### Re: Z-Pinch Renaissance

Posted:

**Mon Jul 08, 2019 12:51 am**not my work but relevant underlined comments are mine.

Consider a 1,000 ton spacecraft with a 10,000 km/s exhaust velocity and an acceleration of 0.722 m/s/s. For a 1 AU trip at constant acceleration, flipping at the midpoint, it will take 10.5 days and consume 66 tons of propellant/fuel.

Now let's add extra mass into the exhaust stream, so that the spacecraft uses propellant at 16 times the rate but expels it at 1/4 the exhaust velocity (thus keeping the same power). This brings the acceleration up to 2.89 m/s/s. We will accelerate for 1/10 the distance, drift for 8/10 the distance, and then decelerate for 1/10 the distance. The trip now takes 7 days and uses 240 tons of propellant, of which only 7 tons is fuel.

in this case propellant is not fuel, we are talking a new way of doing things, we tend to get this confused because in chemical rockets propellant is fuel but in our case they are now different

Bulk inert (non-fuel) propellant is probably cheap (water or hydrogen). Fuel is probably expensive (He-3 and D). The second option gets you there faster and cheaper.

Consider a 1,000 ton spacecraft with a 10,000 km/s exhaust velocity and an acceleration of 0.722 m/s/s. For a 1 AU trip at constant acceleration, flipping at the midpoint, it will take 10.5 days and consume 66 tons of propellant/fuel.

Now let's add extra mass into the exhaust stream, so that the spacecraft uses propellant at 16 times the rate but expels it at 1/4 the exhaust velocity (thus keeping the same power). This brings the acceleration up to 2.89 m/s/s. We will accelerate for 1/10 the distance, drift for 8/10 the distance, and then decelerate for 1/10 the distance. The trip now takes 7 days and uses 240 tons of propellant, of which only 7 tons is fuel.

in this case propellant is not fuel, we are talking a new way of doing things, we tend to get this confused because in chemical rockets propellant is fuel but in our case they are now different

Bulk inert (non-fuel) propellant is probably cheap (water or hydrogen). Fuel is probably expensive (He-3 and D). The second option gets you there faster and cheaper.