One of the first problems that must be solved by any group planning to colonize space is getting there. Rockets are likely to be too slow, too dangerous, and far too expensive when substantial numbers of people, animals, and plants are involved.
Perhaps there is a better way. The electromagnetic launch system designed by Dr. Henry Kolm (formerly of MIT) offers the possibility of putting two-ton payloads into low-Earth orbit in less than two seconds, and with no risk of explosion. Furthermore, it may be able to do so at a rate of up to six payloads an hour at a price of about $10,000 a payload. The cost of developing such a system, says Kolm (who has formed his own company, Electromagnetic Launch Systems), would be considerably less than what has already been spent on the shuttle program.
Attaining escape velocity in two seconds, however, generates acceleration stress of close to 1,000 gravities. Up to now, there has been no way for human passengers to survive such stress. Neutral density encapsulation might make it possible.
Some years ago, Dr. Tom Shaffer of Temple University developed a liquid hydrofluorocarbon that can carry enough oxygen into the lungs to support mammalian life. His original purpose was to save severely premature infants, whose lungs are not able to handle gaseous oxygen. In this, he succeeded. Extensive animal studies and preliminary experiments with human infants show that his new liquid makes it possible to bring fetuses to healthy term after as little as 12 weeks in the womb. But the substance has other applications, one of which is to neutralize almost all the effects of acceleration stress.
Consider: What kills human beings at acceleration much over 30 g is not the acceleration itself, but the fact that the vehicle accelerates at a rate different from that of its passengers, and the different parts of the passengers' bodies also experience different rates of acceleration. This is because of the differences in density between the astronauts' bodies and the environment within the capsule, and differences in density between the lungs and the surrounding body tissues. So an unprotected human in a capsule accelerating at 1,000 g would be killed instantly for two reasons. First, in an air-filled capsule, the more dense human body, even if placed on an acceleration couch, would slam against that couch with bone-shattering force. Secondly, the relative density of the ribs and chest muscles compared to the air pockets in the lungs would cause the ribs to crush the lungs.
Neutral density encapsulation could perhaps solve both problems. The overall density of the human body is nearly the same as that of Shaffer's liquid. By floating an astronaut in a capsule completely filled with the hydrofluorocarbon, and then accelerating the whole capsule, the first source of stress has been removed, since both the capsule and its occupant would now be accelerating at the same rate.
To better understand this point, remember the high-school science experiment with a raw egg. Placed loose inside a tin box which is then thrown against a wall, the egg shatters. If the box with the egg in it is filled with water, however, so that egg and box accelerate and decelerate at the same rate, the egg can survive the throw unbroken. The same principle was applied to living bodies during a rather cruel Italian experiment conducted in the 1960s. The researchers slammed a pregnant rat against a wall at 10,000 g. While the mother rat was killed instantly, the fetuses -- floating as they were in sacs totally filled with amniotic fluid -- survived.
The second source of stress -- the difference in density (and hence rate of acceleration) between chest and lungs -- can be neutralized by having the astronaut breath the liquid. The gag reflex can be overcome by adjusting the substance's temperature and pH. Ethical considerations have so far prevented Shaffer from filling both lungs of a human volunteer, but one lung has been filled, and the liquid has been breathed and later coughed out without harm. Whatever was left in the lung was safely absorbed.
An artist's impression of how a neutral density encapsulation system would look.
Neutral density encapsulation could thus permit the entire "package" -- capsule, astronaut, chest, and lungs -- to be accelerated or decelerated as a single-density whole. When the idea was presented to Shaffer and Kolm, they worked out the physics and concluded that, yes, floating a liquid-breathing astronaut in a completely liquid-filled chamber would offer full protection against up to 1,000 g.
How Henry Kolm's electromagnetic mass driver might appear, if built in the Rockies.
Of course, if the ultimate goal is colonization of the galaxy, rather than merely the solar system, drive systems considerably more "potent" than Kolm's may be required. A Swedish specialist in space medicine has speculated that, if the sinus cavities as well as the lungs are filled, it might be possible to survive even higher accelerations.
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