Testimony of Dr. Robert Zubrin to the Senate Commerce Committee, Oct 29, 2003

Eugen Leitl eugen at leitl.org
Mon Nov 10 03:37:46 PST 2003


On Thu, Nov 06, 2003 at 11:46:17AM -0800, Jim Whitehead wrote:

> > You can get sustainable Moon colonization for the price ticket of
> > a couple of Mars missions. You just have to bootstrap via teleoperated
> > fabbing first. You can't do that on Mars. Two second relativistic lag is
> > already difficult for hand-eye motorics to coordinate (can use local
> > reflexes for augmentation, though).
> 
> Do you have a reference for this? Or, put another way, who are the primary
> proponents of "Moon first"? Zubrin is clearly a leading figure in the "Mars
> first" community.

There have been several proponents of that specific type of Moon bootstrap.
It started with that 1980 NASA workshop http://www.islandone.org/MMSG/aasm/
but it also has more recent believers 

http://www.uh.edu/collegium/print/spr03/pages/moon.html

(I don't agree with that, I believe in lots of small PV arrays in LEO with
realtime beam synthesis, built and launched from Luna).

However, the case stands for its own. In absence of autonomous robots, lunar
fabbing teleoperation is the cheapest and safest way to bootstrap massive
industrial capabilities. 

After you've got a closed-loop ecosystem going, you can send people. (I do
not believe monkeys in space have a future, and in fact that people as we know
them have a future beyond a century, give or take a few decades).

If you look at relativistic interstellar travel, you'll realize that people
vs. smart machines can't compete. There's nothing like beating a kg payload
dragged by a gray sail at 3-6 g. You just can't beat the replication times
from scratch. It's the ultimate gift that keeps on giving. 
 
> Parroting Zubrin's "The Case for Mars"
> (http://www.amazon.com/exec/obidos/tg/detail/-/0684835509/), the reasons you
> would choose Mars over the Moon are:
> 
> * Martian atmosphere protects against solar radiation -- handy during

Rad-hard automation doesn't have a problem with solar radiation. Lunar soil
protects far better against radiation than a thin atmosphere ever could.

> intense solar flare activity. This protection makes surface greenhouses
> easier to create, since you need less shielding in your glass.

Glass greenhouses?! Did you look at the forces on the glass? This is
expensive beyond belief, and rather unsafe (blowouts due to structural
failure and micrometeorite erosion).

If you have to send monkeys to space, a closed-loop ecosystem is best set up
using solid state lamps powered by photovoltaics on the surface (or rectenna
arrays from circumlunar photovoltaics arrays).
 
> * The Martian day is more amenable to greenhouses, since the Martian day is

Martian insolation is but a fraction of the solar flux.

> closer to ours, instead of the 22(?) day long lunar day. Lunar greenhouses
> would require lighting during the lunar night, and this is very energy
> intensive.

There's permanently insulated areas on the lunar poles, where the hydrate
cryotraps are. This is where you start the colonization.
 
> * Mars has more readily accessible water sources than the Moon.

Machines don't need water. Most of industrial processes would profit from a
vaccum (sputtering, electrolysis). You can of course use the polar cryotrap
water for fuel, ecosystems and a few wet industrial processes (I can't think
of many).
 
> * The Martian atmosphere can be leveraged in many ways to provide fuel,
> combution material (for CO2-driven combustion cycles), etc.

Combustion? In space? What for?

CO2 is useless for reaction mass, water is perfect for hydrogen/oxygen
drives, and deep space stuff will be solar sail and ion/plasma drives.

 
> * DeltaV costs are higher for the moon than for Mars (not sure I completely
> understand all the aspects of this argument).

DeltaV assumes material transport. Bootstrap by teleoperation and automated
fabbing very much eliminates material transport. Initial transport is
Earth->Luna, one way. After that, it's Luna->Earth, via linear mass drivers
and aerobraking and/or ion/plasma braking.
 
> > killer human risk,
> 
> Radiation risk is much lower on Mars. Gravity is closer to Earth normal, so

Radiation is a nonissue, because no one is running around on the surface, at
least in person. They're either telecommuting, or sitting some 10 m below
Luna surface.

Radiation is an issue on 6 month transit to Mars. 

> less osteoporosis effects. What risk are you referring to?

Being an astronaut is even more dangerous than being a lumberjack. No canned
monkeys = no human risk. This way you can tolerate high failure rates during
launch.
 
> > just enough atmosphere to ruin your vacuum for industrial processes
> 
> Most industrial processes you'd want to perform would involve the Martian
> atmosphere. Creating a vacuum from Martian atmosphere wouldn't be that

How do you know which industrial process I want to perform? Give me a list of
stuff you want to do; I'll show you that you can do it in a vaccum much
better.

> tricky anyway.

Yes, they will be very tricky indeed. Let's say I want to melt regolith to
sputter semiconductors on top of it, to quickly create solar cell arrays some km^2
sized (you will need more of than on Mars, because the insolation is less
then).

What would you do with power on Mars, I wonder? No way to beam it to Earth.
I thought, that was the whole point of industry in space: it results in ROI,
quick, lots of it.

Luna: mobile mylar foil solar oven on truss (or inflatable, UV polymerized in
sidtu), mobile electron beam welding and 
sputtering rig. Some 100 kg total mass, long lifetime. You get your initial
pure semiconductors from Earth, then make them right there.

Mars: heavy (wind drag) huge (lousy insolation flux) mirror (short lifetime
due to dust erosion) or huge huge huge photovoltaics arrays (to be dusted off
and periodically remade due to dust erosion), vacuum chamber, vacuum pump,
seal, transport system, etc. Some 100 t total mass, complex rig, needs
frequent repairs (can't do that with teleoperation, so monkeys in situ
required).

It doesn't take a genius to realize that Mars vs. Luna completely loses.
Given that space is currently a zero-sum game we simply can't afford a yet
another lunatic experiment, by sending canned monkeys to Mars.

-- Eugen* Leitl <a href="http://leitl.org">leitl</a>
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ICBM: 48.07078, 11.61144 http://www.leitl.org
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