NERVA on the SLS

As General Atomics was testing their NTP (better, NΘP) engine, and various HALEU-driven tugs were exiled from Earth's gravity well, DRACO got canceled. Anyway here is something I missed that (2025) January: deep-space missions.

The idea best-I-can-tell was to give the SLS something to do besides pay off Senators and prance around on the Moon one more (and last) time. The whole design behind that was to inject something serious past Earth L1, directly, without any infrastructure up there. Starship as you (should) know was never meant for this; it is meant for creating that infrastructure - in LEO, namely a fuel and supply depot.

Anyway last year Arthur Beckman et al. figured that a NERVA engine, once delivered far-enough up that the anti-nuke guys wouldn't bother you, could break the (now-meagre) bonds of Earth and spew out some serious I_sp. This particular design promises 900s. That adds 17% payload to a one-way Deimos trip (relative to Hohmann by hydrox' ~500 I_sp, one assumes). Some of this load is the engine itself of course but they're assuming no difference from the chemical engines we've had. Which is quite the assumption given the need for shielding.

Once at Deimos the passengers do the thing where hopefully they establish a base, unspool cable, kick up local spingrav, make more cable out of anhydrous glass, and generally prepare for a gentle landing on the red planet. (More likely they skip Deimos and fool around in the planet itself which this blog has never recommended.) I mean, they might have the extra space for it . . .

Much more savings can be had from visiting further-away planets. Uranus is noted here in this context because we haven't orbited that one yet. For a seven-year trajectory a chemical rocket could hold "6.8-mt" payload. NTP for the same time boosts payload to 14.3: 210% increase! -mind, here the chemical system was egregiously wasteful (Starship can at least aerobrake) and, again, they haven't loaded up the payload at the depot b/c SLS. This goes up and up as we deal with Pluto (read: Kuiper) or interstellar... but I'm ignoring all that, because interstellar might end up with electrons from a solar statite.