Aquarius a nuclear thermal rocket that uses water heated to over 3000 degrees celsius to solve many human interplanetary transportation issues

The Space Enterprise Institute has a proposed design for a reusable interplanetary transport.

Attributes of a reusable interplanetary human spaceflight transport are proposed and applied to example transits between the Earth/Moon system and Deimos, the outer moon of Mars. Because the transport is 54% water by mass at an interplanetary departure, it is christened Aquarius. In addition to supporting crew hydration/hygiene, water aboard Aquarius serves as propellant and as enhanced crew habitat radiation shielding during interplanetary transit. Key infrastructure and technology supporting Aquarius operations include pre-emplaced consumables and subsurface habitat at Deimos with crew radiation shielding equivalent to sea level on Earth, resupply in a selenocentric distant retrograde orbit, and nuclear thermal propulsion.

Advancing in-space nuclear thermal propulsion (NTP) technology to the point where fission reactor core temperatures exceeding 3000° C can be achieved during major translational maneuvers (burns). Under these conditions, water molecules pumped into the core will disassociate into hydrogen and oxygen atoms, and specific impulse ISP near 1000 s could be achieved. This level of efficiency, twice that attainable with chemical propulsion, dramatically reduces total mass for an interplanetary transport of specified payload mass.

When high propulsive efficiency is achieved with water as propellant, the practicality of interplanetary human spaceflight is enhanced in multiple respects.

1.liquid water is easily stored for months or years without exotic thermal conditioning burdens imposed by cryogens or toxicity hazards associated with hypergols.

2. liquid water stored about the crew habitat to support arrival propulsion requirements at an interplanetary destination also serves as an effective radiation shield during interplanetary transit.

3. water is arguably the most common volatile to be found on small bodies such as asteroids and minor moons throughout our solar system, leading to the promise of in-situ resource utilization (ISRU). With ISRU producing
water for propulsion, radiation shielding, and hydration/hygiene near an interplanetary destination, mass to be transported there from Earth in support of crew return is virtually eliminated.

Is technical risk of the presumably higher 3000° C nuclear reactor core temperature necessary to “burn” water
propellant and achieve this ISP (875-1000 ISP) a good trade against the potentially greater difficulties
of refining, storing, and transporting liquid hydrogen, particularly in an ISRU context

There was an 18 page presentation at NASA FISO

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