Random thought: If we have a launch-abort rocket system, could we use it to aid in TLI rather than just discarding it in LEO? | Propulsion Workgroup | Forum

Random thought: If we have a launch-abort rocket system, could we use it to aid in TLI rather than just discarding it in LEO?

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8:52 am
November 17, 2009

brmj

Rochester, New York, United States

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posts 402

I think the title bassiclly speaks for itself.

Main work groups: Propulsion (booster), Spacecraft Engineering, Computer Systems, Navigation and Guidance (software)

10:04 am
November 17, 2009

Rocket-To-The-Moon

Altus, Oklahoma, USA

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posts 685

Very interesting thought. One thing to keep in mind is that these things are wickedly powerful. From the wikipedia article: "The crew were subjected to an acceleration of 14 to 17 g (140 to 170 m/s²) for five seconds."

If that much thrust were used to accelerate the entire crew module + service module it might be more tolerable.

http://en.wikipedia.org/wiki/L…..ape_system

Main Workgroups: Propulsion & Spacecraft Engineering

1:42 am
December 13, 2009

Snyder

Lakewood CO, USA

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posts 7

I believe these abort rockets are jettisoned well before orbit. They are tremendously powerful, but short lived and not built for efficiency.

Once you are in orbit, you would rather have a small (light) engine with high efficiency. Cast off the steel solid brute when it is still low and slow (first stage seperation) but when you have enough speed to coast for a while if you shut the upper stage down early.

9:48 pm
December 13, 2009

Luke Maurits

Adelaide, Australia

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posts 1483

Somehow I completely missed this thread when it was first posted!

Although I haven't voiced this opinion anywhere yet, I have been thinking for a while that we shouldn't bother with a launch-abort rocket system. I know that our design philosophy explicitly says we are not about taking undue risks in the name of simplicity, but Mercury and Apollo both had these systems, and Gemini had an ejection seat system, and as far as I know they none of them were ever actually used for their intended purpose. This suggests to me that (i) it is possible to make the launch platforms safe enough that these aren't strictly necessary and (ii) we can't really be all that certain that they would actually work, i.e. that there would be enough advance warning of a potential disaster to activate the launch abort rockets in time to save the crew.

Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.

1:18 pm
December 17, 2009

Snyder

Lakewood CO, USA

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posts 7

This question is one of the core concepts and arguments over the NASA ARES-I crew launch vehicle. The history is mixed.

The Mercury was never pulled away, but the door was jettisoned accidentally, which almost killed the crew and did lose the capsule.

The Gemini had ejection seats. The crew was so afraid of them, that when they should have been used, they weren't. luckily the

Titan main engines shut down peacefully and the mission flew a few days later. The Apollo never used them, but then again the Saturn was, in many ways, the best launch vehicle ever. There were some times when it was the Commander's discretion however.

We know about the lack of a launch abort system on shuttle. 7 dead. There are 'Black zones' in the flight profile in the shuttle where it is acknowledged that if something goes wrong, everybody dies.

The Soyuz has successfully used it's escape tower rockets. It hurt the crew, but saved there lives when the soyuz booster blew up on the pad.

Space-X is not yet building a launch escape tower for the dragon/Falcon9 vehicle. They are offering the dragon as a crew return, but not launch vehicle for this reason. They estimate $300M for the escape tower. That is more than the development cost for the Falcon I. (probably)

On the topic of ARES-I, because the SRB first stage can not be shut down, the escape rockets need to be considerably more powerful and therefor heavier which drives the weight of the system way up…Which required a better 1st stage that wasn't as reliable and a different second stage …. on and on. P.O.S. (Politically Optimized Stick) but I digress…..

-Gar.

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