Thursday, February 27, 2014

While the cat's away, the rat will play.

Ken is still away, so I'm taking this opportunity to post a piece I've been working on;

The remaining barrier to the colonization of Mars, and a way around it. 

    At the current time, we either have, or are close to having, the hardware and technology available to place colonists on Mars.

On site resource utilization can provide some of the essentials, such as shelter, water, and oxygen. 

There is one glaring exception that's even more important than the above, and unless we find a solution, it makes survival on Mars, or anywhere outside cislunar space, impossible.

This massive sticking point is the shelf life of the fruit of the coffea arabicia; the coffee bean. After harvesting, the clock is ticking, and it's remorseless. The coffee beans require roasting within two months of harvest, and after roasting, they fade within weeks. (Refrigeration can help slightly, but not enough). Going beyond these critical bounds degrades the coffee to supermarket-tin level, which is utterly incapable of sustaining human life. 

Coffee can be grown in greenhouses, and thus on Mars, but it takes several years for a bush to reach production age. The colonists would therefor be facing an utterly unsurvivable coffee bean gap. I suppose it's theoretically possible, sort of, for them to survive this hellish period by utilizing instant coffee, but... could anyone endure such hardships and survive? I think it's both highly unlikely and absolutely inhuman to even contemplate it. 

The answer, the ONLY answer, is a high velocity cargo delivery system for Mars.Conventional cargo transport is simply too slow.

How do you do such a thing? First, keep it simple and focused on the goal. All it has to do is carry a small amount of cargo to Mars and land it on the surface. How much cargo? For a 20 person colony, 50 kilograms a month should suffice, with only a little deprivation.

Travel time? A month or less is needed.  Two weeks would be ideal.

Chemical Rockets? Nowhere near fast enough. The New Horizons Pluto probe (which had the fastest departure speed of any spacecraft) crossed Mars' orbit 39 days after launch, but only via having a small, light payload atop an enormous three-stage rocket, and that's just about the best chemical propulsion can hope to achieve.

Solar-electric? Useless for this purpose due to the time it takes to accelerate.

Fusion propulsion? We ain't got it, which makes using it a tad problematic.

In order to ensure speedy arrival at even sup-optimal orbital alignments, we need a delta/v of about 50 kilometers per second. We absolutely have to have it, so how do we get it? 

The only answer, and thus a necessary prerequisite to any form of deep space or planetary colonization, is electric launch from the Moon. Use a linear accelerator (a rail gun) on the lunar surface. The good news is that very high G rates are obtainable, but the bad news is that unroasted beans are a bit delicate, so at most could handle about 5 g's. (easily obtainable with current tech, even for a capsule weighing a few hundred kg). 

There are a few minor technical problems to address, the first of which is that a 5g rail-gun would need to be several thousand miles long to achieve the needed speed, and we'd need a lot of them to provide the needed launch azimuth flexibility dictated by planetary orbital cycles. The answer is easy enough; the rail gun does not need to be perfectly straight. It can be built at the lunar equator, fully encircling the moon. Once the capsule is accelerated to 50kps, it can simply be released on the appropriate trajectory point.

The second minor issue is power, but a few hundred square miles of solar cells should suffice. 

The coffee transporter vehicle will arrive at Mars at around 55 KPS. This is going to be a very challenging entry profile (atmospheric deceleration is the only option here) but by keeping the payload small and light, you can have a deployable heat shield much larger in diameter than the payload, thus also giving you the ability (via center of gravity adjustments) to do a negative-lift reentry (which you need to stay within the atmosphere at those velocities).

If great care is taken in the design, the attenuated entry heat can be used to roast the beans (though more research is urgently needed on the matter of whether or not hypervelocity Mars entry heating is suitable for optimal roasting of the beans).    

So, we'll need to build a large lunar base in order to construct the launcher.This project will easily be the most expensive in human history (vastly more costly than even a large Mars colony, by several orders of magnitude)  but it's the only way.

I propose to call it "Project Espresso".