Posted on 08/02/2005 8:56:13 AM PDT by jbstrick
I don't see anything inherently unsafe about riding a single SRB to space. Remember it was not the O-ring failure on the SRB that directly doomed the Challenger, rather it was the ensuing explosion of the main (liquid) fuel tank.
A better solution is a lifting-body spacecraft derived from the old Martin X-24A design, scaled up so it can carry up to seven astronauts into low Earth orbit (LEO). Because it dispenses with the big main engines and the cargo compartment, the lifting body can be quite small, probably light enough to be launched by Lockheed Martin Atlas V or Boeing Delta IV derivatives or the proposed launcher that uses a single Shuttle solid rocket booster. With a lifting body, the vehicle can land anywhere there is an 7,000' or longer runway, which means most of the world's commercial airports.
The liquid fuel engines on the Shuttle are throttleable to a degree. Upper stage engines on most large boosters can also be shut down and restarted.
Aerodynamics are MUCH simpler with a stacked design. I am sure the max aeroloading parameters will be relaxed.
With a good escape system in place there should be no reason to throttle the SRB. If you need to shut it off in flight, the mission has already failed and you will be firing the escape system anyway.
It is significant that there has never been a catastrophic SRB failure on the STS. The o-ring defect that destroyed the Challenger was catastrophic only because of its effect on adjacent systems and would not present a significant risk to the proposed manned system.
IMHO, these systems look like a solid replacement for the shuttle. They are by no means ideal, but in the world of aerospace the better is always the enemy of the good.
> All the Titans, Saturns etc. I am sure were on/off
> just like a solid.
Dunno about the throttling, but the SRBs are not "on/off".
They are "on until fuel exhausted". They cannot be shut
down prior to that, and jettisoning them while still
burning at full thrust is apparently not an option.
> Remember it was not the O-ring failure on the SRB
> that directly doomed the Challenger, rather it was
> the ensuing explosion of the main (liquid) fuel tank.
Had the ET burn-thru not ocurred, the asymetric thrust
would probably have shortly caused stack loss by
exceeding the directional control provided by engine
gymballing and aero-surface deflection.
I included the shuttle in my original comment. And I agree there have been plenty of restartable engines, that's not the same thing as "throttleable" in my lexicon.....
They did this with the Saturn. If I recall, even the Atlas that launched John Glenn was throttled. The thrust is configured during the entire launch for optimum, and the flight path is also configured to get the maximum payload to orbit. They don't run at maximum thrust all the way.
This is a land-based recovery capsule. Maybe a parasail like they envisioned for Gemini? Article says it'll land somewhere in the Western US.
Jimmuh Carter forbid the use of titanium on the shuttle. Aluminum is cheaper.
Throttle is probably a misnomer. They control the rate the fuel pumps work. There are limits the pumps can be slowed to without losing the flame, but they can reduce thrust and do so. The entire launch is configured within those limits.
The Saturn's S-IVB upper stage was fully throttleable. I can't speak to the original Titan upper stage, but the ones flying today are, too.
Google "Kliper" for a Russian alternative that I think makes sense.
Why did he do that?
That was an interesting idea but it took too long to develop and by the time the bugs were worked out the Gemini program had ended. Also, a capsule with a parasail lacks the cross-range capability of a true lifting body design, which means control of the spacecraft after re-entry is a bit limited. I'd rather have a true lifting body vehicle, which means after re-entry the flight crew can land plus or minus 500 miles from the intended touchdown point; for example, a lifting body intended to land at Edwards AFB could land as far south as Miramar Marine Corps Air Base and as far north as Beale AFB.
Actually it's done all the time. They blow a hole in the end opposite the nozzle. It's done with the shuttle's SRBs, and with solid stages on ICBMs as well as other space lauch vehicles.
Still I too don't care for the exclusive use of solids, especially ones as large as the Shuttle SRBs, on manned vehicles.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.