Space Tugs & Nuclear Shuttle!
 

Hello All,

The following are more "eye candy" than scale data (although some dimensions are included), but I thought I'd post them in the spirit of the fascinating design study documents that Luke Strawwalker posts on this scale sub-forum. These are proposed NASA Space Tugs (later called OTVs--Orbital Transfer Vehicles) and a NERVA-powered RNS (Reusable Nuclear Shuttle) that was proposed for cislunar and LEO to LMO (Low Earth Orbit to Low Mars Orbit) manned flights. Also:

For once I'm glad that a space project was canceled, because the in-space radiation safety distance figures (100 miles for an operating NERVA rocket engine, for starters) are hair-raising, not to mention the spent NERVA reactor fuel disposal proposals. To safeguard Earth's biosphere, the engines and their nuclear fuel could not be returned to the Earth's surface! (And in the 1960s, gaseous-core fission rockets were proposed!) There is likely more material on these proposed vehicles online, but here is an initial sampling of links:

https://www.google.com/images?q=reu...Dg&ved=0CCUQsAQ

http://www.spacefuture.com/archive/...e_concept.shtml

http://www.wired.com/2012/09/nuclea...n-studies-1971/

Cool! I love that kinda stuff.

As do I--they were good ideas whose only real flaw was that they were presented at a bad time--NASA proceeded as if the Moon Race level of funding would continue indefinitely, when it was just an historical aberration. Modular spacecraft such as the space tug and lunar lander make sense, and I think they will come about in forms more-or-less like those that were envisioned. Also:

The NTR (Nuclear Thermal Rocket) vehicles such as the nuclear shuttle had possibly-insurmountable safety issues, but this doesn't apply to all nuclear power systems for space propulsion use. In addition to the well-proven RTGs (Radioisotope Thermoelectric Generators), small reactors for non-NTR space propulsion systems would not have the radiation safety radius problem of NTRs. Instead of powering ion engines, a reactor could power an array of electrothermal (arc-jet or resisto-jet) thrusters that could use liquid hydrogen, ammonia, methane, or water as their working fluid. Also:

With specific impulse ratings of 700 to 2,000 seconds and thrusts of 100 to 500 millipounds (0.1 - 0.5 pounds) each, an array of a few dozen electrothermal thrusters would produce an aggregate thrust of 25 to 50 pounds, which would result in reasonable accelerations and trip times, even for manned spacecraft. The thrusters' ability to use water, ammonia, or methane would enable such spacecraft to refuel from various celestial bodies, including short-period comets and carbonaceous asteroids (some of which are inactive comet nuclei). These engines were also proposed in the 1960s (the arc-jet thruster was also called a "plasma-pinch engine"). I came across this recent design http://www.space.com/11230-water-po...lar-system.html , called the Space Coach http://spacecoach.org/electrothermal-propulsion/ , for a Mars spaceship that would be powered by water-fueled electrothermal thrusters. These efficient thrusters would also allow travel throughout the solar system.