I have to admit that last post was kind of weak. Most of the good points had already been made, and I’m not sure I actually added anything relevant to the discussion. So, as penance, and since the antibiotics I just took say not to lie down for 30 minutes after taking them, I’m going to try and actually put out some original thought on a topic that I’ve been thinking about for a while.
Monte Davis got me thinking about things again, and lessons from the Shuttle program. One of his big points (if I’m not mangling it unduly) was that the problem with Shuttle wasn’t just that it mixed expendable parts with reusable parts. He pointed out that the fully reusable TSTO designs that had been studied were so challenging that they might have been just as big of a mess (or even worse if that’s imaginable!). The problem was that the Shuttle was just a bridge too far. NASA bit off far more than it was ready to chew. The requirements were too high. They were suffering from the conceit that they could somehow jump straight to a large, high-flight rate reusable space transportation right from the very first generation.
I full-heartedly agree that there’s no way NASA could have developed the monster sized TSTO fully-RLV designs that were dropped in favor of the current Frankensteinian amalgam of expendable and “refurbishable” rocket hardware. What I wonder is if there was a different path that could’ve been taken. One that would’ve allowed for more incremental development. One that would’ve allowed for a truly reusable launch vehicle (albeit of much more modest capabilities). One that wouldn’t have become the mess we have in today’s Shuttle.
I’m not conceited enough to state that I know the following would definitely have been better. But I wanted to toss the idea out for discussion. See what you all think.
One of the big not commonly discussed problems with the Shuttle was that NASA was trying to keep as much of the Saturn team together as possible. They were shutting down both Saturn lines, and wanted to keep as many of the engineers and technicians as they possibly could in a time of tight budgets. Keeping as many Saturn engineers around as possible required a big budget development project. However, money was a lot tighter in the post-Apollo days. In order to get the money for Shuttle, as I understand it, they had to scrap both Saturns, and go snuggling up with the Air Force. They had to make their Shuttle design be everything to everybody. Keeping as many of the Saturn engineers as possible involved in the development of the Shuttle implied very large development costs. Those costs were high enough that they had to get the Air Force on board as well in order to get the funding they needed. In order to do that, they had to bloat the requirements even worse than the original Shuttle concepts. However, the requirements grew quicker than the additional money, and in the end they ended up having to make all sorts of compromises.
What if they had intentionally bitten off a smaller task at first. What if they had retired the Saturn V, and slimmed down the staff for the Saturn IB (or better yet, auctioned it off or allowed the companies involved to commercialize it), and then done a much smaller first generation “shuttle”? This shuttle might have only been capable of putting a couple thousand pounds into orbit, and might not have gone straight to an operation vehicle. This wouldn’t have been a program trying to keep as much of the Saturn team together as possible, or an attempt to replace all existing rockets in one fell-swoop. It would’ve been an X-vehicle in reality.
About a month ago, on NASASpaceFlight.com’s L2 section, there was discussion of some conceptual design work done by Dan DeLong (of XCOR) back in the mid 80s that might have been a good way of doing things. The concepts (“Space Plane” and “Frequent Flyer”) that he developed while working for Teledyne Brown were air-launched HTHL style RLVs. They used a modified 747 carrier plane as the first stage, and a LOX/LH2 powered reusable upper stage. While the bigger “Space Plane” design baselined an SSME and 6 RL-10s for the orbiter, and would’ve been barely launchable on a heavily modified 747, I realized that by dropping the cargo capacity a bit, you could both eliminate the SSME and probably cut the modifications on the 747 substantially.
It’s just an idea, and LOX/LH2 isn’t necessarily the right propellant combination for things, but imagine if a vehicle like that had been built. It wouldn’t have required any new propulsion development, since RL-10s were on-the-shelf technology by then. The system would’ve been a lot more reusable, simple, and safe. The engines were a lot easier to maintain and reuse than the SSME. Since the stage had the tanks inside, it would’ve had a much “fluffier” reentry, which when combined with the lower cross-range design, would’ve allowed for a much more robust TPS system to be used–no need for ceramic tiles. Doing an extensive flight test involving dozens of test flights would’ve been perfectly reasonable. You probably wouldn’t have even needed much better of an escape system than a standard aircraft ejector seat, since most of the failure modes would’ve been a lot more benign than for most typical rockets.
Let’s be honest though, the performance would’ve sucked rocks. You would likely have been lucky to get 3000lbs of useful cargo out of the vehicle (in the unmanned version), or possibly 2-4 people on board. This wouldn’t have been everything for everybody. But it would’ve been an extraordinarily good starting point for learning how to design and operate reusable vehicles.
Anyhow, my half-hour is up, but what do you guys think?
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