Talk:Solar thermal rocket

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This article is or was the subject of a Wiki Education Foundation-supported course assignment. Further details are available on the course page. Peer reviewers: Discusandhammer.

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Diagrams

Can we get some SVG drawings of how the various types of this rocket class work? Does SVG support animation? It might help. Will (Talk - contribs) 18:17, 5 February 2007 (UTC)

Possible variants

A higher specific impulse may be possible by making the heat exchanger and nozzle out of a different material such as Tungsten (3695 K) or possibly Reinforced_carbon-carbon coated with Titanium_boride.

If one thruster can go from LEO to GEO in 7 days four may be able to do it in less than 2 days for a similar amount of fuel. A man rated version of the rocket could get people to the moon and back. A reusable version whose fuel comes in a cartridge would be a lot cheaper then the single trip Earth Departure Stage on the second trip.

Andrew Swallow 20:05, 29 April 2007 (UTC)

If a compound like water can be used as fuel other compounds with lower boiling points like methane or carbon dioxide may work better. Plenty of both on the planets. Andrew Swallow 04:56, 25 June 2007 (UTC)

You really want materials you don't have to go down to a planet to get; because it costs propellant to get the propellant if you do that. That means you may have to use higher boiling points than water, because those materials are more likely to have survived baking out by the Sun closer in to the Earth, where they are more accessible.WolfKeeper 15:33, 25 June 2007 (UTC)

The temperature of concentrated sun light is sufficiently high that it can boil many elements. This boiling will use a lot of energy. If the International Space Station can be hit by meteors then it may be possible to capture meteors and man made space debris. Carbon dioxide and methane can be found in the atmosphere of several planets. The lunar soil contains some interesting substances.

Andrew Swallow 05:19, 26 June 2007 (UTC)

There is one other propellant available - liquid oxygen. There are various ISRU processes for extracting oxygen from the surfaces of the Moon and Mars. Lunar landers need to produce sufficient force to overcome a gravity acceleration of 1.622 m/s/s. Engines that only work in daylight will limit the launch and landing windows. Care will also have to be taken to ensure that very hot oxygen does not set the motor and spacecraft on fire. Andrew Swallow (talk) 19:11, 10 January 2008 (UTC)

The heavy element Bismuth is being used as propellent in several types of ion thrusters to produce extra thrust. It may also work in a solar thermal rocket. Andrew Swallow (talk) 21:06, 7 May 2008 (UTC)

It's probably very good for ion drives. For thermal rockets though you would have to boil it, and the boiling point is 1837 K (presumably @1 bar). It seems possible, but I'm not sure what the point would be; it's cheaper than mercury or xenon, but it's not completely inexpensive, and the Isp would very probably be lower than water (in a rocket the gas reaches sonic speed at the throat and then is multiplied by about 2 in the nozzle, but the speed of sound is inversely proportional to the square root of molecular mass). Nice density though, and the tankage fraction would be excellent, which would compensate to a degree. I also don't know where you get it from in an ISRU scenario, it looks like a pain to purify.- (User) WolfKeeper (Talk) 21:20, 7 May 2008 (UTC)

Solar thermal rocket engines are reaching the point where they have sufficient thrust to take off from the Moon. By simply doubling the thrust they could take a payload from LEO to the lunar surface, resulting in a major increase in usefulness. A change in propellant may improve the thrust. Using the figures from this webpage [1]

F = ma or a = F/m. a = 1000N / 890kg = 1.12 m/s/s. Lunar gravity is 1.62 m/s/s
The Moon can provide ISRU Oxygen, Mars ISRU CO₂, nitrogen and argon. Andrew Swallow (talk) 01:20, 12 May 2008 (UTC)

High thrust version by burning the hydrogen with LOX

A high thrust version of thermal nuclear rockets has been proposed that boosts the thrust by burning the hot hydrogen using liquid oxygen. It is called the LANTR engine. A solar thermal version may be possible. See [2]

Andrew Swallow (talk) 17:30, 25 March 2009 (UTC)

Propellant Storage

Boeing has proposed keeping hydrogen cold in propellant depots by means of a sun shield, basically a shiny curtain. This may work on low thrust rockets. Andrew Swallow (talk) 03:45, 2 October 2009 (UTC)

Missions

Solar thermal rockets have a higher Isp than chemical rockets but (normally) a lower Isp than rival electric propulsion. The Solar Thermal rockets have a higher thrust than electric propulsion with similar sized light collectors. The optics are not effected by radiation so these thrusters can be used by rockets passing through the Van Allen Radiation Belts.

A spaceship with an Isp of 1000 seconds travelling between Low Earth Orbit (LEO) and Earth-Moon Lagrange point L1 (EML1), a Delta-V 3.77 km/s, will need to carry
exp[Delta-V/(Isp * g)]-1 = exp[3770/(1000 * 9.81)]-1 = 0.469 times its mass in fuel.
The return trip needs 1.16 times its mass. This may make using a reusable solar thermal rocket space tug financially viable. Andrew Swallow (talk) 04:09, 4 October 2010 (UTC)

suggestions

overall, this page has quite wonderful information in an encyclopedic tone. There are many cases of missing or underused citations through the page, and the Zegler and Kuttler pdf link is no longer available.

I found a link for it right here, and will let you fix this link when you get a chance. http://bigidea.nianet.org/wp-content/uploads/2016/10/DepotBasedTransportationArchitecture20101.pdf

I think the lead section could use more information which point to the benefits of such an invention which a layperson could understand. This is a highly technical article, which is fine, but stating the seemingly obvious concept that these could potentially reduce the launch costs of commercial satellites and raise performance for interplanetary missions should be added there. Also, I think the second statement

  Solar thermal propulsion is also a good candidate for use in reusable inter-orbital tugs as it is a high-efficiency low-thrust system that can be refueled with relative ease

should be covered in more detail in the main body of the article. I think the sections are all useful and organized well, but I think another section talking about the pro's and con's and likelihood of production could be added. Discusandhammer (talk) 04:30, 22 February 2017 (UTC)

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