Mars seems a little optimistic. Assuming you have a 100kW power source, there’s only around 4 N of thrust available (I’m using the thrust to power ratio of one of the Busek catalog thrusters). The new configuration helps with lifetime but it doesn’t seem to make any substantial change in specific impulse or the standard metric for electric propulsion: mN per kW.
The way to Mars is to get crew to Mars fast.
And low thrust does not work to get to Mars fast- well, it works only in the sense that it not a hohmann transfer.
And can’t get to Mars quickly from earth with a hohmann transfer.
Whereas from Mercury to Mars with hohmann transfer is reasonably
fast.
So making a Mercury to Mars orbit from Earth distance will get you to Mars fairly fast.
And a Mercury to Mars hohmann with patched conic which begin at Earth distance is fast.
And if you could make ion that did this, one would get to Mars fairly fast- but you still have that low thrust slowing things down.
And if use high thrust chemical rocket to do it, one uses a lot of rocket fuel but it’s within the practical limit of delta-v for chemical rocket. And does matter if one uses a lot of rocket fuel.
Because one gets about +3 km/sec from starting from high orbit vs LEO
one starts from high orbit, which swings near earth, and accelerates near earth to change vector and get the Oberth Effect.
Picture a mile (or much more, more being -much- better) long tether somewhere convenient.
Hall/Ion Thruster at the ends for a couple of months.
Fuel efficiency and Angular momentum: High.
Eventually dock with crew on the axis of rotation, elevator to the end.
Release the tether(s). Aiming carefully, naturally.
“Max g experienced” = as low as you’d like.
Braking:
The ship is actually -two- ships and a tether…
I’m nearly positive this has been ruled out, but I’d like pointers to where and when exactly.
A low thrust / high exhaust velocity thruster pairs well with a momentum transfer tether. Of course the counterweight on the tether should be much more massive that the payload launched, which pays off only if you can use the tether for many payloads and reboost between.
A 2 part spacecraft with tether for breaking at the destination seems more dubious, unless the ship is spinning with a largish relative velocity between the parts. With the right relative velocity one part could be dropped in orbit while the other heads elsewhere. But that still leaves the question of the trip home.
I don’t get the statement in the article it takes 100 million times less fuel than with chemical thrusters.
Also the statement that Hall thrusters for Mars mission are limited by 10,000 hour run time is also dubious. That’s 400 days and you wouldn’t run thrusters for a manned mission that long anyway.
Mars seems a little optimistic. Assuming you have a 100kW power source, there’s only around 4 N of thrust available (I’m using the thrust to power ratio of one of the Busek catalog thrusters). The new configuration helps with lifetime but it doesn’t seem to make any substantial change in specific impulse or the standard metric for electric propulsion: mN per kW.
The way to Mars is to get crew to Mars fast.
And low thrust does not work to get to Mars fast- well, it works only in the sense that it not a hohmann transfer.
And can’t get to Mars quickly from earth with a hohmann transfer.
Whereas from Mercury to Mars with hohmann transfer is reasonably
fast.
So making a Mercury to Mars orbit from Earth distance will get you to Mars fairly fast.
And a Mercury to Mars hohmann with patched conic which begin at Earth distance is fast.
And if you could make ion that did this, one would get to Mars fairly fast- but you still have that low thrust slowing things down.
And if use high thrust chemical rocket to do it, one uses a lot of rocket fuel but it’s within the practical limit of delta-v for chemical rocket. And does matter if one uses a lot of rocket fuel.
Because one gets about +3 km/sec from starting from high orbit vs LEO
one starts from high orbit, which swings near earth, and accelerates near earth to change vector and get the Oberth Effect.
Picture a mile (or much more, more being -much- better) long tether somewhere convenient.
Hall/Ion Thruster at the ends for a couple of months.
Fuel efficiency and Angular momentum: High.
Eventually dock with crew on the axis of rotation, elevator to the end.
Release the tether(s). Aiming carefully, naturally.
“Max g experienced” = as low as you’d like.
Braking:
The ship is actually -two- ships and a tether…
I’m nearly positive this has been ruled out, but I’d like pointers to where and when exactly.
A low thrust / high exhaust velocity thruster pairs well with a momentum transfer tether. Of course the counterweight on the tether should be much more massive that the payload launched, which pays off only if you can use the tether for many payloads and reboost between.
A 2 part spacecraft with tether for breaking at the destination seems more dubious, unless the ship is spinning with a largish relative velocity between the parts. With the right relative velocity one part could be dropped in orbit while the other heads elsewhere. But that still leaves the question of the trip home.
I don’t get the statement in the article it takes 100 million times less fuel than with chemical thrusters.
Also the statement that Hall thrusters for Mars mission are limited by 10,000 hour run time is also dubious. That’s 400 days and you wouldn’t run thrusters for a manned mission that long anyway.
Bob Clark