Friday, May 27, 2011

Rebirth Of The Spaceship

Over the last year the space advocate community has splintered into two major groups in answering the question "where should we go next?" Moon First or Mars First. This division was present in the Review of Human Spaceflight (aka Augustine) committee's final report in late 2009, with the surprising conclusion that there isn't the funds for either, suggesting a number of intermediate destinations first - including asteroids. However, as few people consider asteroids to be truly interesting destinations for the human utilization of space (except me!), the debate rages on.

Many Moon First advocates are "Mars Next" advocates while most Mars First advocates are "Moon Again?" detractors. The former claim that Mars exploration will benefit from lunar exploration, particularly in experience and risk reduction, and perhaps the procurement of propellant. The latter claim that lunar exploration is just a distraction and want to avoid the risk of being bogged down by another expensive obligation (read: another ISS).

NASA, and the Congress, is hedging their bets.. declining to select a camp and insisting that the so-called flexible path will have "off-ramps" for either lunar or Mars exploration.

Perhaps as a result of the deferment, an old camp has resurfaced with a strong central tenant: the true "spaceship". Defined loosely as a vehicle which is assembled in orbit and is never intended to land on a planetary body - although it may do aerobraking maneuvers in a planetary atmosphere. Spaceship advocates talk about lander vehicles rarely and, although the Moon is recognized as a nice buoy to fly around in a shakedown cruise, the intended destination is clearly Mars.

For many years, this camp has been silenced by a powerful force: The Mars Society and its charismatic leader. With a desire to cut out all distractions, Bob Zubrin has rallied against "Battlestar Galactica scale plans" for getting to Mars, advocating trips of endurance of small crews in tightly packed modules - small enough to fit on the top of a single heavy lift launch vehicle and launched directly from the surface of the Earth to the surface of Mars. What happened?

It seems that the last 20 years of advocating for the simple, elegant, and dangerous Mars Direct plan has been easily swept aside with just a single picture:

This sharp looking spaceship, with its command deck off to the side like the Millennium Falcon, and its inflatable artificial gravity ring promising Bigelow budget sweetness, has inflamed a deep longing for the sci-fi universe we were all promised - humans exploring space for years at a time with large crews.

The problem is propulsion. The tiny Firefly-like cluster on the rear of the ship is woefully inadequate for even the most advanced nuclear thermal propulsion system. The solar panel array is football fields too small for a solar-electric propulsion (or SEP) system. A chemical rocket stage to throw this vehicle to Mars and back would be so much bigger than the vehicle that we'd have trouble seeing it without zooming in... or so I've heard. How true is this objection?

The first problem comes when the objector talks about assembling the spaceship in low Earth orbit. This is an understandable assumption given that all on-orbit assembly to-date has been done in LEO, namely the international space station. However, for some time now the Earth-Moon Lagrangian points have been identified as the perfect location for staging for deep-space missions. This is not to say that no on-orbit assembly would be done in LEO, but once completed the resulting module could be ferried by a SEP tug up to L1. Whereas crew transfer vehicles would take the faster, more energetic path.

Often platforms at the Lagrangian points have been called "gateway stations" and for good reason. It takes less than 1 km/s of delta-v to go from L2 to a Mars transfer orbit. Transiting a large structure from L1 to L2 requires about 100 m/s of delta-v if you need to do it fast, but can be done with just 10 m/s or less if you take your time.

The Moon is so close and lunar water is so abundant that can be cracked into cryogenic propellants or used for radiation shielding, drinking, grow crops, etc. A purely chemical propulsion system quickly becomes feasible, but some other techniques such as solar sailing appear to be very interesting to me.

Although that could be because I just saw the latest Johnny Depp pirate movie. Arrgghh.

Wednesday, May 18, 2011

You've gotta love him

For anyone who wonders why I still love Bob Zubrin, watch this video:

It's the passion.

For anyone who needs a horrific demonstration of closed world thinking, combined with a little intellectual elitism, read on.

Saturday, May 07, 2011

Please Stop Lying To Children

Here in Australia we have a shameless tradition of claiming celebrities who are not quite Australian. The best example of this is probably Mel Gibson - back when anyone wanted to claim him - who wasn't actually born in Australia, he just lived here for a portion of his childhood. It is generally agreed that anyone who was born in New Zealand can never be considered an Australian (just kidding kiwis, we love you) but if they're famous they're automatically Australian. The common joke is that any celebrity who so much as flies over Australia will be offered citizenship.

Something like the Australian celebrity phenomena happens when people start talking about NASA spinoffs, here's how it works: a speaker creates the implication that civil servant NASA scientists developed some new technology which was subsequently "spun off" to form a commercial product. The most common example of this is Velcro, but there are plenty of others. Whenever you dig into these claims you almost always discover that the entirety of NASA's contribution was in the form of a check. Some people don't even see the deceit in this, suggesting that any NASA funded research is NASA research and therefore any commercial products that result are spinoffs. I've always wondered how the scientists and engineers who do the work to create these products feel about that.

It is an obvious truism that no human-made object could have been placed into space had it not been for the space program of one nation or another. Oh wait, no, that's not a truism at all is it? The first rocket to leave the Earth's atmosphere was a German V2 rocket in 1944, long before anyone had a "space program". Despite this, it seems a lot of well meaning people want to perpetuate the myth that everything in space is a result of the space program.. and a lot of things on Earth too. Watch this short video for my least favorite demonstration:

It disappoints when a speaker says something like this.. it fills you with inspiration for about five seconds, only to have the nagging rational part of your brain chime in with: umm, excuse me? That's not actually true, ya know. I think kids who are inspired by such speakers to follow their dreams will feel terrible betrayal when they eventually discover they've been lied to.

Before anyone accuses me of Tyson bashing, let me say that I'm otherwise a fan of his work and encourage everyone to watch the full 2.5 hour talk. Maybe he doesn't know that NASA didn't invent cordless power drills and their contribution to LASIK eye surgery amounted to writing a check long after it was invented, and maybe he's unaware of the history of the global positioning system and that "space exploration" had nothing to do with it. I don't know, but considering how awesome he is, I find that extremely hard to believe.

But let's take this argument where no-one seems to be willing to go.

We all love the global positioning system - you might say it is the pinnacle of human achievement - surely we should support any program of government spending that can result in fantastic technological marvels becoming such an everyday part of our lives, right? If you don't necessarily agree with that, then perhaps it is because you know the primary justification for building and launching the GPS satellite constellation was global thermonuclear war.

In fact, the development of satellites in general and giant space telescopes in particular, was the cold war need to spy on the Soviet Union. Love the Hubble space telescope? Well then, you should support more government spending on the military industrial complex. Actually, you should long for the days when school children practiced hiding under their desks with visions of nuclear annihilation dancing in their heads. With the Soviet Union gone we'll have to find another enemy but that shouldn't be too hard.

Or - just maybe - you might think that regardless of the spinoffs and the side benefits, it was still bad to have forty years where two great superpowers teetered on the edge of oblivion staring at each other across the void and hoping neither would be so stupid as to make the first move in a game neither side could win.

Similarly, the space program cannot be justified by spinoffs and side benefits. It can't be justified by how many kids are inspired to become scientists and engineers instead of lawyers and doctors - no wait, politicians, yeah that's better. In order to convince your fellow taxpayers that human spaceflight is in the national interest you have to say what it is for and why that is a good thing. We can disagree on what that is, but the last thing we should do is give up and list the side benefits as the actual purpose.. and stop lying to the kids ;)