Time to Mars, rather shocking

[Camacha]

Does that matter?

It was proven with scale models the concept worked, and Carl Sagan commented that it was a much better approach to using nuclear technologies.

Yes , it does. Scale models will not get us to Mars. Or maybe a tiny Mars in a nice orrery.

[Guest]

This pool needs a "2 days" option. Because that's how fast you can get there with a 1G torchship while it's in opposition (it all depends on how close Mars is to Earth at the time you take off).

Now, I've actually calculated possible parameters of a torchship capable of such a trip. I needed it for a little SF story I wrote.

Dry mass: 165T

Mass ratio: 2,6.

Thrust: 3000kN

Isp: 700 000s

Yes, that's an exhaust velocity of 7 million meters per second. It's a toroidal fusion reactor that produces about as much power as the entire humanity uses up in a year. Not impossible if you're optimistic about plasma control technology development, but requires quite a few assumptions and probably about 100 or so years. Oh, and the payload? 30 tons. The dV of such a mission is about 1.5 million m/s. You can get to Mars in 2 months for a fraction of this, carrying a much bigger payload, and that's what any "normal" mission uses.

The deal with that particular torchship was that it was a). Armed with a big frakkin' laser. . Landable on both Earth and Mars, without a dedicated launchpad (though requiring an extra dual-purpose LOX/H2 tank and on-orbit refuelling). It was a military rapid response vessel, completely uneconomic (not that it had to be) and using cutting-edge technology. 2 weeks to Mars seems more plausible, but would still take either a fusion engine or a gas-core nuke. It'd be a 0.1G brahistochrone, for about half a million m/s. Now, an "impulse" (not a Hohmann, but it's a similar kind of transfer) trajectory with 2 months flight time? About 15 000m/s, and you would have fuel left over (I was using a table for a ascent+transfer+landing mission. I subtracted the ascent based on my RSS experience, but not the landing). So, unless you've got a very good reason for such a fast travel, you're better off with a slow cruise.

[Mecha Pants]

If it hasn't been pointed out already, this could probably be done with 1960's era tech. Look at the "Super Orion" 8,000,000t space city/battleship/nightmare machine. It would have been pushed along by the explosions of small atomic shaped-charges, and could have managed 20g acceleration unmanned, or a more reasonable 2-4g with bodies on board. All while potentially bringing a small country worth of stuff along for the ride... The Super Orion's pushplate would have also been made of a transuranic element, so that once you arrived, you could break it down and enrich it into fuel for a nuclear power station.

Now if only it wouldn't, y'know, need to detonate nuclear devices in the atmosphere to get into space, or violate major international treaties about nuclear weapons in space, or cost all the money.

http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29

or

http://projectrho.com/public_html/rocket/enginelist.php#id--Pulse--Orion

[Guest]

The thing with Orion is, it's generally unsuited for anything but unmanned transport. Pulsed thrust is a problem here, even a typical ascent would be very stressful due to inconsistent acceleration. Now imagine living 2 days being slapped with 2Gs (or indeed any noticable acceleration) once per minute (about the pulse rate of an Orion). You'd go insane, consistent gravity, even if low, can probably be gotten used to, but not pulses.

[Mecha Pants]

The orion drive system would actually buffer most of the pulses into one long continuous push, by way of a mechanical recoil absorption system.Only the pushplate and associated recoil pistons would actually feel the hard shocks of detonation. Throttle control would be managed by shots per minute, and could be dialed to whatever rating the mission needs. it could be .5 or 1 or 20 or anything in between.

What it's actually good for is payload to orbit, if you discount the whole radiation and nuclear detonation side effects of launch. In space it's simply okay, not spectacular, when compared to other "blue sky" unlimited budget space systems. The only real benefit it has, is that it doesn't really use anything "new". All the individual pieces are old tech (even older now, seeing as it was proposed in the late 40s, with initial development in the 50s) , with only the full scale construction and testing techniques needed.

Edited March 20, 2014 by Mecha Pants

[Guest]

It would be very hard, near impossible to achieve a complete smooth acceleration with an Orion. Medusa, if anything, but not an Orion. The pistons would have to be too big. Orion would be good for boosting a payload into orbit, perhaps with a chemical 1st stage to take it off the ground, but after that, it travelling anywhere with it would be unbearable, unless you stick to Hohmann transfers and can keep the "burns" short.

[KASASpace]

It would be very hard, near impossible to achieve a complete smooth acceleration with an Orion. Medusa, if anything, but not an Orion. The pistons would have to be too big. Orion would be good for boosting a payload into orbit, perhaps with a chemical 1st stage to take it off the ground, but after that, it travelling anywhere with it would be unbearable, unless you stick to Hohmann transfers and can keep the "burns" short.

Actually the ride would be fairly smooth, as the force is mostly absorbed with shock absorbers. Maybe a little bit bumpy....