Wednesday, October 3, 2018

Putting the Science in Rocket Science


When I was little I wanted to be an astronaut. I was fascinated by space and anything having to do with it. As I got older I realized that probably wasn’t going to be a viable career path for me. First, because I have horrible eye sight and second, because I hate running—seriously there better be something chasing me otherwise I’m not running. But one thing I maintained through the years was a distinct love for math and science. After many years thinking I wanted to be a vet, I decided that wasn’t the right career path for me. But when my mom suggested engineering I thought, sure, why not? The only problem was I had no idea what engineers did.

After a few programs and a course in freshman engineering, I realized I could marry my love of math and science with my love of space and get a degree in aerospace engineering (plus getting to tell people I’m a literal rocket scientist is pretty cool). And it was in senior design class in college that I got one of the hardest but most interesting problems in aerospacedesigning a spacecraft that could take a crew from Earth to Mars and land on the planet. Since it’s a three year trip, one of the requirements was that the ship had simulated gravity.

As discussed in my Misconceptions of Space article in PUTTING THE SCIENCE IN FICTION, creating artificial gravity is not an easy task. In space, rotation is required to generate enough inertial force to push an object against a surface thus giving the object the appearance of experiencing gravity. There’s a delicate balance when it comes to spinning spacecraft. It takes fuel and engines firing in the right directions to create a spin in space. The other option is to get another object to knock you into a spin, but that’s much harder to control. But getting into the spin isn’t the most difficult part. It’s getting the spin at the right speed and direction. If it’s too fast, people are forced against the walls and can’t move, plus you risk making them sick, (think about how hard it is to move on a spinning carnival ride like a teacup or sizzler). If you spin too slow, then you don’t have enough force to keep people on the surface. Then people experience some lesser amount of gravity than they are used to, and would bounce like astronauts on the moon.

There are a couple of factors that affect the gravity—one is mass, the other is radius. The mass of the object in motion and how far it’s located from the center of rotation can both affect the amount of gravity the object experiences. Two objects of the same mass at different locations from the center rotation in the same spacecraft will experience different amounts of gravity.


All of this is a lot to consider before you even get to the spacecraft designs most conducive for spinning. The two most popular options are a tether or a spinning ring. Tethers are the lighter and less complex version. However, one could argue they are less safe because they required a long object hanging out in space that prone to impact or could be severed by space debris. Depending on the design of the craft, a tether of 100ft or more might be required to generate the right force to simulate gravity similar to what we experience on Earth. Tethers also take a while to deploy to full length and run the risk of tangling. On the flip side, a ring while a less prone to being hit by space debris and can't tangle, requires a lot of material which can be expensive and heavy. Not only are the supplies expensive, but the construction is as well. A ring style space craft also requires a very sturdy center of rotation to support the spinning craft and the occasional burst of a thruster to maintain the rate of spin (which means burning fuel occasionally).

All in all simulating gravity in space is tricky business. This in turn presents some interesting what if questions that should get any writer’s brain buzzing.

If you were an architect of long distance space mission, which way would you simulate gravity? Would it compliment your crew’s mission in some way?

And once you have artificial gravity, what things could go wrong that would cause the spacecraft to lose it?

Now your spacecraft is in the middle of nowhere in the galaxy and your crew is bouncing off the walls (literally)… How do they restore gravity before everything that isn’t tied down hurts someone? And if this goes on long enough how do they prevent their muscles from atrophying?

What supplies do you need to fix the problem? Are they near or far? What comes next?

Now go forth and write that story. I bet it’s an interesting one.  

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Science and technology have starring roles in a wide range of genres--science fiction, fantasy, thriller, mystery, and more. Unfortunately, many depictions of technical subjects in literature, film, and television are pure fiction. A basic understanding of biology, physics, engineering, and medicine will help you create more realistic stories that satisfy discerning readers. This book brings together scientists, physicians, engineers, and other experts to help you:
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  • Whether writing about mutant monsters, rogue viruses, giant spaceships, or even murders and espionage, Putting the Science in Fiction will have something to help every writer craft better fiction.
Putting the Science in Fiction collects articles from "Science in Sci-fi, Fact in Fantasy," Dan Koboldt's popular blog series for authors and fans of speculative fiction (dankoboldt.com/science-in-scifi). Each article discusses an element of sci-fi or fantasy with an expert in that field. Scientists, engineers, medical professionals, and others share their insights in order to debunk the myths, correct the misconceptions, and offer advice on getting the details right.

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16 comments:

  1. Nice post, Jamie! That whole different-gravity-based-on-location thing is going to be tricky. Then again, I suppose some gravity is better than no gravity.

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    1. Thanks. and yes it can be really tricky. But as you said soe if better than none.

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  2. Very informative post Jamie!!! So so relevant to science-fiction!

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    1. Thanks. There's so much that goes into space travel.

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  3. Do you think that depictions on film, and in books too, of something like artificial gravity can actually inhibit original thinking? When I think 'artificial gravity' I just see '2001's' spinning wheel. Which is great of course!

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    1. I think so. I think it's going to take some out of the box thinking to get other options. Look at all the technology we got from Star Trek.

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  4. Great post! I tend to forget about tethers, but that might be just what my story needs.
    What are your thoughts on continuous propulsion as a means of artificial gravity? Feasible or not?
    Also, how would you combat the coriolis effect, wherein your head (closer to the axis of rotation), would be moving slower than your feet (further from the axis), causing you and other things to tilt or fall over?
    I am currently writing a story where the crew living in microgravity only experience artificial gravity when they sleep by crawling in a small rotating 'centrifuge,' starting it up, and laying on a bed that keeps their feet and head the same distance away from the axis of rotation. This is all to alleviate some of the negative health effects from prolonged micro-gravity.

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    1. Yeah most people dont use tethers because they aren't as "sexy" and fun looking as rings and have potential issues as stated in the post. Continuous propulsion could be an option but you'd need a continuous fuel source to support it which can be tricky. Fuel is heavy, can be dangerous to cart around etc. but if you can think of a clever way to manufacture it on the fly that could be neat.

      In terms of the differences between gravity in the feet and head, I don't think the sensation would vary that much in gravity affects, but if you had multiple rings spaced out you might experience different gravity between the two rings if they are spaced far apart. This page with the gravity equation can help calculate the difference if you change the radius or mass http://nova.stanford.edu/projects/mod-x/ad-surfgrav.html

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  5. Great article, Jamie! Just recently rewatched 2001, and was thinking that movie focused so much on how they generated gravity, and today, most films just ignore it, and have people walking around spaceships with no indication of how they stick to the floor.

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    1. That's so true a lot of hollywood ignores physics. I think we take it for granted how hard it is to generate gravity in space.

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  6. Great post, Jamie! So interesting about gravity.

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    1. Thanks! It's definitely and interesting thing to study.

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  7. Love science. Started writing in third grade and it was a sci-fi novelabout space ships and such. Still a geek to this day!

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    1. Nice! Sounds like you write about some really cool stuff.

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