|Ask yourself how it would change space exploration if every city could
afford to launch an exploration vehicle to Mars? What if the average corporation
could afford to launch a reconnasince platform to Mars? What if every school
could control it's own grapefruit sized
orbiter? You guessed it. NASA would be out of business PDQ except for the
one thing they still do well: celestial navigation, writing papers and posting
them on the internet.
Go one step further. If a Mars explorer were the size of a grapefruit, you wouldn't need a 300 foot rocket. You would only need a lamp post sized rocket. A rocket that would fit on an F-16. F-16's that fly thousands of useless missions per day could easily keep their killing skills sharp by launching Mars missions instead.
If you're not familiar with how this works, it's pretty exciting. A lamp-post rocket is attached to the belly of an F-16. The F-16 takes off, climbs to 40,000 feet and gets into an accelerating flight profile in a slightly downward descent. After it has used over half its fuel, it accelerates to Mach 2+. Then it pitches and climbs straight up with full afterburners and "weweases the secwet weapon", which in this case is not a weapon at all, but rather a mission to Mars. The lamppost thus avoids the huge fuel penalty of climbing to 80,000+ feet at Mach 2+ and proceeds to go to Mars courtesy USAF. A poor man's space shuttle, if you will.
Perhaps affiliating yourself with the Air Force, even for a moment, is more than you can bear. Here is a convenient neighborhood counterproposal that is almot as good. The real enemy of the early launch profile is air resistance. With thin polyethylene (dry cleaner bag) balloons, one can float the launch vehicle to 100,000 feet. You can then launch from there. Of course this is not the towering phallic demonstration of a terrestrial launch, but it gets the job done.
To be honest (and practical!) there are parts of Viking which should first microtech, parts which should go millitech and so on. I just love guilt by association, but if we were to use existing microtechnology fabrication methods we could go to Mars NOW with the approach outlined.
Some interesting relationships between nanotech and space exploration arise, specifically in the areas of RF antennas, power, and video. These will be explored in later articles.
The upshot of this is that we must think in terms of the local application of milli, micro and nanotechnology as opposed to "going baNanos". One can't shrink everything, everywhere, all at the same rate, because different machine functions are ruled by different scaling laws. A good example is sample return. We could return one atom from Mars, but that wouldn't be very interesting. Iron is the same there as it is here. (Richard Feynmann, who demonstrated how Challenger crashed with a glass of cold water and some O-ring has a beautiful discussion of elemental ubiquity in his book of excerpted physics lectures, "Six Easy Pieces".) We could return one gram of Mars soil. That would be more interesting. We could return 90 pound cement sacks, one a time, or in a symphony of little Martian niblets.
If we include sample return on a Mars Mission we have chosen a big design driver. Sample size, more than any other parameter drives how big the rocket motors, spacecraft structure, and control actuators have to be. We can make everything else smaller than a speck, but that speck will still have to sit on a fairly good sized hunk of space hardware. How big might that hardware have to be?
Well the following calculation is wrong and flawed, but it tends in the general direction. Assume that 0.1 percent of the gross launch weight can make it to Mars. Assume that 0.26 percent of the launch weight at Mars can make it back to Earth. How big a vehicle will we be sending?
Let me punctuate this further as follows. At any given instant of history, there is a minimum cost, minimum size way to get things done. In 1492 it took three clunky sailboats to get across the Atlantic. In 1927 it took one small airplane 14 hours and 25 minutes. In 1927 one could still take three multi-ton clunky sailboats, but you didn't have to.
The minimum cost curve, memory factory example serves us here.
There is one bogey that won't go away at any scale, and that is the need to communicate in flight. It turns out that the antenna on the vehicle must be a minimum size just to work, and that turns out to be pretty big. In the limit, if any nanotechnology (which is mostly religion at this writing) or microtechnology (which is mostly fact) approach is successful
RF antenna size problems will control the appearance and design.
A while back I did a sketch for a very small jet engine. It turns out that a limiting factor of how small a jet engine can be is the speed of sound versus the rate at which the rotor must turn. Said another way, I believe that there is a rotor so small, that it must turn much faster than the speed of sound, in order to digest sufficient fluid in order to run. But fluid won't travel faster than sound in turbomachinery, thus there is a smallest possible turbojet. Just like when we were kids and hear that there is a largest possible insect. When bugs get too big, their skeletons get too heavy to move. Life is the size it is for a reason. Which is pretty peculiar given how big the universe is.
Anyway, back at the ranch. The smallest that an RF antenna can be is controlled by the size of the antenna back home. The product of the areas of the two antennas must by a certain size in order to have two-way (or even one-way) communication, especially when one starts getting a long way from home. This slightly helps NASA stay in the space autocracy business, because they currently control the three biggest antennae in the world, on three different continents. I am sure they are glad to hear this, but I'm sure they're not surprised.
So in the limit, nanotech spacecraft, or more honestly, microtech spacecraft become all antenna, most likely parabolic dishes whose electronics have become a glowing incandescent dot on the back. The dish must serve as a heat sink as well since as circuits get smaller, they run hotter, for a given number of gates.
There is a another -can't-be-smaller-than-this size fixer and that is the size of the lens on the video camera. The lens must be at least larger than 900 nanometers, since that is the wavelength of red light. Now we might decide that we only want to see green light (550 nm) or blue light (450 nm), but that kind of decision making is bad design. Bad design nonetheless successfully practiced on the Tiros-N series of spacecraft for the last 35 years. (there is no blue sensor on ANY of the weather orbiters, based on the rationale that all we care about is clouds, not earth, sigh)
Now if the lens on our video camera is 1 micron (1000 nm) across, then we have to let the photons in one at a time (so to speak). If the spacecraft is far from anything resembling a planet or other spacecraft this is fine, but if you want to have images, you need to let more than one pixel in at a time, because the spacecraft is moving, and thus the image is always changing. If we define simultenaeity as a certain threshold of image blur, this will immediately give us the minimum sized camera we need. But that is computing the design from the fanciful bottom of things. A more realistic one is, what is the smallest camera we can economically design and deploy on our grapefruit sized spacecraft.
(definition of microtech 10 -100 kg, source)
The benefits are that now things are small enought
During the proposal, funding and design phase to the testing of a 1/2 scale descending prototype.
Due to an unbelievably arcane set of circumstances the tractor rockets never arrived.
The windmills in Tehachapi.
The little motel.
The Drape Problem.
The BRS angle. Jeff Peltier and the wad of suspension lines.
The ballasted C.G.
Faster better cheaper.
The pixie dust.
The little call from the contractor.
The meeting in Stone's office.
Taking him at his word.
Muirhead's prayerful backstabbing of Collins.
Dara Sabahi and Carl Buck's scorning of the laced release.
Carl Buck's carefully calculated move.
The Ranger 7 remarks at the initial meeting.
In an afternoon Greg Hickey and I designed a heat
Up to know, scientists have ruled what gets put on all spacecraft, which has led to some very questionable decisions. Example, gravity boom to measure nerdic fluctuations OR video camera so everyone can see? Ummmm, gravity boom.