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Sturgeon's House

Why Shuttle Was A Good Thing - And How I Reusability?


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Shuttle takes a lot of criticism, and according to my most recent estimates, approximately 52.4% of it - globally - comes from me, so pay attention. I'm about to praise it.

If you pay attention to spaceflight, you'll find that there's a couple of reasons to why we don't have colonies on other planets yet. One reason is that spaceflight isn't cheap. The other reason is that spaceflight isn't cheap because it isn't safe.

Alright, so why isn't spaceflight cheap? Well, imagine building a wonderful, awesome, complex thing, with lots of fiddly moving bits, and then you send it off to do what it does, and it explodes and is destroyed. You'd be pretty bummed, right? Rockets are designed to do that every single time they fly. That big Saturn V rocket that took us to the Moon, it didn't come back. The only thing that did come back was that little thing at the top that looked like Madonna's tit, and none of those ever flew again, nor could they. But some rockets do come back, like Space Shuttle. Those require a huge number of man-hours to refurbish and bring back to flying condition, and sometimes, despite the best efforts of those folks, they break up over Texas anyway.

Which brings me to my next point: spaceflight isn't cheap because it isn't safe. You know how awful paying insurance on your car is? Well, imagine paying insurance on a controlled explosion designed to throw something eight times faster than a rifle bullet. Even if it's not carrying dudes, that's probably not cheap. So spaceflight needs to become safer and surer, so the insurance premiums come down. It might help if we didn't let grandma drive the rocket; she's really too old to have a license.

So we need a rocket that's safe and reusable, ideally. That's where the Shuttle comes in.

Shuttle was neither safe, nor the kind of cheaply reusable we need, but it wasn't expendable, either. Shuttle had a lot of problems, but one thing it did genuinely contribute is experience with reusable systems. There are reusable hydrolox engines now that, without Shuttle, may never have existed. The Orbiter (that's the plane-looking bit) itself wasn't a dead end, either; the USAF's X-37B is currently flying, gaining us even more experience with reusable systems.

There's a very old metaphor, that what we can do now is only because we stand on the shoulders of giants. This conveys the value of experience, of building on previous accomplishments to achieve something great. Brilliant minds and ideas, foolproof engineering (no such thing! snorts my old boss), and eureka! moments dominate our minds because they are the sexiest part of progress, but more valuable than all of those, is having the experience, the shoulder of the giant to stand on to go somewhere new.

Shuttle, for all its faults, gave us an absolutely priceless body of experience in reusability (130 flights! That means a plurality of human flights into space have been on a reusable vehicle). Ultimately, it will be reusability and safety that open the door to space and let us explore the stars. Some have suggested it would have been better to not do Shuttle and instead do Apollo derived vehicles - there may be merit to this, but it must not be underestimated how important Shuttle has been in improving our understanding of reusability.

Now, how do we do reusability? Well, here's an email I sent to my father exploring an idea about that:
 

 

 

I've been thinking about space launch reusability, and how to accomplish it - most importantly with a low expenditure of man-hours.

One idea that came to mind is, is there a possibility that engineers are trying too hard to improve the efficiency of launchers by shaving weight everywhere and anywhere possible, instead of trying to improve the durability of components so that they can be reused?

I don't have a good appraisal of this situation, but modern launch vehicles are very efficient in terms of their construction. It seems almost a tautology to me that, if reusability is hard because it's expensive (e.g., every reused component must be inspected before reflight - I think the ideal is that this will eventually not be the case, right?), then launchers should be made more durable and less efficient.

Lord knows we have good launchers - take Shuttle as an example. If you decided, hey, we're going to make Shuttle Mk. II, and it's exactly like Shuttle Mk. I, except that it is strong as snot (say - replace or augment the heat tiles with protective shielding or a material that's thermally resistant and also doesn't fail when hit by foam) and can only lob 15 tonnes into orbit.

Of course no one would do that. But maybe they would if it were Falcon 9-esque, but with a reduced payload? If that really did pay off, wouldn't your flight rate go way up, and wouldn't your cost/kg go way down? At that point, who cares how inefficient the launcher is?

 

And as I said to him,

Alright, your turn. Tell me everything that's wrong with what I just said.

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I'd say that cutting capability down considerably in order to drive prices down is absolutely vital, I'd be totally behind that Shuttle II that puts less into orbit if it were something that could be launched affordably for the vast majority of missions. Frankly if reusable components are too expensive because the maintenance is painful but recycling their materials and building new would work better do that, because that way you're building more components and bigger production lines drive costs down in a way dudes in clean suits don't. However, push the limits because part of the point is to keep the technology progressing. A lot of the goal is to cause change, so leading the target is good sense.

 

Light can very often be good because weight is a huge contributor to a feedback loop requiring progressively bigger rockets. Ounces hurt, so you'd better trim down. The goal is a spaceborne A4D because we're looking for the inflection point where it gets as cheap as possible to get a pound to orbit, because in my opinion we're trying to make it as cheap as possible to launch things, because that opens up the market much wider. The more launches the better. For that we want something that is a fixed purpose ship for hauling things of a given weight that includes a significant fraction of the things that are currently and would be were the price to fall launched. The biggest thing we absolutely do not need is to burden it with any other requirements.

 

This goes to the biggest problem with the shuttle in my opinion; they had to get it to satisfy Air Force requirements for a cold warrior sattelite carrier, including the capability to go on an orbit around the Earth's poles, deploy a reconnaissance sattelite, retrieve an errant spacecraft or even capture an enemy spacecraft and return to its launch site after only one orbit. If you've ever wondered where the 1,100 mile cross range requirement came from, there it is. So every time the Shuttle went up, it was paying for dead weight wings that weren't needed for the civilian mission. This sort of thing drives costs up. The Air Force also wanted the bay to go from 50k pounds to 15 x 60 feet that could hold 50k to 65k pounds and have doors that could easily open up into space (sattelite shenanigans again). That ruled out a lifting body. Again this adds to the amount of weight the thing was carrying around that did nothing, and meant that the shielding had to be tiles again because of weight requirements. (Source courtesy of NASA) I also tend to feel that sucking it up and using disposable heavy lift rockets to do space station carrying is probably better because the goal is to make space missions and space technology cheaper, not specifically to drive down the cost of heavy lift. This is personal opinion though.

 

The Shuttle was a great idea, the problem was we got an F-111B rather than an F-14. Yes my analogies are entirely to naval aircraft, why do you ask?

 

I like the looks of the X-37 though, that looks good.

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The point that the crossrange requirement caused problems is an important one. One of the documents I have laying around mentions a 1,000 kilometer crossrange requirement. Naturally, that's going to increase your wing area, which increases your weight, which increases the mass of your launch system, etc. If you can somehow convince the Air Force to ditch that requirement (STS never did the kind of mission that required it anyway), I'd recommend something with a shape more similar to the X-24 or L-301. Those will still give you enough lift to get you in the general vicinity of a runway, and cuts out most of your extraneous dry mass that would go into the wings. Having less sharp leading edges also helps with heating (heat transfer rate at hypersonic speeds is proportional to 1/sqrt(radius)). If you've got a lighter vehicle, you can either stick it on a smaller launch system, and that could get rid of the requirement for parallel staging. 14 astronauts saved. Alternatively, you can do like Sturgeon mentioned, and make the thing a lot more robust using your extra weight.

 

Personally, I'd also recommend decoupling the cargo carrying and astronaut transport roles. Stick your big payloads on expendible launch vehicles, and use the reusable vehicle as your crew taxi. Alternatively, do it the other way around, and use the reusable unmanned launcher to work out the kinks in reusability. Speaking of which, I would have personally done something like the X-37 (as a resuability testbed) before the shuttle. Use a smaller, less expensive, and unmanned vehicle to get our procedures for reusability down pat.

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So I think Unstart and I have pretty similar ideas. I don't know how well that sort of idea would have fared politically, because some people think furthering scientific development and advancing the knowledge of the universe isn't a good goal, and filling the Air Force requirements made it look nice to the cold warriors, but I think the cost of that weight really killed a lot of the potential of the program.

 

Alternate idea. Ditch the cross range requirement by building a second base 1000 miles away. Pretty sure a base pair in the right part of Texas and Florida would get things done in that respect. That would at least save the cost of the wings. The box fuselage might still be a thing because of some of the requirements for bringing satellites down, but at least we've transferred some of the cost away from every single mission into a single sunk cost, which turns it from a downside to being able to mercilessly weild the sunk cost fallacy against the government to get more missions launched.

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Minor issue with that; the Air Force was planning on launching shuttles into polar orbit (to overfly the commies) out of Vandenberg AFB, and 1,000 miles west of Vandenberg AFB is the Pacific Ocean (also, the vast majority of Soviet satellites orbit at high inclinations, so you probably couldn't launch out of Florida to intercept).

 

Naturally, after insisting on this requirement, the USAF proceeded to launch a grand total of 0 shuttle missions out of Vandenberg.

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Of course they were going to launch them out of Vandenberg, and there's no islands ~1000 mi west of there. I'm going to need a bit of a sitdown regarding the geometry for launching out of California vs. Florida, but that'll probably be a bit of a non-starter with the single orbit requirement. I'm not sure there's a decent solution other than not tying the future of the space program to an F-111 writ large, then.

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From numerous discussions on rocketpunk manifesto (which is an awesome site btw, if a bit neglected) my impression is that part of the problem is that there simply isn't a market for more launches and no concievable way to develop one sans... well, more launch capacity.

The old economic chicken-and-egg issue, basically.

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