World B4
my bad y'all
- Joined
- 25 June 2017
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The TAU spacecraft was an attempt to get the most out of a space shuttle launch in terms of distance, estimating that with an incredibly advanced nuclear electric engine they could reach 100 AU in 50 years 505 AU in roughly 30 years, with 2/3 of the first year spent escaping earth orbit. The spacecraft had a mass of 25,000kg including a 14,000kg propulsion module that would jettison after a decade, payload was to be 5000kg, 550 AU is a distance I've seen referenced as the requirement for a telescope that uses our sun as a gravitational lens, and since a some of the originally intended TAU missions are no longer necessary, this strikes me as a good objective for half the range, and there are a number of advancements that might make this new distance record possible and even affordable. First the challenge. Current nuclear electric technology is far from the requirements for the TAU mission. With 6000kg the concept wanted a 1 mw reactor to provide a 250km/s exhaust velocity, and that's the mass of the 40kw reactor Nasa is looking to deploy in the near future. Russia's TEM plans to be 20,300kg with a 1mw reactor, and won't reach 7 km/s. My solution to this is a combination of brute force and extra wiggle room. The principle advantage we have today is that instead of a billion per shuttle launch, we can plan to use Starship. Spacex is reportedly planning on getting costs down to 10 mil per launch, currently it's about 100 mil for test articles, and I think 75 mil each for a 2 launch deal is a reasonable starting point, to hopefully go down by the time the mission is ready. 150 mil is cheap for the kind of mass needed, as no other even heavy lift launcher can operate for under 90, and carry far less. Each Starship, with a reusable mission planned, can carry in exess of 90,000kg to leo. I believe that by working with international and commercial partners and using cutting edge technologies, 180,000 kg of wet mass spacecraft placed in leo is enough to take us that far out in a reasonable time, say 30 years. I think it would be smarter to add more power systems to the 6000kg reactor and try to use efficent/reduced payload mass/power demand, and use modern spacecraft batteries that can go through tens of thousands of cycles. I think NASA and the U.S. government are happy to let cooperation with Russia end with the ISS, and besides that much extra mass would mean a higher cost I want to avoid, so 1mw will be a pipe dream for now. My genius plan is to literally attempt an all of the above approach. 45kg rtgs can add kilowatts each, and closer to home a combination of 325kg ROSA arrays and a beamed power receiver for receiving solar power from power sats and/or a Breakthrough test laser can help out and be ejected upon irrelevance, replacing the unrealistic 6000kg reactor with an achievable multi-power source for ~8500kg that might be able to propel a reduced 2500kg payload using modern electrical propulsion systems, hopefully making up enough difference to be worthwhile. Of course, any doable mass savings would help, and I believe the best way to use the remaining starship payload is to use a kick stage. Using the ZBO/RBO tanks NASA is developing, a hydrogen tank can be carried in the first starship with the spacecraft, and sit in orbit as the craft accelerates. When it is near escape velocity, the second Starship can launch a space tug with an NTR, which is set to enter space for the first time for DARPA's Draco mission. It can dock with the extra tank, match the craft's velocity, and if it's already going fast enough that the the first tank was jettisoned by then to reach it, re-using some or all of the docking mechanisms could be possible. The tug will then expend itself to accelerate the craft, brute forcing the velocity problem through sheer weight of the lightest atom of all. Of course, exotic but not superbly so engines like pulsed ntr could make the math better, but I don't see them as a short term reality. The convergence of several advancements, 4 power source types, and a more modest payload mass may make this possible and affordable, supporting a wide range of companies could provide the political will (lobbying(bribery)) in the U.S. and, international partners could be brought in to support payload development on their own dime, since the data will be shared anyway. Of course, if reactor development allows for a simplified power system, that's just grand. The cost of a single Artemis mission, in exess of 4.1 billion, seems more than enough to purchase tech from companies and organizations already developing it with their own funding, tech that already exists, and attract the best help for the tech to be developed. New Horizons cost 800mil, so a 2.2 billion total is probably a reasonable starting point for something to go further and be bigger, with 1.5 billion to support the telescope, and 500 mil for cost overruns. Reaching and operating at that distance would be record breaking, and allow for unprecedented imaging. Doing it for less than 4 billion dollars seems almost a bargain.
spacenews.com
NASA plans for lunar fission power systems face fiscal challenges
Advocates of nuclear power systems for lunar exploration are calling on NASA to find ways to continue development amid fiscal challenges and competing priorities.
spacenews.com
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