Wednesday, October 13, 2010

Out-There Ideas of Yesteryear

I'm a bit of a sucker for a novel concept, as strange as they can be. Usual thing to happen is that I'll find a concept at the end of a train of links, investigate it for a while (which can be minutes, or it can be days), toss it around, and then decide whether I like the notion or not. Some ideas I like for their engineering sense, even if at the expense of practicalities. There are others I like and/or remember for the romance or cool factor--this is a large part of my continued fondness for airships, despite the fact that they've been obsolete in most applications since about the 1940s, if not earlier.

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).
Douglas Paracone
So, what you have here is are two one-man open spaceships, each with with a single manually pointed solid rocket motor and some cold gas thrusters to orient. After you've retrofired, you pull a lever and inflate a foam-filled aeroshell around the back of the chair (or in the MOOSE it actually encases you), and then sit back and enjoy the 4000 k air whipping past your head. Once the show's over in the Paracone, the design of the aeroshell and chair slow you to a terminal velocity of 42 km/hr before crushing to absorb even that, and you step off, hopefully onto the same continent you were aiming for while your friend in the MOOSE activates his parachute for his landing. If you two weren't so lucky (maybe you have hand tremors like my grandfather?) and you messed up, then what's left of you might be scattered across the countryside. Fun ride!

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).
Look at this! Standard equipment is a 3 meter non-ablative aeroshell with a foam core, a rear-mounted solid retro-motor, some cold-gas thrusters for alignment, and a nifty little heads-up display for your pilot to guide you in on. Truly the LEXUS of space compared to Paracone or MOOSE, but by using suits and fitting three to a unit instead of one (spreading the weight of the more-accurate guidance and alignment out over three men), you still only need 140 kg of dead mass per person. Not too shabby. Still, I really can't see it being used as anything but the last of the last ditch efforts. I love the idea, but I really, really am not sold on the notion of the open-top 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.

That is indeed a rocket the size of a destroyer floating on the open ocean next to an aircraft carrier. Your eyes do not deceive you, you merely wish they did. Sea Dragon was an innovative idea for reducing the cost and complexity of rocket launches by accepting higher dead-weight than normal coupled to a truly enormous rocket design that looks like Werner Von Braun and Mike Griffin's group project. The idea of saving money was actually pretty smart: the rockets were designed to be built with cheaper but heavier materials to looser tolerance but with higher safety factors, so the net was a heavier-for-the-same-capability but overall cheaper launch vehicle. So instead of the spacecraft to carry your 10 ton sat to space massing 20 tons dry, maybe it masses 40, but at less cost. (Something similar to this exists in the modern notion of 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.
The Sea Dragon that Truax designed as the final goal was to be huge, almost double the length of the Saturn V and more than double the diameter. Gross mass on launch was to be something on the order of 18,000 metric tons, and  the payload to orbit a staggering 450 tons--enough mass to launch the entire ISS and a Apollo moon mission at the same time. Why it's depicted as only launching a CSM with those stats I do not know, but it's this huge size that leads to much of my issues with this concept.

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.

1 comment:

  1. Disagree. If they can get ISS up there at $220/kg instead of how it was done, it would more than pay for the whole development cost. Can you imagine the simple telescopes you could send up with a 75 foot diameter pay load fairing?

    And if I was re-entering, there is something poetic and elemental about doing it alone, with a view of stars and flames. I wouldn't want to be the first guy to try it out. But if it was a safe enough ride... Yes please!