Saturday, August 14, 2010

The Ways We Frustrate Kessler

Like I mentioned the other day, the biggest stumbling block to a consistent human presence in space beyond laboratory outposts in low Earth orbit is cost - but justification is right behind. No one is going to invest the vast sums of money required into space development without a damn good reason. Whether or not such reasons exist depends on your viewpoint; from time to time, I've come across people who don't believe that there's any reason for humans to leave Earth. Personally, I think those people are just the necessary polar opposite of those who think that we're on the cusp of a space gold rush to exploit lunar helium-3 reserves - despite the fact that, as Charles Stross wrote about recently, helium-3 could just as easily be manufactured on Earth.

Oh, and we're decades away from actually being able to use it for anything. Justifying lunar development with helium-3 is akin to Columbus going to the New World to look for petroleum.

A NASA concept of a lunar base, circa 1977, equipped with a mass driver for payload launches - and presumably bombardment of Earth with lunar rocks in case the Loonies want to make a go for independence.

So the question becomes this - why develop the moon at all? What could be worth the cost? Different people would have different answers, but one of mine is this: resilience. A human presence on Luna could insulate Earth, and assist with remedial efforts, in the event of a Kessler syndrome, another thing I've mentioned before.

The Kessler syndrome is a result of cascading levels of orbital debris - since everything in orbit is moving at multiple kilometers per second, even incredibly small fragments have incredible kinetic energy behind them, and objects as innocuous as lost screws could severely damage something like the International Space Station. Debris unchecked creates more debris, and while limited atmospheric drag could clear out low Earth orbit in a matter of years, other orbits - like ones used by portions of the Earth satellite network - would be choked with debris for long spans of time.

Launching through those clouds of debris would be an abortive proposition at the best; it's expensive to get something into orbit as it is, without ships needing the mass of armor proof against high-velocity impacts. In the event of a Kessler syndrome the satellite network would gradually but surely be crushed to nothing, and no new launches from Earth would be forthcoming; it wouldn't take long for replacement satellites to be shredded and their wreckage to become part of the problem. Even if some satellites in very high orbits were insulated from the main debris fields, they woudl eventually cease to function and couldn't be replaced or repaired.

So, fancy living in a world without satellites? Without the comsat constellations that provide you with mobile phone service or weather forecasts or hurricane warnings? It's only a few steps more preferable than a world without zinc.

Installations on Luna could sidestep this problem. At the very least, installations there and in the Lagrange points could serve as communications relays if the satellite network was gone. More importantly, a presence on Luna could enable remediation of the problem; while launching from Earth would be prohibitive due to debris danger, no similar problem would exist for lunar launches - and the low lunar gravity would make launches far less expensive in terms of propellant necessary to achieve escape velocity.

I know it's expensive. Cost is not the only arbiter of necessity. A thing that needs to be done, but costs a lot of money, still needs to be done.

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