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Flexible Hammock SpaceShip with electric propulsion


vasimv
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Hope this is really new, i couldn't find any similar design for a spaceship. What you think, the design is feasible?

My idea is a cheap spaceship with electric propulsion (low thrust, high delta-v) which could be used as a probe or small (tens of tonns) cargo hauler. The ship contains few parts connected with 1mm steel+copper cables - two propulsion modules (can be more than two, connected in triange/square/etc shape) and large solar panel array (flexible panels or multiple small panels with flexible connections between). Basically, it is hammock in space. :) After launch - propulsion modules slowly position themselves at predefined distance between, rotate panels so they get maximum power and start accelerating with same acceleration, constantly checking distance/orientation. Since acceleration is quite low - stress to panels will be minimal. Modern microcontrollers shouldn't have any problem to keep modules in correct formation.

Eeach propulsion module weight 2-3 tonns (without propellant) has:

VASIMR engine VX-200 (200kW power, 5N thrust, 5000 Isp)

8 small ion engines used for precise orientation

10 tonns propellant tank

Rotation mechanism for the array

Some rechargable batteries for ion engines and a control system with cameras/laser rangefinder.

 

Solar panel array has 4000 m2 (20mx200m) of solar panels for 400kW electrict output, weights 10 tonns

 

Steel+copper cable 1mm diameter (used to carry panels and for transferring power to propulsion modules), weights 2 tonns

 

This ship will able to carry up up to 40 tonns load (loaded on top of propulsion modules in two 20x tonns chunks), dry weight 18 tonns, loaded with propellant - 38 tonns. Delta-V without load - 36 km/s, with full load - 14.5km/s, enough to travel to Mars (without load - doesn't need any launching window even) and back. Since thrust is very small, acceleration and capture burns will be very long (weeks or even months). Travels to Venus or Mercury will be more efficient as there is more sunlight and VASIMR engine can use more power to give better Isp. The ship can be launched by something like Falcon Heavy to LEO (folded like scroll for 2x modules version or like origami for other versions). Cannot land, just orbit-to-orbit missions.

For deep-space travels - a 20-40MW laser from Earth or Moon can be used to power it or to save propellant (more power - better Isp).

FM62Zag.png

 

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A flying carpet!

But really, it is a pretty good idea. Tension members are generally less massive than structural components designed for compression loads. Have you checked if 1 mm alloy wire can handle the currents required? It might throw a wrench into your mass budget if you need more cable. I'm not sure what the ion thrusters help with, though. If you need RCS, maybe just use hydrazine instead?

The only problem is that under thrust, the hammock will fold up as it tugs the craft together. Maybe use one VASIMR module and hang two carpet panels from arms on the side? maybe you can rotate the module to get the panels to the correct orientation?

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33 minutes ago, SOXBLOX said:

A flying carpet!

But really, it is a pretty good idea. Tension members are generally less massive than structural components designed for compression loads. Have you checked if 1 mm alloy wire can handle the currents required? It might throw a wrench into your mass budget if you need more cable. I'm not sure what the ion thrusters help with, though. If you need RCS, maybe just use hydrazine instead?

The only problem is that under thrust, the hammock will fold up as it tugs the craft together. Maybe use one VASIMR module and hang two carpet panels from arms on the side? maybe you can rotate the module to get the panels to the correct orientation?

1mm steel wire rope cable should easily handle 10N. There will be a bit more stresses than just thrust but should be in its limits since no gravity or aerodynamic resistance, just some solar wind (which could help even when starting to Mars). Unfortunately, i'm not an engineer myself,  not able to calculate :( I see only potential problem with high current in these cables but with high voltage configuration (40000V or more) in the panel it would be just 10A current, should work. VASIMR requires high voltage anyway.

I don't think folding is real problem as modules always can use ion engines to push themselves away and sun will be almost always available on its flypath to power them, small batteries will be used as backup. We can even start rotate whole ship during non-thrust time, so modules will be pushed in opposite direction by centrifugal force (available power will be much less but still a lot to keep ship working). That will save ion engines propellant and power but requires good mass balancing.

Mass budget is pretty conservative (4000m2 panels may weight under 7 tonns even, array may be arranged in 40x100m shape to lower stretching and reduce cable length, etc), so a lot of room to improve.

Edited by vasimv
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