Wednesday, October 27, 2010

A Matter of Some Gravity...

If you compare manned vessels in hard science fiction, soft science fiction, and speculative fiction, you'll see a lot of variations. But there's one thing nearly all of them will have in common: artificial gravity. Why? Let's look at the reasons and some of the issues involved in making it practical.

Gearing Up

Okay, I saw this the other day and meant to post it, but...well, homework. So it's coming now. It's not spaceflight, but does appeal to my core demographic of "me, coming back to find links to stuff I thought was cool". It's a demonstration of the operation of what look like impossibly-shaped gear mechanisms.
Watch Video Here

The gears in this video are myriad in design and wonderful to watch in motion: Square gears! Spiral gears! Fish-shaped gears! There's a lot of clever design work here, and the result is amazing to behold. Each new mechanism brought me a fresh sense of "Nah, it couldn't really work like that, could it?" and then a "Wow! Guess it can!" I'm particularly interested in what the odd shapes due to rotation rates--two circular gears have a constant rate of rotation when spinning one another, but it looks like there may be some interesting effects going on here with some of the arrangements.

Looking at it reminded me of a pair of videos I found a while back about mechanical computers. As I said in the "Out There Ideas of Yesteryear" post, I like ideas that are novel or unusual, because even if their own merits are no longer greater than their drawbacks, they can provide an interesting outside perspective on the ideas that are more mainstream. Thus, I find mechanical or analogue computers fascinating, because in addition to the fascinating engineering and design elements of them they also offer an outside view back at the amazing modern computers we (or at least I know I) often take for granted. As an engineer in an era when computer cycles are so cheap and plentiful that the average household has access to many times the computing power used to send men to the moon and mostly uses it for watching cute web videos, it's amazing to look at the kinds of tools my predecessors--perhaps even people I may work alongside once I graduate--had to make due with and admire the kinds of ingenuity they used to work around these limitations.
A Boy and His Slipstick
Me messing around with the ThinkGeek slide rule
I received for my birthday last month
Tools like the slide rule, which for decades was as symbolic of the technical fields as the stethoscope is of medicine but has now vanished almost completely, or mechanical computers of the sort used to aim bombs, torpedoes, and guns in WWII used elegant applications of problem analysis and mathematical tricks to
do with simple mechanisms what we today do with digital calculators and computers. Admittedly, a slide rule  is less powerful a portable, general-use tool than, say, the TI-83 I keep in my backpack or on my desk, and the mechanical computers I mentioned were limited by their construction to a limited set of uses while a digital computer doing the same tasks can also be reprogrammed to do others, but their obsolescence now does little to reduce my admiration of their incredible history of design and use.

Further information on mechanical computing mechanisms can be found in this 1950s-era training video about naval gunnery control computers, or in OP 1140, a 1944 Navy publication that serves as a fairly definitive reference on the topic of mechanical analogue computers. If you have the time, at least check out the video; it offers some of the same kinds of mind-expanding feelings as the gearing video at the top of this post, but with the added benefit of learning a few things about the history of computing.

Monday, October 25, 2010

Seems Like it's Been Forever...

Well, school's been running me pretty ragged lately, so I haven't had time to sit down and write down the thoughts I've had the last week or so, which I'd like to rectify . However, there's a couple different topics, so let's start with the one that caught my interest most recently: The ISS just surpassed the Mir record to take the top spot on longest  uninterrupted human presence in space. It turns ten years old in a week or so at the start of November. A neat series of desktop images of the ISS assembly sequence up until 7-15-2009 is here, but reflecting on these images made me remember something.

Despite now being the oldest manned object in space and all its scientific value so far, the ISS isn't done yet. There's still the Permanent Multipurpose Module, the Alpha Magnetic Spectrometer, and at least one more Russian module, the Multipurpose Laboratory Module. It's been operated for almost ten years, and it's only just now almost done. That's...incredible. Now admittedly, some of those delays haven't been the fault of the ISS, but rather of the Shuttle, and the modularized design of ISS means that it's been a capable scientific platform even while not being completed, but it's still kind of incredible that it's not quite finished yet.

It's especially incredible to me because of a video I saw the other day of the Bigelow Aerospace booth at the International Symposium on Private and Commercial Spaceflight. It's a neat video, showing some nice physical models of the first station they're currently working on, based off two Sundancer modules, one BA 330, and a propulsion/docking node. There's also cutaways of the Sundancer and BA 330, and a cutaway of a Bigelow module sized for a 100 ton 8-m launch vehicle coming in at 2,100 cubic meters, and the booth manager mentions a 70-ton 8-m-launch-diameter module sized at 1150 cubic meters. Both of these HLV-sized modules (which happen to fit well onto a J246 or J130 launch vehicle like SLS may resemble) would exceed ISS by a significant margin in terms of volume, and do so with a single launch.

BA 2100 (100-ton, 8 m fairing, 2100 cubic meters)
What's really interesting to me is that with the kind of diameter this module type could have (about 16 m), it's enough of a spin radius that a full-sized centrifuge creating a significant fraction (20%-80%) of Earth's gravity is possible without requiring spin rates that are too extreme. Thus, the living section of the station could be in spin gravity, with the labs and mechanical spaces in zero-g, and the whole thing inside the pressure barrier of the module. The hub could be pre-installed as part of the rigid core along with bearings and utility connections to the fixed portion of the station, with the rim/floor and the spokes attached to the hub to complete the assembly as part of fitting out the unit once it was inflated on-orbit. Such a centrifuge could provide increased crew comfort and enable research into the effects of life at different gravitational levels over time.

I have more on the big list of Things I Want to Talk About, but I think I'm done for now. As a closer, I offer a Sesame Street segment featuring my favorite JAXAnout, Soichi Noguchi. I'm not sure when this was filmed exactly, it must have been before his departure from the station back in June, but it appears to have aired fairly recently. Regardless, it made me smile. I used to watch Sesame Street all the time when I was little, I always enjoyed it, and I hope the kids watching it now got a kick out of this bit.

Additionally, I'm going to once again recommend checking out the series of images of the ISS under assembly that I mentioned up above. They can be found here, and it's really interesting to see how the station has grown and changed over the years.

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.