|Above: Factual Airship-Launched Fighters (USS Akron, ZRS-4, US Navy)|
Below: Acceptable Substitute to Play on Weekends (Crimson Skies still)
Aerospace produces a lot of these sorts of things; there's whole sites and blogs full of interesting prototypes like the Curtis Ascender or the Burnelli lifting bodies or this thing that made interesting use of the technology of the time, and occasionally actually contributed something useful to more, well, to be frank successful aviation projects. However, the concepts that tend to really stick in my mind are space-related, especially from the first two decades or so of spaceflight.
I was up early yesterday (see: sleep schedule, issues with) and after an unsuccessful attempt to watch the ISS as it passed over the terminator (it wasn't high enough on the horizon to be seen over the trees and buildings of campus, and my ten minutes of planning couldn't get me someplace better) I was browsing a few favorites, and stumbled across a few new ones. While I was on the thought train, I thought I might as well mention it here on Engineer in Progress, because...hey, I said "whatever I feel like," and I feel like it.
My two favorite "out there" notions (of the "how strange, neat to think about, now go back to work on something sensible") are the opposite ends of the size scale: the monstrosity that was Sea Dragon and little re-entry lifeboats like MOOSE or the Paracone idea. So let's start small and then go big. Let's say it's the 1960s, and you're planning a space station. Now obviously, if things go wrong, your crew wants a way to get home fast, but whatever entry system this is means extra mass you have to launch. If you need a big 9 ton capsule for every six crew, then your 30 man crew (astronauts were always going to be men and there would always be large crews aboard stations in these plans) needs 45 tons of just re-entry lifeboats. That's...a lot. That's tons of pressure vessels, tons of control panels, tons of the heath shields to decelerate all those tons of equipment, just to bring down maybe 2.5 metric tons of actual astronauts. So, as rocket scientists tend to do, they looked for something lighter to do the job, and boy did they come up with a doozy.
If you thought a Mercury capsule was just too big with the heat shield six inches behind your seat and the control panel and periscope a foot in full front of your face, with the parachutes just in front of that....well, do I have some re-entry systems for you. Let's start off with the cheap end of the line with the Douglas Paracone and the General Electric MOOSE (Man Out Of Space, Easiest--I'll note they didn't say safe, they said easy).
Still not buying it? I can see you are a person of refined and luxurious taste, so let's show you the big luxury model, the top of the line minimum-mass lifeboat. Allow me to present the GE life raft (again via astronautix).
cabriolet spaceship. This last one actually saw some testing, but nothing more than drop tests and foam mixtures. I'd love to explain this to the tourists on a space hotel, wouldn't you?
Well, say the mission planners, if you're going to splurge on all that, clearly we'll need a bigger launch vehicle. Big and cheap, because we are not made of money, so the extra performance has to fit the budget. Well, okay, allow me to present without further ado: Sea Dragon.
Minimum Cost Design)
So maybe you can build the rockets cheaper, now to launch cheaper. This is where the "Sea" part comes in. Normally, launch infrastructure is expensive and complex. VAB, HAB, crawlers, strong backs, erectors, it's a lot of stuff all for the purpose of assembling, rolling out, and going vertical. Is it really needed for an exploration-class rocket? Robert Truax, who worked on the Polaris and Thor missiles, didn't think it was. Instead, his minimum-cost launcher would be built at a shipyard, towed empty out to sea, filled with LOX and LH2 from electrolysis of sea water (which is what the aircraft carrier is up to above, its reactors are providing the power for all this), then when everything is ready you simply fill some trim tanks at the tail and it sinks to a vertical orientation. Light the engines, lift off, and you're going. This was actually tested with the Sea Bee and Sea Horse rockets, modified sounding rockets and missiles to test the trimming and underwater ignition. Apparently, reuse was possible, and the ignition worked well enough. So maybe this is indeed possible, even if it means everything does now have to be salt-water resistant. Let's talk about the elephant in the room---why the vehicle is sized to launch elephants.
See, I can grasp the notion of Minimum Cost Design. I'm not an adherent of the build-it-out-of-1/2-inch-steel group, but I can see where the notion comes from. But the benefits of those lower cost-per-vehicle only really pay off with frequent launches. Over the last 20 years, we've barely launched 450 tonnes altogether. Where would the payloads be to justify such a huge rocket flying more than once? Even with 60s funding, I don't see it, not right off the bat. And in order to do this, you have an enormous vehicle, with just two enormous pressure-fed engines. Oh yes, those engines on there, each large enough to take a Saturn V up the throat? Those are to be pressure-fed to avoid "complexity". Complexity? How about combustion instability from runaway pressure waves the size of houses? It took seven years to stop combustion issues from killing the F1 on test stands, and if it hadn't been started in the late fifties as a research project, it would have delayed the entire moon program. This thing is supposed to be orders of magnitude bigger. Seems like a fun R&D program.
Is bigger always better? No, I don't think so. And to be honest, I can't believe Traux did either, it seems to clash with the very notion of reduced complexity his version of MCD wanted. I get that capability shapes mission shapes payload shapes launcher shapes capability and on in a vicious cycle that you have to break somewhere, but why with a 450-ton IMLEO beast to break the bank too? I've heard the term "Battlestar Galactica" use to refer to mission plans with more mass and cleverness then they have to by people who like things like Mars Direct, but Sea Dragon is the cream of that in my view. Maybe if they'd tried the core notion of a sea-launched cheaply-built booster with a more practical payload (20 tons? 50?), then it might have actually done something to contribute instead of falling into the history books.
Best is the enemy of good enough, too much cleverness and shooting for perfect can kill a project as dead as not enough cleverness or doing shoddy work. The little lifeboats and the giant Sea Dragon stick in my head as good examples of this, on the end of "what can we do without by being clever" and "what can we build to launch the biggest thing EVAR". I try and hold myself to the same standards--I have to, with how I can get caught up in fancy if I don't reign myself in (see: zeppelins, above). Maybe some time I'll talk about past and current designs I think hit the balance in a good way. Or maybe I'll talk about lunar comsats.
If you've made it all the way through this to here, more power to you, I know I don't have any clue when to shut up once I warm to a topic, no matter how little anyone but me cares. As a reward, check out Contact Light, it's a reconstruction of restored film from on-board and ground cameras and mission audio tapes to produce a full audiovisual recreation of the Apollo 11 moon landing. It's about 17 minutes, so not quick, but the history is amazing. I hope someday not too far off that I or at the least someone of my generation will be at the consoles or controls making this happen again.