NA/R - Solar Electric Spacecraft for Asteroid Belt Exploration (1970)

A design by North American/Rockwell for the same contract as the TRW 'Solar Electric Multi Mission Spacecraft'. Unlike that vehicle, which was intended for use for a variety of missions, this spacecraft was optimised for untargeted asteroid belt exploration, though with it's particle and fields dominated instrument fit out, it could also have been used for 'out of ecliptic' missions.


Solar electric propulsion asteroid belt mission study. Final Report. Vol. 1, Summary Report
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19700014164.pdf

Solar electric propulsion asteroid belt mission study. Final Report. Vol. 2, Technical Report
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19700014165.pdf

Solar electric propulsion asteroid belt mission study. Final Report. Vol. 3, Program Development Plan
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19700014166.pdf

Was this actually feasible in a 70s timeframe? Given that ion engines only really matured by the 2000s, it seems a bit early.

Was it a funding thing? With say 20-30 billion dollars, could kW/kg range electric thrusters (30km/s Hall effect, ion, whatever) been developed in the 70s? There were a range of proposals for nuclear electric reactors, so power seems to be no object.

Given the sheer number of nuclear electric proposals (up to lunar tug sized) in the 60s, one gets the impression that this was indeed the case, but the field of electronics has advanced a lot since then, and our cutting edge electric thrusters don't seem much better performance wise.

Definitely funding. Money was still flowing into the Vietnam war during the early 1970s despite, or indeed because of Vietnamization, but that was just disguising the real killer of American innovation and progress, the hideously expensive so-called 'Great Society' initiative, whose ongoing effects would continue eating the United States' lunch for the rest of the decade. Matters were not helped one bit by other (often related) idiotic political & economic policies such as the infamous 'Nixon Shock'.

chimeric oncogene said:

Was this actually feasible in a 70s timeframe? Given that ion engines only really matured by the 2000s, it seems a bit early.

Was it a funding thing? With say 20-30 billion dollars, could kW/kg range electric thrusters (30km/s Hall effect, ion, whatever) been developed in the 70s? There were a range of proposals for nuclear electric reactors, so power seems to be no object.

Given the sheer number of nuclear electric proposals (up to lunar tug sized) in the 60s, one gets the impression that this was indeed the case, but the field of electronics has advanced a lot since then, and our cutting edge electric thrusters don't seem much better performance wise.

Click to expand...

There's at least two issues there: the solar panels and the electric propulsion. Would 1970s solar cell technology have been sufficient to provide that power? If yes, then that's a non-issue. If no, would more money have made a difference? I sorta suspect it would not, because a lot of money was put into advancing solar cells, both for terrestrial and space use. I don't think more money would have improved that technology any faster.

As for electric propulsion, I think that more money would have been required and could have advanced the technology. Electric propulsion was always one of several different in-space propulsion technologies funded over many decades, but it took a big funding push in the 1990s to really advance it. And at least part of that was an existence proof--until NASA flew a mission that proved what it could do, most spacecraft designers were reluctant to touch it. (And an existence proof required an expensive spacecraft.) That said, there are some subtle aspects to the technology that might not have been pushed much faster with lots more money. For instance, the control system that regulates the power conversion (the electricity coming from the solar panels into what is used for the electric engine) is complex. That may have benefited primarily from overall improvements in electronics over the decades and a specific funding push in the 1970s might not have helped all that much.