How to Get to Mars

NASA wants to go to Mars. Great!

The approach, as the agency has been publicizing with fancy graphics like the one below, seems to consist of the following:

NASA’s tentacles travel to Mars

  • Send astronaut Scott Kelly to the International Space Station for one year, to learn about the effects of zero gravity.
  • Perform the Asteroid Redirect Mission, moving a near-Earth asteroid into lunar orbit, to prove that solar electric propulsion works in space.
  • Assemble a Mars transfer spacecraft in distant Earth orbit out of components launched on the Space Launch System.
  • Pack everything astronauts need for a round trip to Mars on the new spacecraft and send them on their way!
  • Keep the spacecraft in space for future trips to Mars. Bring the astronauts and supplies back and forth separately.

Not that these aren’t good brainstorming ideas, but they are not how I would get to Mars. I am too confident and impatient for this plan.

For one thing, we can probably skip this one-year mission. In fact, NASA, I can help you out by zipping straight to the conclusions: Being in zero gravity for a year results in bone loss, muscle atrophy, a compromised immune system, radiation exposure, and changes to the shape of the astronauts’ eyes. We know all that already. Similarly, we already know that solar electric propulsion works – quite effectively, robustly, and scalably – in space. Commercial satellites are flying solar electric propulsion right now, with more on the way. Heck, NASA itself has been flying solar electric propulsion, on missions like Dawn, since the turn of the millennium! Nothing needs proving here. We can take the known technology and use it.

Now, assembling a Mars transfer spacecraft, sending it onward, and reusing it for further exploration – that I like. Here is how I would do it.

First, get one of the companies developing solar-electric propulsion satellites to build a number of spacecraft buses. They will probably run a few tens of millions of dollars each, and they can ride up to space on Falcons, Arianes, or Atlases. (That’s bargain basement stuff for NASA!) Then, tie them together. All I really want are the propulsion systems. Each spacecraft has a propulsion system with something around 10 kW power, and NASA wants to get up to around 100 kW to go to Mars. So, by my rocket science calculations, we need…ten satellites. Or maybe, if we strip out all the telecommunications payloads that these satellites usually carry but I don’t care about for this application, maybe we can get the number down to five-ish.

Four of 'em stuck together

Four of ’em stuck together (with obligatory blue ion engine exhaust)

Somebody would probably have to do some thinking about the best way to support all these stuck-together satellites. Maybe a truss of some kind. But I’m not too worried about that, because NASA has two decades of experience building modular things and sticking them to trusses in space. They can just do what they do best, using their own well-proven techniques.

Now we need a place to put our astronauts. Preferably a place that has some accommodations for solving the problems that Scott Kelly will be confirming. Many of the major physiological issues with space travel have to do with being in zero gravity. Too bad our Mars transit vehicle can’t bring gravity along with it.

Oh, wait! Science fiction knows the answer. It’s known the answer for decades! Spin the spacecraft. The astronauts get to live with a force akin to gravity, pulling them outward along the spin axis.

But building a giant ring-ship takes a lot of time, effort, energy, and resources. I have something different in mind. Something simpler:

My Mars transit vehicle is finished!

My Mars transit vehicle, finished!

On the right, that’s supposed to be an inflatable, cylindrical habitat. (Inflatable things would be terrific for space construction, because they only need a small launcher. Since everything on my vehicle is made of small components, we can launch them once a month instead of once every two years, if they needed a super-heavy launcher like SLS.) This inflatable habitat is tied to the central propulsion core by tethers, or maybe trusses of some type. The astronauts would feel “gravity” pulling them toward the right-hand side of this image (and a little bit downward, because of the thrust). On the left is a dumb counterweight: I’ve drawn it to evoke the empty upper stage of a rocket. It could maybe be long-term storage, but its main purpose is simply to be dead weight to make the spinning easier. The whole vehicle would rotate about the thrust axis, rapidly enough to give the crew at least lunar or martian gravity levels. (The illustration isn’t to scale!)

I’d do one last thing before I send this to Mars with a crew. I’d pack the transit vehicle with enough food, water, and air to get the astronauts to Mars, and for their surface stay.

Not enough to get back, though.

Instead, I would bring seeds. When the astronauts land on Mars, the first thing they will do is become high-tech space farmers. They are going to grow all the food for their return trip on Mars’ surface.

Why would I want to do that? Well, for one thing, seeds are smaller and less massive than full-grown food products. They are probably less expensive – in an energy sense – to get to Mars than those food products would be. Then, on Mars, we can get water and carbon dioxide from the atmosphere, to fuel plant growth. So, over the whole mission, I’m actually saving time and money. There’s also a second reason, one I find more compelling. What’s the point of this whole endeavor if we don’t come out of it knowing how to colonize and explore other planets, and keep colonizing and exploring them? Learning to use the resources on other worlds is fundamental to the future of space exploration. We know Mars has water, we know it has oxygen, and we even know that we might be able to grow crops in its soil. We should focus on that idea and advance it. In other words, I think that – both pragmatically and philosophically – it would be shortsighted and silly to attempt Mars exploration using only what supplies we can bring from the Earth.

We need a space program that focuses on developing the technology to use the resources on Mars to support further Mars exploration. We need to do this in a modular, reusable, scalable manner. We need to make sure our astronauts – no, our pioneers – have the tools, the materials, the infrastructure, and the autonomy to solve their own problems. In other words, we need to stop thinking about how to put a few guys in spacesuits on Mars, and stop thinking about how to have astronauts do science on Mars, and instead think about how to colonize Mars. That requires a lot of little things to come together, with more than a few big things in the mix as well. But, for the most part, we have the technology. We’ve had it for my entire lifetime. We need a space program with the right stuff to use it.

That’s how to take a journey to Mars.

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