If we ever get to mine the moon, electric rail launchers are seen by many as the most viable method of sending off our spoils. Dead easy with low gravity and no atmosphere, but not so easy from Earth. The gravity we could overcome with a longer rail or more power, but not the atmosphere. We could turn the rail vertical and put it in a high tower on top of a mountain, but it's difficult to build a tower much over 600 metres and expect it to stay up there in even normal weather. Short rail
with lots of air above it.
In the early days of flying, racing was a popular sport. This often involved flying out, round a pylon, and back. The "Pylon Turn" that was soon discovered involved banking as soon as you were level with the pylon, pointing your wing at the pylon, and keeping it there until you had gone right around. (see figure 1)
The American gunships in Vietnam had their guns bolted down and pointed sideways, so when the pilot flew a pylon turn around an enemy position, the guns were always pointed at the enemy. A missionary in South America took the principle a stage further to pick up mail and drop supplies at remote villages. He flew a pylon turn above the village while a bucket was lowered on a long rope. The bucket hung in the one spot near the ground, and the villagers easilyemptied and then filled it. (see figure 2)
The PTW is only intended to take off and fly for a launch or series
of launches, so would need an airfield. Unfortunately, airfields 40 kilometres
in diameter are hard to come by, so maybe a suitable sized piece of sheltered
water would be best. Add a number of floats along the underside of the
beam. A piece of water that comes to mind is Lake Titicaca in Peru and
Bolivia. It's plenty big enough on either side of the border, is fairly
calm, is already at 3811 metres, and is only 16
degrees from the equator. The pylon (15 metres high approx) could be in the middle of a square barge-type platform. (see figures 3 and 4)
The launch velocity would depend on the weight (power available and
the beam's ability to absorb the recoil effects) and the payload's resistance
to g forces; but I see no problems with launch velocities of, say 1.5 to
3 kilometres/second. Not enough for orbit, true, but most pure rocket-based
systems will already have burned 70 to 80% of their fuel. A comparatively
small upper stage could boost the payload to orbit, correcting any slight
off aim as it did so. High winds and rain could play havoc with launching
in all sorts of ways; so like an ultralite, the PTW would only fly on the
good days. When you are having a true good day you could launch almost
as fast as you could load onto
Now lets' look at the feasability through the eyes of an accountant. Would the PTW be cheap to build and operate? Er...Yes and No. Yes by comparison to the Space Shuttle or Venture Star, but still hundreds of millions of dollars. What PTW has to offer is the ability to launch, not several times nor even several tens of times, but several thousands of times a year. This means high turnover. And high turnover, as every accountant with a gleam in his eyes knows, means low unit costs which translates into lower prices and fat profits.
Is the market large enough to absorb the vastly increased unit launch production? Hell, no! The existing market consists mostly of government in various guises, and commercial TV satellites. Even if the price fell to $100/pound, the existing market might only triple or quadruple in size. What is missing from the equation is Industry.There is not a single industry in space, and at current prices, there is not the slightest thought of putting one there. Get the launches down in price and frequent flying enough, and Industry will establish in space and make new superstrong alloys, giant perfect crystals, new chemicals and materials, new drugs that they've been bragging about by the thousands of tons, and oh no, here comes the space tourist industry.
by R.J. Knell
© R.J. Knell 1997
As far as I know, this is an original concept of mine, put in the public domain February 17, 1997.
Comments and discussion appreciated.
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