LA-4541-MS

I was just reading a declassified document this week-end about Nuclear
Pulsed Space Propulsion Systems (LA-4541-MS)

http://www.lepp.cornell.edu/~seb/celestia/orion/

It has some great analysis of the limits of nuclear pulse vehicles.
Namely, figures 4 and 5 which gives mass scaling laws for nuclear
pulse vehicles. Very large payload fractions, very small propulsor/
pulse-unit fraction. Larger vehicles are favored over smaller ones.

Another interesting concepts which I find interesting is the
discussion of Appendix A - laser concepts and considerations. Here
the requirements for a minimal nuclear fusion is discussed, and what
might be needed to achieve that with lasers.

According to the document, the optimum time width to deliver this
energy is between 1e-10 and 1e-7 seconds to take advantage of the
resonant absportion which occurs near the plasma frequency of the
medium.

Depending on efficiency of laser coupling 2e+4 J to 1e+6 J are needed
to burn milligram quantities of D+T - depending on how the plasma is
confined and heated. One interesting concept is the creation of a
disposable chemical laser attached to the pulse unit. Rather than
using an explosive plastic like C4 to compress and heat a nuclear
core, here a chemical lasing system is created that achieves the same
effect.

A hydrogen flouride laser operating at 1 atm possesses 1e+6 J per
cubic meter according to the document with reactoin times on the order
of 1e-9 seconds. Increasing pressures increase energy density. 150
atm produce 1.5e+8 J per cubic meter.

If 2e+4 J are needed, and 2e+8 J per cubic meter of H2 and F2 gas
reacting in a pressure vessel at 200 atm - means that a container of
only 1e-4 cubic meters, or 100 ml - is needed to detonate a Lithium-6-
Deuteride system - with a Deterium-Tritium 'spark-plug'. The entire
system occupies less than 500 milli-liters - 1/2 liter - of volume.

1,000 pulse units are required to achieve orbit.

5,000 pulse units provide transport anywhere in the inner solar system
in forty days or less at low constant acceleration once on orbit.

Vehicle sizes of approximately 500,000 tons with an empty weight of
150,000 tons - made mostly of steel - appear immediately feasible.

This is between the mid-range and super orion nuclear pulse ships.

http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29

There are three momentum absorber configurations discussed.

a. Pusher plate
b. magnetic blanket
c. internal system

A shaped pusher plate, that is sort of a hybrid between a and c is not
explicitly discussed, but such a system appears possible on a large
scale, given the data in this paper.which allows a pusher plate to be
very efficient. Shaping the pulse wave achieves the same effect.

What appears immediately possible is that a perfectly clean
interplanetary freighter that is capable of giving us access to solar
system resources on the same scale, cost and time-frame as oceanic
freighters give us access to the world's resources.

At typical aerospace development costs of $5.3 milion per ton, the
vehicles would cost $2.65 trillion each. Obviously using steel
construction throughout, and allowing for the high energy density of
the fuels has the potential to reduce costs. How low? Well,
perhaps as low as $2,600 per ton - 1/500th the cost of an aerospace
project. , This would make the vehicle $400 million - about twice the
cost of a LNG super-tanker, which costs about $200 million. LNG
tankers are far more expensive than conventional tankers, which are
half again as much to construct new.

A cone 300 m tall and 200 m diameter at the base, would have a total
volume of 6,283,185 cubic meters. Allowing 100 m length of the 200 m
momentum absorber for the momentum conditioning unit,

This is a payload volume 9.76x that of the Emma Maersk's 643,140 cubic
meters. This implies a payload of 107,464 shipping containers (14
tons each) and from that a structural fractoin using the tables in the
document described here, 450,000 tons empty, 1,950,000 tons full, and
an additional 550,000 tons of propellant - for a maximum take off
weight of 2.5 million tons.

Something like this vehicle could pioneer the opening of the solar
system - erecting cities on the moon and mars - establishing mines on
Ceres and Eros - putting up power satellite networks - placing
remotely operated factories in space.

This could have been done in the 1970s, it can be done today.

Humanity ships 6 billion tons of material per year. The average US
citizen uses 4 tons of material per year - apart from the coal and oil
used. Humanity using materials at the same rate as the average US
citizen today would consume 26 billion tons of material per year.

With 40 day cycle times, a ship can carry out 9 transfers in a year.
With 1.5 million tons transferred per trip each ship represents 13.5
million tons of payload. So, 2,000 such ships have the potential to
supply the human race with mateirals from sources off-world, at the
same rate the USA citizen uses materials today.

Energy is a different issue. Sunlight streams to Earth from off-world
every day, in quantities that are large compared to the rate at which
we use energy. Humanity currently uses 15 trillion watts of energy -
the United States uses energy at 4 trillion watts rate. With only 0.3
billion people, this means that if the average person in the world
used energy at the USA per capita rate total energy use would rise to
87 trillion watts.

To meet this expanded energy need requires that first, solar arrays of
solar panels be erected on Earth to produce low-cost hydrogen to
displace fossil fuel use. Then, solar pumped lasers be orbited to
beam band-gap matched light to the existing solar panels, increasing
their output 30x - - provinding for long term growth and stability.

To avoid polllution it is also recommended that refining, smelting,
refining, fabricating, growing, harvesting, all be done on orbit in
large pressure vessels. Rich asteroids and asteroidal fragements are
shipped back to Earth orbit, and using solar energy, tele-operated
robots, and tooling - brought to orbit on a large scale- products food
and fiber are made and deorbited directly to end users on demand.

In this way the global economy rises from $70 trillion today to $400
trillion in 25 years while air pollution is eliminated, and mining,
farming, factories, refineries, and so forth on Earth are transferred
to orbit - cleaning up our water and land as well as air.
..
.

Relevant Pages

  • Re: Space travel not war
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    (sci.space.policy)
  • Practical space travel and unlimited growth
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    (sci.space.policy)
  • Re: Space travel not war
    ... scrap of fossil and nuclear energy, or else it's another war (hot or ... no nation can grow strong in a world beset by problems all ... 300 million tons of natural gas. ... By adding more solar panels, more hydrogen is generated, and that is ...
    (sci.space.policy)
  • Re: "The Only Thing They Learn" -- does anyone else find it irritating?
    ... much fewer solar plants. ... Solar energy will be available for much longer. ... nuclear energy is a stop-gap solution, ... Alternative energy sources, including solar power, do have real limits ...
    (rec.arts.sf.written)
  • Re: Attn: Mr. Mook
    ... green/renewable energy is worth how many terawatts? ... The cost of alternative energy sources has to do with capital costs. ... The recurring cost of energy for nuclear and solar sources (solar is ...
    (sci.energy.hydrogen)
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