Wednesday, June 29, 2011

Free Time? What Free Time?

It's been busy for me, between work and some health issues for my mom, so I haven't had as much time to blog as I might have liked. That's as far as I'll go towards making excuses for my lack of posts the last week or two. However, that's not to say I haven't been working on stuff, just not much and not for very long at a time, and I haven't had any time beyond those work periods to write about them. On that catch-up note, here's an entire project of mine I've yet to even have the chance to talk about here.

About two weeks ago, I was contacted by someone who wanted some help rendering something. You may have heard of the Nautilus-X spacecraft proposal, a design for a long-term reusable orbit-to-orbit vehicle, built in multiple launches using ISS operational experience. The most striking feature for many people is the centrifuge ring, which is spun to create the illusion of gravity. This tends to excite space fans, since centrifuges have this whole air of sci-fi about them, and yet are still plausible, except for all the messy little engineering details like making the plumbing and wiring work across a rotating interface or the effects on maneuvering of essentially having a 30 ton gyroscope mounted to your ship.
Nautilus-X, front perspective view showing centrifuge ring
Nautilus's centrifuge is interesting because it proposes to use inflatable structures for much of the ring. It consists of a rigid hub, connected by a rigid passage tube to a rigid ring section. The ring itself is a mix of such rigid sections linked by inflatable sections (the other two rigid sections are connected by extending trusses to the hub, and serve to help support the ring in spin). Compacted, it's a very tight package, and makes good use of the rigid components where rigid is of benefit and inflatable where inflatable is best. On-orbit, the trusses would extend the ring sections, then the ring would be inflated and fitted out with habitat equipment: sleep stations, communal living areas, perhaps a sickbay or other equipment where gravity would pay off. The idea is interesting, if a bit of what Robert Zubrin would call a "Battlestar," an over-complicated slightly over-built spacecraft, but it's a big dream and I like those. The images of a test centrifuge attached to the ISS as a tech demo especially appeal to me. I've often lamented the loss of the funding for the Centrifuge Accomadations Module, and the lack of really good data on the reaction of the human body to varying gravity levels (including prolonged sub-Earth levels, like a Mars colony might have) and the rotation rates possible before biology and gravity gradients become an issue. With these two pieces of data, it'd actually be possible to design a 2001-style station or a spacecraft like the Discovery (or indeed Nautilus) with some kind of artificial gravity centrifuge.

Demo Centrifuge at ISS
The person who contacted me asked if I might be willing to try to render a conceptual cutaway of the interior of the ring. I used to spend days in middle school doodling diagrams of spacecraft and drawing scale floor plans of them, so this appealed to me, especially since it'd be a nice chance to press my modeling chops. It seemed like a fun thing to try and do--design a possible interior in a relatively small-diameter rotating centrifuge. I should be clear that neither he nor I has any real idea of the internal layout of the Nautilus, I'm not sure one exists at this time, despite all the nifty images of the ISS demo module. Thus, the following is only my best guesses, and as much informed by the design of boats and mobile homes as by valid spacecraft design principles. I hope Winchell Chung can forgive the transgression the previous sentence represents, but it's about the best I can do for the moment. Engineer in progress, it says so in the title.

Anyway, so to start, I needed to establish the physical parameters of the ring. It has been stated in presentations of the concept to have a diameter of 60 feet, and from the image above, scaling from the core (stated in another slide to have a width of 6.5 m), the ring's minor exterior radius looks to be about 4 m or so. Taking into account inflatable walls with a thickness of 16 inches, on the order of Bigelow's designs, this produces an interior diameter of about 134" (Yes, Imperial units. Deal with it. I did.). This gives a volume of around 425 cubic meters, about right for 6 people's occupation for up to two years. It's worth noting that combined with timing this animation of Nautilus (yielding 10 seconds per spin, or 6 RPM), the ship is basically designed to yield Martian gravity: 1/3 Earth gravity.

Cross-sections of Ring
To create the interior of this ring, I defined a flat floor as shown above, based on a minimum overhead of 6 feet. I show a centerline passage of 36" and a passage going past a partitioned room (shown with 36" bed), with 30" of floor space, and some extra elbow room. I then broke down the ring into rooms using these arrangements, and created the design below in Adobe Inventor. The "roof" level is a 78" ceiling: enough to give some head room even for tall people like myself, but not quite towering. With all the area under the floor available for use by utilities, I think that when I get around to modeling a ceiling, it'll be much more of narrow enclosed (?) utility run along the middle than the illustrated flat surface at 78" above the floor, a duct as opposed to a drop ceiling.
Attempt at Nautilus Floor Plan
Click  Image for Full Size
After some refinements and modifications based on discussion with the person who requested the work, I was satisfied enough to begin rendering the ring in Inventor. I rendered each portion (cabins, heads, the mess/galley area, the gym, stowage, the lab and medical bays) separately, so I could assemble them in any order, and so that changes to any on of duplicated rooms like the heads or the cabins would be reflected in all of them with the click of a mouse the next time I opened the assembly. Some rendered animation of the model are below (my first attempt at it with Inventor and it kind of shows--note for future: floors and background should contrast more). I'm hoping to refine both the model and my method of showing it off a bit more, but I'm pretty happy with the start of it. 

View One (Click to play)

View Two (Click to play)


  1. This is an unrelated topic.
    I really don't know how blogger works and I am very lazy.
    I was wondering with the shuttle retiring, what would America have had achieved if it had not gone with the shuttle. If NASA had stuck with Apollo style capsules and simply used the stuff that launched the shuttle to launch a capsule and meaningful payload. Similar to what we did with Skylab and Mir.

    Its quite sobering, we probably could have 10X more stuff up there now.
    If we did not do anything but go to LEO with this stuff we would have an impressive infrastructure by now.

  2. Just looked up the shuttle gross weight 240k lbs(with payload). Wow, I guess the more you know about engineering the more you realize how wasteful it really was.
    I think my guess of 10X more stuff was pretty close.

  3. Congrats, Rich. You've just re-developed the concept of a Shuttle-Derived Heavy Lift Vehicle (SD-HLV). The basic shuttle stack (2x4 segment SRBs, 3x SSME, stock external tank) has a payload of about 65 or 70 metric tons to orbit, depending on how you count things and how you attach your payload. Side-mount using the existing Shuttle mounts is quicker to develop, but harder to evolve and still places payloads in line of foam-strike. In-line with the payload on top needs a new front to the LOX tank to be able to support a payload up there and a new bottom to the ET to support engines and a thrust structure.

    Switch up to 4xSSME on the core stage and you can mount an upper stage that can allow 100 metric tons or so to LEO. And for probably not much more per flight than the Shuttle with its relatively modest 10-15 metric tons. It does indeed seem like a waste and you're not the first to think of it. Witness the National Launch System NLS-1 proposal, which is basically this, or the Jupiter rocket concept proposed by the DIRECT team of outside advocates and disgruntled NASA employees about the same time as Ares I and Ares V were rapidly turning into a boondoggle and taking the rest of Constellation with them. Both of those were theoretically Shuttle-derived, but in far more limited (and thus more complicated) ways. Ares V used different engines, tanks, boosters, while Ares 1 shared only the basic SRB design.

    Personally, I have harbored some hope that the result of the last two years or so of budgetary uncertainty might result with something like Jupiter, backed up with an investment in commercial crew alternatives like Dreamchaser and Dragon that could be a core to a new robust space program to follow up Shuttle, but it's beginning to seem more and more remote the longer NASA goes without commiting to any particular alternative and Congress, the President, and NASA administration (in no particular order of responsibility) let the agency's skilled workforce and purpose-built tool that could enable a true SDHLV tio be done reasonably quickly and cheaply wither on the vine.

    It's actually been rather painful: I thought I might be one of the new engineers to join the spaceflight workforce as Constellation would be ramping up, that I could do the same kinds of great things my great-uncle Robert Chilton did with Mercury, Geminii, and Apollo. That still could happen at a private company like SpaceX, Bigelow, Masten, XCor, Armadillo, or in the space division of a company like Boeing, but it's seeming more and more like NASA's not the place to look for innovation and direction anymore.

    I suppose in the meantime I've got nothing better to do than keep dreaming my dreams and working on my skills in the hopes that there'll still be chances to do cool stuff by the time I'm out of college and able to help for real. I realize this is about as much of a tangent to your comment as yours was to mine, Rich, but I've needed to get this off my chest for a while and it seemed too depressing to dump into a post by itself.

  4. You're not the only dreamer Rob! I have a technical question for you: regarding the Nautilus centrifuge, how will NASA overcome the problem of protecting a pressurized atmosphere between moving parts (ie: where the turning hub joins the main fuselage). Would air pressure against some kind of rubber flange on a disk plate suffice? Just curious.