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Relativistic Rocketry
Robert Forward suggested the production of positrons and their storage
as a means to implement advanced propulsion. In one instance, positron/electron production of shaped gamma rays is used to make compact aneutronic fusion a reality. This solves the problem of the industrial access to the Solar System. The other instance is the use of directed gamma rays themselves as a photonic rocket. These ideas have been picked up by the National Research Council and is available for public review in A REVIEW OF UNITED STATES AIR FORCE AND DEPARTMENT OF DEFENSE AEROSPACE PROPULSION NEEDS http://www.nap.edu/catalog.php?record_id=11780 The density achieved with positron storage is limited based on method of storage. http://www.icarusinterstellar.org/bl...antiparticles/ Arthur Clarke suggested in a private conversation that it might be possible to create a way to cause a positron-electron to somehow bind in a semi-neutral condenstate without annihilating, and then excite the condensate to annihilate in the engine. If positron/electron pairs could be stored as densely as hydrogen in liquid hydrogen, then you'd get about 140 grams per cubic meter. Of course creating anti-hydrogen and storing it to combine with hydrogen attains 70 kg per cubic meter. Protons and anti-protons though produce intermediate pions which reduce engine efficiency somewhat with current proposed designs. An anti-matter powered vehicle accelerate at 1/10th gee would deliver a payload fraction of 26.92% a distance of 4.328 light years in 12.72 years ship time, 13.65 years Earth time. The ship attains 57.6% the speed of light mid journey. Using a solar sail for the first half of the journey and anti-matter rockets for the second half increases payload fraction to 51.89% Once a laser set up placed at alpha-centauri, laser light sails can be used throughout the entire journey, and both ways to maintain commerce between stars. Now, a 12.72 year journey is possible with suspended animation, which is a medical reality today. http://www.ted.com/talks/mark_roth_s...animation.html It turns out we've known since World War One how to do it. Truly amazing. A whiff of 1,000 ppm of H2S can cause a person to pass out. Reducing oxygen and temperature quickly - puts the person in suspended animation. Raising temperature and oxygen reverses the process in most cases. If this could be made into a simple automated process - people could be brought in and out of suspension quickly and reliably at low cost. This would reduce their cost of living and increase their utility. If you had a limited fixed income - say an annuity - you could live better when you were animated if you spent long times suspended. |
#2
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Relativistic Rocketry
Without black holes, without anti-matter, it is possible to send
payloads to nearby stars in reasonable times using solar sails and fusion rockets. A laser light sail operating at 0.33 gee for 1 year accelerates a payload to 32.8% light speed after traversing 0.17 light years. It takes 1.02 years Earth time. At the target star, using a fusion powered rocket with 33,000 km/sec exhaust speed requires that 95.48% of the total mass be fusion propellant, leaving 4.52% payload (including structure (but not necessarily the sail)) Total trip time 13.9 years - Earth time and 13.2 years ship time including acceleration and slowing. High temperature laser light sails operate at very high power levels and can be quite compact. In other posts I have postulated self-replicating machine cells that are capable of transforming planets in days. A 1.5 kg payload with a 500 kg solar sail and 23.5 kg lithium-6 deuteride propellant - is a model of a minimum unmanned probe. A 1.5 metric ton payload with a 500 metric ton solar sail and 23.5 metric ton lithium 6 deuteride propellant - is a model of a minimum piloted probe - equipped with a suspended animation capability. 525 kg system accelerating at 0.33 gee using a laser light sail requires 254 GW of laser energy. This is collected by a 360 m diameter satellite in an orbit 3.7 million km from the Sun. A 525 ton system requires 1,000x more power and 1,000x more area which is 31.6x the diameter - 11.4 km in diameter - in the same orbit around the Sun. |
#3
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Relativistic Rocketry
Relativistic rocket calculation page has been taken down!
Here's a derivation of the relevant equations in a 1995 AIAA paper by my friend Bob Forward; http://www.relativitycalculator.com/...tions/AIAA.pdf How to build an Anti-matter rocket for interstellar missions http://www.aiaa.org/Participate/Uploads/2003-4676.pdf Here's an overview; http://en.wikipedia.org/wiki/Relativistic_rocket Most spreadsheets will not do hyperbolic trig functions which are needed to do these calculations. So, you will have to use the EXP - exponential functions to calculate them yourself using; http://mathworld.wolfram.com/HyperbolicTangent.html TANH(x) --- (EXP(x)-EXP(-x))/(EXP(x)+EXP(-x)) --- (EXP(2*x)-1)/(EXP(2*x)+1) http://mathworld.wolfram.com/HyperbolicSine.html SINH(x) --- (EXP(x)-EXP(-x))/2 http://mathworld.wolfram.com/HyperbolicCosine.html COSH(x) --- (EXP(x)+EXP(-x))/2 You can use this information to calculate how long it would take to travel to the nearest stars. There are 109 stars and 8 brown dwarf stars within 20 light years of Earth. http://www.atlasoftheuniverse.com/nearstar.html From this data a whole host of early interstellar campaigns can be developed. From this point we can see that using laser light sails and anti- matter rockets produce the following chart; Year Distance Stars People People/star AD Light Yr No. MM MM 2040 25 229 9,293.3 40.67 2065 50 1,828 12,338.0 6.75 2090 75 6,170 16,380.2 2.65 2115 100 14,625 21,746.7 1.49 2140 125 28,564 28,871.3 1.01 2165 150 49,359 38,330.1 0.78 2190 175 78,381 50,887.9 0.65 2215 200 117,000 67,559.7 0.58 2240 225 166,588 89,693.6 0.54 2265 250 228,516 119,079.1 0.52 Basically, one pair of cylinders per star system are sufficient to house every man woman and child and maintain them at a high living standard after 2140 AD while only 41 pairs are needed to house everyone in 2040. http://www.nss.org/settlement/space/oneillcylinder.htm |
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