Milli-g flip-n-burn

Let's talk Nyrath Nomograms. These are slide-rule type charts where you stick a pin in your [Tsiolkovsky] mission, whip out your ruler, and estimate what magnitude of power you need to lower your mass ratio.

For instance Princeton was promising I_sp 50,000 (N/N)s, if you could come up with 10 MW energy. I thought if I stuck around Venus' halo and harvested hydrogen, I could do that. Fatima Ebrahimi's not on Chung's chart but you can put 'er up on the right above VASIMR.

The slight issue I saw (and why I stuck the poor lady with station-keeping) is that specific-impulse isn't everything. First off (more so for Ebrahimi) where're those megawatts coming from. You often need thrust, too - dependent on cargo. And apparent delta-V isn't everything if we can do a Crazy Hermann. All this stuff I see about liftoff and, for that matter, Hohmann - or any other transfer mission - has that Barrier To Entry, which is thrust / weight / mass. If your thrust is only good enough to get your delta-V to Hohmann at the moment you need to get out, you've gained nothing. Ebrahimi's piddling 100 N will just hose down your lab with propellant.

Here is another option, for those hoping to economise on thrust: the flip-n-burn, which the nerds call "brachistochrone". Suppose I wanted a 0.098 ms^-2 acceleration then deceleration. That is microgravity which I'd not ask of any crewmen - but it may be good for cargo. Also I am in space so I'm unworried about irradiating Canada.

Hence the interest in UltraSafe's low-grade solid NTR. Say the AEC lets us use NTR-liquid in space at what, 15 km/s. Pity: for 0.098 ms^-2 its mass ratio is horrible. NTR-liquid turns out not to work either. You're just lugging a radioactive propellant tank from Earth to Venus (but quickly!).

I think, though, the chart also implies 9.8 millimeters per square-second. Why isn't it there? Partly because the Sun interferes in the mm s^-2 range, 6 of these near Earth. On any transfer orbit, apo' and peri', acceleration orthogonal to direction is highest, more so on peri'; and the speed is least. That much, UltraSafe can give us... to outward planets like Mars, anyway. That much and more, Princeton's other fusion-reaction team can certainly give us.