Friday, May 18, 2012

Building the Enterprise

Recently came across buildtheenterprise.org, a site containing a plan to build a starship like the USS Enterprise from Star Trek. Despite some huge technical issues, lemme just come out first and say THANK YOU. Whoever you are, BTE-Dan, thank you for dreaming big. The world needs people to dream bigger. There's been an awful lack of big thinking ever since we put a man on the moon (over 40 years ago!). Neal Stephenson, one of my favorite authors, describes the problem in this talk:


Just a warning, if you haven't already watched the above - it's kinda depressing. He mentions how "I saw the best minds of my generation writing spam filters." Okay, I might have worked on Gmail.... Point taken, Neal.

Anyway, the Enterprise site lays out a crazy plan to build the friggin' Enterprise.

Image credit - Chris Martin of Evil Starship Factory

It's got some issues, though. One of the big things that I think is completely glossed over is how to actually assemble the thing in space. We've assembled reasonably large structures in space before, but the ISS is only 72.8m x 108.5m x 20m (according to Wikipedia), and that took an awful long time to put together. The Enterprise is almost 1000m long, so it's an order of magnitude bigger. I guess not completely out of reason, but I think the cost estimates are far too conservative ($1 trillion over 20 years).

Another problem seems to be the "gravity wheel", the large spinning wheel to simulate 1g of gravity for comfortable and healthy living aboard. Some various problems I've seen mentioned are:

The gravity wheel is in the wrong plane for control of the ship. Meaning you wouldn't be able to see where you're going, cause you'll be spinning around, so your "forward" is not the ship's "forward", except for a brief moment during each revolution (which would certainly be dizzying).

Well, this criticism only holds if you expect the real Enterprise to be like the fictional Enterprise, with a big window at the front of the bridge. But it doesn't take a lot of thought to realize that any orientation for the spinning wheel would render this impossible. However, who said anything about a window? Clearly this can be solved with a giant, extremely high-resolution digital display showing a live video feed of the direction you're headed, and having the controls also based on the direction you're heading rather than the direction you're actually facing (since again, you're constantly spinning around).

That being said, I do think the gravity wheel is in the wrong plane, but not for this reason. Due to Newton's Third Law, shouldn't the rotation of such a massive wheel spin the ship in the opposite direction (someone please correct me if this assumption is wrong)? If so, you'd want the gravity wheel spinning perpendicular to the direction of motion. However, in the Enterprise-type design, that would leave an awfully strange and unbalanced (even more so) ship. Otherwise, in the current design, one of the engines would need to constantly fire to offset the spinning of the ship, which is a waste of power.

It seems much better to have a simpler design for the ship, for instance something more like the Von Braun Space Station, or a derivative design like this:

Image taken from http://drexfiles.files.wordpress.com/2009/11/ringship07.jpg.

Now that would be a sick design. I could also imagine having the main engine in the center, and auxiliary engines located on the outside of the ring with the ability to move around the ring as needed. This way, it's very easy for the ship to accelerate without tumbling, and in case one or even two engines fail, the ship can still function properly. If the main and one auxiliary fail, the remaining engine can move around the ring at a constant rate, keeping the ship more or less balanced, or since the engines are already moving around the ship, can move into a center location. Plenty of interesting possibilities.

The gravity wheel will be affected by the constant acceleration of the ship. That is, since acceleration vectors are added, the ship's forward acceleration will be added with the rotational acceleration, meaning that "gravity" is different all around the wheel.


Luckily, for the first two generations of the ship, it doesn't really matter, since the targeted constant accelerations are 0.002g and 0.02g, which would be barely noticeable, unless you have an obsession with constantly weighing yourself.

By the time we reach a 1g constant acceleration in the third generation of the ship, well, it should be clear that there's no need for a spinning wheel at all =). At a constant acceleration of 1g, the "back wall" of the ship will already have a nice 1g force acting on it, so that entire surface will be perfectly hospitable to the starship inhabitants. Perhaps the ship's design will work like a giant transformer, putting most of the accessible spaces on this "back plane" of the ship, for a comfortable 1g journey to the next star system.

Anyway, it's fun to think about these things, but in the meantime, I'm beyond psyched for the SpaceX launch to the ISS on Saturday. So awesome what those guys have accomplished in such a short time. Can't wait till I can help the race for the future.
   


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