landing mass it would probably need re-fueling which would beg the question "from what?"

If the ascent fuel is not brought as cargo then the propellant could be brought by a second lander and transferred by a rover.  Later Lunar ISRU Propellant Inc may sell the ascent (or round trip) propellant.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: john smith 19 on 08/03/2011 11:11 pm

If the ascent fuel is not brought as cargo then the propellant could be brought by a second lander and transferred by a rover.  Later Lunar ISRU Propellant Inc may sell the ascent (or round trip) propellant.

It's an intriguing idea. Feasibility depends on the total impulse available on the "Super Draco" thrusters and mass as it goes into its landing burn. I'm not sure how detailed a spec Spacex have issued on this.

Note also this requires it separate from the support module which houses the solar cells, and I'm not sure it *can* re-couple, which it would have to do for the roughly 3 day trip back to Earth.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 08/03/2011 11:33 pm
Not for near term use, but a group in Japan is developing a solid state lithium ion battery with double the charge density of liquid, instant charging and a very wide temp range;  100°C to -100°C.  Handy for such uses.  Article is in Nature Materials.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Michael Bloxham on 09/04/2011 01:38 am
I'm not sure if it has been explicitly discussed elsewhere, but I was curious as to how the LAS motors would be squeezed in with the current Draco OMS system. So to satisfy my curiosity I made a few jpegs of how I think it will work (and based on the CGI models):
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jason1701 on 09/04/2011 04:26 am
That's a really excellent analysis.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 09/04/2011 04:37 am
I'm not sure if it has been explicitly discussed elsewhere, but I was curious as to how the LAS motors would be squeezed in with the current Draco OMS system. So to satisfy my curiosity I made a few jpegs of how I think it will work (and based on the CGI models):

I like it too.
 
Notice how your downward pointing Draco has an opening down near the heatshield, which makes sense, whereas the CGI has it coming out high, near the top of the unpressurized volume, which doesn't seem right.

Your Super Dracos seem a bit larger than the existing Dracos.  How did you arrive at the size? By what would fit or from the CGI?  Can someone here calculate the area they would need, given the required thrust per engine, and likely parameters for Hydrazine/Nitrogen Tetroxide engines driven by some high pressure system?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Michael Bloxham on 09/04/2011 11:04 am
Don't read too much into the tea leaves! It was just a quick-and-dirty photoshop - not much 'analysis' in it ;-)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Raul on 09/04/2011 08:34 pm
I'm not sure if it has been explicitly discussed elsewhere, but I was curious as to how the LAS motors would be squeezed in with the current Draco OMS system. So to satisfy my curiosity I made a few jpegs of how I think it will work (and based on the CGI models):
Nice Photoshop modification. :)

 For SuperDraco-LAS and Earth landing it can be ok.

 But for Mars SuperDraco-landing will be necessary also a bit more fuel. And there is very limited space at service section for that in present Dragon.
 
To Mars it will fly probably with Raptor stage (EDS). And Raptor will have 5m diameter.
 So, why should be not increased Dragon-Mars lander heat shield diameter to 5m too? For Mars atmosphere will be bigger heat shield much better.
 And appropriate Dragon extension (something like equipment/reentry module at Gemini), give enough space for bigger fuel tanks for such landing.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: M_Puckett on 09/04/2011 08:48 pm
If one were trying to land a Dragon on the moon with as much remaining propellant as possible, it would seem a crasher stage would make sense.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris-A on 09/05/2011 03:49 am
The CGI does seem to show the TPS extends outward around the Super Draco's.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 09/05/2011 11:43 am
To Mars it will fly probably with Raptor stage (EDS). And Raptor will have 5m diameter.
 So, why should be not increased Dragon-Mars lander heat shield diameter to 5m too? For Mars atmosphere will be bigger heat shield much better.
 And appropriate Dragon extension (something like equipment/reentry module at Gemini), give enough space for bigger fuel tanks for such landing.


Do we know for a fact that Raptor would be 5m?
Anyway, the constraint is really PLF diameter, not stage diameter.
A wider heatshield would, I presume, completely invalidate what is known about Dragon's behaviour as an entry vehicle.
The extra heatshield area would of course help in a Mars entry, but not by nearly enough to hit the 'sweet spot' where you avoid the need to develop ground-breaking new supersonic retropropulsion or hypersonic drag devices.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: oldAtlas_Eguy on 09/05/2011 04:36 pm
To Mars it will fly probably with Raptor stage (EDS). And Raptor will have 5m diameter.
 So, why should be not increased Dragon-Mars lander heat shield diameter to 5m too? For Mars atmosphere will be bigger heat shield much better.
 And appropriate Dragon extension (something like equipment/reentry module at Gemini), give enough space for bigger fuel tanks for such landing.


Do we know for a fact that Raptor would be 5m?
Anyway, the constraint is really PLF diameter, not stage diameter.
A wider heatshield would, I presume, completely invalidate what is known about Dragon's behaviour as an entry vehicle.
The extra heatshield area would of course help in a Mars entry, but not by nearly enough to hit the 'sweet spot' where you avoid the need to develop ground-breaking new supersonic retropropulsion or hypersonic drag devices.

For detail discussion about Raptor and the logical size of the Raptor stage tanks see this thread:

http://forum.nasaspaceflight.com/index.php?topic=22601.120 (http://forum.nasaspaceflight.com/index.php?topic=22601.120)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Michael Bloxham on 09/30/2011 05:17 am
In case you missed it :D
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Michael Bloxham on 09/30/2011 05:53 am
Notice how your downward pointing Draco has an opening down near the heatshield, which makes sense, whereas the CGI has it coming out high, near the top of the unpressurized volume, which doesn't seem right.

Interestingly, I see that this hasn't changed in the latest CGI model either. But again - tea leaves?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: grr on 10/01/2011 05:33 am
Not for near term use, but a group in Japan is developing a solid state lithium ion battery with double the charge density of liquid, instant charging and a very wide temp range;  100°C to -100°C.  Handy for such uses.  Article is in Nature Materials.

Probably too early, but hopefully in the next couple of years, there is a better replacement.
http://www.sciencedaily.com/releases/2011/09/110929074021.htm

They have not given specs on it, but it is more like a cap than a battery (electron storage vs chemical change). As such, charges should be in the million range vs. 1000s.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: billh on 10/01/2011 01:31 pm
Probably too early, but hopefully in the next couple of years, there is a better replacement.
http://www.sciencedaily.com/releases/2011/09/110929074021.htm

They have not given specs on it, but it is more like a cap than a battery (electron storage vs chemical change). As such, charges should be in the million range vs. 1000s.
That looks like very interesting research. The linked article doesn't really explain how it works, but it references a paper by the same researchers titled: Polarizable energy-storage membrane based on ionic condensation and decondensation.. That sounds like an approach that combines chemical and electrical storage. A very interesting strategy for increasing the energy density. I hope we hear more in the future from these guys.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 12/17/2011 09:38 pm
SpaceX has a functional capsule, which puts it ahead in many areas, but it lacks the crew safety systems which the other vendors have already gotten a jump on in developing. 

http://www.nasa.gov/pdf/610830main_CCDev2_Public_20111209_508.pdf

This update shows abort testing in Q2 2012.  Pretty soon.  If testing shows that LAS works as anticipated, is SpaceX "pretty much there" in terms of long lead items?  Could they do crew trips in 2013 or 2014 from that point if they had a contract to do so? 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 12/17/2011 09:41 pm
Do they have a life support system, docking system, crew access tower?

How many missions have they flown and how many have they berthed to the ISS?  How many launches will they do in the next two years?  2? maybe 4?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 12/17/2011 09:55 pm
Do they have a life support system, docking system, crew access tower?
Those are precisely the things I am wondering about in terms of lead time.  A year?  Two?  Five?  What's a realistic estimate assuming funding isn't a constraint?

How many missions have they flown and how many have they berthed to the ISS?  How many launches will they do in the next two years?  2? maybe 4?
Whether it's one or twelve prior to a crew mission, they will have a fair idea of ISS protocols.  Trying to figure out requirement differences between berthing for resupply and docking for biological cargo (and staying attached for a long time) seems like something that SpaceX would be naturally trying to figure out already. 

I think I've missed your point.   
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 12/17/2011 10:03 pm
If SpaceX can't do over 2 launches a year within a couple years, they will be majorly hurting.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 12/17/2011 10:18 pm
Do they have a life support system, docking system, crew access tower?
Those are precisely the things I am wondering about in terms of lead time.  A year?  Two?  Five?  What's a realistic estimate assuming funding isn't a constraint?

How many missions have they flown and how many have they berthed to the ISS?  How many launches will they do in the next two years?  2? maybe 4?
Whether it's one or twelve prior to a crew mission, they will have a fair idea of ISS protocols.  Trying to figure out requirement differences between berthing for resupply and docking for biological cargo (and staying attached for a long time) seems like something that SpaceX would be naturally trying to figure out already. 

I think I've missed your point.   

They have a lot to do before even considering crew launches
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 12/18/2011 12:14 am
Weren't they teamed with Paragon for life support? They met all their milestones this year....

http://www.paragonsdc.com/docs/CCT-ARS%20Press%20Release.pdf
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: tigerade on 12/18/2011 02:42 am
They have a lot to do before even considering crew launches

Is that where the 2017 figure is coming from?

Is the life support system in the crewed version going to be significantly different than the current environment control system in the cargo dragon?

Crew Access Tower, how long will that take?

Docking system, how long?  How much more complex will this be compared to the berthing mechanism?

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: pathfinder_01 on 12/18/2011 05:45 am

Is that where the 2017 figure is coming from?

From NASA, not Space X.  It is when they are expecting CCREW to be ready to serve the ISS. In addition it takes 2 years to order a Soyuz and we are booked till 2016 with the Russians.

Quote
Is the life support system in the crewed version going to be significantly different than the current environment control system in the cargo dragon?

Yes. Current cargo version has enough life support for some lab animals(mice) from launch, but not humans. It has enough life support to allow you to work inside it in space, but not enough to suport a crew from launch to landing(it is sorta like the MPLM).

Quote
Access Tower, how long will that take?

Don't know but Elon wants to launch Falcon 9 six times before carring crew so that the bugs are worked out. That would put it around 2013 assuming no more slips(big assumption there!).

Quote
Docking system, how long?  How much more complex will this be compared to the berthing mechanism?

Docking system is already seleted( international docking standard) by NASA. ISS needs to get current docking port upgraded to international docking standard which is expected to happen circa 2013/2014.


Berthing is not appropriate for crewed dragon if dragon is to function as emergancy escape too. Berthing requires use of the robot arm both to come and to go which is not a good thing to require in an emergancy. In theory you could rig a system that would allow dragon to leave without the arm in an emergancy, but frankly it is better to go for docking.  With docking dragon can undock for a time period and then come back(i.e tempory evacutation).  With a riged system it would likely be a one way trip
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Nathan on 12/18/2011 07:41 am
Docking system is already seleted( international docking standard) by NASA. ISS needs to get current docking port upgraded to international docking standard which is expected to happen circa 2013/2014.




How is that upgrade happening? Russian launch/mission
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jorge on 12/18/2011 08:04 am
Docking system is already seleted( international docking standard) by NASA. ISS needs to get current docking port upgraded to international docking standard which is expected to happen circa 2013/2014.




How is that upgrade happening? Russian launch/mission

No, Cargo Dragon.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chandonn on 12/18/2011 11:05 am
Docking system is already seleted( international docking standard) by NASA. ISS needs to get current docking port upgraded to international docking standard which is expected to happen circa 2013/2014.




How is that upgrade happening? Russian launch/mission

No, Cargo Dragon.

IIRC, last I read here on NSF the NDS adapters would be brought up on HTV as unpressurized cargo.  Has this changed?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: subzero788 on 12/18/2011 11:13 am
Interesting discussion, but way off topic
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 12/18/2011 12:55 pm

Is the life support system in the crewed version going to be significantly different than the current environment control system in the cargo dragon?


there is no life support system in the cargo dragon, just fans.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 12/18/2011 03:07 pm
it takes 2 years to order a Soyuz and we are booked till 2016 with the Russians.
  If it only takes 2 years to order Soyuz, why would NASA book the Russians until 2016 when a less expensive domestic capability may be ready sooner than 2016?  Just curious what the reasoning is.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 12/18/2011 03:54 pm
it takes 2 years to order a Soyuz and we are booked till 2016 with the Russians.
  If it only takes 2 years to order Soyuz, why would NASA book the Russians until 2016 when a less expensive domestic capability may be ready sooner than 2016?  Just curious what the reasoning is.

because it isn't going to be ready
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 12/18/2011 05:13 pm
it takes 2 years to order a Soyuz and we are booked till 2016 with the Russians.
  If it only takes 2 years to order Soyuz, why would NASA book the Russians until 2016 when a less expensive domestic capability may be ready sooner than 2016?  Just curious what the reasoning is.
because it isn't going to be ready
Even if that is 98% certain, why not order the 2016 soyuz in 2014 instead? 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: apace on 12/18/2011 05:24 pm
Even if that is 98% certain, why not order the 2016 soyuz in 2014 instead? 

Because human space flight, ISS operations and international cooperation doesn't work like ordering a PC from your retailer? Don't forget that there is extensive astronaut training at the russian space centers.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: oldAtlas_Eguy on 12/18/2011 06:28 pm
FYI one of the long poles in the tent for ISS receiving VVs is the NDS which will be available NET Q1 2015. The design of the standard NDS adapter is a CBM to NDS. So SpaceX can either purchase the adapter or have NASA give them the plans so SpaceX can build their own. The NDS adapter design is government owned. That makes adding the NDS to the Dragon very simple. Just bolt the NDS adapter to the CBM on the Dragon.

See the details about the NDS problems in this thread:
http://forum.nasaspaceflight.com/index.php?topic=27261.30 (http://forum.nasaspaceflight.com/index.php?topic=27261.30)

Even if the rest of Dragon is ready in 2014, ISS would not be. That would not keep SpaceX from flying a mostly CC Dragon minus seats and crew interfaces as a cargo to the ISS prior to 2015 to prove out most systems such as carrying along the LAS to show the new Dragon’s reentry is without problems and the life support system work for the duration of the flight.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 12/18/2011 06:54 pm
I really, really doubt SpaceX would just bolt on an adapter. They'd likely integrate the NDS port into Dragon itself.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 12/18/2011 08:06 pm
I really, really doubt SpaceX would just bolt on an adapter. They'd likely integrate the NDS port into Dragon itself.

Yep, otherwise the mass penalty would likely be too high. The Dragon pressure vessel is built welded together from several pieces - it won't be too hard to replace the top section with something that can an NDS port can attached directly to.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: oldAtlas_Eguy on 12/18/2011 08:34 pm
I really, really doubt SpaceX would just bolt on an adapter. They'd likely integrate the NDS port into Dragon itself.

Yep, otherwise the mass penalty would likely be too high. The Dragon pressure vessel is built welded together from several pieces - it won't be too hard to replace the top section with something that can an NDS port can attached directly to.

In that case SpaceX will have to design and build their own NDS to a spec that has not been fully finalized. Although it should be good enough to design most of it.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: antiquark on 01/18/2012 03:09 pm
Say we use Apollo as a baseline, wouldn't the LAS be severely underpowered? The Apollo escape tower produced 147,000 lbs of thrust. The Dracos only produce 90 lbs. Even if you modified eight Dracos, they would each need 18,000 lbs of thrust. To give some perspective, the main engine on the Apollo Service module produced 20,500 lbs of thrust.

Sounds like there's a huge difference in the LAS performance from the Apollo era.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Ronsmytheiii on 01/18/2012 03:16 pm
Say we use Apollo as a baseline, wouldn't the LAS be severely underpowered? The Apollo escape tower produced 147,000 lbs of thrust. The Dracos only produce 90 lbs. Even if you modified eight Dracos, they would each need 18,000 lbs of thrust. To give some perspective, the main engine on the Apollo Service module produced 20,500 lbs of thrust.

Sounds like there's a huge difference in the LAS performance from the Apollo era.

Falcon 9 is a much smaller LV, and Dragon is a much lighter capsule.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Ben the Space Brit on 01/18/2012 03:17 pm
Sounds like there's a huge difference in the LAS performance from the Apollo era.

Don't forget that, fully loaded, Dragon only weighs about 1/3 of a Lunar Apollo.  The aerodynamics (and thus drag for the LAS to beat) are probably different, given the different vehicle geometries.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 01/18/2012 03:28 pm
Say we use Apollo as a baseline, wouldn't the LAS be severely underpowered? The Apollo escape tower produced 147,000 lbs of thrust. The Dracos only produce 90 lbs. Even if you modified eight Dracos, they would each need 18,000 lbs of thrust. To give some perspective, the main engine on the Apollo Service module produced 20,500 lbs of thrust.

Sounds like there's a huge difference in the LAS performance from the Apollo era.

The current Dracos are not the abort Dracos
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: wolfpack on 01/18/2012 03:48 pm
Say we use Apollo as a baseline, wouldn't the LAS be severely underpowered? The Apollo escape tower produced 147,000 lbs of thrust. The Dracos only produce 90 lbs. Even if you modified eight Dracos, they would each need 18,000 lbs of thrust. To give some perspective, the main engine on the Apollo Service module produced 20,500 lbs of thrust.

Sounds like there's a huge difference in the LAS performance from the Apollo era.

I've heard SpaceX refer to a "Super Draco" design. I'm guessing this would be an engine with a lot higher thrust capability, plus throttling to support the "flip-over" needed during a LAS abort (downrange butt-first so the chutes open properly). The tractor LAS has to do the same thing, too.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jorge on 01/18/2012 04:52 pm
Sounds like there's a huge difference in the LAS performance from the Apollo era.

Don't forget that, fully loaded, Dragon only weighs about 1/3 of a Lunar Apollo.

Umm, no. Remember the Apollo LES only pulled the CM off the stack, not the CSM. So it's irrelevant whether it's a Lunar Apollo or a LEO Apollo, since the CM masses were similar (around 5800 kg). The gross mass of a crew Dragon is not publicly known but I would doubt it's a third of 5800 kg.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: antiquark on 01/18/2012 05:21 pm
since the CM masses were similar (around 5800 kg). The gross mass of a crew Dragon is not publicly known but I would doubt it's a third of 5800 kg.

It's hard to find info with wikipedia being down today, but the fully loaded weight (with crew) of the command module was 13,000 lb = 5900 kg, and the "wet mass" of the Dragon capsule is 4,540 kg according to this somewhat out-of-date page:

http://www.flightglobal.com/news/articles/picture-spacex-reveals-first-dragon-engineering-unit-212634/

So the Dragon is 77% the weight of the CM, if this number is accurate.

Actually that page says that the crewed Dragon weighs 7000 kg, which is more than the command module. But that page is quite old...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 01/18/2012 05:29 pm
Remember to include the mass of the launch escape tower (including protective covering of the capsule, jettison motor, etc), too, which can be QUITE substantial (3 or more tons), comparable to almost the mass of the capsule itself.

Dragon crew is to have an integrated abort system (with the propellant being needed for on-orbit maneuvering anyway), thus its mass (versus no abort system) can be a lot less (no protective covering needed, no jettison motor, etc... each of those can be several hundred pounds each).
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: jedsmd on 01/18/2012 05:40 pm
Remember to include the mass of the launch escape tower (including protective covering of the capsule, jettison motor, etc), too, which can be QUITE substantial (3 or more tons), comparable to almost the mass of the capsule itself.

Dragon crew is to have an integrated abort system (with the propellant being needed for on-orbit maneuvering anyway), thus its mass (versus no abort system) can be a lot less (no protective covering needed, no jettison motor, etc... each of those can be several hundred pounds each).

On the other side; dragon thrusters are skewed and cosine losses need to be considered.  Could be as much as 30% increase in thrust required for a given acceleration.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 01/18/2012 05:45 pm
Remember to include the mass of the launch escape tower (including protective covering of the capsule, jettison motor, etc), too, which can be QUITE substantial (3 or more tons), comparable to almost the mass of the capsule itself.

Dragon crew is to have an integrated abort system (with the propellant being needed for on-orbit maneuvering anyway), thus its mass (versus no abort system) can be a lot less (no protective covering needed, no jettison motor, etc... each of those can be several hundred pounds each).

On the other side; dragon thrusters are skewed and cosine losses need to be considered.  Could be as much as 30% increase in thrust required for a given acceleration.

Probably - but hard to tell without seeing a final thruster location. (Some crew dragon renderings have had the abort thrusters extend slightly outside the conical shape, which would reduce cosine losses) The Apollo LAS didn't fire straight down either - so it also had cosine losses.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 01/18/2012 05:46 pm
Remember to include the mass of the launch escape tower (including protective covering of the capsule, jettison motor, etc), too, which can be QUITE substantial (3 or more tons), comparable to almost the mass of the capsule itself.

Dragon crew is to have an integrated abort system (with the propellant being needed for on-orbit maneuvering anyway), thus its mass (versus no abort system) can be a lot less (no protective covering needed, no jettison motor, etc... each of those can be several hundred pounds each).

On the other side; dragon thrusters are skewed and cosine losses need to be considered.  Could be as much as 30% increase in thrust required for a given acceleration.
LAS towers are also canted (and have plume impingement on the capsule, which lowers the effective thrust as well).

And we don't yet know the exact technical details of the abort thrusters. We don't know the angle they will be canted at. It's also possible they will surprise with some solution with very low angle, like holes in the heatshield or pop-out thrusters. But seem unlikely, but we don't know, yet. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: jedsmd on 01/18/2012 05:52 pm
Remember to include the mass of the launch escape tower (including protective covering of the capsule, jettison motor, etc), too, which can be QUITE substantial (3 or more tons), comparable to almost the mass of the capsule itself.

Dragon crew is to have an integrated abort system (with the propellant being needed for on-orbit maneuvering anyway), thus its mass (versus no abort system) can be a lot less (no protective covering needed, no jettison motor, etc... each of those can be several hundred pounds each).

On the other side; dragon thrusters are skewed and cosine losses need to be considered.  Could be as much as 30% increase in thrust required for a given acceleration.
LAS towers are also canted (and have plume impingement on the capsule, which lowers the effective thrust as well).

And we don't yet know the exact technical details of the abort thrusters. We don't know the angle they will be canted at. It's also possible they will surprise with some solution with very low angle, like holes in the heatshield or pop-out thrusters. But seem unlikely, but we don't know, yet. 

Other questions are how much acceleration do you need and for how far?  Does escaping from a F9 have the same requirements as escaping from a Saturn 5?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 01/18/2012 06:07 pm
On top of all that, the Apollo LES itself weighted 3.65tonnes (8klbs). Plus, we ignore completely the thrust of the SuperDracos.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: dcporter on 01/18/2012 06:20 pm
Other questions are how much acceleration do you need and for how far?  Does escaping from a F9 have the same requirements as escaping from a Saturn 5?

Much less escaping needed from a much smaller rocket.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: simonbp on 01/24/2012 03:59 pm
Much less escaping needed from a much smaller rocket.

It's not the size that matters, it's the acceleration. Saturn V was a fairly gentle ride, as the inboard engines of the S-IC and S-II were shut down early to keep it down. Presumably SpaceX will do something similar to keep the acceleration down on crewed F9s. Thus, it's probably a pretty similar environment.

Big solids with big thrust are the real kicker for acceleration, which is why the Orion LAS is so darn big (and why a Shuttle escape capsule was effectively impossible). The high thrust of the Titan II first stage is again a reason why Gemini didn't have an escape tower.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 01/24/2012 04:05 pm
Much less escaping needed from a much smaller rocket.

It's not the size that matters, it's the acceleration. Saturn V was a fairly gentle ride, as the inboard engines of the S-IC and S-II were shut down early to keep it down. Presumably SpaceX will do something similar to keep the acceleration down on crewed F9s. Thus, it's probably a pretty similar environment.

Big solids with big thrust are the real kicker for acceleration, which is why the Orion LAS is so darn big (and why a Shuttle escape capsule was effectively impossible). The high thrust of the Titan II first stage is again a reason why Gemini didn't have an escape tower.
Also, it depends on the size of the likely fireball. Saturn V is a very big fireball. Ares I is a big fireball plus a rain of fire and brimstone (i.e. flaming chunks of solid propellant which like to melt your parachutes).
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 01/24/2012 04:08 pm
..the inboard engines of the S-IC and S-II were shut down early to keep it down. Presumably SpaceX will do something similar to keep the acceleration down on crewed F9s.

The past two F9 flights have shut down two first stage engines to limit acceleration towards the end of the burn.  My recollection is that SpaceX plans to use the throttling capability of the Merlin 1Ds to limit acceleration on the evolved F9, which will be introduced on F9 #7.

But does that matter in an abort where all the engines woud be shut down?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: HMXHMX on 01/24/2012 04:14 pm
Much less escaping needed from a much smaller rocket.

It's not the size that matters, it's the acceleration. Saturn V was a fairly gentle ride, as the inboard engines of the S-IC and S-II were shut down early to keep it down. Presumably SpaceX will do something similar to keep the acceleration down on crewed F9s. Thus, it's probably a pretty similar environment.

Big solids with big thrust are the real kicker for acceleration, which is why the Orion LAS is so darn big (and why a Shuttle escape capsule was effectively impossible). The high thrust of the Titan II first stage is again a reason why Gemini didn't have an escape tower.

My understanding of why Gemini didn't require a tractor escape system is the propellants can't detonate, only deflagrate.  Thus the overpressure is very low, along with the a reduced diameter fireball.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: simonbp on 01/24/2012 09:03 pm
My understanding of why Gemini didn't require a tractor escape system is the propellants can't detonate, only deflagrate.  Thus the overpressure is very low, along with the a reduced diameter fireball.

That may be true as well. The acceleration at first stage burnout, though, for Gemini-Titan was about 6g, so a multi-g abort at that point likely would have blacked out the crew. For reference, the acceleration at second stage burnout was 7g, the highest I know of for a manned spacecraft.

http://en.wikisource.org/wiki/NASA_Project_Gemini_Familiarization_Manual#BOOST_AND_STAGING

But does that matter in an abort where all the engines woud be shut down?

If you can command the engines to shut down down, you don't need an escape system in the process. The point of a separate escape rocket is really for when an engine undergoes a "rapid unexpected self-disassembly"...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 01/24/2012 09:30 pm
But does that matter in an abort where all the engines woud be shut down?

If you can command the engines to shut down down, you don't need an escape system in the process. The point of a separate escape rocket is really for when an engine undergoes a "rapid unexpected self-disassembly"...

You still need a LAS even if the engines shut down, particularly for times like the first few seconds after launch.  But if an engine does a RUD, it doesn't matter how much thrust it WAS producing.  There is no more booster acceleration to outrun, just the conflagration and debris.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: HMXHMX on 01/24/2012 09:50 pm
My understanding of why Gemini didn't require a tractor escape system is the propellants can't detonate, only deflagrate.  Thus the overpressure is very low, along with the a reduced diameter fireball.

That may be true as well. The acceleration at first stage burnout, though, for Gemini-Titan was about 6g, so a multi-g abort at that point likely would have blacked out the crew. For reference, the acceleration at second stage burnout was 7g, the highest I know of for a manned spacecraft.

http://en.wikisource.org/wiki/NASA_Project_Gemini_Familiarization_Manual#BOOST_AND_STAGING

But does that matter in an abort where all the engines woud be shut down?

If you can command the engines to shut down down, you don't need an escape system in the process. The point of a separate escape rocket is really for when an engine undergoes a "rapid unexpected self-disassembly"...

High-altitude Gemini aborts assumed Stage Two engine shutdown.  The OAMS would have been used to separate the spacecraft.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 01/25/2012 02:22 am
But does that matter in an abort where all the engines woud be shut down?

If you can command the engines to shut down down, you don't need an escape system in the process. The point of a separate escape rocket is really for when an engine undergoes a "rapid unexpected self-disassembly"...

You still need a LAS even if the engines shut down, particularly for times like the first few seconds after launch.  But if an engine does a RUD, it doesn't matter how much thrust it WAS producing.  There is no more booster acceleration to outrun, just the conflagration and debris.

The abort system is not sized to outrun a booster (Ares I aside) because the engines are shutdown.  It sized to outrun the shock wave from a low altitude explosion (Titan II aside).  An LAS is not needed for second stage flight, the "orbital adjust" engines are sufficient to put the proper distance between the spacecraft and malfunctioning booster
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 02/01/2012 02:26 pm
This was just sent as an email update by SpaceX:

Quote
Hawthorne, CA – Space Exploration Technologies (SpaceX) has successfully test fired SuperDraco, a powerful new engine that will play a critical role in the company’s efforts to change the future of human spaceflight.

http://www.youtube.com/watch?v=PUUnYgo1-lI

Quote
“SuperDraco engines represent the best of cutting edge technology,” said Elon Musk, SpaceX CEO and Chief Technology Officer. “These engines will power a revolutionary launch escape system that will make Dragon the safest spacecraft in history and enable it to land propulsively on Earth or another planet with pinpoint accuracy.”

The SuperDraco is an advanced version of the Draco engines currently used by SpaceX’s Dragon spacecraft to maneuver on orbit and during reentry. As part of SpaceX’s state-of-the-art launch escape system, eight SuperDraco engines built into the side walls of the Dragon spacecraft will produce up to 120,000 pounds of axial thrust to carry astronauts to safety should an emergency occur during launch.

NASA’s Commercial Crew Program awarded SpaceX $75 million in April of last year to begin work developing the escape system in order to prepare the Dragon spacecraft to carry astronauts. Less than nine months later, SpaceX engineers have designed, built and tested the engine.

In a series of recent tests conducted at the company’s Rocket Development Facility in McGregor, Texas, the SuperDraco sustained full duration, full thrust firing as well as a series of deep throttling demonstrations.

SpaceX’s launch escape system has many advantages over past systems. It is inherently safer because it is not jettisoned like all other
escape systems. This distinction provides astronauts with the unprecedented ability to escape from danger at any point during the launch,
not just in the first few minutes. The eight SuperDracos provide redundancy, so that even if one engine fails an escape can still be carried
out successfully.

SuperDracos can also be restarted multiple times if necessary and the engines will have the ability to deep throttle, providing astronauts with precise control and enormous power. In addition, as a part of a recoverable Dragon spacecraft, the engines can be used repeatedly, helping to advance SpaceX’s long-term goal of making spacecraft more like airplanes, which can be flown again and again with minimal maintenance between flights.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: apace on 02/01/2012 02:33 pm
So, every SuperDraco provide at least 15'000 pounds trust? Looks like the SuperDraco's has not a lot in common with the normal Dracos beside the name?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 02/01/2012 02:36 pm
Looks like the SuperDraco's has not a lot in common with the normal Dracos beside the name?

That should have been fairly obvious once you took a look at Draco thrust levels and thrust levels required for abort.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: mrhuggy on 02/01/2012 02:39 pm
This was just sent as an email update by SpaceX:

Quote
Hawthorne, CA – Space Exploration Technologies (SpaceX) has successfully test fired SuperDraco, a powerful new engine that will play a critical role in the company’s efforts to change the future of human spaceflight.

Quote
“SuperDraco engines represent the best of cutting edge technology,” said Elon Musk, SpaceX CEO and Chief Technology Officer. “These engines will power a revolutionary launch escape system that will make Dragon the safest spacecraft in history and enable it to land propulsively on Earth or another planet with pinpoint accuracy.”

The SuperDraco is an advanced version of the Draco engines currently used by SpaceX’s Dragon spacecraft to maneuver on orbit and during reentry. As part of SpaceX’s state-of-the-art launch escape system, eight SuperDraco engines built into the side walls of the Dragon spacecraft will produce up to 120,000 pounds of axial thrust to carry astronauts to safety should an emergency occur during launch.

NASA’s Commercial Crew Program awarded SpaceX $75 million in April of last year to begin work developing the escape system in order to prepare the Dragon spacecraft to carry astronauts. Less than nine months later, SpaceX engineers have designed, built and tested the engine.

In a series of recent tests conducted at the company’s Rocket Development Facility in McGregor, Texas, the SuperDraco sustained full duration, full thrust firing as well as a series of deep throttling demonstrations.

SpaceX’s launch escape system has many advantages over past systems. It is inherently safer because it is not jettisoned like all other
escape systems. This distinction provides astronauts with the unprecedented ability to escape from danger at any point during the launch,
not just in the first few minutes. The eight SuperDracos provide redundancy, so that even if one engine fails an escape can still be carried
out successfully.

SuperDracos can also be restarted multiple times if necessary and the engines will have the ability to deep throttle, providing astronauts with precise control and enormous power. In addition, as a part of a recoverable Dragon spacecraft, the engines can be used repeatedly, helping to advance SpaceX’s long-term goal of making spacecraft more like airplanes, which can be flown again and again with minimal maintenance between flights.

Looks like they been feeding that Draco with some Steroids.

I have to say that engine looks quite good I wonder what the thrust levels etc are for it.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: apace on 02/01/2012 02:45 pm
Looks like the SuperDraco's has not a lot in common with the normal Dracos beside the name?
That should have been fairly obvious once you took a look at Draco thrust levels and thrust levels required for abort.

Still wondering, how they get all this engines, fuel, electronics in the small space around the pressurized capsule.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: JohnFornaro on 02/01/2012 02:54 pm
Super Dracos. 

Excellent multi-purpose rocket engine, used for abort and landing.  Not disposable.  Restartable.  Throttleable.  $75M to develop and test.

Way to go, SpaceX.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ThereIWas3 on 02/01/2012 03:03 pm
Further down in that email is this picture showing a propulsive landing.  Interesting that the background shown is Mars rather than Florida. :)

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 02/01/2012 03:03 pm
Quote
As part of SpaceX’s state-of-the-art launch escape system, eight SuperDraco engines built into the side walls of the Dragon spacecraft will produce up to 120,000 pounds of axial thrust to carry astronauts to safety should an emergency occur during launch.
To me, the context implies axial to dragon.  That implies that the superdracos are more than 120000/8 = 15k.  Perhaps 20000+ pounds of thrust each is a reasonable guess.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: apace on 02/01/2012 03:06 pm
Quote
As part of SpaceX’s state-of-the-art launch escape system, eight SuperDraco engines built into the side walls of the Dragon spacecraft will produce up to 120,000 pounds of axial thrust to carry astronauts to safety should an emergency occur during launch.
To me, the context implies axial to dragon.  That implies that the superdracos are more; perhaps 20000+ pounds of thrust each. 

Looks like, yes. Otherwise they have not written "axial" in this context. To compare, one SuperDraco has the same trust like the Apollo service module main engine...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Ben the Space Brit on 02/01/2012 03:18 pm
Interesting that the background shown is Mars rather than Florida. :)

I believe that's a reference to the 'Red Dragon' Discovery-class Mars probe proposal.  As it stands, Dragon's current predicted performance is only barely adequate for a fully-propulsive Mars landing and then only for a small number of ultra-deep depressions on the surface.

Landing on Earth will benefit from a far denser atmosphere to further brake the vehicle during descent.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kevin-rf on 02/01/2012 03:31 pm
Oh, I thought being in the future, the landing site was in Florida after global warming had really kicked in ;)


I wonder how hard it would be for spaceX to make a small sat. launcher with the Super Draco's.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/01/2012 03:32 pm
Further down in that email is this picture showing a propulsive landing.  Interesting that the background shown is Mars rather than Florida. :)
That's just recycled from one of their existing videos.

Full-duration, full thrust.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ChefPat on 02/01/2012 03:43 pm
We still don't know what the fuel is?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 02/01/2012 03:48 pm
We still don't know what the fuel is?

From the look of the exhaust, specifically the reddish edges of the exhaust it looks like the same stuff Dracos use, NTO/MMH. That was the idea all along, to share the propellant load with prop for on-orbit use.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: A_M_Swallow on 02/01/2012 03:57 pm
Looks like the SuperDraco's has not a lot in common with the normal Dracos beside the name?

That should have been fairly obvious once you took a look at Draco thrust levels and thrust levels required for abort.

Since there is a very big difference in the engines a new name would be expected.  There are plenty of birds and names of dragons around.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jason1701 on 02/01/2012 04:04 pm
Super Dracos. 

Excellent multi-purpose rocket engine, used for abort and landing.  Not disposable.  Restartable.  Throttleable.  $75M to develop and test.

Way to go, SpaceX.

Less, actually, as their SAA has many milestones not dealing specifically with SD.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 02/01/2012 04:40 pm
NASA post with a few more details....

http://www.nasa.gov/exploration/commercial/crew/spacex_superdraco.html

Quote
SpaceX Test Fires Engine Prototype for Astronaut Escape System

One of NASA's industry partners, Space Exploration Technologies (SpaceX), completed a full-duration, full-thrust firing of its new SuperDraco engine prototype at the company’s Rocket Development Facility in McGregor, Texas. The firing was in preparation for the ninth milestone to be completed under SpaceX's funded Space Act Agreement (SAA) with NASA's Commercial Crew Program (CCP).

“SpaceX and all our industry partners are being extremely innovative in their approaches to developing commercial transportation capabilities,” said Commercial Crew Program Manager Ed Mango. “We are happy that our investment in SpaceX was met with success in the firing of its new engine.”

Nine months after CCP awarded SpaceX $75 million to design and test its Dragon spacecraft with a launch abort system, the company test fired its SuperDraco development engine to demonstrate its capabilities of keeping an astronaut crew safe during launch and ascent. The engine produced full thrust within approximately 100 milliseconds of the ignition command. It also fired for 5 seconds, which is the same amount of time the engines would burn during an emergency abort.

"Eight SuperDracos will be built into the sidewalls of the Dragon spacecraft, producing up to 120,000 pounds of axial thrust to quickly carry astronauts to safety should an emergency occur during launch," said Elon Musk, SpaceX chief executive officer and chief technology officer. "Those engines will have the ability to deep throttle, providing astronauts with precise control and enormous power."

SuperDracos are powered by the same propellant that powers the 18 Draco thrusters Dragon will use to maneuver in orbit and during re-entry. To achieve the power necessary to quickly carry the spacecraft out of harm’s way, SuperDraco engines would burn through propellant 200 times faster than the engines Dragon uses for orbital maneuvers. 

"Crews will have the unprecedented ability to escape from danger at any point during the launch because the launch abort engines are integrated into the side walls of the vehicle," Musk said. "With eight SuperDracos, if any one engine fails the abort still can be carried out successfully." 

Ultimately, SpaceX intends for the Dragon and SuperDraco engines to be fully reusable, which will help advance the company's long-term goal of making spacecraft more like airplanes that can be flown repeatedly with minimum refurbishment. SpaceX has 10 milestones to meet under the Commercial Crew Development Round 2 (CCDev2) agreement, which continues through at least May. 

All of NASA's industry partners continue to meet their established milestones in developing commercial crew transportation capabilities that will ferry U.S. astronauts to and from the International Space Station, reducing the amount of time America is without its own system. .

For more information about NASA's Commercial Crew Program, visit: 

http://www.nasa.gov/commercialcrew
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: TrueBlueWitt on 02/01/2012 04:42 pm
Interesting that the background shown is Mars rather than Florida. :)

I believe that's a reference to the 'Red Dragon' Discovery-class Mars probe proposal.  As it stands, Dragon's current predicted performance is only barely adequate for a fully-propulsive Mars landing and then only for a small number of ultra-deep depressions on the surface.

Landing on Earth will benefit from a far denser atmosphere to further brake the vehicle during descent.

Would it be possible(and make sense) to either areodynamically or with small thrusters keep Draon flying forward edge down and then only use one pair of Super Dracos(with near Zero Cosine Loss) for all but the final stage of the descent?  How much overall efficiency would be gained? Is there sufficient thrust in a pair of Super Dracos for this to work?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ChefPat on 02/01/2012 04:42 pm
We still don't know what the fuel is?

From the look of the exhaust, specifically the reddish edges of the exhaust it looks like the same stuff Dracos use, NTO/MMH. That was the idea all along, to share the propellant load with prop for on-orbit use.
Do we know for certain it's that & not NOFBX?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 02/01/2012 04:45 pm
The NASA post says it's the same as the Draco's, and from the NOFBX page its flames are bluish white..
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 02/01/2012 04:53 pm
Do we know for certain it's that & not NOFBX?

NOFBX still hasn't been flight proven, why would they risk it now?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/01/2012 04:59 pm
Interesting that the background shown is Mars rather than Florida. :)

I believe that's a reference to the 'Red Dragon' Discovery-class Mars probe proposal.  As it stands, Dragon's current predicted performance is only barely adequate for a fully-propulsive Mars landing and then only for a small number of ultra-deep depressions on the surface.

Landing on Earth will benefit from a far denser atmosphere to further brake the vehicle during descent.

Would it be possible(and make sense) to either areodynamically or with small thrusters keep Draon flying forward edge down and then only use one pair of Super Dracos(with near Zero Cosine Loss) for all but the final stage of the descent?  How much overall efficiency would be gained? Is there sufficient thrust in a pair of Super Dracos for this to work?
Interesting question. Couldn't be used during the initial deceleration phase, though, because the side of Dragon doesn't have heat tiles on it (nor is the shape there conducive to the aerothermal environment).

At first glance, though, the SuperDracos appear to point roughly through the center of mass of the Dragon (which helps the stability a lot in the case of engine-out during abort). So maybe there's something to it. Still, seems like a kludge.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 02/01/2012 05:14 pm
Couldn't be used during the initial deceleration phase, though, because the side of Dragon doesn't have heat tiles on it

Would this be something that could be slapped on after the fact without too much trouble?  Some picaX segments up the sides?  (For a Mars landing, it seems that less heatshield material would be required to ablate versus an Earth landing but I'm just guessing on that). 

(nor is the shape there conducive to the aerothermal environment).
Would some disruptive fire from the leading edge thruster(s) create some envelope of protection?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/01/2012 05:22 pm
Couldn't be used during the initial deceleration phase, though, because the side of Dragon doesn't have heat tiles on it

Would this be something that could be slapped on after the fact without too much trouble?  Some picaX segments up the sides?  (For a Mars landing, it seems that less heatshield material would be required to ablate versus an Earth landing but I'm just guessing on that). 

(nor is the shape there conducive to the aerothermal environment).
Would some disruptive fire from the leading edge thruster(s) create some envelope of protection?
You can't "just slap on" anything, here.

This sort of question need a lot of analysis if its going to work. If it's definitely not going to work, it might just require a napkin or two.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: mr. mark on 02/01/2012 06:35 pm
Super Draco thruster, SDT, test fire.

 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Proponent on 02/01/2012 06:49 pm
NASA post with a few more details....

http://www.nasa.gov/exploration/commercial/crew/spacex_superdraco.html

Quote
SpaceX Test Fires Engine Prototype for Astronaut Escape System

<snip>

"Crews will have the unprecedented ability to escape from danger at any point during the launch because the launch abort engines are integrated into the side walls of the vehicle," Musk said

Now SpaceX has NASA repeating its lie about Dragon being the only spacecraft ever to provide an escape option all the way to orbit.  In fact, every crew-carrying craft except Voskhod and the Shuttle has had that capability.

EDIT:  Deleted erroneous '*' in SpaceX quote.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: dcporter on 02/01/2012 06:52 pm
I'd love to hear some more analysis on this.  Musk repeats it often enough to make it sound true, but I've heard it vociferously denied around here that Apollo had blackout periods.  I've also heard Musk refer specifically to the LAS tower jettison as the point at which things could go wrong (albeit they never have); could this be what he's talking about?  Since you don't have to jettison anything, you've removed a potential failure point?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Proponent on 02/01/2012 06:56 pm
I imagine that failure to jettison the tower would have led to loss of both mission and crew.  But the basic point is that Apollo jettisoned the tower only once it was possible for escape to be effected with the SPS.  As for black zones, no doubt the probability of a successful abort--by no means 100%--varied with mission phase.  It may be that SpaceX's pusher system provides better safety, but to say it's the only spacecraft providing escape options all the way to orbit is blatantly false.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 02/01/2012 07:00 pm
I think he's merely pitching the fact a fast escape from a failing vehicle could be made all the way to orbit, not just until LAS jettison. Whether that is really needed once you get out of the atmosphere can be (and has been) debated repeatedly.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 02/01/2012 07:24 pm
I found this interesting:
Quote
The engine produced full thrust within approximately 100 milliseconds of the ignition command.
How does this compares with the solids? Is this transient slow, normal or fast for a small liquid?

Quote
It also fired for 5 seconds, which is the same amount of time the engines would burn during an emergency abort.
That's 120klf x 5secs a total of 600klf.s x cosine losses. So...
1) How much would seem like reasonable for cosine losses? 30 degrees?
2) How do you define safe in an abort situation? x amount of distance, speed difference or total acceleration? Would 7.5G be a reasonable ceiling for an abort? Or more like 10G? Just for 5 seconds and eye balls out you could do 20G easily.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: yg1968 on 02/01/2012 07:29 pm
NASA post with a few more details....

http://www.nasa.gov/exploration/commercial/crew/spacex_superdraco.html

Quote
SpaceX Test Fires Engine Prototype for Astronaut Escape System

<snip>

"Crews will have the unprecedented ability to escape from danger at any point during the launch because the launch abort* engines are integrated into the side walls of the vehicle," Musk said

Now SpaceX has NASA repeating its lie about Dragon being the only spacecraft ever to provide an escape option all the way to orbit.  In fact, every crew-carrying craft except Voskhod and the Shuttle has had that capability.

They mean that their LAS still works past the time that a tower system has been jettisoned.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 02/01/2012 07:33 pm
Do we know, or can we deduce, whether SD is pump or pressure fed?

(My assumption would be pressure-fed for instant start capability)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 02/01/2012 07:52 pm
I'd love to hear some more analysis on this.  Musk repeats it often enough to make it sound true, but I've heard it vociferously denied around here that Apollo had blackout periods.  I've also heard Musk refer specifically to the LAS tower jettison as the point at which things could go wrong (albeit they never have); could this be what he's talking about?  Since you don't have to jettison anything, you've removed a potential failure point?
You seem to have forgotten that the Apollo CSM had a very nice AJ10-137 that could very separate the CSM from the S-IVB if in an emergency after the LES had been ejected.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/01/2012 07:53 pm
Do we know, or can we deduce, whether SD is pump or pressure fed?

(My assumption would be pressure-fed for instant start capability)
We can deduce it is pressure-fed.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: simonbp on 02/01/2012 08:00 pm
Measuring the thrust angle in that Mars landing image as ~50 degree from vertical, and assuming each thruster has 15 klb of thrust gives a total effective vertical thrust of 0.7 MN. For comparison, a single Merlin 1D has 0.6 MN of thrust...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Namechange User on 02/01/2012 08:07 pm
NASA post with a few more details....

http://www.nasa.gov/exploration/commercial/crew/spacex_superdraco.html

Quote
SpaceX Test Fires Engine Prototype for Astronaut Escape System

<snip>

"Crews will have the unprecedented ability to escape from danger at any point during the launch because the launch abort* engines are integrated into the side walls of the vehicle," Musk said

Now SpaceX has NASA repeating its lie about Dragon being the only spacecraft ever to provide an escape option all the way to orbit.  In fact, every crew-carrying craft except Voskhod and the Shuttle has had that capability.

They mean that their LAS still works past the time that a tower system has been jettisoned.

And other vehicles, past and planned for the future, will also have an escape option, both with and without a tower jettison. 

SpaceX is really not plowing new ground here, as much as they want to claim they are. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 02/01/2012 08:09 pm
I've taken measures of the SuperDracos angle from the Red Dragon video (50 degrees) and the Reusable Landing (40 degrees). Those would mean that if it axially does 6,804kgf (15,000klbf):

Cos(50 deg)=0.643
-> 4,373kgf (9.64klbf) impulse per SuperDraco or 34,990kgf (77.13klbf) total

Cos(45 deg)=0.707
-> 4,808kgf (10.60klbf) impulse per SuperDraco 38,490kgf (84.85klbf total)

Cos(40 deg)=0.766
-> 5,212kgf 11.49klbf impulse per SuperDraco 41,700kgf (91.93klbf total)

If the Dragon fully loaded weights 10,200 kg (22,440lb), that would mean an acceleration of what? 3.5G, 3.8G and 4.1G?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: tigerade on 02/01/2012 08:10 pm
Neat video.  I imagine that SpaceX will build a dragon or two just for the sake of full-scale tests of the LAS.  (sound correct?).  I am also wondering if testing the LAS engines will be part of the normal qualification testing for each flight.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/01/2012 08:12 pm
Taking angles from the video is going to be misleading. It's for PR purposes. If the cosine losses are too great, they may be forced to look at other approaches like larger exterior engine pods, pop-out engines (which I recall being suggested in some NASA Mars propulsive reentry concepts), etc, at least when it comes time to use the thrusters for something other than abort. Obviously, those "solutions" present their own host of problems.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Namechange User on 02/01/2012 08:15 pm
Neat video.  I imagine that SpaceX will build a dragon or two just for the sake of full-scale tests of the LAS.  (sound correct?).  I am also wondering if testing the LAS engines will be part of the normal qualification testing for each flight.

It would be a silly waste of resources to build a "Dragon or two", which I interpret to mean full-up vehicles, just to qualify the LAS.

Also, no doubt the engines will be tested prior to delivery for integration to make sure they meet spec requirements.  As for hot-firing them afterward or on every "flow" (assuming reusability) is likely not required or at least should not be if turnaround and maintenance is done correctly. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris Bergin on 02/01/2012 08:18 pm
FYI I'll be covering this tomorrow with a wider angle approach of looking a the LAS dev since CxP, MLAS....and through to this one with SpaceX.

Today was about the orbiters, understandably.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: tigerade on 02/01/2012 08:19 pm
It would be a silly waste of resources to build a "Dragon or two", which I interpret to mean full-up vehicles, just to qualify the LAS.

Perhaps a "dummy" dragon or some reused dragons?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: apace on 02/01/2012 08:23 pm
It would be a silly waste of resources to build a "Dragon or two", which I interpret to mean full-up vehicles, just to qualify the LAS.

Perhaps a "dummy" dragon or some reused dragons?

If they want to test also controlled landing, they need something like a full dragon (parachutes, dracos, electronics, telemetry, etc.)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 02/01/2012 08:28 pm
It would be a silly waste of resources to build a "Dragon or two", which I interpret to mean full-up vehicles, just to qualify the LAS.

I thought both Boeing and SpaceX talked about a max-Q abort test. Probably not with flightworthy capsules, but I did get the impression they were going to waste a launch vehicle in the process, unless they go the way of Apollo and Little Joe II.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Namechange User on 02/01/2012 08:29 pm
It would be a silly waste of resources to build a "Dragon or two", which I interpret to mean full-up vehicles, just to qualify the LAS.

Perhaps a "dummy" dragon or some reused dragons?

If they want to test also controlled landing, they need something like a full dragon (parachutes, dracos, electronics, telemetry, etc.)

Certain systems are needed.  Not everyone of them one would find on a fully operational Dragon.

Also, I would hope SpaceX starts off right and decides to qualify the LAS first and then incremental steps to powered-landing if and when it still makes sense from a technical, schedule, cost/business-case perspective. 

A LAS, per the absolute risk-adverse, is essential to fly crew.  A powered-landing is not. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Namechange User on 02/01/2012 08:32 pm
It would be a silly waste of resources to build a "Dragon or two", which I interpret to mean full-up vehicles, just to qualify the LAS.

I thought both Boeing and SpaceX talked about a max-Q abort test. Probably not with flightworthy capsules, but I did get the impression they were going to waste a launch vehicle in the process, unless they go the way of Apollo and Little Joe II.

I'm sure most will have some sort of plan to do this and test/certify the LAS.  If they want to use a full-up launch vehicle or something else, that is a trade for them to make based on the circumstances/opportunities/risks associated with their internal workings.

But, a full-up vehicle that is flight-worthy in every respect is not required to test the LAS and hence why I said that would seem to be a silly waste of resources. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: apace on 02/01/2012 08:32 pm
Also, I would hope SpaceX starts off right and decides to qualify the LAS first and then incremental steps to powered-landing if and when it still makes sense from a technical, schedule, cost/business-case perspective. 

If you follow the latest announcements of SpaceX, it looks like they go this way. They have downscaled a lot to a more realistic PR about their progress... (in my opinion).
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: apace on 02/01/2012 08:34 pm
But, a full-up vehicle that is flight-worthy in every respect is not required to test the LAS and hence why I said that would seem to be a silly waste of resources. 

I had in mind, that Orbital was contracted to deliver a rocket for one of the max-q tests of one of the new capsules manufacturers... but I have not in mind which one it was.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 02/01/2012 08:44 pm
Neat video.  I imagine that SpaceX will build a dragon or two just for the sake of full-scale tests of the LAS.  (sound correct?).  I am also wondering if testing the LAS engines will be part of the normal qualification testing for each flight.

It would be a silly waste of resources to build a "Dragon or two", which I interpret to mean full-up vehicles, just to qualify the LAS.

There was a photo a while ago that showed a whole bunch of dragons in various stages of development (was it 8 of them?).  Anyways, if these are intended as reusable systems, it isn't like they would expect the dragons to be wasted.  But they would need to replace a parachute for each test I suppose. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Cherokee43v6 on 02/01/2012 08:56 pm
Neat video.  I imagine that SpaceX will build a dragon or two just for the sake of full-scale tests of the LAS.  (sound correct?).  I am also wondering if testing the LAS engines will be part of the normal qualification testing for each flight.

It would be a silly waste of resources to build a "Dragon or two", which I interpret to mean full-up vehicles, just to qualify the LAS.

There was a photo a while ago that showed a whole bunch of dragons in various stages of development (was it 8 of them?).  Anyways, if these are intended as reusable systems, it isn't like they would expect the dragons to be wasted.  But they would need to replace a parachute for each test I suppose. 

There was something I read a year or more ago that indicated that NASA had a requirement (at least initially) that only 'new' Dragons would be allowed to berth with the ISS.

Seems to me that if this were true, then those flown Dragons would easily be available for LAS test vehicles.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 02/01/2012 09:11 pm
There was something I read a year or more ago that indicated that NASA had a requirement (at least initially) that only 'new' Dragons would be allowed to berth with the ISS.

Seems to me that if this were true, then those flown Dragons would easily be available for LAS test vehicles.

No such requirement

http://forum.nasaspaceflight.com/index.php?topic=21923.msg856850#msg856850
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jason1701 on 02/01/2012 09:29 pm
But, a full-up vehicle that is flight-worthy in every respect is not required to test the LAS and hence why I said that would seem to be a silly waste of resources. 

I had in mind, that Orbital was contracted to deliver a rocket for one of the max-q tests of one of the new capsules manufacturers... but I have not in mind which one it was.

Are you thinking of Orion? The ascent abort test was supposed to happen last year. I haven't heard of Orbital doing anything for the new capsules.


Neat video.  I imagine that SpaceX will build a dragon or two just for the sake of full-scale tests of the LAS.  (sound correct?).  I am also wondering if testing the LAS engines will be part of the normal qualification testing for each flight.

It would be a silly waste of resources to build a "Dragon or two", which I interpret to mean full-up vehicles, just to qualify the LAS.

There was a photo a while ago that showed a whole bunch of dragons in various stages of development (was it 8 of them?).  Anyways, if these are intended as reusable systems, it isn't like they would expect the dragons to be wasted.  But they would need to replace a parachute for each test I suppose. 

Those Dragons were all CRS, which are probably unfeasible to be converted to crew.

Neat video.  I imagine that SpaceX will build a dragon or two just for the sake of full-scale tests of the LAS.  (sound correct?).  I am also wondering if testing the LAS engines will be part of the normal qualification testing for each flight.

It would be a silly waste of resources to build a "Dragon or two", which I interpret to mean full-up vehicles, just to qualify the LAS.

There was a photo a while ago that showed a whole bunch of dragons in various stages of development (was it 8 of them?).  Anyways, if these are intended as reusable systems, it isn't like they would expect the dragons to be wasted.  But they would need to replace a parachute for each test I suppose. 

There was something I read a year or more ago that indicated that NASA had a requirement (at least initially) that only 'new' Dragons would be allowed to berth with the ISS.

Seems to me that if this were true, then those flown Dragons would easily be available for LAS test vehicles.

It's a contract requirement that SpaceX build a new Dragon for each CRS flight. This could change if they get a CRS extension. The Dragons could be reused as Labs, but almost certainly not for LAS testing. The requirements and designs are more different than they seem.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: rcoppola on 02/01/2012 09:30 pm
It was mentioned in the press release that the Super-Dracos burn for 5 seconds at %100 thrust for a Launch abort. For a powered landing, even with deep throttling, where is the extra fuel stored, seeing as how propellent is shared between Dracos for orbital and re-entry maneuvers and Super-Dracos for powered landing?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: rsnellenberger on 02/01/2012 09:59 pm
It was mentioned in the press release that the Super-Dracos burn for 5 seconds at %100 thrust for a Launch abort. For a powered landing, even with deep throttling, where is the extra fuel stored, seeing as how propellent is shared between Dracos for orbital and re-entry maneuvers and Super-Dracos for powered landing?


Are there fuel & oxidizer lines in the umbilical (or space for them)?  If so, they could size the capsule's tanks to the largest single demand (probably powered landing) and then use tanks in the trunk to keep the capsule's tanks fully topped-off throughout the mission.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 02/01/2012 10:01 pm
I've taken measures of the SuperDracos angle from the Red Dragon video (50 degrees) and the Reusable Landing (40 degrees). Those would mean that if it axially does 6,804kgf (15,000klbf):

Cos(50 deg)=0.643
-> 4,373kgf (9.64klbf) impulse per SuperDraco or 34,990kgf (77.13klbf) total

Cos(45 deg)=0.707
-> 4,808kgf (10.60klbf) impulse per SuperDraco 38,490kgf (84.85klbf total)

Cos(40 deg)=0.766
-> 5,212kgf 11.49klbf impulse per SuperDraco 41,700kgf (91.93klbf total)

If the Dragon fully loaded weights 10,200 kg (22,440lb), that would mean an acceleration of what? 3.5G, 3.8G and 4.1G?

I measured 48 degrees so, in Imperial units heaven help me, 120,000 lbf axial implies 15,000 lbf axial from each of eight SDs and 22,400 lbf total thrust each.

I don't think you need to use the angles to calculate the acceleration during abort because the release stated "120,000 pounds of axial thrust ", so with a weight of 22,400 lb the acceleration is 5.4 G.

It also seems that the business about LAS all the way to orbit is kind of silly.  SpaceX seems to be over-empasizing that they have a single LAS system that stays with them, while Apollo, Gemini, etc could have aborted from a second stage failure with other systems, as said by several people. 

What is not clear is why SpaceX doesn't tout more loudly the standard, very big benefit of a reuseable LAS:  they can test it full-up and they can bring it back whole for post-test evaluation.  (Orion's LAS did come back after the test, but....)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 02/01/2012 10:04 pm
It was mentioned in the press release that the Super-Dracos burn for 5 seconds at %100 thrust for a Launch abort. For a powered landing, even with deep throttling, where is the extra fuel stored, seeing as how propellent is shared between Dracos for orbital and re-entry maneuvers and Super-Dracos for powered landing?


Are there fuel & oxidizer lines in the umbilical (or space for them)?  If so, they could size the capsule's tanks to the largest single demand (probably powered landing) and then use tanks in the trunk to keep the capsule's tanks fully topped-off throughout the mission.

There are no Draco or Super Draco tanks in the trunk.  All of the fuel and oxidzer is in the Dragon.  How else could the do powered landings? Where they are going to fit all it is a mystery.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: dcporter on 02/01/2012 10:08 pm
I'd love to hear some more analysis on this.  Musk repeats it often enough to make it sound true, but I've heard it vociferously denied around here that Apollo had blackout periods.  I've also heard Musk refer specifically to the LAS tower jettison as the point at which things could go wrong (albeit they never have); could this be what he's talking about?  Since you don't have to jettison anything, you've removed a potential failure point?
You seem to have forgotten that the Apollo CSM had a very nice AJ10-137 that could very separate the CSM from the S-IVB if in an emergency after the LES had been ejected.

Yessss seems I have. Handy, that. What about Soyuz, any blackouts with its (I assume) tower las? Or is SpaceX really, as has been suggested, making a revolution out of nothing?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 02/01/2012 10:10 pm
Use non-spherical tanks to up capacity?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jason1701 on 02/01/2012 10:21 pm
It was mentioned in the press release that the Super-Dracos burn for 5 seconds at %100 thrust for a Launch abort. For a powered landing, even with deep throttling, where is the extra fuel stored, seeing as how propellent is shared between Dracos for orbital and re-entry maneuvers and Super-Dracos for powered landing?


Are there fuel & oxidizer lines in the umbilical (or space for them)?  If so, they could size the capsule's tanks to the largest single demand (probably powered landing) and then use tanks in the trunk to keep the capsule's tanks fully topped-off throughout the mission.

There are no Draco or Super Draco tanks in the trunk.  All of the fuel and oxidzer is in the Dragon.  How else could the do powered landings? Where they are going to fit all it is a mystery.

They might change the mold line - increase the capsule's dimensions.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Namechange User on 02/01/2012 10:30 pm
It was mentioned in the press release that the Super-Dracos burn for 5 seconds at %100 thrust for a Launch abort. For a powered landing, even with deep throttling, where is the extra fuel stored, seeing as how propellent is shared between Dracos for orbital and re-entry maneuvers and Super-Dracos for powered landing?


Are there fuel & oxidizer lines in the umbilical (or space for them)?  If so, they could size the capsule's tanks to the largest single demand (probably powered landing) and then use tanks in the trunk to keep the capsule's tanks fully topped-off throughout the mission.

There are no Draco or Super Draco tanks in the trunk.  All of the fuel and oxidzer is in the Dragon.  How else could the do powered landings? Where they are going to fit all it is a mystery.

They might change the mold line - increase the capsule's dimensions.

rcoppola,

It's all about prop management.  You assess how much is needed for any given mission.  There are certain things one knows they will want to do. 

Change attitude in orbit, that can be baselined for a "standard" mission, ISS or otherwise. 

Deorbit.  That can also be baselined for a "standard" mission with vehicle weight, altitude, etc.

Landing.  That can also be baselined for a "standard" mission with a given vehicle weight.

Throw a "fudge-factor" of some sort on it if one wants, size the tanks for that. 

Protect for the necessary "red-lines".  The abort case would be enveloped by the above because the reality is the vehicle will not likely be doing a powered-landing. 

Jason,

The above can hopefully fit within the open bays and spaces of the current mold line.  If not, changing that now would essentially be building a whole new Dragon in many respects (aero, thermal, etc).  If there is not sufficent room for the required prop, I would think that SpaceX would want to trade if "starting over" and the money invested in that is really worth it versus what they expect to gain from doing powered-landings and the expected costs divedends there. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: QuantumG on 02/01/2012 10:51 pm
Getting mad that SpaceX and NASA are repeating some claim that you've Clearly Shown To Be False (tm) in an Internet forum is a little silly. Go find someone with credibility (read: a claim to celebrity expert status), and have them write a nice letter to Mr Musk or the CCP office explaining why they are wrong. Ask for a retraction or a clarification and it'll probably happen.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: rcoppola on 02/01/2012 11:32 pm
Thanks for the response OV-106. I'll be watching this closely. I am very curious to see if the current mold-line and the baselines that you mentioned will allow for propulsive landing with the current Dragon config. Maybe I'll just e-mail the folks at SpaceX and see if I can get a definitive answer. Probably not, but hey, it's only e-mail..
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 02/01/2012 11:56 pm
Couldn't be used during the initial deceleration phase, though, because the side of Dragon doesn't have heat tiles on it

Would this be something that could be slapped on after the fact without too much trouble?  Some picaX segments up the sides?  (For a Mars landing, it seems that less heatshield material would be required to ablate versus an Earth landing but I'm just guessing on that). 

(nor is the shape there conducive to the aerothermal environment).
Would some disruptive fire from the leading edge thruster(s) create some envelope of protection?
You can't "just slap on" anything, here.

This sort of question need a lot of analysis if its going to work. If it's definitely not going to work, it might just require a napkin or two.


Is it reasonable to guess that this might be part of the reason for the significant cosine loss design? 

Also, at 4 seconds into the video, we see some displays that look like the Cockpit of a Tesla model S.  Are those screens likely?  Or will there be more knobs and handles than depicted here? 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 02/02/2012 12:07 am

It also seems that the business about LAS all the way to orbit is kind of silly.  SpaceX seems to be over-empasizing that they have a single LAS system that stays with them, while Apollo, Gemini, etc could have aborted from a second stage failure with other systems, as said by several people. 


Much the engine out capability which only exists for less than 1/3 of the flight.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: crab nebula2 on 02/02/2012 01:04 am
Now that the super Draco's have been demonstrated I'm wondering what is the next likely test for the LAS.  A pad abort would seem to be the least expensive test of the integrated LAS, and it could be conducted at a remote site, but won't a max Q abort test eventually be needed?  Would a max Q test need a full Falcon 9 first stage with a dummy 2nd stage?  And would it have to be conducted at the Cape?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Matthew Haywood on 02/02/2012 01:18 am
Thanks for the response OV-106.

Yes, very interesting. This is only a forum chat, but I hope you don't get shouted down by blogavists who only want to hear about fluffy clouds on SpaceX discussion.

I love the company, but the worst fear is lack of examination from the public, because when that day comes, as it does to all companies, and they have a big failure, like they have three times before, the realization this is rocket science will be required, more than fanboys dissing NASA and thinking SpaceX will save us all.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: antiquark on 02/02/2012 01:19 am
It's actually amazing that each superDraco has the same thrust as the Apollo CSM main engine.  Keep in mind that the AJ10-137 engine was around 10 feet in length, about the same height as the entire Dragon capsule.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kevin-rf on 02/02/2012 01:30 am
It's actually amazing that each superDraco has the same thrust as the Apollo CSM main engine.  Keep in mind that the AJ10-137 engine was around 10 feet in length, about the same height as the entire Dragon capsule.

I am sure you could give a Super Draco the similar sized vacuum optimized bell. It would improve the ISP, but there are considerable trade-offs. SpaceX is sacrificing ISP for a compact high thrust system that works at sea level. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Namechange User on 02/02/2012 01:42 am
It's actually amazing that each superDraco has the same thrust as the Apollo CSM main engine.  Keep in mind that the AJ10-137 engine was around 10 feet in length, about the same height as the entire Dragon capsule.

I am sure you could give a Super Draco the similar sized vacuum optimized bell. It would improve the ISP, but there are considerable trade-offs. SpaceX is sacrificing ISP for a compact high thrust system that works at sea level. 

A vacuum-optimized bell for something that is intentionally meant to be used in the atmosphere predominantly would not be a smart thing.  The trade is to size the bell to wherever the "sweet-spot" is that gives the best performance across the operating altitude without geting flow separation in the nozzle.   
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: beancounter on 02/02/2012 02:02 am
Thanks for the response OV-106.

Yes, very interesting. This is only a forum chat, but I hope you don't get shouted down by blogavists who only want to hear about fluffy clouds on SpaceX discussion.

I love the company, but the worst fear is lack of examination from the public, because when that day comes, as it does to all companies, and they have a big failure, like they have three times before, the realization this is rocket science will be required, more than fanboys dissing NASA and thinking SpaceX will save us all.

Well you've just said that they've had 3 failures already, although to be fair, you should characterise one of them as a test, but anyway, the fact is that they've had failures in all their vehicles (characterising 'failure' broadly here) and they continue on improving their hardware and no doubt software.  Isn't that what it's all about?  There aim is to make space travel more reliable (by using modern tech) and more cost efficient which incidentally isn't NASA's brief so far as I'm aware.  A report just out, in fact, disses on NASA for relying on 40 year old technology.  It doesn't need me adding to it.
The bit around public scrutiny is balony as well.  NASA is providing that where it's required, in the COTS and CCDev programs.  The rest is only SpaceXs business since they are a private company.  How much public scrutiny takes place with Boeing, LockMart, Orbital, et al?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Namechange User on 02/02/2012 02:16 am
There aim is to make space travel more reliable (by using modern tech) and more cost efficient which incidentally isn't NASA's brief so far as I'm aware.  A report just out, in fact, disses on NASA for relying on 40 year old technology.  It doesn't need me adding to it.

Last time I checked, Dragon was a capsule.

Last time I checked, Falcon was a rocket that follows the conventional laws of physics.

Last time I checked, SpaceX has not invented anything fundamentally new. 

Last time I checked, Merlin was based off of NASA's Fastrac engine.

Now I don't know what the "report" specifically mentioned as I have trouble calling it up on my vacum-tube computer and punch-card reader.  I wonder if the "report" also was critical of the automotive industry for still making vehicles with the internal combustion engine and wheels. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Andy USA on 02/02/2012 03:18 am
Thread slightly trimmed, so now back on track. However this is a specific subject thread on a SpaceX section.

This means this thread is only for the subject title. Elon's car company is off topic entirely anyway.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Proponent on 02/02/2012 04:08 am
NASA post with a few more details....

http://www.nasa.gov/exploration/commercial/crew/spacex_superdraco.html (http://www.nasa.gov/exploration/commercial/crew/spacex_superdraco.html)

Quote
SpaceX Test Fires Engine Prototype for Astronaut Escape System

<snip>

"Crews will have the unprecedented ability to escape from danger at any point during the launch because the launch abort* engines are integrated into the side walls of the vehicle," Musk said

Now SpaceX has NASA repeating its lie about Dragon being the only spacecraft ever to provide an escape option all the way to orbit.  In fact, every crew-carrying craft except Voskhod and the Shuttle has had that capability.

They mean that their LAS still works past the time that a tower system has been jettisoned.

Apollo's abort system worked past the time that the tower was jettisoned too.  Following tower jettison, Apollo's escape system was much like Dragon's:  it made use of an engine integrated into the spacecraft that was normally used for purposes other than launch abort.  I don't see what justifies Musk's use of the word "unprecedented" in regard to Dragon.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: QuantumG on 02/02/2012 04:10 am
I don't see what justifies Musk's use of the word "unprecedented" in regard to Dragon.

You're not going to get an answer from him here. If you do, please do let us all know.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: AS-503 on 02/02/2012 04:13 am
Super Draco thrust DOES NOT equal Apollo CSM thrust.
There is no way a single Super Draco is in the ballpark of 20,500lbs.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: nblackwell on 02/02/2012 04:18 am
Based on what? And define "ballpark".

Super Draco thrust DOES NOT equal Apollo CSM thrust.
There is no way a single Super Draco is in the ballpark of 20,500lbs.


Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/02/2012 04:19 am
Super Draco thrust DOES NOT equal Apollo CSM thrust.
There is no way a single Super Draco is in the ballpark of 20,500lbs.


Ummm, why not? High enough pressure, big enough throat and you get 20klbf. It's not some sort of contest, anyway.

Of course, it surely only shares propellant and a name with the Draco thruster.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jason1701 on 02/02/2012 04:35 am
NASA post with a few more details....

http://www.nasa.gov/exploration/commercial/crew/spacex_superdraco.html (http://www.nasa.gov/exploration/commercial/crew/spacex_superdraco.html)

Quote
SpaceX Test Fires Engine Prototype for Astronaut Escape System

<snip>

"Crews will have the unprecedented ability to escape from danger at any point during the launch because the launch abort* engines are integrated into the side walls of the vehicle," Musk said

Now SpaceX has NASA repeating its lie about Dragon being the only spacecraft ever to provide an escape option all the way to orbit.  In fact, every crew-carrying craft except Voskhod and the Shuttle has had that capability.

They mean that their LAS still works past the time that a tower system has been jettisoned.

Apollo's abort system worked past the time that the tower was jettisoned too.  Following tower jettison, Apollo's escape system was much like Dragon's:  it made use of an engine integrated into the spacecraft that was normally used for purposes other than launch abort.  I don't see what justifies Musk's use of the word "unprecedented" in regard to Dragon.

Wouldn't the SPS take longer to turn on, and accelerate the stack slower, than would Dragon's LAS? If so, could we call Dragon's LAS safer?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Proponent on 02/02/2012 05:16 am
I can see how Dragon's LAS might provide a little more margin than an SPS abort, but I would think that if the improvement were large, Apollo's designers probably would have kept the Apollo LES tower attached longer and accepted the weight penalty.  In any case, the ability to abort all the way to orbit is not unprecedented.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 02/02/2012 07:47 am
What sort of isp can be guesstimate for the Super Draco? Given the few details we now have of it, that is.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 02/02/2012 11:21 am

Wouldn't the SPS take longer to turn on, and accelerate the stack slower, than would Dragon's LAS? If so, could we call Dragon's LAS safer?

Why?  If it doesn't need to*, then it is a meaningless point?

* hint, it doesn't need to.  The air density is low therefore a shock wave doesn't propagate enough energy to matter.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 02/02/2012 11:23 am
Super Draco thrust DOES NOT equal Apollo CSM thrust.
There is no way a single Super Draco is in the ballpark of 20,500lbs.

Based on what information.  Or is your point based on your Apollo bias.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: TrueBlueWitt on 02/02/2012 01:24 pm
Is there enough Dv available with a to ensure Dagon could steer itself to a water landing somewhere close to land..  Or predefined landing sites like shuttle could with TAL?  That would be a major advantage in abort scenarios above traditional Solid Fueled LAS.  Correct?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Cinder on 02/02/2012 01:35 pm
Is there enough Dv available with a
.. with a ?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: yg1968 on 02/02/2012 01:43 pm
Is there enough Dv available with a
.. with a ?
way
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: AS-503 on 02/02/2012 01:47 pm
Shoot....you guys are a tough crowd.

My comment about Super Draco not being equal to the Apollo CSM thrust was related to this comment posted by anitquark....

   "It's actually amazing that each superDraco has the same thrust as the Apollo CSM main engine.  Keep in mind that the AJ10-137 engine was around 10 feet in length, about the same height as the entire Dragon capsule."

I now realize my vague wording of "ballpark" was not an optimal choice.
I simply meant not equal.

Isn't the *apparent* thrust for the Super Draco aprox. 15,000lbs?
If so, this in the "ballpark" of 20,500lbs...again my poor choice of words.

As for Jim.....he knows I have an Apollo bias....but I also have a Kool-Aid smile thanks to SpaceX.

Go SpaceX!
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kevin-rf on 02/02/2012 02:00 pm
AS-503

I think the answer is, is the Super Draco has a short truncated nozzle, where the CSM had the long nozzle to maximize the ISP in a Vacuum. You could make a Super Draco with a large vacuum optimized nozzle, but that is not the environment that the super draco is ment to operate in.

If you give the Super Draco a vac. optimized nozzle, the vac. thrust will increase putting you in the "ball park". But again the Super Draco is not ment as much for vacuum operations but operations that are not in vacuum (LAS and propulsive sea level landings).
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: antiquark on 02/02/2012 02:06 pm
Isn't the *apparent* thrust for the Super Draco aprox. 15,000lbs?
If so, this in the "ballpark" of 20,500lbs...again my poor choice of words.

The press release says the axial thrust of all 8 Super Dracos is 120,000 lbs. So if you factor in the cosine loss of 0.707 (45 degrees) you get

120000 / 8 / 0.707 = 21,216 lbs.

So actually pretty close to the CSM thrust.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: AS-503 on 02/02/2012 02:18 pm
Jim's comment about my Apollo bias has got me thinking...

With the comparisons of Apollo CSM to the new Super Draco.......

As we know, the Crewed Dragon will apparently fly with the Draco powered abort and landing system with parachutes included for redundancy.

 
My question is: Could this system do an "Apollo 8" by using the new Super Draco configuration to do the LOI braking burn AND (of course) the TEI burn?

If this is the case a lunar orbit mission with *no* service module propulsion would be possible.

If the Super Dracos have enough propellant/DeltaV for this mission profile, then the parachutes would most likely be the only landing option after such a mission profile.


Any thoughts?

Jim, please don't ask "what for?" when it comes to a manned lunar orbit mission. I just get all teary-eyed when I think about humans *visiting* the Moon, but I also realise that there is almost no *practical* value for such a mission.

   
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: AS-503 on 02/02/2012 02:25 pm
Would'nt the effective thrust translate to [120000/8]cos(45)= 10,605lbs effective thrust through the center-line of the capsule per Super Draco?

Your math shows [120000/8]/cos(45), when should'nt it be multiplied by cos(45)?
Assuming that 45 is the actual degree of offset of the Super Draco within the walls of the Dragon.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Ben the Space Brit on 02/02/2012 02:30 pm
My question is: Could this system do an "Apollo 8" by using the new Super Draco configuration to do the LOI braking burn AND (of course) the TEI burn?

No, and it has nothing to do with the engines.  Crewed Dragon, as it is planned, is an LEO-only vehicle.  It doesn't have the shielding, cooling and communications sysetm it would require for any BEO flight.  A BEO Dragon would be a heavier vehicle and might need a redesign before it could fly with the planned abort system.

That aside, I undestand that extra hypergol tanks can be carried in the trunk, greatly increasing the RCS and LAS propellent supply.  This potentially could turn Super-Draco into an ad-hoc MPS of sorts.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 02/02/2012 02:54 pm
Jim's comment about my Apollo bias has got me thinking...

With the comparisons of Apollo CSM to the new Super Draco.......

As we know, the Crewed Dragon will apparently fly with the Draco powered abort and landing system with parachutes included for redundancy.

 
My question is: Could this system do an "Apollo 8" by using the new Super Draco configuration to do the LOI braking burn AND (of course) the TEI burn?

If this is the case a lunar orbit mission with *no* service module propulsion would be possible.

If the Super Dracos have enough propellant/DeltaV for this mission profile, then the parachutes would most likely be the only landing option after such a mission profile.


   

Thrust does not equate to impulse.
The SME and draco are sized for different missions and uses.  Just because they have the same thrust doesn't mean they can do the same things.   The Dragon (as is) does not have the propellant capacity for a lunar mission
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: AS-503 on 02/02/2012 03:40 pm
Hey Jim,

Is this (below) what you were refering to with regard to impulse?

Impulse = F/W. Where F is average thrust in pounds and W is propellant consumed in pounds per second. The pounds cancel out and we are left with a measure of efficiency with units of seconds.

Because we do not know what "W" is with regard to the Super Draco we can not know what it's specific impulse is.

I know you don't need a refresher on what impulse means, I just wanted to be sure we are talking about the same thing. Thanks

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kabloona on 02/02/2012 03:48 pm
Would'nt the effective thrust translate to [120000/8]cos(45)= 10,605lbs effective thrust through the center-line of the capsule per Super Draco?

Your math shows [120000/8]/cos(45), when should'nt it be multiplied by cos(45)?
Assuming that 45 is the actual degree of offset of the Super Draco within the walls of the Dragon.

The press release states that the 8 Super Dracos built into the side walls would combine for an AXIAL thrust of up to 120klbf. The word AXIAL implies that its 120klbf AFTER multiplying by .707 for cosine loss. Therefore, to obtain thrust of one Super Draco, divide by .707 and then by 8. That's what antiquark did.

As for the assumption of a 45 degree angle, if you slap a protractor on the artist's conceptual "photo" of a Dragon landing, the exhaust plumes come out spot on at 45 degrees. Assuming the artist is not assuming  ;)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: dunderwood on 02/02/2012 03:49 pm
Specific Impulse is thrust exhaust velocity divided by the gravitational constant, leaving units of seconds.

Impulse usually refers to Force x Time.  Impulse is measured in things like 'Newton-seconds' or 'pound-seconds.'

Edit: Corrected, per Robotbeat.  Brainfart on my part.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 02/02/2012 03:51 pm
Would'nt the effective thrust translate to [120000/8]cos(45)= 10,605lbs effective thrust through the center-line of the capsule per Super Draco?

Your math shows [120000/8]/cos(45), when should'nt it be multiplied by cos(45)?
Assuming that 45 is the actual degree of offset of the Super Draco within the walls of the Dragon.

The press release states that the 8 Super Dracos built into the side walls would combine for an AXIAL thrust of up to 120klbf. The word AXIAL implies that its 120klbf AFTER multiplying by .707 for cosine loss. Therefore, to obtain thrust of one Super Draco, divide by .707 and then by 8. That's what antiquark did.
Could Chris get a quote on this? it has been a source of discussion. I don't think that the thrust of each SD would be a proprietary thing (I hope).
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/02/2012 04:04 pm
Specific Impulse is thrust divided by the gravitational constant, leaving units of seconds.

Impulse usually refers to Force x Time.  Impulse is measured in things like 'Newton-seconds' or 'pound-seconds.'
No, specific impulse is exhaust velocity divided by gravitational acceleration.

You can have a little thruster and a big rocket engine with the same Isp but orders of magnitude different thrust.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 02/02/2012 04:15 pm
Specific Impulse is thrust divided by the gravitational constant, leaving units of seconds.

Impulse usually refers to Force x Time.  Impulse is measured in things like 'Newton-seconds' or 'pound-seconds.'

Bingo.  And time is related to propellant capacity
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: oldAtlas_Eguy on 02/02/2012 05:06 pm
Depending on the actual SD engine thrust of somewhere between 15klbf and 21klbf, the ISP with a Dragon propellant load of 1290kg is somewhere between 211s and 299s. If a better prop load number is available for the Crew Dragon then a better accurate ISP value range can be generated.

SD Thrust(kgf) * 5sec / prop weight(kg) = ISP
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lobo on 02/02/2012 05:11 pm
AS-503

I think the answer is, is the Super Draco has a short truncated nozzle, where the CSM had the long nozzle to maximize the ISP in a Vacuum. You could make a Super Draco with a large vacuum optimized nozzle, but that is not the environment that the super draco is ment to operate in.

If you give the Super Draco a vac. optimized nozzle, the vac. thrust will increase putting you in the "ball park". But again the Super Draco is not ment as much for vacuum operations but operations that are not in vacuum (LAS and propulsive sea level landings).

Keep in mind that Elon seems to really want Dragon landing on Mars, and Mars is not a vacuum, but not far from it.  Like 1% of EArth at Sea Level?  HOw would that near vacuum environment effect the SuperDraco's when trying to land on Mars, if they are the same as being developed now?  i"m not sure how you could add nozzle to them, without them sticking way out, and burning off during atmospheric entry.  Granted, that's a long way down the road, but it's an interesting question nonetheless.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lobo on 02/02/2012 05:18 pm
My question is: Could this system do an "Apollo 8" by using the new Super Draco configuration to do the LOI braking burn AND (of course) the TEI burn?

No, and it has nothing to do with the engines.  Crewed Dragon, as it is planned, is an LEO-only vehicle.  It doesn't have the shielding, cooling and communications sysetm it would require for any BEO flight.  A BEO Dragon would be a heavier vehicle and might need a redesign before it could fly with the planned abort system.

That aside, I undestand that extra hypergol tanks can be carried in the trunk, greatly increasing the RCS and LAS propellent supply.  This potentially could turn Super-Draco into an ad-hoc MPS of sorts.

Couldn't plume impingement from SuperDraco's firing along side the trunk, damage a trunk?  Would you want to fire them with any trunk still attached?

Perhaps a new trunk could be designed to withstand the impingement?...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: TrueBlueWitt on 02/02/2012 05:19 pm
Is there enough Dv available with a
.. with a ?

Is there enough fuel in the Dragon and thrust with super Dracos to change trajectory so comes down at predefined "abort" sites.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: wolfpack on 02/02/2012 05:23 pm

Is there enough fuel dragon with super Dracos to change trajectory so comes down at predefined "abort" sites.

I would think the overriding premise of an abort is to save the crew. Since it's a capsule with parachutes, why does the landing site matter? As longs as it is reachable by SAR, it's good enough. Also, wouldn't the abort burn up all the propellant? Seems it would be safer to descend through the atmosphere without any propellant load remaining in the tanks.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: peter-b on 02/02/2012 05:26 pm
I don't understand the units being used in this thread. kgf? Seriously? What's wrong with Newtons?  >:(
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kch on 02/02/2012 05:35 pm
I don't understand the units being used in this thread. kgf? Seriously? What's wrong with Newtons?  >:(

Nothing -- they're very tasty (unless you don't like figs)!  ;)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: deltaV on 02/02/2012 05:49 pm
I don't understand the units being used in this thread. kgf? Seriously? What's wrong with Newtons?  >:(
Multiplying by 1 is a lot easier than multiplying by 9.8whatever.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 02/02/2012 05:50 pm
I don't understand the units being used in this thread. kgf? Seriously? What's wrong with Newtons?  >:(
Newtons are great for acceleration in space. Kgf are slightly easier for launch vehicles and LAS. You have to advantages. For knowing T/W at the surface, it's easier. And since the difference in acceleration is 9.8, which is equal amount to the gravity constant, you get your acceleration directly as Gs, rather than m/s when using N.
As soon as you start calculating cos(b).G as an additional vector, you'd better using N. That's why Russians usually quote their rockets in kgf.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/02/2012 05:57 pm
AS-503

I think the answer is, is the Super Draco has a short truncated nozzle, where the CSM had the long nozzle to maximize the ISP in a Vacuum. You could make a Super Draco with a large vacuum optimized nozzle, but that is not the environment that the super draco is ment to operate in.

If you give the Super Draco a vac. optimized nozzle, the vac. thrust will increase putting you in the "ball park". But again the Super Draco is not ment as much for vacuum operations but operations that are not in vacuum (LAS and propulsive sea level landings).

Keep in mind that Elon seems to really want Dragon landing on Mars, and Mars is not a vacuum, but not far from it.  Like 1% of EArth at Sea Level?  HOw would that near vacuum environment effect the SuperDraco's when trying to land on Mars, if they are the same as being developed now?  i"m not sure how you could add nozzle to them, without them sticking way out, and burning off during atmospheric entry.  Granted, that's a long way down the road, but it's an interesting question nonetheless.
Even without any nozzle extension, the Isp will be considerably higher in vacuum than at Earth surface pressure.

For a Dragon landing on Mars, I suspect there would be modifications done to improve Isp (such as a larger nozzle) and thus payload mass, even if the propaganda right now is that the same vehicle (essentially unchanged) could be used for both Earth and Mars.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: TrueBlueWitt on 02/02/2012 06:18 pm

Is there enough fuel dragon with super Dracos to change trajectory so comes down at predefined "abort" sites.

I would think the overriding premise of an abort is to save the crew. Since it's a capsule with parachutes, why does the landing site matter? As longs as it is reachable by SAR, it's good enough. Also, wouldn't the abort burn up all the propellant? Seems it would be safer to descend through the atmosphere without any propellant load remaining in the tanks.

Your statement "reachable by SAR" is the key.. For Abort scenarios where you don't need to burn all the Fuel for high G accleration away from the stage.. can you use some of that fuel to change trajectory so your landing would be much more readily accessible by SAR.. or to avoid landing in areas of bad weather where SAR would have difficult time reaching the capsule.

What does the trajectory look like to ISS? What are the zones they'd land in at each point in an Abort?  Somehow I don't think dumping in the North Atlantic, or in the mountains somewhere in Northern europe/Russia in Winter.. let's say 500 miles from nearest SAR base in bad weather would be good for crew survivability.

My question is.. would the ability to steer away from bad weather/terrain, and/or abort to predetermined landing zones near SAR assets help your LOC numbers.. and decrease potential weather scrubs due to bad weather. in the likely abort zones.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: cuddihy on 02/02/2012 06:46 pm
Jim's comment about my Apollo bias has got me thinking...

With the comparisons of Apollo CSM to the new Super Draco.......

As we know, the Crewed Dragon will apparently fly with the Draco powered abort and landing system with parachutes included for redundancy.
 
My question is: Could this system do an "Apollo 8" by using the new Super Draco configuration to do the LOI braking burn AND (of course) the TEI burn?

If this is the case a lunar orbit mission with *no* service module propulsion would be possible.

If the Super Dracos have enough propellant/DeltaV for this mission profile, then the parachutes would most likely be the only landing option after such a mission profile.


My answer with these restrictions would be a clear "NO", you can't fit enough propellant mass (1290 kg in cargo*corrected*) in the capsule to do this, even if you expand the tanks into the current hull area. (which makes it even more cramped).

I don't understand the restriction of no additional SM propulsion really, since you have to have the Dragon SM ("trunk") to provide power and cooling anyway. So why not add a single modified "SM" SDT in the trunk, with Vacuum nozzle, tanking & plumbing to support?

The additional mass is made up for by getting rid of Cosine losses & increased vacuum efficiency of a "SM" SDT vs. using the abort engines. In other words, to do this without a SM external to the capsule engine you have to add a larger mass of tanking & propellants than you save by using already installed engines.

**with numbers:

assume loaded dragon crew + trunk =~6500 kg
assume Super Draco Is=~280s. with expected Cosine loss ~.80. Ergo Ve=~2200 m/s
assume Dragon crew boosts prop loading to 1600 kg
dry Dragon crew + trunk = 4900 kg

Max delta v using LAS = 2200*ln(6500/4900) = 621 m/s

Delta V required for (LOI+TEI) = 850 m/s (pretty normal profile, google it)

Interestingly, if you use Dracos instead of SDTs, with Is 304, Ve=2384 m/s, and it's closer, 673 m/s, but still not 850 m/s.

Of course, it's more than enough for a lunar flyby, still short for a LOI/TEI

****

Anyway, I know this answer pulls it OT, but I needed to explain why a LAS doesn't work for LOI and TEI, even if the launcher alone can get you fully into TLI.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/02/2012 07:11 pm
Jim's comment about my Apollo bias has got me thinking...

With the comparisons of Apollo CSM to the new Super Draco.......

As we know, the Crewed Dragon will apparently fly with the Draco powered abort and landing system with parachutes included for redundancy.
 
My question is: Could this system do an "Apollo 8" by using the new Super Draco configuration to do the LOI braking burn AND (of course) the TEI burn?

If this is the case a lunar orbit mission with *no* service module propulsion would be possible.

If the Super Dracos have enough propellant/DeltaV for this mission profile, then the parachutes would most likely be the only landing option after such a mission profile.


My answer with these restrictions would be a clear "NO", you can't fit enough propellant mass (1800 kg) in the capsule to do this, even if you expand the tanks into the current hull area. (which makes it even more cramped).

I don't understand the restriction of no additional SM propulsion really, since you have to have the Dragon SM ("trunk") to provide power and cooling anyway. So why not add a single modified "SM" SDT in the trunk, with Vacuum nozzle, tanking & plumbing to support?

The additional mass is more than made up for by getting rid of Cosine losses & increased vacuum efficiency of a "SM" SDT vs. using the abort engines. In other words, to do this without a SM external to the capsule engine you have to add a larger mass of tanking & propellants than you save by using already installed engines.

Anyway, I know this answer pulls it OT, but I needed to explain why a LAS doesn't work for LOI and TEI, even if the launcher alone can get you fully into TLI.
Depends entirely on the lunar altitude your tend to insert in. If you do a mission profile similar to Orion's first planned crewed mission, I'm not so sure the answer would be "no." Of course, you probably wouldn't use the abort engines for it but the regular Dracos.

For Apollo, LOI was about 900m/s and TEI was about 1km/s. But that was Low Lunar Orbit. Higher lunar orbit (or a Lagrange Point) like Orion's first manned mission would be a lot lower delta-v requirements, depending on how long you're willing to wait. Could get down to around half a km/s delta-v total, which should be doable with a lightened Dragon or slightly expanded prop tanks. Not saying this is a good idea. Of course, a Zond-like trajectory would clearly be possible.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: oldAtlas_Eguy on 02/02/2012 07:21 pm
I posted this in another thread and should answer some questions about usability of FH, SD in a CSM role where it is an addition to the Trunk. Not using the LAS thrusters for any of it leaving them for a propulsive landing or emergency contingencies. This hopefully will quiet the OT discussion of this and redirect the discussion to the following thread:
http://forum.nasaspaceflight.com/index.php?topic=27639.15 (http://forum.nasaspaceflight.com/index.php?topic=27639.15)
Quote
I was doing a what if:
Using a vac optimized SD (ISP 290s) on a stretched Dragon Trunk with a 5,000 kg prop load on top of its normal Dragon and Trunk weight of 9,500kg bringing total weight to 15,000kg, the TLI payload weight of an FH, then this configuration would have a “CSM” like delta V of 1.15km/s. This is sufficient to dock with an EML1/2 Gateway and do the return burn to deliver cargo or crew to the Gateway (return is ~.7km/s leaving ~.4km/s for maneuvering to the Gateway, without burning any of the Dragon’s internal prop load except for RCS tasks.

This is just to show that the SD’s have a far greater possible use than just as a LAS in SpaceX’s future.

For the Moon Dragon to and from EML1/2 is the extent all the existing or soon too exist propulsion and spacecraft elements can do. If you’re looking to land a Dragon on the surface there is just not enough capability to do it with the existing or soon to exist systems.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jason1701 on 02/02/2012 08:14 pm
The above can hopefully fit within the open bays and spaces of the current mold line.  If not, changing that now would essentially be building a whole new Dragon in many respects (aero, thermal, etc).  If there is not sufficent room for the required prop, I would think that SpaceX would want to trade if "starting over" and the money invested in that is really worth it versus what they expect to gain from doing powered-landings and the expected costs divedends there. 

There is not enough space in the service section for eight Estes motors, let alone hydrazine monsters with all the associated plumbing. The problem isn't the prop - Dragon's total prop supply may not be increased. Rather, it's the volume requirement of the eight engines. There is absolutely no way to fit those in the current service section. The mold line will be changed, without a doubt.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 02/02/2012 08:15 pm
Before using additional SD on a trunk, have anyone considered using a Kestrel engine? Those are TRL 8, you know, and have better isp.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: oldAtlas_Eguy on 02/02/2012 08:23 pm
Before using additional SD on a trunk, have anyone considered using a Kestrel engine? Those are TRL 8, you know, and have better isp.

The problem with a Kestrel engine is prop storage over several weeks. otherwise it would be a good choice.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lobo on 02/02/2012 10:14 pm

Is there enough fuel dragon with super Dracos to change trajectory so comes down at predefined "abort" sites.

I would think the overriding premise of an abort is to save the crew. Since it's a capsule with parachutes, why does the landing site matter? As longs as it is reachable by SAR, it's good enough. Also, wouldn't the abort burn up all the propellant? Seems it would be safer to descend through the atmosphere without any propellant load remaining in the tanks.

Your statement "reachable by SAR" is the key.. For Abort scenarios where you don't need to burn all the Fuel for high G accleration away from the stage.. can you use some of that fuel to change trajectory so your landing would be much more readily accessible by SAR.. or to avoid landing in areas of bad weather where SAR would have difficult time reaching the capsule.

What does the trajectory look like to ISS? What are the zones they'd land in at each point in an Abort?  Somehow I don't think dumping in the North Atlantic, or in the mountains somewhere in Northern europe/Russia in Winter.. let's say 500 miles from nearest SAR base in bad weather would be good for crew survivability.

My question is.. would the ability to steer away from bad weather/terrain, and/or abort to predetermined landing zones near SAR assets help your LOC numbers.. and decrease potential weather scrubs due to bad weather. in the likely abort zones.

Well, I'm no expert, so this is all pure specualtion, but the advantage the DRagon system has, beyond the obvious ones, is that it's riding on a liquid rocket, and they don't need to outrun a burning SRB.  If the F9 blows up, then the LAS system should only need a short burn to get clear of the plume and debris which would be rapidly decelerating.  If the abort is due to a non-explosive reason, like a critical guidence problem, or critical multi-engine problem, then the engines would be shut down right after the abort, so again, likely only a short LAS burn to get clear of the decelerating F9 core. 
I think I heard DRagon could abort-to-orbit if the abort was late enough during the ascent, and in that case, it might require a longer LAS burn, but then they could maneuver DRagon to pick a favorable reentry profile.

In the first two cases, I could see potentially not a full LAS burn, so that there would be propellent left to do some course corrections to get a favorable descent area.  In the latter case, they'd be in low orbit and the RCS system could position them into a reentry profile for a favorable target zone.

Agian, that's speculation,.  Maybe there's only enough propellent in the LAS system to -just- clear a plume/debris cloud or a shut down F9 core, and none left for anything more.  But, if they are sizing this system to do a full propulsive landing, I'd think there'd be more propellent than just the burn that'd be required to get clear of a debris cloud or shut down core.  Guestimate.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: cuddihy on 02/02/2012 10:42 pm
The above can hopefully fit within the open bays and spaces of the current mold line.  If not, changing that now would essentially be building a whole new Dragon in many respects (aero, thermal, etc).  If there is not sufficent room for the required prop, I would think that SpaceX would want to trade if "starting over" and the money invested in that is really worth it versus what they expect to gain from doing powered-landings and the expected costs divedends there. 

There is not enough space in the service section for eight Estes motors, let alone hydrazine monsters with all the associated plumbing. The problem isn't the prop - Dragon's total prop supply may not be increased. Rather, it's the volume requirement of the eight engines. There is absolutely no way to fit those in the current service section. The mold line will be changed, without a doubt.

Haa haa haa. Can I ask how you know this? If true that pretty much kills the "we're building Dragon cargo so that it already meets crew requirements" argument for SpaceX.

It also explains with all the PR why they have never released a picture that shows how crowded the service section actually is -- the pretty CADs always show lots of space in there.

As well as "Dragon will already have flown to the Space Station multiple times" argument. If the mold line changes, you are indeed now talking about a different spacecraft. Period. I wonder if Musk had had it to do over again if he would have made Dragon bigger.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris Bergin on 02/03/2012 02:26 am
Here's my article on this.

1) I didn't want to run with this news yesterday, as yesterday was about the orbiters, obviously.

2) I didn't want to just rehash SpaceX's presser, so I did a 1960s to Mars style article covering the likes of the Constellation's LAS efforts....I'll give it a standalone article given SpaceX is one part of this:

SpaceX Dragon advancing the Launch Abort System to new heights
http://www.nasaspaceflight.com/2012/02/spacex-dragon-advancing-launch-abort-system-new-heights/
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: QuantumG on 02/03/2012 02:31 am
I didn't want to just reharsh SpaceX's presser

This is why we love Chris.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris Bergin on 02/03/2012 02:32 am
Cause I make silly spelling mistakes on the forum? ;D

(I meant "rehash" :D)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: SpaceX_MS on 02/03/2012 02:43 am
Here's my article on this.

1) I didn't want to run with this news yesterday, as yesterday was about the orbiters, obviously.

2) I didn't want to just rehash SpaceX's presser, so I did a 1960s to Mars style article covering the likes of the Constellation's LAS efforts....I'll give it a standalone article given SpaceX is one part of this:

SpaceX Dragon advancing the Launch Abort System to new heights
http://www.nasaspaceflight.com/2012/02/spacex-dragon-advancing-launch-abort-system-new-heights/

You're not afraid to give NASA a black eye over Constellation, are you! Superb article, covered us really well as usual, appreciate it! Beats the lazy reporting we got for this event.

Love the Mike Griffin drawing!! Looks like something out of Elementary School "when I grow up, I'm going to be a rocket scientist".
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: antiquark on 02/03/2012 02:48 am
FWIW,  Apollo was able to abort all the way into orbit:

http://en.wikipedia.org/wiki/Apollo_abort_modes

However the escape tower wasn't necessary for the later stages.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris Bergin on 02/03/2012 02:55 am
Thanks sir! Got to say, however, I didn't give CxP a black eye, just wrote it up as it happened. Their tests went well, but the program was in trouble pretty much from the start and it never recovered.

Not for me to give anyone a black eye, just reporting documentation and let everyone else make up their own minds.

Heh, yeah - the Griffin sketch is a gift that keeps on giving ;D
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lee Jay on 02/03/2012 02:59 am
That is a really great article, Chris!
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: RocketmanUS on 02/03/2012 03:12 am
Here's my article on this.

1) I didn't want to run with this news yesterday, as yesterday was about the orbiters, obviously.

2) I didn't want to just rehash SpaceX's presser, so I did a 1960s to Mars style article covering the likes of the Constellation's LAS efforts....I'll give it a standalone article given SpaceX is one part of this:

SpaceX Dragon advancing the Launch Abort System to new heights
http://www.nasaspaceflight.com/2012/02/spacex-dragon-advancing-launch-abort-system-new-heights/

You're not afraid to give NASA a black eye over Constellation, are you! Superb article, covered us really well as usual, appreciate it! Beats the lazy reporting we got for this event.

Love the Mike Griffin drawing!! Looks like something out of Elementary School "when I grow up, I'm going to be a rocket scientist".
Should have seen a picture in a book of the drawings made for the Apollo Saturn V VAB and launch pads on a paper napkin I believe it was. It was over 20 years ago I saw it. Don't remember the book. The drawing ( crude blueprint ) was hard to understand but we still went to the moon anyway.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: dragon44 on 02/03/2012 03:12 am
Chris, couple things I noticed in the article.

"...SpaceX claiming they could lose one of the six abort engines ..." should be eight abort engines.

"...commonality between the 16 maneuvering engines built into Dragon..." should be 18.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris Bergin on 02/03/2012 03:38 am
Chris, couple things I noticed in the article.

"...SpaceX claiming they could lose one of the six abort engines ..." should be eight abort engines.

"...commonality between the 16 maneuvering engines built into Dragon..." should be 18.


Yep, that was corrected - thanks to a PM (note to all, corrections must be via PM or e-mail, or I might not get to see the correction for hours!) - within 5-10 mins of publication, so refresh the article and it'll right! :)

(Excuse, writing till 4am can be dangerous ;D)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 02/03/2012 09:06 am
Great article (as usual!)
Is the five second firing duration new information? Another factor in working out what the prop load and/or isp of Super Draco might be.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: jabe on 02/03/2012 10:59 am
curious,
thoughts on the extra loads on the dragon during the Superdraco firing..  I'm assuming the cabin will need extra strengthening?
jb
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Nomadd on 02/03/2012 11:42 am
curious,
thoughts on the extra loads on the dragon during the Superdraco firing..  I'm assuming the cabin will need extra strengthening?
jb
I'd assume Super Draco thrust would be tied to the same structure as the interstage. Is abort thrust expected to be much more than max launch thrust?
 Even if it is, the capsule must have been designed with that in mind from the start.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 02/03/2012 11:50 am
You're not afraid to give NASA a black eye over Constellation, are you! Superb article, covered us really well as usual, appreciate it! Beats the lazy reporting we got for this event.
Dear SpaceX_MS. We've had a couple of discussions here about the SD. Mainly, we didn't quite got clear if the 120klbf is after considering the cosines losses, and thus each SD has somewhere between 21klbf and 18klbf. I've been discussing this on the Wikipedia page, and without written data we can't really get the correct numbers. Could you please, if it's not proprietary, state the maximum thrust at sea level of the SD, without taking in considerations any of those things?
I ideally, I would love if you could add a technical data section to your page, since I've been trying to get the history of the Merlin 1 engine. All from available data, of course. Let me put a small example that has merited some very loud discussions here. Namely, if the Merlin 1D's turbopump was designed at SPX, and if it is going to be built by you. I wouldn't consider that a super secret, particularly if you did both (design and mft). So, if you could disclose that sort of trivia it would be greatly appreciated.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris Bergin on 02/03/2012 04:07 pm
Great article (as usual!)
Is the five second firing duration new information? Another factor in working out what the prop load and/or isp of Super Draco might be.

Thanks!

The five second firing duration is confirmed in the NASA release on this, which was slightly different to the SpaceX release.

NASA:
"The engine produced full thrust within approximately 100 milliseconds of the ignition command. It also fired for 5 seconds, which is the same amount of time the engines would burn during an emergency abort."
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: iamlucky13 on 02/03/2012 10:42 pm

Love the Mike Griffin drawing!! Looks like something out of Elementary School "when I grow up, I'm going to be a rocket scientist".

Laugh all you want, but most engineers really aren't very good at freehand sketching, although freehand sketching is often a huge part of initial concept generation. All it needs to do is get the basic point across.

Drafting is a completely different type of drawing.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: cuddihy on 02/04/2012 04:26 am
I wonder how much change to the moldline would be required to fit in 8 SDTs? The natural thought is to just imagine a continuation of the Dragon cone to a wider diameter at the bottom, extending this to a wider trunk, and rearranging items to keep Cm and Cp in approximately the same locations.

After thinking about this, I took another look at the video on the recent update and noticed the abort presentation seems to show just this! Although it's "shot" from far away, you can see that the trunk portion is substantially larger than even the recent COTS 2/3 addition for solar panel covers.

It would also make the inside a little roomier, but the main effect would be to increase the standoff and volume between the bottom of the pressure vessel skirt and the outer mold line.

Of course, you could do it with a much smaller extension that kept the pressure vessel basically the same size and just increased the bottom diameter. But then it seems a bit of a waste given that Jim has said the Dragon CRS as built is very volume-limited, not so much by launch weight.

I'm sure on the launcher side that this is supported by the studies for F9 5m fairing, which would be similar in aerdynamic profile.

At the risk of being exposed as a worse artist than Mike Griffin and a ripoff of the Dragon user guide I'll attach a bad drawing. In this version I guess the base diameter would rise to 3.7 m and the height to 3 m.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/04/2012 05:20 am
Let's first see real evidence that the external mold line needs to be substantially changed.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ciscosdad on 02/04/2012 06:07 am
I love the concept in Dragon. Elegant and efficiently useful. When I first saw the apollo escape tower (a good many years ago) I pondered for a fair while on using all that impulse rather than just discarding the thing. If only it was that simple!
There is one smallish nitpick though:
Has anyone done a risk assessment on having those motors and that much propellent so close to the crew? I assume the bigger the rocket motor the bigger the problem you can have if it fails.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 02/04/2012 02:09 pm
As far as mold line changes to accommodate the SC's - I think SpaceX has thought a little further ahead than some give them credit for. Note how this *2007* update from them ( http://www.spacex.com/updates_archive.php?page=121007 ) shows an image from a CFD simulation (At 15.5 degrees angle of attack) - and that this Dragon model has four mold line "bumps" that cargo Dragons lack - and only recent images/videos of crew Dragons show evidence of. These are apparently the locations of the 8 SC engines. (in four groups of two)

It is of course a possible that the SC engine and its propellant requirements will require further changes, if larger and/or more complex than expected - but I think this is at least evidence of them thinking ahead.

Or it is something completely different and I am misinterpreting what I am seeing. But the location of those "bumps" sure seem to match SC locations awfully well.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: cuddihy on 02/04/2012 04:29 pm
As far as mold line changes to accommodate the SC's - I think SpaceX has thought a little further ahead than some give them credit for. Note how this *2007* update from them ( http://www.spacex.com/updates_archive.php?page=121007 ) shows an image from a CFD simulation (At 15.5 degrees angle of attack) - and that this Dragon model has four mold line "bumps" that cargo Dragons lack - and only recent images/videos of crew Dragons show evidence of. These are apparently the locations of the 8 SC engines. (in four groups of two)

It is of course a possible that the SC engine and its propellant requirements will require further changes, if larger and/or more complex than expected - but I think this is at least evidence of them thinking ahead.

Or it is something completely different and I am misinterpreting what I am seeing. But the location of those "bumps" sure seem to match SC locations awfully well.

I would think external pods sticking out into the reentry plasma are a farther departure from cargo Dragon than just a 1.1x1.1 scale up.

Just saying that while you might be right about those tiny bumps, if what those who have seen the guts of COTS 2/3 Dragon say is true, you need much bigger bumps than that to house engines and plumbing. A lot has happened since 2007.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 02/04/2012 05:39 pm
I would think external pods sticking out into the reentry plasma are a farther departure from cargo Dragon than just a 1.1x1.1 scale up.

Where is this 1.1 scale number coming from? Anyway as can be seen in the CFD image, they have *already* done modeling with small 'external pods'.

Just saying that while you might be right about those tiny bumps, if what those who have seen the guts of COTS 2/3 Dragon say is true, you need much bigger bumps than that to house engines and plumbing. A lot has happened since 2007.

Several have seen glimpses of the post-flight COTS1 Dragon, yes - but as the COTS2/3 Dragon appears to several changes to the service section, I don't doubt that the "guts" of a crew Dragon will end up looking quite different. We'll just have to wait and see.

They aren't idiots (as some here seem to believe) - I guess that is the core point I'm trying to make.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: woods170 on 02/04/2012 06:24 pm
The above can hopefully fit within the open bays and spaces of the current mold line.  If not, changing that now would essentially be building a whole new Dragon in many respects (aero, thermal, etc).  If there is not sufficent room for the required prop, I would think that SpaceX would want to trade if "starting over" and the money invested in that is really worth it versus what they expect to gain from doing powered-landings and the expected costs divedends there. 

There is not enough space in the service section for eight Estes motors, let alone hydrazine monsters with all the associated plumbing. The problem isn't the prop - Dragon's total prop supply may not be increased. Rather, it's the volume requirement of the eight engines. There is absolutely no way to fit those in the current service section. The mold line will be changed, without a doubt.

OK. So you work for SpaceX?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: FinalFrontier on 02/04/2012 08:11 pm
So correct me if I am wrong but the fundamental question here is whether or not they can actually fit 8 of these "super draco" thrusters into the existing engineering section of dragon or whether they will need to widen/lengthen the vehicle to hold them right?



Seems like they will need to make external changes or suffer losing internal volume. But who knows, the dimensions of the SD engines in their entirety are not yet clear (at least I don't think they are).

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: FinalFrontier on 02/04/2012 08:14 pm
AS-503

I think the answer is, is the Super Draco has a short truncated nozzle, where the CSM had the long nozzle to maximize the ISP in a Vacuum. You could make a Super Draco with a large vacuum optimized nozzle, but that is not the environment that the super draco is ment to operate in.

If you give the Super Draco a vac. optimized nozzle, the vac. thrust will increase putting you in the "ball park". But again the Super Draco is not ment as much for vacuum operations but operations that are not in vacuum (LAS and propulsive sea level landings).

Keep in mind that Elon seems to really want Dragon landing on Mars, and Mars is not a vacuum, but not far from it.  Like 1% of EArth at Sea Level?  HOw would that near vacuum environment effect the SuperDraco's when trying to land on Mars, if they are the same as being developed now?  i"m not sure how you could add nozzle to them, without them sticking way out, and burning off during atmospheric entry.  Granted, that's a long way down the road, but it's an interesting question nonetheless.
Even without any nozzle extension, the Isp will be considerably higher in vacuum than at Earth surface pressure.

For a Dragon landing on Mars, I suspect there would be modifications done to improve Isp (such as a larger nozzle) and thus payload mass, even if the propaganda right now is that the same vehicle (essentially unchanged) could be used for both Earth and Mars.


Most likely if you were going to take dragon to mars it would be attached to a larger mission  module complex (hab unit, research unit, ect) and would (I guess in this role), just act as the vehicle to take you down to the surface and back up again. Similarly it would act as the entry module once you got back to earth. At least I *think* that's what they are suggesting. But either way were along way from seeing that happen.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 02/04/2012 10:22 pm
Most likely if you were going to take dragon to mars it would be attached to a larger mission  module complex (hab unit, research unit, ect) and would (I guess in this role), just act as the vehicle to take you down to the surface and back up again. Similarly it would act as the entry module once you got back to earth. At least I *think* that's what they are suggesting. But either way were along way from seeing that happen.

I think the suggestion relates to the 'Red Dragon' proposal which some people at AMES are apparently looking into.
I really wouldn't worry at this stage about how Dragon would fit into a manned Mars mission because any modifications to it would be 'in the noise' compared to the overall cost/complexity of such a task.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: FinalFrontier on 02/04/2012 10:54 pm
Most likely if you were going to take dragon to mars it would be attached to a larger mission  module complex (hab unit, research unit, ect) and would (I guess in this role), just act as the vehicle to take you down to the surface and back up again. Similarly it would act as the entry module once you got back to earth. At least I *think* that's what they are suggesting. But either way were along way from seeing that happen.

I think the suggestion relates to the 'Red Dragon' proposal which some people at AMES are apparently looking into.
I really wouldn't worry at this stage about how Dragon would fit into a manned Mars mission because any modifications to it would be 'in the noise' compared to the overall cost/complexity of such a task.

Indeed. Although its always interesting to brainstorm about what a "red dragon" would actually look like :)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: sanman on 02/04/2012 11:32 pm
So if the SuperDraco Thrusters manage to prove themselves for Earth re-entry for return missions from LEO or ISS, what will the next target be for SuperDraco to prove itself? Mars? Or the Moon first? Logically speaking, which would be the best place to first try out SuperDraco for landing somewhere other than Earth?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: tigerade on 02/05/2012 12:03 am
So if the SuperDraco Thrusters manage to prove themselves for Earth re-entry

This is seeming like a big "if" at the moment.  But let's not worry about it too much, the bigger priority is proving the engines for it's original purpose, the LAS.  Also as far as I know the current Dragon is not designed for BEO missions so the discussions of where else the Dragon could land are pretty moot.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 02/05/2012 09:52 am
Can anyone draw any useful design insights from these cropped stills from the video?  Interested in the rectangular features between where the fuel lines enter.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: simonbp on 02/05/2012 04:37 pm
Max delta v using LAS = 2200*ln(6500/4900) = 621 m/s

Delta V required for (LOI+TEI) = 850 m/s (pretty normal profile, google it)

That's actually on the low side for LOI/TEI, and must assume a pretty high orbit with no accounting for the near-constant adjustments needed for the Moon's very uneven gravity field.

However, 621 m/s is plenty (post TLI) for getting to EML-2 and back (assuming propulsive gravity assists both ways). :)

Also, in-space you would probably just fire one thruster at a time and thus not worry about cosine losses (thus removing your factor of 0.8 ).
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 02/05/2012 04:50 pm
In-space you would probably use the regular Draco engines. They use the same propellant and probably have better ISP.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: cuddihy on 02/05/2012 04:51 pm
Max delta v using LAS = 2200*ln(6500/4900) = 621 m/s

Delta V required for (LOI+TEI) = 850 m/s (pretty normal profile, google it)

That's actually on the low side for LOI/TEI, and must assume a pretty high orbit with no accounting for the near-constant adjustments needed for the Moon's very uneven gravity field.

However, 621 m/s is plenty (post TLI) for getting to EML-2 and back (assuming propulsive gravity assists both ways). :)

Yes, I agree, I was trying to give the most optimistic assumptions I could. 6500 kg is also way low for a crew dragon with LAS.

Quote

Also, in-space you would probably just fire one thruster at a time and thus not worry about cosine losses (thus removing your factor of 0.8 ).

But this is a good one I didn't consider at all, that does improve things quite a bit. Max delta v in this case is 777 m/s.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/05/2012 05:28 pm
Max delta v using LAS = 2200*ln(6500/4900) = 621 m/s

Delta V required for (LOI+TEI) = 850 m/s (pretty normal profile, google it)

That's actually on the low side for LOI/TEI, and must assume a pretty high orbit with no accounting for the near-constant adjustments needed for the Moon's very uneven gravity field.
...
Lunar mascons are really only a significant issue for low lunar orbits, anyway.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: newtype_alpha on 02/05/2012 09:19 pm
So correct me if I am wrong but the fundamental question here is whether or not they can actually fit 8 of these "super draco" thrusters into the existing engineering section of dragon or whether they will need to widen/lengthen the vehicle to hold them right?



Seems like they will need to make external changes or suffer losing internal volume. But who knows, the dimensions of the SD engines in their entirety are not yet clear (at least I don't think they are).



They're slightly larger than the regular dracos but not to the point that you would have to enlarge the vehicle to hold them; there's still plenty of room in the service section to fit them and their plumbing, provided of course you allow a little bit of protrusion through the outer shell (which is what those little pod things are for).

I don't think the fit of the thrusters is really even an issue at this point. I'm much more interested in the issue of using these thrusters as landing jets in the future manned version. Presumably you would throttle those engines down so they don't consume quite as much fuel quite as quickly, but after a complete mission in space with maneuvering and deorbit burn it'll only have about 400kg of propellant left for the braking thrust at landing. With nothing else on board except crew, that'd be a Delta-V of about 221m/s, which I'm not completely sure is enough to ensure a safe landing under thrust (it would sort of depend on Dragon's terminal velocity and I have no idea how to calculate that).
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: nacnud on 02/05/2012 10:09 pm
My SWAG for Dragons terminal velocity would be about 40 to 70 m/s

Using guesstimates and this on line terminal velocity calculator - http://exploration.grc.nasa.gov/education/rocket/termvr.html

Anyone else want a go?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 02/05/2012 10:49 pm
A while back I posted my WAG based on a different calculator & it was 120 m/s, give or take the odd assumption.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: charliem on 02/06/2012 03:38 am
Area = pi * 3.6^2 / 4 = 10.18 m2
Mass = 7.2 mt

I've been unable to find the drag coefficient (Cd) for Dragon so I calculated terminal speed for various values I think reasonable.

On Earth (air density 1.224 kg/m3 at sea level)
Cd / Terminal Velocity:

0.5 / 150.5 m/s
0.6 / 137.4 m/s
0.7 / 127.2 m/s
0.8 / 119.0 m/s
0.9 / 112.2 m/s
1.0 / 106.4 m/s

On Mars (atmosphere density 0.02 kg/m3 at zero elevation).
Cd / Terminal Velocity:

0.5 / 1177.9 m/s
0.6 / 1075.2 m/s
0.7 / 995.5 m/s
0.8 / 931.2 m/s
0.9 / 877.9 m/s
1.0 / 832.9 m/s
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 02/06/2012 03:48 am
Area = pi * 3.6^2 / 4 = 10.18 m2
Mass = 7.2 mt

I've been unable to find the drag coefficient (Cd) for Dragon so I calculated terminal speed for various values I think reasonable.

On Earth (air density 1.224 kg/m3 at sea level)
Cd / Terminal Velocity:

0.5 / 150.5 m/s
0.6 / 137.4 m/s
0.7 / 127.2 m/s
0.8 / 119.0 m/s
0.9 / 112.2 m/s
1.0 / 106.4 m/s

On Mars (atmosphere density 0.02 kg/m3 at zero elevation).
Cd / Terminal Velocity:

0.5 / 1177.9 m/s
0.6 / 1075.2 m/s
0.7 / 995.5 m/s
0.8 / 931.2 m/s
0.9 / 877.9 m/s
1.0 / 832.9 m/s

It is not too far from Apollo CM

"The Apollo Command Module used a spherical section forebody heatshield with a converging conical afterbody. It flew a lifting entry with a hypersonic trim angle of attack of −27° (0° is blunt-end first) to yield an average L/D (lift-to-drag ratio) of 0.368."

Hillje, Ernest R., "Entry Aerodynamics at Lunar Return Conditions Obtained from the Flight of Apollo 4 (AS-501)," NASA TN D-5399, (1969).

Three minutes with Google...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Proponent on 02/06/2012 03:56 am
The lift-to-drag ratio is not the same thing as the drag coefficient, and the drag coefficient at low speeds will differ (my guess: it will be higher) from that at hypersonic speeds.  It will also depend on angle of attack.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: QuantumG on 02/06/2012 04:00 am
Yeah, I love it when people use Cd as a constant for wildly different velocities in wildly different regimes of the atmosphere.

http://en.wikipedia.org/wiki/Drag_Coefficient

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/06/2012 04:03 am
Lift/drag is obviously not the same as drag coefficient (Cd). Am I missing something here, Comga? (Though a lifting reentry does indeed make a significant difference in EDL performance... That makes our analysis here more difficult and less back-of-envelope-able.)

Also, two points: Dragon might not necessarily reach terminal velocity in time to slow down before hitting the dirt (a little analysis in MATLAB may be able to show this in the ballistic case). Also, a very large portion of Mars is below "zero" altitude, and parts of it (Hellas Basin) are several miles below "zero" altitude, with significantly greater atmospheric density. Most of the northern hemisphere is pretty far below "zero" altitude, too. That obviously helps Dragon. Dragon may have a much lower (or even negative) payload in the highlands.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/06/2012 04:25 am
Yeah, I love it when people use Cd as a constant for wildly different velocities in wildly different regimes of the atmosphere.

http://en.wikipedia.org/wiki/Drag_Coefficient


And that's not what that formula is saying. That's merely the definition of the drag coefficient, which you then can use for basically any velocity (and assume is constant) short of the trans-sonic regime (and you have to still be in essentially continuum fluid dynamics... which for Mars is roughly 7-9 scale heights, or about anything below 70-100km in altitude, depending on the size of the object reentering).

And the subsonic drag coefficient IS roughly constant and for a lot of shapes stays the same order of magnitude no matter what your velocity is or your atmosphere.

Do you have a graph handy, or just a snarky response? ;)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: charliem on 02/06/2012 04:46 am
Very interesting study about aerodinamics of the Apollo capsule at hypersonic speeds: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670027745_1967027745.pdf

Its not applicable to the regimes we are talking about (sea level, low speed, zero angle of attack) but makes me think that the drag coefficient for Dragon might be greater than 1 at those conditions.

In that case Terminal Velocity'd be even less.

1.2 / 97.1 m/s
1.4 / 89.9 m/s
1.6 / 84.1 m/s
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: simonbp on 02/06/2012 03:18 pm
Lunar mascons are really only a significant issue for low lunar orbits, anyway.

Low orbit like the kind any LOR mission would use. You can't really get in an orbit around the Moon high enough around that they have no long-term effects (the Moon's Hill radius is 33 lunar radii, still close enough for aspherical gravity effects).

Also, "mascons" are 1960's-era anachronism from when we only knew about the nearside gravity field (and thus features associated with nearside volcanism) the real lunar gravity field is much more intricate.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: wolfpack on 02/06/2012 03:55 pm
So correct me if I am wrong but the fundamental question here is whether or not they can actually fit 8 of these "super draco" thrusters into the existing engineering section of dragon or whether they will need to widen/lengthen the vehicle to hold them right?



Seems like they will need to make external changes or suffer losing internal volume. But who knows, the dimensions of the SD engines in their entirety are not yet clear (at least I don't think they are).



I suppose it's entirely possible that not even SpaceX knows at this point. To me, the critical path would look something like this:

1. Make the engine work
2. Make the engine fit

There is no requirement that Crew Dragon = Cargo Dragon, as far as I know.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/06/2012 04:06 pm
Lunar mascons are really only a significant issue for low lunar orbits, anyway.

Low orbit like the kind any LOR mission would use. You can't really get in an orbit around the Moon high enough around that they have no long-term effects (the Moon's Hill radius is 33 lunar radii, still close enough for aspherical gravity effects).

Also, "mascons" are 1960's-era anachronism from when we only knew about the nearside gravity field (and thus features associated with nearside volcanism) the real lunar gravity field is much more intricate.
Correct on all accounts, but the effects are much less severe (as far as delta-v requirements, which was the context) at higher orbits. As I read your post, it seemed like you were implying like there'd be high delta-v requirements (i.e. x00m/s) from the unevenness of the lunar field, perhaps even for short-term (sortie) missions at high orbits, which seems very unlikely to me. It's needed to take them into account for detailed mission planning, but shouldn't need much delta-v other than for typical trajectory adjustments you'd need even for a spherical Moon (high lunar orbit, short mission).
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 02/06/2012 06:04 pm
Would it be possible(and make sense) to either areodynamically or with small thrusters keep Draon flying forward edge down and then only use one pair of Super Dracos(with near Zero Cosine Loss) for all but the final stage of the descent?  How much overall efficiency would be gained? Is there sufficient thrust in a pair of Super Dracos for this to work?
...the side of Dragon doesn't have heat tiles on it (nor is the shape there conducive...though, the SuperDracos appear to point roughly through the center of mass of the Dragon...
...Some picaX segments up the sides?  Remember, this is just for the propulsive phase before landing (after the heatshield has scrubbed a lot of the energy away). 

Also would some disruptive fire from the leading edge thruster(s) create some envelope of protection (with the plume)?

Is it reasonable to guess that this might be part of the reason for the apparent "cosine loss design"?

Because the questions above were first posted with a distraction related to "Model-S like screens" and the thread was trimmed, I am curious whether there were responses to the above that no longer appear. 

Like TrueBlueWitt, I'm still curious about whether it would be possible to "keep Dragon flying forward edge down and then only use one pair of Super Dracos (with near Zero Cosine Loss) for all but the final stage of the descent?"

As opposed to being a "kludge", it seems to me that the impact would be significant (almost no cosine losses versus large cosine losses).  I think this could work on Earth or Mars.  I would love to hear some more opinions.  Thanks in advance. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 02/07/2012 03:58 am
Lift/drag is obviously not the same as drag coefficient (Cd). Am I missing something here, Comga?

Naw.  I missed more.  My findings aren't really that useful, but look at the discussion and responses they got.  It's worth my being derided when people post such good links.  Lots of stuff to read here, if only I had the time.  Someday....
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/07/2012 04:05 am
Oh, by the way, I think there are some special orbits around the Moon that are stable (in spite of the mascons--whatever you want to call them).
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: cuddihy on 02/07/2012 04:57 am

Like TrueBlueWitt, I'm still curious about whether it would be possible to "keep Dragon flying forward edge down and then only use one pair of Super Dracos (with near Zero Cosine Loss) for all but the final stage of the descent?"

As opposed to being a "kludge", it seems to me that the impact would be significant (almost no cosine losses versus large cosine losses).  I think this could work on Earth or Mars.  I would love to hear some more opinions.  Thanks in advance. 

Possible but probably not a bright idea in an atmosphere.
1.  Keep inmind the SDTs only will fire 'roughly' through the Cm. No guarantees on the Cp and any aerodymic forces or just offset from Cm will change direction of the thruster and introduce roll.
2. if you're using them to decelerate you have to point the thruster in the direction opposite travel. So your crew will be rather uncomfortable. And you will have to slew back to "butt down" to land with all thrusters anyway. So overall, it's fine for in-space course corrections that have a smaller impulse-time window than a Draco can provide. Otherwise it's better to take the cosine hit.

In fact it probably makes more sense to use a Trunk with single SDT as a crasher stage rather than using LAS propulsion that has to fit in the capsule.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/07/2012 01:58 pm
...
In fact it probably makes more sense to use a Trunk with single SDT as a crasher stage rather than using LAS propulsion that has to fit in the capsule.
Yeah, I have to say that if Dragon is going to be landing on a lot of the places it supposedly could land, it'll be paired with a crasher stage of some sort.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Proponent on 02/07/2012 03:19 pm
My findings aren't really that useful, but look at the discussion and responses they got.  It's worth my being derided when people post such good links.

Sorry if my post seemed like derision (and I didn't even provide any links); please think of it as factual in content but perhaps brusque in presentation.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: balan h20 on 02/07/2012 06:40 pm

Like TrueBlueWitt, I'm still curious about whether it would be possible to "keep Dragon flying forward edge down and then only use one pair of Super Dracos (with near Zero Cosine Loss) for all but the final stage of the descent?"

As opposed to being a "kludge", it seems to me that the impact would be significant (almost no cosine losses versus large cosine losses).  I think this could work on Earth or Mars.  I would love to hear some more opinions.  Thanks in advance. 

Possible but probably not a bright idea in an atmosphere.
1.  Keep inmind the SDTs only will fire 'roughly' through the Cm. No guarantees on the Cp and any aerodymic forces or just offset from Cm will change direction of the thruster and introduce roll.
2. if you're using them to decelerate you have to point the thruster in the direction opposite travel. So your crew will be rather uncomfortable. And you will have to slew back to "butt down" to land with all thrusters anyway. So overall, it's fine for in-space course corrections that have a smaller impulse-time window than a Draco can provide. Otherwise it's better to take the cosine hit.

In fact it probably makes more sense to use a Trunk with single SDT as a crasher stage rather than using LAS propulsion that has to fit in the capsule.
The module will still have the sixteen draco thrusters that are used for manuvering in addition to the eight super draco for landing, so what would be the difference in using those sixteen thrusters to manuver in the final stages of landing to adjust the landing as did the lunar landers of the Apollo era.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 02/07/2012 06:51 pm
so what would be the difference in using those sixteen thrusters to manuver in the final stages of landing to adjust the landing as did the lunar landers of the Apollo era.

Insufficient thrust of the regular Dracos. I'd wager that any single Super Draco section firing alone would pose more controlability problems than regular Dracos could handle and even that's assuming a single SD thrust vector passed through the Dragon CG, which I don't think is really the case.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: strangequark on 02/07/2012 06:55 pm
Can anyone draw any useful design insights from these cropped stills from the video?  Interested in the rectangular features between where the fuel lines enter.

It's underexpanded (http://en.wikipedia.org/wiki/File:Rocket_nozzle_expansion.svg), very low area ratio (but that's expected). The rectangular features look like a thermal standoff to me (if I'm looking at what you're looking at). Might have been necessary because these things give off a lot more heat than a regular Draco, so they have to be more concerned about the surrounding hardware.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/07/2012 06:55 pm
I see no reason why SpaceX, with their pretty extensive in-house design and manufacturing capabilities and vertical integration, wouldn't just develop a custom lunar lander more like the Soviet or Apollo lander designs. You have to do all the manufacturing and certification and design anyway, might as well do it right.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: balan h20 on 02/07/2012 07:11 pm
I may be dense but I dont see how you can not change the angle of descent if you add two manuvering draco pointinting up on one side and two pointing down on the other. That has to chang the angle a hair or two and that would make the dragon creep in the direction of the dangle. All factors being even if you add an upward element to on side and a downward to the other it has to change the angle.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 02/07/2012 07:24 pm
I may be dense but I dont see how you can not change the angle of descent if you add two manuvering draco pointinting up on one side and two pointing down on the other.

It's not a matter of changing the angle, it's a matter of actually *keeping* that angle. In the real world there is no way to *perfectly* aim thrust of an engine through the center of mass of a vehicle and even the slightest mispointing will induce a rotational torque on the vehicle. What happens if this torque is greater than the lowly Dracos can counter?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: balan h20 on 02/07/2012 07:46 pm
You are already through the atmosphere and approaching the ground. What you want to do is to change the angle to move the craft latteraly across the surface prior to setting down. You do this at three or four kilo above the surface to land in a more appropriate area. No different than changing the landing area on a water landing in an airplane or switching to a different runway  or doing a go round. I had to do a go round at Jeckel Island GA because of a fishing trawler in the inland seaway on final crossing the runway. If they plan to land this thing on planets they are going to have to manuver like the lunar alnder to keep from landing on a boulder or on a the side of a incline.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 02/07/2012 07:49 pm
If they plan to land this thing on planets they are going to have to manuver like the lunar alnder to keep from landing on a boulder or on a the side of a incline.

I imagine they would use throttling of the 4 sections of SDs to do that and only possibly use Dracos for finer attitude adjustments. You're talking about using a single Super Draco (or two) on the same side of the spacecraft to eliminate cosine losses. That's a different beast control-wise.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: HMXHMX on 02/07/2012 10:48 pm
Can anyone draw any useful design insights from these cropped stills from the video?  Interested in the rectangular features between where the fuel lines enter.

It's underexpanded (http://en.wikipedia.org/wiki/File:Rocket_nozzle_expansion.svg), very low area ratio (but that's expected). The rectangular features look like a thermal standoff to me (if I'm looking at what you're looking at). Might have been necessary because these things give off a lot more heat than a regular Draco, so they have to be more concerned about the surrounding hardware.

Can you estimate what the area ratio may be?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: darkenfast on 02/08/2012 04:23 am
Here's a question: are there any figures for the ignition reliability of pressure-fed bi-propellant engines versus solid-fuel motors? These are both mature technologies, but I wonder how they compare.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 02/08/2012 04:36 am
Here's a question: are there any figures for the ignition reliability of pressure-fed bi-propellant engines versus solid-fuel motors? These are both mature technologies, but I wonder how they compare.
The bipropellant is hypergolic in this case. As long as both fuel and oxidizer make contact, they will ignite. So bipropellant in this case needs no ignition system.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: sanman on 02/08/2012 08:31 am
The bipropellant is hypergolic in this case. As long as both fuel and oxidizer make contact, they will ignite. So bipropellant in this case needs no ignition system.

Well, then what about the safety of this arrangement? If its hypergolic, then isn't there also the danger of unwanted ignition or explosion? Did they investigate any alternatives, or did they just decide that whatever works for Draco is good enough for SuperDraco?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 02/08/2012 08:43 am
If its hypergolic, then isn't there also the danger of unwanted ignition or explosion?

Ignition occurs when they mix and they mix in the combustion chamber after valves upstream open.

You also have to let go of the notion that a LAS will be 100% safe with no failure modes of its own. NASA expects any abort system to be at least 90% reliable, i.e. less than 1/10 chance of a failed abort once it's initiated. A LAS is not a silver bullet to *guarantee* you won't have a bad day.

Isn't there a saying in the fighter pilot world that an ejection is an attempted suicide to escape certain death...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Maciej Olesinski on 02/09/2012 09:45 pm
Not sure if that one was posted before - not in this topic for sure.
Super Draco testing without fancy music ;)
http://www.youtube.com/watch?v=VP_kGlmOH9U
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: SebastianB on 03/31/2012 08:24 am
The recent update about the safety advisory panel contains a new graphic of a crewed Dragon spacecraft.

http://www.spacex.com/press.php?page=20120329 (http://www.spacex.com/press.php?page=20120329)

In that graphic the abort/landing engines are housed in protruding boxes on the sidewalls with a recessed area below instead of being fully sleek with the sidewalls as previously shown in the RTLS video.
I assume this graphic shows a relatively recent design since it also has the attachments for the solar panel fairings on the trunk.

I know that I shouldn't read to much into these graphics...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: dcporter on 03/31/2012 01:04 pm
I know that I shouldn't read to much into these graphics...

They do seem to get more accurate over time though.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jason1701 on 03/31/2012 06:12 pm
I don't see how the SuperDracos could be housed in those fairings without protruding into the pressure vessel.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 03/31/2012 06:36 pm
I don't see how the SuperDracos could be housed in those fairings without protruding into the pressure vessel.
That's not without precedent. The Apollo lunar lander ascent engine protruded into the crew cabin.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jason1701 on 03/31/2012 07:29 pm
I don't see how the SuperDracos could be housed in those fairings without protruding into the pressure vessel.
That's not without precedent. The Apollo lunar lander ascent engine protruded into the crew cabin.

True, but SpaceX probably wants to keep the pressure vessel as similar to the cargo version as possible. Doing otherwise would add to cost and schedule. Also, the first round of crew accommodation tests did not show a modified pressure vessel; we'll see if the second round does. I think SpaceX will increase the height of Dragon without changing the pressure vessel, so as to create space in the service section for the SuperDracos.  If they add a cylindrical rather than conical section, they wouldn't have to modify the heat shield.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 03/31/2012 07:55 pm
I don't see how the SuperDracos could be housed in those fairings without protruding into the pressure vessel.
That's not without precedent. The Apollo lunar lander ascent engine protruded into the crew cabin.

True, but SpaceX probably wants to keep the pressure vessel as similar to the cargo version as possible. Doing otherwise would add to cost and schedule. Also, the first round of crew accommodation tests did not show a modified pressure vessel; we'll see if the second round does. I think SpaceX will increase the height of Dragon without changing the pressure vessel, so as to create space in the service section for the SuperDracos.  If they add a cylindrical rather than conical section, they wouldn't have to modify the heat shield.
Changing the pressure vessel is less of a concern than you make it sound like, certainly less than your alternative, which would significantly change the reentry dynamics, etc.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: TrueBlueWitt on 03/31/2012 09:58 pm
I know that I shouldn't read to much into these graphics...

They do seem to get more accurate over time though.

Does this mean they're changing the nozzle angle to decrease cosine losses?   Even 10 degrees would give you roughly 10% overall improvement.. That is significant and could close the gap or increase margins for some abort/landing scenarios.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: cuddihy on 03/31/2012 10:09 pm
The recent update about the safety advisory panel contains a new graphic of a crewed Dragon spacecraft.

http://www.spacex.com/press.php?page=20120329 (http://www.spacex.com/press.php?page=20120329)

In that graphic the abort/landing engines are housed in protruding boxes on the sidewalls with a recessed area below instead of being fully sleek with the sidewalls as previously shown in the RTLS video.
I assume this graphic shows a relatively recent design since it also has the attachments for the solar panel fairings on the trunk.

I know that I shouldn't read to much into these graphics...

I would take this as confirmation that the guy who said he had seen the service section and that there wasn't room for 8 estes motors much less eight abort engines was correct.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 03/31/2012 11:30 pm
I know that I shouldn't read to much into these graphics...

They do seem to get more accurate over time though.

I wouldn't say that.  There are many questionable elements in this graphic.  The Trunks have pontoon-ish items for the solar panels, but they don't protrude sufficiently into the volume of the Trunks to provide volume for the folded solar panels.  In the upper right there is the end of the original centered ISS solar panel that was moved long ago to an end of the Truss.  The JEM is not quite correct, with too many, too prominent EVA handles.  Lots of little things.

It is interesting that new features were added specificaly to the Crew Dragon depiction, but I would not rely on that as what will be built.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: dcporter on 04/01/2012 04:28 am
Sure, the videos are still a PR exercise. I guess I should have said, they seem to get less idealized over time.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 04/01/2012 06:35 am
I guarantee SpaceX knows where the abort thrusters can fit and where they can't and basically what they need to do to fit them. Heck, they probably have the CAD files already drafted, and NASA has probably already seen some of them. People here are acting like they discovered some fatal flaw in their plan, and that's just ridiculous on the face of it. They've already test fired several versions of SuperDraco, after all.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jason1701 on 04/01/2012 02:49 pm
I guarantee SpaceX knows where the abort thrusters can fit and where they can't and basically what they need to do to fit them. Heck, they probably have the CAD files already drafted, and NASA has probably already seen some of them. People here are acting like they discovered some fatal flaw in their plan, and that's just ridiculous on the face of it. They've already test fired several versions of SuperDraco, after all.

Not disputing that, just that the animations rarely reflect the actual design, and significant modifications to Dragon's moldline may be required.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 04/01/2012 02:57 pm
True, but SpaceX probably wants to keep the pressure vessel as similar to the cargo version as possible. Doing otherwise would add to cost and schedule.
I suspect that they will be the same.  ie. The cargo dragons will propulsively land also, once the ability is demonstrated.  Probably before crewed actually. 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lurker Steve on 04/01/2012 03:08 pm
True, but SpaceX probably wants to keep the pressure vessel as similar to the cargo version as possible. Doing otherwise would add to cost and schedule.
I suspect that they will be the same.  ie. The cargo dragons will propulsively land also, once the ability is demonstrated.  Probably before crewed actually. 

If they are counting on propulsive landing, then they are going to have challenges making even the 2017 date.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: MP99 on 04/01/2012 04:41 pm
The recent update about the safety advisory panel contains a new graphic of a crewed Dragon spacecraft.

http://www.spacex.com/press.php?page=20120329 (http://www.spacex.com/press.php?page=20120329)

In that graphic the abort/landing engines are housed in protruding boxes on the sidewalls with a recessed area below instead of being fully sleek with the sidewalls as previously shown in the RTLS video.
I assume this graphic shows a relatively recent design since it also has the attachments for the solar panel fairings on the trunk.

I know that I shouldn't read to much into these graphics...

Nice spot.

Good first post - welcome.

cheers, Martin
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 04/01/2012 06:49 pm
If they are counting on propulsive landing, then they are going to have challenges making even the 2017 date.
Sorry for not being clear.   I should have said that propulsive landing will likely be operationally attempted on unmanned dragons prior to crews being propulsively landed.  I think that manned and unmanned dragons will have the same pressure vessel mold-line because they will eventually both land propulsively (one with biological cargo, and one without). 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: dcporter on 04/02/2012 01:56 am
Right. COTS is a development program, as is CCDev. Each is going to fund improvements to the Dragon, but I suspect that at the end of the day there will be one model of Dragon which acts basically the same whether it has racks or seats.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: beancounter on 04/02/2012 04:46 am
Right. COTS is a development program, as is CCDev. Each is going to fund improvements to the Dragon, but I suspect that at the end of the day there will be one model of Dragon which acts basically the same whether it has racks or seats.

Well I think that was always the intention.  Utilising the same basic structures et al provides for reduced costs over unique items for each separate use.  That's been their philosophy since start up and they seem to have kept pretty much to it.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 04/02/2012 12:16 pm
Right. COTS is a development program, as is CCDev. Each is going to fund improvements to the Dragon, but I suspect that at the end of the day there will be one model of Dragon which acts basically the same whether it has racks or seats.
Exactly.  The next development program which would expand dragon's capability would be Red Dragon (if it happens).  Based on the projected cost including science instruments ($500M), it seems that related changes/upgrades to dragon would likely be less than $200M-$300M.  What new features might this include?  I suspect it would be focussed on software (including automated descent propulsion) and communications hardware.  Perhaps the trunk would get an option for a larger solar array too.  Whatever changes it brought, I suspect it would bring most (if not all) changes necessary for dragon rider trips around the moon.       

Other than perhaps re-examination of  NOFBX or other alternatives (if the need arises for a specific purpose) may be the only remaining upgrade for this version of dragon, but I see that as low probability. 

I do see potential for a much larger methane ISRU version of dragon in the future.  But that probably wouldn't be even discussed until Elon feels ready to make a Mars architecture public.  And that probably won't be until he either wants to IPO SpaceX, or has at least propulsively landed a rocket stage (operationally and not just grasshopper). 
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: SF Doug on 04/02/2012 04:02 pm
I know that I shouldn't read to much into these graphics...

They do seem to get more accurate over time though.

Does this mean they're changing the nozzle angle to decrease cosine losses?   Even 10 degrees would give you roughly 10% overall improvement.. That is significant and could close the gap or increase margins for some abort/landing scenarios.

Perhaps they no longer think they need the individual thrust vectors to be through the center of mass.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: RDoc on 04/02/2012 04:37 pm
Perhaps they no longer think they need the individual thrust vectors to be through the center of mass.
It doesn't seem from the earlier illustrations they ever were designed to go through the center of mass does it? It seems likely the center of mass, particularly with cargo, would be well below the vertical midpoint and roughly radially centered. The thrust vectors I believe always intersected the radial center well above the midpoint, actually near the top of the pressure vessel.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kttopdad on 04/02/2012 06:21 pm
Does anyone have an educated guess on whether the Dracos are individually tanked or fed from common tanks?

Dean
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Ben the Space Brit on 04/02/2012 07:26 pm
Does anyone have an educated guess on whether the Dracos are individually tanked or fed from common tanks?

It's been established that the Dracos and Superdracos will be fuelled from a single common system.  FWIW, I think building the RCS/LAS system in self-contained pods that could be swapped, reconditioned and possibly applied to other spacecraft might be a good idea.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: jwade on 04/03/2012 03:05 am
Does anyone have an educated guess on whether the Dracos are individually tanked or fed from common tanks?

It's been established that the Dracos and Superdracos will be fuelled from a single common system.  FWIW, I think building the RCS/LAS system in self-contained pods that could be swapped, reconditioned and possibly applied to other spacecraft might be a good idea.

From all of the various cutaway CAD drawings, the Draco set test fire video, the shots of the partly exposed dracos on the COTS1 dragon on display in DC,  it really looks like each set of dracos is basically a self contained module with separate tanks and plumbing that are then cross connected.   Interestingly there appear to be two different modules, a 4 draco set for the hatch side of the dragon and a 5 draco set for the back side.   There are a total of 4 modules (4+4+5+5=18 total dracos per dragon)

The 2010 Spacex archived updates page. http://www.spacex.com/updates_archive.php?page=2010 (http://www.spacex.com/updates_archive.php?page=2010) states: "A system of valves provides redundant cross-connection between the propellant tanks for maximum reliability", although I have never seen a picture that clearly shows this.    Do you have a better source or picture?   

Edit: clarified draco quantities
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 04/03/2012 07:45 am
Sounds a bit like the Shuttle's OMS pods. Essentially self-contained units, but with a propellant transfer capability. Seems to be the best of all worlds. Especially on a capsule where you need to have control over the centre of gravity and therefore want an even distribution of propellant across all of the tanks.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris-A on 04/03/2012 01:24 pm
There is a photo from a powerpoint that displayed the center section of dragon with aluminum hydraulic lines.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: jwade on 04/03/2012 10:05 pm
I guarantee SpaceX knows where the abort thrusters can fit and where they can't and basically what they need to do to fit them. Heck, they probably have the CAD files already drafted, and NASA has probably already seen some of them. People here are acting like they discovered some fatal flaw in their plan, and that's just ridiculous on the face of it. They've already test fired several versions of SuperDraco, after all.

I don't mean to be disrespectful, but I am not sure this is true.    SpaceX clearly uses an iterative design process and we have seen significant changes in components that have already flown.    For example, the dragon trunk/solar panel farings.    They clearly investigated significant resources designing and builiding at least test articles of a composite trunk before switching to the current aluminum design.  (See the picture from corroded nut).    The addition of the solar panel fairings extending out from the trunk and the change in mold line and aerodynamics does not look to me like something that was planned for in the original design but was forced by the reality of the solar panel deployment design and volume requirements.    I could be wrong but I would think they would have at least done a more acurate simulated trunk for either of the first two flights had they known what it was going to look like.

I am speculating of course, but I would bet that some propulsion and mechanical engineers at SpaceX are sitting in a conference room still trying to identify a final pipeing and manifold configuration for the flight superdracos that will actually fit into the structure.    The switch to a pusher LAS was clearly done long after the initial dragon design and engineering pathfinder construction so I would still be very surprised if the final propulsively landed dragon ends up sharing the same basic moldline with the current version.   Unfortunately, we can speculate all we want to, but we will probably never know the answer about where SpaceX is in the design process and we will have to wait to see the first real crewed dragon hardware to know for sure how they have solved this.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 04/03/2012 10:15 pm
Yeah, I'm not trying to say I think the SpaceX design is completely set in stone, only that they surely have thought a lot about exactly how big the thrusters need to be, where they can fit, and probably have detailed CAD files of one possible solution to the problem. Considering their pretty impressive past accomplishments (from largely clean-sheet designs), they're at least competent enough to have thought about where the thrusters can fit.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: corrodedNut on 04/08/2012 01:15 am
http://www.youtube.com/watch?v=iI5muoB7ErI&list=UUGLF2l0YJk4BC7zdRRfY9sQ&index=1&feature=plcp

At 1:16:50 Elon says "...even when we have propulsive landing capability, there will still be an emergency parachute...kind of like the Cirrus aircraft"

That system uses a small rocket to ensure proper parachute deployment, even in a stall or at very low airspeeds.

http://cirrusaircraft.com/innovation/?item=parachute#products

Let the speculation begin!



Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 06/18/2012 09:36 pm
Perhaps this is a better thread for it - A new tweet from Elon Musk that just went out: https://twitter.com/elonmusk/status/214831794103664640

Quote
Elon Musk ‏@elonmusk
Just fired our Superdraco escape rocket engine at full thrust! Needed to carry astronauts on Dragon pic.twitter.com/ef86qbWF
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 06/18/2012 09:39 pm
This appears to be a new vertical SD test stand at McGregor, TX. It looks different than the Merlin stands, and I assume the hole is too small for Merlin firings as well.

Can anyone guess a size of the engine based on this image?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Halidon on 06/18/2012 09:56 pm
In my head, I just heard Crocodile Dundee say "now that's a thruster."

I wonder if they will test paired thrusters on the stand before progressing to "hopper"-style tethered testing.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Alpha Control on 06/18/2012 09:59 pm
This appears to be a new vertical SD test stand at McGregor, TX. It looks different than the Merlin stands, and I assume the hole is too small for Merlin firings as well.

Can anyone guess a size of the engine based on this image?

Lars,
I see a blue staircase in the background that gives a sense of the scale of the platform. To my eyes then, the engine doesn't seem large - 1-2 ft high? (just my very rough guess).
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: modemeagle on 06/18/2012 10:10 pm
I calculated, using some educated guesses on some parameters, that the chamber is ~ 14" dia and ~18" long, which is very close to the size of the chamber for the 1D (also calculated with a few guesses).  The nozzle should be ~16 inches for Pe=Pa.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: HMXHMX on 06/18/2012 10:22 pm
I calculated, using some educated guesses on some parameters, that the chamber is ~ 14" dia and ~18" long, which is very close to the size of the chamber for the 1D (also calculated with a few guesses).  The nozzle should be ~16 inches for Pe=Pa.

Based on the mockup exhibited at Space Tech Expo, I'd estimate the exit is 8 inches in diameter.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 06/18/2012 10:22 pm
This may help... Using the camera position and perspective, I have highlighted two vertical red bars that would be the same actual height.

Now all we need to know is the height of the guide rail to know the dimensions of the SD thrust chamber.

Does anyone know what the standard height is of a guide/safety rail like that? ;)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: MikeAtkinson on 06/18/2012 10:29 pm
The nozzle should be ~16 inches for Pe=Pa.

It looks underexpanded to me.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: MikeAtkinson on 06/18/2012 10:31 pm
This may help... Using the camera position and perspective, I have highlighted two vertical red bars that would be the same actual height.

Now all we need to know is the height of the guide rail to know the dimensions of the SD thrust chamber.

Does anyone know what the standard height is of a guide/safety rail like that? ;)


That helps, but I think the camera is slightly above the top of the thrust chamber, so that the red scale line on the rail should be a bit smaller.

[edit: the horizon is 2/3 up the picture, so the camera is pointing down slightly.]
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: HMXHMX on 06/18/2012 10:32 pm
The nozzle should be ~16 inches for Pe=Pa.

It looks underexpanded to me.

This engine is also used for landing.  In that mode, it has to be able to deeply throttle.  I estimate it throttles about 8:1, maybe 10:1, from the max abort thrust level.  They will have designed for no separation at the most deeply throttled sea level condition.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 06/18/2012 10:34 pm
That helps, but I think the camera is slightly above the top of the thrust chamber, so that the red scale line on the rail should be a bit smaller.

Nope - pay attention to the horizon. Both of the red bars end at the same level - the horizon. If the camera was above the thrust chamber, the horizon would be above it.

Quote
[edit: the horizon is 2/3 up the picture, so the camera is pointing down slightly.]

It doesn't matter - if a picture includes a horizon line - that line is exactly horizontal. (and the virtual triangle formed from the camera to the edge horizon points is 100% even/flat) It doesn't matter if the camera was pointing mostly up or down.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: modemeagle on 06/18/2012 10:37 pm
My numbers were based on a 132psi chamber pressure (just a guess).
I have been thinking for a while that their system is much higher which would make the chamber smaller then my estimated size.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: DigitalMan on 06/19/2012 04:05 am
This is nice:

http://twitter.com/elonmusk/status/214831794103664640/photo/1
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: modemeagle on 06/19/2012 04:43 am
This may help... Using the camera position and perspective, I have highlighted two vertical red bars that would be the same actual height.

Now all we need to know is the height of the guide rail to know the dimensions of the SD thrust chamber.

Does anyone know what the standard height is of a guide/safety rail like that? ;)

quick search came up with 42" for railing
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 06/19/2012 04:55 am
Would need to throttle more than 10:1 for Red Dragon I think.  Or maybe they'll only fire 4 superdracos instead of all 8 for that.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 06/19/2012 05:03 am
IIRC at the Mars Concepts and Approaches conference they were talking an SD throttling range of 5% to 100%.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Robotbeat on 06/19/2012 05:11 am
Of course with the very low Martian pressure, separation isn't an issue.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kevin-rf on 06/19/2012 01:58 pm
Considering the level of under expansion, you would have to be landing Dragons on Venus before you have a separation issue.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 06/19/2012 05:39 pm
On Red Dragon it was going to make 7g. At 5 tonnes, 0.375g of Mars gravity, that's 368kN? That's 82.7klbf. That's 69% of throttle.
Hover on Earth's sea level would require just 49kN, or 11klbf, that's 9.1% with eight SD, 18.2% for four. More reasonable.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 06/19/2012 08:21 pm
On Red Dragon it was going to make 7g. At 5 tonnes, 0.375g of Mars gravity, that's 368kN? That's 82.7klbf. That's 69% of throttle.
Hover on Earth's sea level would require just 49kN, or 11klbf, that's 9.1% with eight SD, 18.2% for four. More reasonable.
Red dragon planned to have a very slow final descent after the 7 g phase.  Hover on Mars = .38 g or lower. 

6.9% using only 4... 

That's throttling from 100% to less than 3.5% if using all 8.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 06/19/2012 08:30 pm
Red Dragon might have a 50% strong version of the SDs.  And only 4, since LAS is not really needed.
(I realize a presentation last week said 7 g slow-down, but I don't know if that's SpaceX's plan, or is just carrying over the LAS acceleration, as-is, to the Mars scenario.)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 06/19/2012 09:26 pm
I think the 7G slow-down was just the result of using existing Dragon capabilities with the least change... In the thin martian air, you want to make the heat shield and atmosphere friction do as much work as possible to slow down. (no chutes in this scenario)

So with the thrust available, a last-ditch 7G burn of most of the propellant is the most efficient use of the SD thrusters.

(I don't think SpaceX were behind this, this seems to be more of an outside analysis of how best to use a Dragon to land cargo on Mars)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 06/19/2012 09:33 pm
As long as you're near terminal velocity when you start firing, you haven't wasted any aerobraking, and since the approach is very shallow, you can afford a longer burn.

The delta-V is of course in the propellant, not the engines, but having less engine weight means you have more payload mass.

I think less engines is definitely under "minimum change", and maybe even "weaker engines" - but I'm not an expert on this last one.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: DavidH on 06/19/2012 10:58 pm
So here's a novice question:
Q: The SuperDraco is a hypergolic engine right? That means horribly nasty chemicals (ie, hydrazine), right? So with a hypergol engine this size, how far from humanity does this test have to take place and how long do you have to wait before a human can access the test stand? Do you have to flush the scene with sprinklers and then wait for an hour? That's a GOB (not an acronmym) of hydrazine. I'd imagine there to be some unburnt fuel lying around even if burnt hydrazine is safe (which I don't know is the case.)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: WmThomas on 06/19/2012 11:40 pm


(I don't think SpaceX were behind this, this seems to be more of an outside analysis of how best to use a Dragon to land cargo on Mars)


Steve Davis of SpaceX, one of the senior engineers on Dragon, was a co-author of the "Ice Dragon" proposal. It would be surprising to learn that he didn't know about this 7g burn concept. I'll ask him when I see him weekend after next.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 06/20/2012 12:06 am
They certainly could have been involved. It was just my (probably erroneous) impression.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: yg1968 on 06/21/2012 03:50 am
https://twitter.com/elonmusk/status/215478323147575297

Quote
Dragon will use four pairs of side mounted Superdraco engines. Can function with up to four out.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: plank on 06/21/2012 11:19 am
https://twitter.com/elonmusk/status/215478323147575297

Quote
Dragon will use four pairs of side mounted Superdraco engines. Can function with up to four out.

How will they be protected them from reentry?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Crispy on 06/21/2012 11:39 am
https://twitter.com/elonmusk/status/215478323147575297

Quote
Dragon will use four pairs of side mounted Superdraco engines. Can function with up to four out.

How will they be protected them from reentry?

They should be well behind the shock wave and won't require additional protection.

(http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=28486.0;attach=413858;image)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Prober on 06/21/2012 01:52 pm
https://twitter.com/elonmusk/status/215478323147575297

Quote
Dragon will use four pairs of side mounted Superdraco engines. Can function with up to four out.

How will they be protected them from reentry?

They should be well behind the shock wave and won't require additional protection.

(http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=28486.0;attach=413858;image)

thought one side of the Dragon takes the heat?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: DigitalMan on 06/21/2012 01:58 pm
https://twitter.com/elonmusk/status/215478323147575297

Quote
Dragon will use four pairs of side mounted Superdraco engines. Can function with up to four out.

How will they be protected them from reentry?

They should be well behind the shock wave and won't require additional protection.

(http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=28486.0;attach=413858;image)

thought one side of the Dragon takes the heat?


Look more closely.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: peter-b on 06/21/2012 01:58 pm

thought one side of the Dragon takes the heat?

Um, isn't that what Crispy's image shows?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Crispy on 06/21/2012 02:06 pm
The base takes the heat. You might be thinking of the blackening of the sides of the capsule visible immediately after recovery.
(http://images.gizmag.com/inline/dragon_lands.jpg)
This is not due to direct heating by the extremely hot plasma. It's part radiative heating of the paint, from the hot plasma passing by, and part deposition of particles from the ablating heat shield. Neither of which are going to be any problem for the superdraco pods.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kirghizstan on 06/21/2012 02:13 pm
so the albative material getting into the super dracos won't have any impact on their performance?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 06/21/2012 03:39 pm
so the albative material getting into the super dracos won't have any impact on their performance?
Not sure we know enough about it.  It might be a benefit.  It might be a detriment.  It might be neither.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: SpacexULA on 06/21/2012 03:56 pm
The black dust on the Dragon is not from the sides being super heated, it's from all the ablation of the thermal protective system.

As you can see from the COTS1 and COTS2 dragons, anything brushing the capsule wipes the powder right off.

If you really wanted to upset SpaceX, go after the Dragon with soap and water and it will likely look like it's barely been used (and not be nearly as interesting to look at).

The nozzle for the superdraco is also ablative, it should already be signed for a much ruffer life than some dust coming off the ablative.  (Ok, it's most likely not ablative after reading back, thanks ugordan!)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: mr. mark on 06/21/2012 04:00 pm
In other words, it's not burnt its dirty.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 06/21/2012 04:01 pm
The nozzle for the superdraco is also ablative

It is?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Crispy on 06/21/2012 04:12 pm
so the albative material getting into the super dracos won't have any impact on their performance?
I'd be amazed if it made any measurable difference whatsoever.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ugordan on 06/21/2012 04:15 pm
so the albative material getting into the super dracos won't have any impact on their performance?
I'd be amazed if it made any measurable difference whatsoever.

Quite likely, but when it comes to spaceflight one should never underestimate the ability of "insignificant" things to ruin your day.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Crispy on 06/21/2012 04:33 pm
Oh indeed. I fully expect them to test and measure, I just don't expect them to find any issues. But they have to know for sure...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ChefPat on 06/22/2012 12:49 pm
I wonder if the "nostrils" on the landing SD's could have some type of protective plug/cover that would pop off when they're fired for the landing maneuver?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Crispy on 06/22/2012 01:48 pm
I wonder if the "nostrils" on the landing SD's could have some type of protective plug/cover that would pop off when they're fired for the landing maneuver?
They're abort motors too, remember. That means keeping things simple. You don't want a pop-off cover to accidentally not pop off in an abort situation.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 06/22/2012 01:53 pm
I wonder if the "nostrils" on the landing SD's could have some type of protective plug/cover that would pop off when they're fired for the landing maneuver?
They're abort motors too, remember. That means keeping things simple. You don't want a pop-off cover to accidentally not pop off in an abort situation.
Significant pressure from the expansion of hypergolics might make this idea fairly foolproof.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Prober on 06/24/2012 01:01 am
The base takes the heat. You might be thinking of the blackening of the sides of the capsule visible immediately after recovery.
(http://images.gizmag.com/inline/dragon_lands.jpg)
This is not due to direct heating by the extremely hot plasma. It's part radiative heating of the paint, from the hot plasma passing by, and part deposition of particles from the ablating heat shield. Neither of which are going to be any problem for the superdraco pods.

Ok, but would not the deposits clog the engines if not operating?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: MP99 on 06/24/2012 09:32 am
Ok, but would not the deposits clog the engines if not operating?

That was my thought, too.

cheers, Martin
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: starsilk on 06/24/2012 04:15 pm
Ok, but would not the deposits clog the engines if not operating?

That was my thought, too.

cheers, Martin

perhaps they have to be running at very low throttle during reentry?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: ArbitraryConstant on 06/24/2012 04:31 pm
You don't want a pop-off cover to accidentally not pop off in an abort situation.
It's difficult to imagine a way a cover wouldn't pop off with the thrust of SD behind it.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: tnphysics on 06/24/2012 06:38 pm
Yeah...they could be thin plastic or metal covers that would burst and be blown clear
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: JBF on 06/24/2012 08:11 pm
Yeah...they could be thin plastic or metal covers that would burst and be blown clear

Don't they do that already for the thrusters?

(http://www.cbc.ca/gfx/images/news/photos/2012/05/18/li-spacex-dragon-620-ap2585.jpg)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Alexsander on 06/28/2012 05:19 pm
Perhaps this is a better thread for it - A new tweet from Elon Musk that just went out: https://twitter.com/elonmusk/status/214831794103664640

Quote
Elon Musk ‏@elonmusk
Just fired our Superdraco escape rocket engine at full thrust! Needed to carry astronauts on Dragon pic.twitter.com/ef86qbWF

Can't wait to see the first operational test, with a unmanned Dragon hovering on air with the SuperDracos. Maybe next year?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: MP99 on 06/28/2012 05:54 pm
Yeah...they could be thin plastic or metal covers that would burst and be blown clear

Don't they do that already for the thrusters?

I don't think those could remain on through re-entry, which was the question.

cheers, Martin
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: AnalogMan on 10/21/2012 12:14 am
Perhaps this is a better thread for it - A new tweet from Elon Musk that just went out: https://twitter.com/elonmusk/status/214831794103664640 (https://twitter.com/elonmusk/status/214831794103664640)

Quote
Elon Musk ‏@elonmusk
Just fired our Superdraco escape rocket engine at full thrust! Needed to carry astronauts on Dragon pic.twitter.com/ef86qbWF

Can't wait to see the first operational test, with a unmanned Dragon hovering on air with the SuperDracos. Maybe next year?

Flight tests of the Dragon launch abort systems for Pad Abort and In-Flight Abort are currently estimated to be in 4Q13 and 2Q14 respectively (from September 18, 2012 presentation).

http://www.nasa.gov/pdf/698590main_NAC%20Presentation%209-18_508.pdf
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: guckyfan on 10/21/2012 07:02 am

Can't wait to see the first operational test, with a unmanned Dragon hovering on air with the SuperDracos. Maybe next year?

That would be cool. But I don't expect it so soon. It is not required for launch abort and that is what they need to achieve. After launch abort the landing will be in water using parachutes.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/21/2012 05:18 pm

Can't wait to see the first operational test, with a unmanned Dragon hovering on air with the SuperDracos. Maybe next year?

That would be cool. But I don't expect it so soon. It is not required for launch abort and that is what they need to achieve. After launch abort the landing will be in water using parachutes.



I think we'll see hover before the abort test.  It's easier to start slow and increase the testing envelope, so by the time it's an all-or-nothing test, there's more confidence in the vehicle's flight performance.

Also, it's not established that every abort scenario depletes the propellant tanks, and even when coming down with parachute, even a small amount of active control can make the difference between a safe landing and injury or loss of life.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: spectre9 on 10/22/2012 01:12 am
Abort tests are always high gee.

Ripping the crew capsule away from any possible explosion.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Comga on 10/26/2012 08:35 pm
This is from an article in Discovery News: (http://news.discovery.com/space/spacex-cargo-return-dragon-station-121026.html)

"The key part of the (Dragon) upgrade (to crew carrier) is an emergency escape system so astronauts can be sprinted away from the rocket in case of an accident during launch.

SpaceX plans a launch pad abort test next year and an inflight abort test in 2014.

"We're going to launch a Falcon 9 with a Dragon on top and go up to around max Q (the point of maximum aerodynamic pressure on a vehicle) and show that we can punch it off the top and safely bring the crew away even in that critical flight regime," Reisman said last week at the International Symposium of Personal and Commercial Spaceflight in New Mexico.

If all goes as planned, SpaceX plans to test fly a Dragon capsule with its own astronauts aboard in May 2015"

Have we heard all this explicitly stated before?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: CuddlyRocket on 10/27/2012 10:33 am
A question from a layman.

As max Q occurs pretty early on flight, does SpaceX need a Falcon 9 with the full set of nine engines for this test flight? They presumably need much less fuel as they have no need to get into orbit and therefore need much less thrust for both takeoff and achieving max g as well as max Q (could they get these to coincide?).

Presumably they also don't need the second stage engine (and avionics etc). Would it be wise to replace the engines with ballast of equivalent size and weight? Do they need a second stage at all and instead just mate the Dragon directly onto the first stage?

All in all, such a test flight might not cost as much as first appears?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: guckyfan on 10/27/2012 11:21 am
A question from a layman.

As max Q occurs pretty early on flight, does SpaceX need a Falcon 9 with the full set of nine engines for this test flight? They presumably need much less fuel as they have no need to get into orbit and therefore need much less thrust for both takeoff and achieving max g as well as max Q (could they get these to coincide?).

Presumably they also don't need the second stage engine (and avionics etc). Would it be wise to replace the engines with ballast of equivalent size and weight? Do they need a second stage at all and instead just mate the Dragon directly onto the first stage?

All in all, such a test flight might not cost as much as first appears?

I am also a layman. But it seems to me a second stage all by itself would be enough, with the Merlin vac replaced by a first stage Merlin. Probably not fully fuelled to ensure sufficient thrust for takeoff.

Some had speculated that it could be done with the Grashopper but that is probably too heavy with its landing gear.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Nomadd on 10/27/2012 12:28 pm
 No reason for a second stage, but the cost of a few engines and some fuel is insignificant compared to the rest of the test. There would be little reason to fly a unique 1st stage configuration that wouldn't be as valid for testing because of the different nature of thrust, acceleration, engine shutdown and behavior of the launcher during separation.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: john smith 19 on 10/27/2012 01:34 pm
A question from a layman.

Presumably they also don't need the second stage engine (and avionics etc). Would it be wise to replace the engines with ballast of equivalent size and weight? Do they need a second stage at all and instead just mate the Dragon directly onto the first stage?

All in all, such a test flight might not cost as much as first appears?
Feasible but a *bad* idea. You're sort of in the Ares !-X test territory.  If you're going to *prove* to NASA  that Dragon will escape from the rocket under worst case conditions the LV should be as much like the *standard* LV as possible.
The money you save will be *dwarfed* by the processing and manpower costs you spend trying to separate the separation phenomena of the test from those caused by the differences between test and real stages.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/27/2012 04:02 pm
It would be a good opportunity to try to land a first stage though...

Assuming Grasshopper made advanced flights by then, this is a chance to have a first stage at a high altitude and speed, but without the reentry interface integrated in yet.  (which at some point they'll start testing too, in parallel)

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: douglas100 on 10/27/2012 04:20 pm
It would be a good opportunity to try to land a first stage though...

I  think it would be a bad idea. The point of the test is to get a high fidelity simulation of a real abort. If they are going to use an F9 as reported, then it makes sense to use an unmodified first stage and an inert ballasted second stage with the Dragon mounted on it in the usual way.

The first stage recovery effort should remain a separate program and not be used to introduce extra complexity and cost into what is already a vital test.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 10/27/2012 04:26 pm
Feasible but a *bad* idea. You're sort of in the Ares !-X test territory.  If you're going to *prove* to NASA  that Dragon will escape from the rocket under worst case conditions the LV should be as much like the *standard* LV as possible.
The money you save will be *dwarfed* by the processing and manpower costs you spend trying to separate the separation phenomena of the test from those caused by the differences between test and real stages.

Bear in mind NASA didn't expend a Saturn V when testing the LES for Apollo, so there is precedence for using a bespoke launcher solution.
IANARS but I would expect at the very least a dummy second stage.

SpaceX aren't rolling Falcons and Dragons off the production line like sausages. If they can avoid expending a full LV I'm sure they will. They were very to combine the COTS demos, for example.


Less likely, but does another company offer a vehicle which would match the performance requirements?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: guckyfan on 10/27/2012 04:55 pm
Feasible but a *bad* idea. You're sort of in the Ares !-X test territory.  If you're going to *prove* to NASA  that Dragon will escape from the rocket under worst case conditions the LV should be as much like the *standard* LV as possible.
The money you save will be *dwarfed* by the processing and manpower costs you spend trying to separate the separation phenomena of the test from those caused by the differences between test and real stages.

Bear in mind NASA didn't expend a Saturn V when testing the LES for Apollo, so there is precedence for using a bespoke launcher solution.
IANARS but I would expect at the very least a dummy second stage.

SpaceX aren't rolling Falcons and Dragons off the production line like sausages. If they can avoid expending a full LV I'm sure they will. They were very to combine the COTS demos, for example.


Less likely, but does another company offer a vehicle which would match the performance requirements?

Most unlikely, that a vehicle from another company could do it at a better price. I don't know though why a second stage alone could not do the trick. It has the same diameter so similar aerodynamics for the Dragon. Using throttle and calculating the weight it should be possible to come quite close to the conditions of a first stage with a second stage mockup. If that is not good enough, only a full Falcon 9 will do.


Quote
"We're going to launch a Falcon 9 with a Dragon on top and go up to around max Q (the point of maximum aerodynamic pressure on a vehicle) and show that we can punch it off the top and safely bring the crew away even in that critical flight regime," Reisman said last week at the International Symposium of Personal and Commercial Spaceflight in New Mexico.

Anyway this sounds clear enough. They plan to launch a full Falcon 9. Anybody knows the payment for this milestone?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/27/2012 05:17 pm
It would be a good opportunity to try to land a first stage though...

I  think it would be a bad idea. The point of the test is to get a high fidelity simulation of a real abort. If they are going to use an F9 as reported, then it makes sense to use an unmodified first stage and an inert ballasted second stage with the Dragon mounted on it in the usual way.

The first stage recovery effort should remain a separate program and not be used to introduce extra complexity and cost into what is already a vital test.

On the contrary - if they can do it, it means the F9R are going to be the run of the mill in the relatively near future, so might as well test with them.

Besides, everything "special" is going to happen after capsule separation. An F9R is a very good simulator to an F9 up until stage separation.  So if you're going to throw away a stage, might as well make it a test flight.

(Still will need to pop out the second stage or second stage simulator, and you don't want to do that at Max Q - I see that as the major obstacle here, but I think it is solvable)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: aero on 10/27/2012 05:17 pm
Hmm - I wonder if the avionics software will be far enough along for SpaceX to do a soft landing test in the ocean after the abort. That is, test a safe return of the first and second stages.

Of course the safe return of the Dragon is basic to the abort test.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: joek on 10/27/2012 05:46 pm
Anybody knows the payment for this milestone?
$30M (milestone #14, April 2014).  However, I wouldn't make too much of the amount; attempting to correlate milestone payments with SpaceX costs/expenditures is iffy at best.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: joek on 10/27/2012 05:47 pm
On the contrary - if they can do it, it means the F9R are going to be the run of the mill in the relatively near future, so might as well test with them.

Besides, everything "special" is going to happen after capsule separation. An F9R is a very good simulator to an F9 up until stage separation.  So if you're going to throw away a stage, might as well make it a test flight.

I have doubts that "F9R are going to be the run of the mill in the relatively near future" will be within the next several years--after all, F9 v1.1 isn't even in regular service yet.

Moreover, SpaceX has yet to show F9R is recoverable under nominal conditions.  Recovery after an failure that causes an abort--much less at max-q--is going to be significantly more difficult, not to mention of dubious value.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/27/2012 06:03 pm
On the contrary - if they can do it, it means the F9R are going to be the run of the mill in the relatively near future, so might as well test with them.

Besides, everything "special" is going to happen after capsule separation. An F9R is a very good simulator to an F9 up until stage separation.  So if you're going to throw away a stage, might as well make it a test flight.

I have doubts that "F9R are going to be the run of the mill in the relatively near future" will be within the next several years--after all, F9 v1.1 isn't even in regular service yet.

Moreover, SpaceX has yet to show F9R is recoverable under nominal conditions.  Recovery after an failure that causes an abort--much less at max-q--is going to be significantly more difficult, not to mention of dubious value.

Well, we're talking about a landing from post-max-q condition in 2014 - not completely out of the realm of possibilities if Grasshopper flies well in 2013.  This won't be a completed F9R, but if in parallel they are working on the reentry interface, it means 2015 or 2016 for a full F9R, and so doing the abort test of the F9R is representative since it only applies to crewed flights.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 10/27/2012 06:14 pm
Most unlikely, that a vehicle from another company could do it at a better price.
Agree, I was only throwing the idea out there. They like to do everything 'in house' by all accounts, but at the end of the day Elon is a businessman and for a one-off test flight if another company can offer the service at less cost then why not?

Quote
I don't know though why a second stage alone could not do the trick. It has the same diameter so similar aerodynamics for the Dragon. Using throttle and calculating the weight it should be possible to come quite close to the conditions of a first stage with a second stage mockup.
Interesting idea, I think the biggest issue might be verifying the TVC authority with such a short stack. The cost of a rocket isn't all in the pieces of metal.

Quote
If that is not good enough, only a full Falcon 9 will do.
Or a stock first stage and boilerplate second stage. Absolutely no need to carry along a flightworthy second stage merely to dump it in the ocean.

Quote
Quote
"We're going to launch a Falcon 9 with a Dragon on top and go up to around max Q (the point of maximum aerodynamic pressure on a vehicle) and show that we can punch it off the top and safely bring the crew away even in that critical flight regime," Reisman said last week at the International Symposium of Personal and Commercial Spaceflight in New Mexico.

Anyway this sounds clear enough. They plan to launch a full Falcon 9.

I still don't think they'd be mad enough to throw away a real second stage. IMHO the most likely candidates are, in order:
- F9 first stage + dummy second stage
- F9 first stage alone
- Full F9
- Custom vehicle based on first stage, reduced engine compliment
- Custom vehicle based on second stage
- Grasshopper
- A.N.Other company's vehicle.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: LucR on 10/27/2012 06:36 pm
I still don't think they'd be mad enough to throw away a real second stage.

Couldn't they just separate the Dragon around MaxQ and then continue to orbit with secondary payloads on the second stage? Or does the abort use up resources that would be needed for that? E.g. gravity losses because of required engine cutoff or throttling or perhaps some fuel?

(First post here, IANARS)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: joek on 10/27/2012 06:36 pm
Well, we're talking about a landing from post-max-q condition in 2014 - not completely out of the realm of possibilities if Grasshopper flies well in 2013.  This won't be a completed F9R, but if in parallel they are working on the reentry interface, it means 2015 or 2016 for a full F9R, and so doing the abort test of the F9R is representative since it only applies to crewed flights.

Yes, but consider the conditions which would cause an in-flight abort, and the resulting conditions, especially at max-q.  I seriously doubt SpaceX will expend much effort considering recovery for those (presumably rare) cases--at least until well after they have mastered recovery under nominal conditions.

I don't understand "doing the abort test of the F9R is representative since it only applies to crewed flights".  How would F9R be representative of what will be used for crewed flights?  Especially given (emphasis added):
Quote from: SpaceX CCiCap SAA, pg. 2a.13
10. Flight Review of Upgraded Falcon 9 (November 2013)

Scope: SpaceX will conduct a review of a launch of the upgraded Falcon 9 launch vehicle demonstrating the operation of enhanced first-stage M1D engines, stage separation systems, enhanced second-stage MVacD engine and mission-critical vehicle telemetry during flight. Demonstration of the upgraded launch vehicle will serve as a risk reduction for the planned inflight abort test (Milestone 15). This review will also provide data to support human certfication of the Falcon 9 launch vehicle. The upgraded vehicle has higher performance, adding additional margin for the Commercial Crew Program.

The SpaceX contribution value includes the Falcon 9 upgrade development work performed during the period from CCICap authority to proceed through the first flight of the upgraded Falcon 9.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: go4mars on 10/27/2012 06:58 pm
Unlikely idea alert:

Perhaps SpaceX could do the abort off an extended trunk version.  Or maybe even a regular trunk.  What's inside the trunk?  Other customers that go to orbit after the abort.  Would need extra insulation presumably (to survive dragons breath), but the extra mass for that could be offset by not having to carry the dragon from maxq to orbit.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/27/2012 07:18 pm
I still don't think they'd be mad enough to throw away a real second stage.

Couldn't they just separate the Dragon around MaxQ and then continue to orbit with secondary payloads on the second stage? Or does the abort use up resources that would be needed for that? E.g. gravity losses because of required engine cutoff or throttling or perhaps some fuel?


Launch vehicle engines are shutdown in an about
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/27/2012 07:32 pm
Yes, but this is a test of the capsule, not the rocket, so a different behavior of the rocket does not necessarily degrade the test.  As has been pointed out, NASA did not even always use the same rocket during the LAS test.

The argument will have to be why escaping from a throttled-down rocket invalidates the test of the capsule.

However, since in a real abort situation the rocket will indeed be completely shut down, adding such a capability just for the sake of the test seems not worth the time and effort.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/27/2012 07:33 pm

The argument will have to be why escaping from a throttled-down rocket invalidates the test of the capsule.


It can't throttle down enough or even fast enough to simulate a cutoff.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: guckyfan on 10/27/2012 07:34 pm
I still don't think they'd be mad enough to throw away a real second stage.

I am afraid, if the second stage alone will not do it they will have to use a real second stage and a full Falcon 9. Its flight avionics control the first stage too. So about the only thing they could spare is the engine. They could replace it with a dummy or one that has been tested to the limits.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 10/27/2012 07:39 pm
I still don't think they'd be mad enough to throw away a real second stage.

I am afraid, if the second stage alone will not do it they will have to use a real second stage and a full Falcon 9. Its flight avionics control the first stage too. So about the only thing they could spare is the engine. They could replace it with a dummy or one that has been tested to the limits.

Grasshopper seems to do fine without a second stage controlling it, so it must be possible to integrate the avionics with the first stage.
All you would need is a length of steel barrel section simulating the mass of the second stage. Put the avionics wherever is most convenient. Shades of Ares 1-X perhaps but in this case I think it's perfectly legitimate.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: joek on 10/27/2012 09:14 pm
Unlikely idea alert:

Perhaps SpaceX could do the abort off an extended trunk version.  Or maybe even a regular trunk.  What's inside the trunk?  Other customers that go to orbit after the abort.  Would need extra insulation presumably (to survive dragons breath), but the extra mass for that could be offset by not having to carry the dragon from maxq to orbit.

As you suggest, unlikely.  Unless the customer prefers an apogee measured in fathoms.  Seriously, this is going to be a major hurdle, there is more than enough to deal with to get CTS up and running by 2016-2017, and SpaceX and NASA need to keep their eye on that ball.

Complicating matters by introducing goals not directly relevant to CCiCap/CTS makes no sense; nor would I expect NASA to tolerate or pay for such.  The cost of failure could be extremely high, as in: SpaceX's position vs. the competition eroded beyond repair; or worse, bringing into question the viability/safety of the entire CTS program.

I hope and expect that decisions will be based on minimizing CCiCap/CTS program risk, and that anything which increases that risk will be rejected.  Anything not directly and specifically related to demonstrating crew safety as part of the in-flight abort test is IMHO at best a Really Bad Idea; get over it.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: kirghizstan on 10/27/2012 09:25 pm
this test will be done at max-q secondaries are not possible
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 07:01 am

The argument will have to be why escaping from a throttled-down rocket invalidates the test of the capsule.


It can't throttle down enough or even fast enough to simulate a cutoff.

That's true, but I'm drawing from the fact that tests on previous systems (e.g. Apollo) used a completely different rocket, so didn't simulate the exact conditions either.

In fact, there are no "exact conditions", since an abort can happen in all sorts of scenarios.  I figure if they can escape from an (as you said) partially throttled down rocket, then it's a good enough test for the capsule LAS.

You get all the measurements you need from the capsule, and you know that your rate of separation from a fully shut-down rocket would have been even greater, since once the LAS is firing and the capsule completes the aerodynamic separation, they are independent flying objects.

Not saying they will necessarily do it, just saying that it should be feasible  if the F9R is advanced enough at that point in time.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: CuddlyRocket on 10/28/2012 07:11 am
Launch vehicle engines are shutdown in an about

Surely that's an abort scenario towards the ideal end whereas the LAS must pass worst-case scenarios? A scenario more towards the worst-case end is where the engines don't shut down on abort so that the Falcon 9 is still accelerating behind the Dragon on separation.

Was the Apollo LES tested with the booster engines shut-down or still running?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/28/2012 10:05 am
A scenario more towards the worst-case end is where the engines don't shut down on abort so that the Falcon 9 is still accelerating behind the Dragon on separation.


That isn't a plausible scenario
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 12:49 pm
A scenario more towards the worst-case end is where the engines don't shut down on abort so that the Falcon 9 is still accelerating behind the Dragon on separation.


That isn't a plausible scenario

Jim - think this through:

a) Abort planning starts out in unexpected, rare conditions.

b) A sudden structural failure can produce momentary thrust.  IIRC Challenger's ET pushed forward as it was failing.

c) Thrust makes the LAS scenario different, and mostly more difficult. However, "different" by itself is not a show stopper, since previous tests were done "differently".

What matters is how much difference there is.  Testing at low altitude and speed, for example, is a) too different and b) and easier test.  Testing on a different rocket at similar aerodynamic conditions is acceptable. 

Popping off of a throttled down stage at max-Q, IMO, is an acceptable test from the capsule and LAS's point of view.

However:

Continuing with the stage later for a landing might be impractical.  The stage is already at max-Q, and so can't flip around until it has slowed down a lot, which it has to do head-first.  Such a low-speed flip-around is way out of the normal playbook for an F9R, and since it is only relevant for this test, I am not sure it is worth their effort to develop it.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/28/2012 12:54 pm

b) A sudden structural failure can produce momentary thrust.  IIRC Challenger's ET pushed forward as it was failing.
 

Again, not plausible for ELV's
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: douglas100 on 10/28/2012 01:10 pm

Continuing with the stage later for a landing might be impractical.  The stage is already at max-Q, and so can't flip around until it has slowed down a lot, which it has to do head-first.  Such a low-speed flip-around is way out of the normal playbook for an F9R, and since it is only relevant for this test, I am not sure it is worth their effort to develop it.

No, as I said in my previous post it's a bad idea. Why do you insist on over complicating something which is already difficult to do and critical to crew safety?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 04:25 pm

Continuing with the stage later for a landing might be impractical.  The stage is already at max-Q, and so can't flip around until it has slowed down a lot, which it has to do head-first.  Such a low-speed flip-around is way out of the normal playbook for an F9R, and since it is only relevant for this test, I am not sure it is worth their effort to develop it.

No, as I said in my previous post it's a bad idea. Why do you insist on over complicating something which is already difficult to do and critical to crew safety?

Wait...  I'm saying that the post-separation recovery might be too complicated, and you're saying "no, it might be too complicated"

All I have to say to that is that the post separation recovery might be too complicated.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 04:32 pm

b) A sudden structural failure can produce momentary thrust.  IIRC Challenger's ET pushed forward as it was failing.
 

Again, not plausible for ELV's

You have to address a,b and c as a whole, since the argument stands even if b is not plausible.

Second, why do you think that a situation where there's residual thrust is so implausible?  I can see why it would be smaller maybe, and I can see why we'd all hope the LAS fired before its effect even occured, but I can't see why it is so utterly implausible.

Third, why do you think that such residual thrust is so destructive to the LAS test?


Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 10/28/2012 06:45 pm
Look on how the liquid engines generate thrust and on how are they instrumented and controlled. There's really no way the it will keep pushing. It might explode, but not keep pushing. Completely different case with the solids.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 07:18 pm
Look on how the liquid engines generate thrust and on how are they instrumented and controlled. There's really no way the it will keep pushing. It might explode, but not keep pushing. Completely different case with the solids.

This is not about solids of course - they are obviously a different beast.

I was talking about a transient push as the tank fails.  IIRC the Challenger ET actually pushed forward during failure.

In an ELV, the situation will be that a large amount of propellant ignites with ambient air near the rapidly disintegrating engine bay, and that push is transmitted through the vehicle during some brief period of failure.

The exact mechanism doesn't matter.  I don't see what's wrong with doing a LAS test from a rocket that's throttled down.

Unless SpaceX will pull a miracle by way of recovering the stage after separation, however, it doesn't matter for this test.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 10/28/2012 07:23 pm
It must add an unwanted degree of complication to have to consider an intact LV throttling back up and aiming to continue through to orbit, whilst a Dragon is somewhere overhead performing an abort demo.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: modemeagle on 10/28/2012 08:08 pm
During the test they can shut down the engines and abort the Dragon off the top of the stack.   Then have it release the dummy 2nd stage (why waste a multimillion dollar 2nd stage when a mass simulator is enough).  They can dump the remaining propellant/ballast and recover the stage with a parachute.  They will already be there to recover the capsule, why not get the stage too.

Simulating nominal trajectory, abort yields the following data:

Maximum altitude should be ~ 17.3 km. 
Maximum velocity should be ~ 416 m/s or mach 1.39.
Range of impact ~ 23 km.
Time of abort ~ 76.8 seconds
Time of impact ~ 214.5 seconds (no parachute)
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: baldusi on 10/28/2012 08:33 pm
Not everybody has the LOX tank on top/fuel on botom on the core (like the ET), nor H2 and RP-1 react in the same way, nor does the engine failure necessarily causes a catastrophic failure like the SSRB did to the ET.
So you propose not to actually demonstrate the whole failure detection+shutdown process (99% of chance) to test the 1% transient push? It's a matter of demonstrating the most likely failure case.
In the particular case of the Falcon v1.1, the GG cycle is very gentle and most failure will be detected. Any red line on temperature or pressure or even rotational speed would generate a shutdown command. And even if you have a rupture, there's a very nice precedent that, for the fuel dome at least, has a good change of not generating any fraticide. So the sort of failure that you are thinking is extremely difficult to replicate, at least for the Falcon 9.
The Atlas V, might have the sort of failures that where made famous by the Zenith. But even in that case, there's a very important difference between a detonation and a deflagration. I suspect that what you see as likely, is a deflagration, which is subsonic by nature. Since we are talking of a demonstration at MaxQ, well into the supersonic regime, it's not really an issue.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 08:48 pm
Not everybody has the LOX tank on top/fuel on botom on the core (like the ET), nor H2 and RP-1 react in the same way, nor does the engine failure necessarily causes a catastrophic failure like the SSRB did to the ET.
So you propose not to actually demonstrate the whole failure detection+shutdown process (99% of chance) to test the 1% transient push? It's a matter of demonstrating the most likely failure case.
In the particular case of the Falcon v1.1, the GG cycle is very gentle and most failure will be detected. Any red line on temperature or pressure or even rotational speed would generate a shutdown command. And even if you have a rupture, there's a very nice precedent that, for the fuel dome at least, has a good change of not generating any fraticide. So the sort of failure that you are thinking is extremely difficult to replicate, at least for the Falcon 9.
The Atlas V, might have the sort of failures that where made famous by the Zenith. But even in that case, there's a very important difference between a detonation and a deflagration. I suspect that what you see as likely, is a deflagration, which is subsonic by nature. Since we are talking of a demonstration at MaxQ, well into the supersonic regime, it's not really an issue.

No.....  I wasn't suggesting that at all.

From scratch.

I said that in the time frame they propose for the LAS test, F9R development might be advanced enough (e.g. high altitude Grasshopper flights, initial F9R hardware with flight landing gear) that they may have the ability to do the LAS test off of a preliminary F9R and try to reclaim it.

There are two issues:
1:  Is this a valid LAS test
2:  Is this possible from the first stage's point of view.

On 2, I think the answer is no.   After Max-Q, and still heading forward, they are so far outside of the normal envelope of a returning F9R that it will be too much effort of solving a new problem.  It won't be anywhere near a "sub-problem of the full return sequence".   I will be very happy to be proven wrong on this one.

On 1, given the way that previous LAS tests deviated from the "real thing", I don't see a problem with the LAS system being tested off of a throttled down first stage, which will later try to land. (not continue to orbit)

That's all I said.  I didn't propose to complicate any test to simulate the upward thrust of an exploding rocket.  I said that the throttled down thrust is not that big of a deal as far as ruining the test.

How these arguments wonder around....
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/28/2012 09:02 pm

The exact mechanism doesn't matter.  I don't see what's wrong with doing a LAS test from a rocket that's throttled down.


70% is not really throttling down
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/28/2012 09:04 pm

On 1, given the way that previous LAS tests deviated from the "real thing", I don't see a problem with the LAS system being tested off of a throttled down first stage, which will later try to land. (not continue to orbit)



which tests "deviated" from the real thing?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 10/28/2012 09:09 pm

On 1, given the way that previous LAS tests deviated from the "real thing", I don't see a problem with the LAS system being tested off of a throttled down first stage, which will later try to land. (not continue to orbit)



which tests "deviated" from the real thing?

Presumably referring to Little Joe?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 09:16 pm

The exact mechanism doesn't matter.  I don't see what's wrong with doing a LAS test from a rocket that's throttled down.


70% is not really throttling down

The assumption was F9R, so we have 8 engines shutting down completely, and center engine throttling down to whatever the Merlin 1D can do. And since in the F9R the center engine has to be restartable, they might be able to shut it down too.  Either way.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/28/2012 09:17 pm

On 1, given the way that previous LAS tests deviated from the "real thing", I don't see a problem with the LAS system being tested off of a throttled down first stage, which will later try to land. (not continue to orbit)



which tests "deviated" from the real thing?

Presumably referring to Little Joe?

Which was designed to simulate the same abort conditions.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 09:53 pm

On 1, given the way that previous LAS tests deviated from the "real thing", I don't see a problem with the LAS system being tested off of a throttled down first stage, which will later try to land. (not continue to orbit)



which tests "deviated" from the real thing?

Presumably referring to Little Joe?

Which was designed to simulate the same abort conditions.


On 1, given the way that previous LAS tests deviated from the "real thing", I don't see a problem with the LAS system being tested off of a throttled down first stage, which will later try to land. (not continue to orbit)



which tests "deviated" from the real thing?

Presumably referring to Little Joe?

Which was designed to simulate the same abort conditions.

LJII was a multi-stage solid rocket.  The entire dynamic environment till separation could not have been the same as a full Saturn V.  And how did they shut it down before LAS activation, to simulate the shutting down of the Saturn V engines?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/28/2012 10:06 pm

LJII was a multi-stage solid rocket.  The entire dynamic environment till separation could not have been the same as a full Saturn V.  And how did they shut it down before LAS activation, to simulate the shutting down of the Saturn V engines?


There was no need to simulate the entire dynamic environment, just the most severe ones.  LJII was a single stage rocket with multiple motors.  It used different motor combinations to achieve specific abort conditions such as Max Q, high altitude and such.   There is no need for the motors to be "shutdown".  They burn out on their own.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 10:11 pm

LJII was a multi-stage solid rocket.  The entire dynamic environment till separation could not have been the same as a full Saturn V.  And how did they shut it down before LAS activation, to simulate the shutting down of the Saturn V engines?


There was no need to simulate the entire dynamic environment, just the most severe ones.  LJII was a single stage rocket with multiple motors.  It used different motor combinations to achieve specific abort conditions such as Max Q, high altitude and such.   There is no need for the motors to be "shutdown".  They burn out on their own.

So the entire different set of solid motors, plus the fact that they have to shut down on their own (in whatever transient happens there) - all of that is an acceptable difference.

But if one engine out of nine throttles down instead of shuts down - that's a show stopper?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/28/2012 10:28 pm

But if one engine out of nine throttles down instead of shuts down - that's a show stopper?

No, the whole idea that the aborting Dragon doesn't affect the falcon and leaves it intact is a stretch
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/28/2012 10:31 pm

So the entire different set of solid motors, plus the fact that they have to shut down on their own (in whatever transient happens there) - all of that is an acceptable difference.
?

What do you mean "difference"?  As long as  conditions at max q are met, it doesn't matter how they are achieved.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 10:37 pm

So the entire different set of solid motors, plus the fact that they have to shut down on their own (in whatever transient happens there) - all of that is an acceptable difference.
?

What do you mean "difference"?  As long as  conditions at max q are met, it doesn't matter how they are achieved.

Go back and read you own posts.  You were all in my face that doing a LAS abort from a throttled down rocket was not a real test since the last remaining engine won't throttle down fast enough to simulate a "real" rocket shutdown.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/28/2012 10:42 pm

But if one engine out of nine throttles down instead of shuts down - that's a show stopper?

No, the whole idea that the aborting Dragon doesn't affect the falcon and leaves it intact is a stretch


Well, there will certainly be some aerodynamic effect due to the change in aerodynamic shape.   Can the rocket recover?  I don't know.  Neither do you though.  We have the one data-point that a rocket with all engines operating can recover from a highly disruptive event, but it is not quite the same situation.

The only reason to try this stunt is if such a recovery is within the flight envelope that the F9R will be able to handle.  We know it will be able to handle re-entering tail first at a pretty high speed and maintain stability.  We don't know whether it can handle recovering from a head-first flight, presumably by slowing down and flipping.  Like I said - sounds difficult.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/28/2012 11:01 pm
We have the one data-point that a rocket with all engines operating can recover from a highly disruptive event, but it is not quite the same situation.


That doesn't even apply or in the same family.  Many similar events have happened such as SRM's not jettisoning, fins falling off, two engines shutting down, etc.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/28/2012 11:03 pm

So the entire different set of solid motors, plus the fact that they have to shut down on their own (in whatever transient happens there) - all of that is an acceptable difference.
?

What do you mean "difference"?  As long as  conditions at max q are met, it doesn't matter how they are achieved.

Go back and read you own posts.  You were all in my face that doing a LAS abort from a throttled down rocket was not a real test since the last remaining engine won't throttle down fast enough to simulate a "real" rocket shutdown.


Conditions would include no or little thrust from the booster
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/29/2012 12:34 am

So the entire different set of solid motors, plus the fact that they have to shut down on their own (in whatever transient happens there) - all of that is an acceptable difference.
?

What do you mean "difference"?  As long as  conditions at max q are met, it doesn't matter how they are achieved.

Go back and read you own posts.  You were all in my face that doing a LAS abort from a throttled down rocket was not a real test since the last remaining engine won't throttle down fast enough to simulate a "real" rocket shutdown.


Conditions would include no or little thrust from the booster

k, this doesn't even parse anymore.  I'm done for the day...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: CuddlyRocket on 10/29/2012 11:48 am
That isn't a plausible scenario

Plausible is irrelevant; it's possible that counts with an escape system.

Granted, planning for an abort would include a command to shut down the engines. But such commands require the equipment that initiates the command, and the equipment that acts upon it, to be working. Possibilities might be very low that that would ever not be the case, but very low is not zero.

I thought engineers understood Murphy's Law?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/29/2012 12:37 pm
That isn't a plausible scenario

Plausible is irrelevant; it's possible that counts with an escape system.

Granted, planning for an abort would include a command to shut down the engines. But such commands require the equipment that initiates the command, and the equipment that acts upon it, to be working. Possibilities might be very low that that would ever not be the case, but very low is not zero.

I thought engineers understood Murphy's Law?

Wrong.   Plausible is relevant and possible is irrelevant.  It is called risk management. You can't design something to cover 100% of the situations or the costs will be enormous.  One designs for the most likely situations and not all and especially those with little chance of happening.

Also, by your logic, the spacecraft would not get the abort signal and therefore remain attached to the booster.

There are many scenarios on shut downing engines.  There are engine controller that are located near the engine, that actually shutdown the engine and they can do it independent of the launch vehicle avionics.  It can be based on engine health, a signal from the avionics, or from the FTS, or even a lack of comm from the avionics.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/29/2012 03:14 pm
That isn't a plausible scenario

Plausible is irrelevant; it's possible that counts with an escape system.

Granted, planning for an abort would include a command to shut down the engines. But such commands require the equipment that initiates the command, and the equipment that acts upon it, to be working. Possibilities might be very low that that would ever not be the case, but very low is not zero.

I thought engineers understood Murphy's Law?

yes, but don't worry about it - this argument got really senseless, time to move on.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/29/2012 03:17 pm
That isn't a plausible scenario

Plausible is irrelevant; it's possible that counts with an escape system.

Granted, planning for an abort would include a command to shut down the engines. But such commands require the equipment that initiates the command, and the equipment that acts upon it, to be working. Possibilities might be very low that that would ever not be the case, but very low is not zero.

I thought engineers understood Murphy's Law?

yes, but don't worry about it - this argument got really senseless, time to move on.

So when you get the correct answer and you don't like it, just change the subject.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 10/29/2012 03:21 pm
That isn't a plausible scenario

Plausible is irrelevant; it's possible that counts with an escape system.

Granted, planning for an abort would include a command to shut down the engines. But such commands require the equipment that initiates the command, and the equipment that acts upon it, to be working. Possibilities might be very low that that would ever not be the case, but very low is not zero.

I thought engineers understood Murphy's Law?

Wrong.   Plausible is relevant and possible is irrelevant.  It is called risk management. You can't design something to cover 100% of the situations or the costs will be enormous.  One designs for the most likely situations and not all and especially those with little chance of happening.


That is why there are no parachutes on commercial airplanes and ejection seats don't cover the whole flight envelope.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: daj24 on 10/29/2012 03:42 pm


That is why there are no parachutes on commercial airplanes and ejection seats don't cover the whole flight envelope.

WAY WAY off topic but this brought up a memory of an old TV show (60's) called Ripcord.  Once they were in a commercial flight that was failing for some reason (hey! the memory is only SO good) and they had the passengers parachute out of the plane.  And this is what brought this up: Assuming that they actually had parachutes for everyone on board (doubtful)  how long do you think it would take to carry/drag each and every protesting passenger to the open door and push/toss them out! lmao!
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Kaputnik on 10/29/2012 03:51 pm
The parachuting-from-an-airliner is pretty ridiculous because it depends on the aircraft being in controlled, stable, level flight at low altitude, and to maintain that state over a fairly long period of time to complete the evacuation.

Mind you, those same constraints didn't stop parachutes being added to the Shuttle after RTF...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/29/2012 05:09 pm
That isn't a plausible scenario

Plausible is irrelevant; it's possible that counts with an escape system.

Granted, planning for an abort would include a command to shut down the engines. But such commands require the equipment that initiates the command, and the equipment that acts upon it, to be working. Possibilities might be very low that that would ever not be the case, but very low is not zero.

I thought engineers understood Murphy's Law?

yes, but don't worry about it - this argument got really senseless, time to move on.

So when you get the correct answer and you don't like it, just change the subject.

Jim - towards the end there you were flailing so far from the original argument that I don't think you even remember what the question was, never mind the answer...   

So in short, no, not biting, not changing the subject, just walking away...
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Chris Bergin on 10/29/2012 08:58 pm
Heh. No Internet fighting!
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/31/2012 06:15 pm
I've been mulling this over.  Maybe it is possible to bring the stage back after all.

Here's the sequence of events as I see it.  (only as "possible" - nothing predictive here, since I know nothing of SpaceX's actual plans)

An under-fueled, preliminary F9R first stage carries a Dragon (using an adapter - no second stage necessary) to max-q.

The stage shuts down 8 engines, and throttles down the last engine, which causes the rocket to behave similarly to an abort scenario (except for the added thrust).

Dragon fires the LAS, and is gone.

Even with one engine, the stage should be in controlled flight.  It will have to overcome the separation event of the Dragon, and otherwise will be slowing down due to air resistance and gravity.

It is important that even with one engine, t/w > 1, since it means it is possible for the stage to slow down while maintaining a nose-up attitude and upwards trajectory. (otherwise, it would have to follow an arced trajectory down into the ocean)

As it is slowing down while climbing up, the stage can reduce thrust and start falling down, tail first.  This is basically the "flip" maneuver, except there are no significant side loads.

Now the stage is reproducing what will happen towards the end of a regular re-entry - starting after the slow-down of the entry interface - which is why it might be worth it for SpaceX to do this - instead of throwing away a first stage, they get a "free" high-altitude landing trial.

FWIW, they don't even need a flight landing gear - they can go through this test and then dunk it in the ocean - the value is in validating an increased portion of the flight envelope.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: spectre9 on 10/31/2012 10:42 pm
How does a shortened Falcon 9 get the same data?

I'm guessing it doesn't.

Ascent abort will be done with the real deal with all the computers and gizmos that will be on a real flight.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 10/31/2012 11:42 pm
I'm a he, but, oh wow, I'm speechless  :)

---

Max-q is a combination of altitude, velocity, and acceleration.  You can hit all of them if you can control the amount of fuel loaded and the thrust profile.   (Reference back to Little Joe II)   

As an aside, max-q is the worst case loading on a *normally* operating rocket and the worst case escape scenario should not be the same, since we assume the rocket stopped accelerating.

EDIT - I went reading, I think I have my definition wrong, but the point still holds...   [going to read some more...]

EDIT2 - yeah, I had some other explanation in mind.  no matter.  Good use of the the strike-through feature.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 11/01/2012 12:23 am

As an aside, max-q is the worst case loading on a *normally* operating rocket and the worst case escape scenario should not be the same, since we assume the rocket stopped accelerating.


No, it is the worst case.  max-q is a period of time and not instantaneous.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 11/01/2012 12:51 am
Yes, the aerodynamic load peaks as a function of speed and air density. 

The rocket structure also experiences an acceleration load, but if the engines throttle to keep it constant, than the peak of aerodynamic load is also the peak of total load, and we're all in agreement.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: hkultala on 11/01/2012 07:50 am
Yes, the aerodynamic load peaks as a function of speed and air density. 

The rocket structure also experiences an acceleration load, but if the engines throttle to keep it constant, than the peak of aerodynamic load is also the peak of total load, and we're all in agreement.


You are making a big false assumption with your if.

The engines throttle to keep acceleration under some structural limit. That limit is always much higher than the acceleration at max-q.

The rocket starts going vertically to quickly rise to lower atmospheric density, max-q happens relatively early phase of flight where the air still has some density left.

Limiting max acceleration to the acceleration at max-q would mean couple of things:
1) there would be much more gravity losses
2) if the throttling is not done by shutting down whole engines, throttling down engine thrust would also decrease isp (all rocket engines have best isp at full thrust)

So making max acceleration happen at max-q would mean the rocket would waste a lot of potential capasity.

Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 11/01/2012 12:34 pm
Yes, the aerodynamic load peaks as a function of speed and air density. 

The rocket structure also experiences an acceleration load, but if the engines throttle to keep it constant, than the peak of aerodynamic load is also the peak of total load, and we're all in agreement.

Aero loads are not the same as structural loads.  Peak acceleration occurs near engine shutdown and not max-q.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 11/01/2012 01:37 pm
I agree.  peak acceleration occurs as the rocket becomes lighter and so easier to push, and also emptier,  and so easier for the tanks to handle.

Max-q, as I corrected earlier, is only about the aerodynamic pressure, and occurs relatively early.

Does anyone know, btw, at what angle to the horizontal the F9 flies (let's be specific - in the last mission) when hitting max-Q?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Jim on 11/01/2012 02:56 pm
and so easier for the tanks to handle.


Can't say that either.  It is a function of pressure, acceleration and propellant remaining, and therefore peak structural loading of the tanks may occur before peak acceleration, whereas for non tank structures, it is a peak acceleration.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: simonbp on 11/01/2012 03:50 pm
Heh. No Internet fighting!

Obligitory. http://xkcd.com/386
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 11/01/2012 05:23 pm
and so easier for the tanks to handle.


Can't say that either.  It is a function of pressure, acceleration and propellant remaining, and therefore peak structural loading of the tanks may occur before peak acceleration, whereas for non tank structures, it is a peak acceleration.

Didn't say the peaks coincided, just that towards the end of the burn, two processes are at play - increasing acceleration due to lower mass, and depletion of propellant and thus reduction of column height in the tanks.  The overall effect of loads is a combination of those.

Anyway, back to LAS.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: MP99 on 11/01/2012 06:36 pm
Heh. No Internet fighting!

Obligitory. http://xkcd.com/386

Ironic, when there was only one word!   ;)  http://www.merriam-webster.com/dictionary/obligatory (http://)

Had to point it out in the circumstances! And it's not even bedtime, yet.

cheers, Martin
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: meekGee on 11/01/2012 07:53 pm
Heh. No Internet fighting!

Obligitory. http://xkcd.com/386

Ironic, when there was only one word!   ;)  http://www.merriam-webster.com/dictionary/obligatory (http://)

Had to point it out in the circumstances! And it's not even bedtime, yet.

cheers, Martin

Seriously funny....
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: corrodedNut on 11/16/2012 09:57 pm
Details? From today's Royal Aeronautical Society lecture:

"Duncan Law-Green @Rocketeer_UK
SuperDracos 6-8gs, will boost through sound barrier in 4s"
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: docmordrid on 11/16/2012 11:11 pm
Details? From today's Royal Aeronautical Society lecture:

"Duncan Law-Green @Rocketeer_UK
SuperDracos 6-8gs, will boost through sound barrier in 4s"

Whooah....and I thought 0-100 in 5-6 seconds was a rush :-p
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: AndyX on 07/15/2013 01:40 am
Details? From today's Royal Aeronautical Society lecture:

"Duncan Law-Green @Rocketeer_UK
SuperDracos 6-8gs, will boost through sound barrier in 4s"


What do the Tower LAS do in comparison to that?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Lars_J on 07/15/2013 02:48 am
Details? From today's Royal Aeronautical Society lecture:

"Duncan Law-Green @Rocketeer_UK
SuperDracos 6-8gs, will boost through sound barrier in 4s"


What do the Tower LAS do in comparison to that?

What tower LAS do you mean? It all depends on how fast it needs to be able to get away from the LV. F9 should have a relatively benign worst case scenario compared to something sitting on top of solid(s). One could make a tower LAS with SD thrusters if one wanted.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: beancounter on 07/15/2013 03:40 am
Details? From today's Royal Aeronautical Society lecture:

"Duncan Law-Green @Rocketeer_UK
SuperDracos 6-8gs, will boost through sound barrier in 4s"


What do the Tower LAS do in comparison to that?

What tower LAS do you mean? It all depends on how fast it needs to be able to get away from the LV. F9 should have a relatively benign worst case scenario compared to something sitting on top of solid(s). One could make a tower LAS with SD thrusters if one wanted.

Ok more specifically, does anyone know what g forces is the MPCV tower LAS expected to pull and is it more or less that the SDs?  I'm assuming it would be greater as solids can't be turned off and so the capsule has to escape an accelerating lv.  Yes?  No?  Anyone?
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Elmar Moelzer on 07/15/2013 04:02 am

Ok more specifically, does anyone know what g forces is the MPCV tower LAS expected to pull and is it more or less that the SDs?  I'm assuming it would be greater as solids can't be turned off and so the capsule has to escape an accelerating lv.  Yes?  No?  Anyone?
I might be remembering this wrong, but AFAIK, yes they need to pull more gs because of the solids. IIRC that was one often critizised point about the Ares1.
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Garrett on 07/15/2013 10:43 am
Details? From today's Royal Aeronautical Society lecture:

"Duncan Law-Green @Rocketeer_UK
SuperDracos 6-8gs, will boost through sound barrier in 4s"

Whooah....and I thought 0-100 in 5-6 seconds was a rush :-p

Amazing acceleration, but for exact times to the sound barrier, here's what I work out:
avg acceleration     
time to sound barrier
4g
8.7 s
5g6.9 s
6g5.8 s
7g5.0 s
8g4.3 s
8.7g4.0 s
9g3.9 s

Assumptions:
 - sound barrier is 340 m/s (i.e. sea level sound barrier)
 - 1g = 9.8 m/s2
 - initial velocity is zero
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: MP99 on 07/15/2013 11:27 am
Details? From today's Royal Aeronautical Society lecture:

"Duncan Law-Green @Rocketeer_UK
SuperDracos 6-8gs, will boost through sound barrier in 4s"

Whooah....and I thought 0-100 in 5-6 seconds was a rush :-p

Amazing acceleration, but for exact times to the sound barrier, here's what I work out:
avg acceleration     
time to sound barrier
4g
8.7 s
5g6.9 s
6g5.8 s
7g5.0 s
8g4.3 s
8.7g4.0 s
9g3.9 s

Assumptions:
 - sound barrier is 340 m/s (i.e. sea level sound barrier)
 - 1g = 9.8 m/s2
 - initial velocity is zero

Which direction are you firing relative to ground? Suspect you need to do a vector addition of 1g downwards for gravity. If you start out horizontally, the fall adds slightly to your net speed.

But, for instance, 0.999g whilst sitting on the ground - never. Not enough thrust to lift off the ground.

cheers, Martin
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: R7 on 07/15/2013 11:28 am
what g forces is the MPCV tower LAS expected to pull and is it more or less that the SDs?

Max 15g.

http://www.nasa.gov/pdf/450266main_PA-1_Team_FS.pdf
Title: Re: SpaceX: Advanced Launch Abort System (LAS)
Post by: Garrett on 07/15/2013 11:45 am

Which direction are you firing relative to ground? Suspect you need to do a vector addition of 1g downwards for gravity. If you start out horizontally, the fall adds slightly to your net speed.
But, for instance, 0.999g whilst sitting on the ground - never. Not enough thrust to lift off the ground.
cheers, Martin
Am firing directly upwards, as I presume that's a decent approximation to the Dragon LAS profile. Was calculationg g-forces as an addition to gravity, but after your comment and a quick search online, I see that I misused the term. So yes, I need to add 1g so that an acceleration of 1g would mean sitting still on the ground.
avg acceleration     
time to sound barrier
5g
8.7 s
6g6.9 s
7g5.8 s
8g5.0 s
9g4.3 s
9.7g4.0 s
10g3.9 s

Note that the "4 seconds" number mentioned earlier could have come from somebody mistakenly subtracting the 1g.