Orion Tweaks

[vogon13]

{moved from The Unexplained}

{sorry, I can't allow a serious post of mine to wind up in the the septic tank}




I am considering another tweak to the Orion nuclear impulse concept.

We have previously discussed segmental pusher plate designs and see the increase in top speed/payload of the craft with this improvement. (as mass of vehicle decreases, a smaller pusher plate is needed, discarding annular segments increases vehicles performance by reducing mass you have to decel at the target star)

Now let's consider utilizing the shed pusher plate material. Instead of just jettisoning it, recycle it into propulsion module casings.

There is an enormous quantity of material available here, and at first it seems you could never use all that material in the casings. Well, you can. The casings actually become more efficient in focusing the energy towards the pusher plate with increasing mass of the casing, and due to inertial confinement, it actually increases the yield/efficiency of the modules.

A hotter reaction, and greater confinement of the energy towards the pusher plate can really bump the performance of our craft.

I am loathe to do math, but this is a significant bump in what an Orion interstellar vehicle could do for us.

I am noodling out if we were not at .1C before, we are now. Flight times to alpha centauri are under 100 years now. And recall, that 20 million ton payload, this gets the makings of a viable colony there in one flight.

 

[justinc210]

I am a mechanical engineering student...and I am a little worried by this idea. For one you are taking a massively complicated dynamic system (a spaceship) and exciting it with one very large impulse at regular intervals. The result will almost certainly be high levels of mechanical fatigue on the entire structure of the craft as well as a dangerous level of acceleration experienced by the crew. Chemical rockets are optimized to provide the most steady operation possible through the use of turbine pumps and accumulators in the fuel lines to even out pressure spikes. So why would you want to make a craft that took the opposite approach and worked on sudden jerks instead of an even push?

In my opinion a better way to harness the nuclear energy would be to use the reaction to provide heat energy directly to the working fluid of the rocket engine. Or...like Project Daedalus, you could use a somewhat continuous nuclear reaction to generate a highly energetic discharge out the back of the craft.

I think the general lesson to be learned here is that the only way we will ever reach the stars will be through harnessing nuclear power. Anything else just doesn't have enough oomph.

 

[vogon13]

Hi justinc210,


in past threads we have looked at distributing the mass of the cores and casings over the structure of the pusher plate, in fact anything you are taking that is solid and can withstand a good thwack can ride there. We are looking at reducing the sprung mass to as small as possible. Fragile cargo, crew, instrumentation, etc, will be in the shock absorber equipped portion of the craft. Dyson, et al, looked at tuned and untuned dynamic shock absorption systems, I have no preference. Maintenance of the shock system during the flight is a crucial mission success criteria.

Distributing the payload (precisely) over the pusher plate can reduce peak accelerations in the pusher and can extend it's fatigue life. Moving the payload around on the pusher can be used to steer the vehicle, btw, instead of complicating the propulsion module ejection system to be able to hook and slice.

I also suspect the fatigue life of the pusher is probably more governed by hydriding than mechanical shock. Ameliorating the hydriding problem might be to detonate a few propulsion charges at sub optimum range and ablate the hydrided layer off the pusher. Or if calculations show metallurgical remedies to hydriding are better, then we fix the problem that way. Or maybe we anneal the pusher with a laser.

We have looked at perhaps trimming an annular segment from the pusher several times during the acceleration phase, perhaps at yearly intervals. Simple jettisoning of the segments was the first idea, but recycling the stuff into hotter, more efficient propulsion might help what appears to be an inevitable loss of potency of the nuclear materials during the cruise portion of the flight. IIRC, most of the fission charges to date have tamper and casings measured in inches, imaging having a foot to play with, You might get another 3 to 6 dB bang for your buck.

Trimming the pusher also allows a longer cruise towards the target before decel begins. This means a shorter flight as more of the distance is covered at the higher cruise speed. Accel still might take 30 years, but decel might be 15 or less.

 

[MeteorWayne]

Physics is not the right forum for thios either, vogon. I'll probably move it to SB&T tomorrow.

 

[andrew_t1000]

I've always had a problem with the Orion concept.
I would have thought Deadelus which is pretty much the same thing, but with magnetically focused fusion instead and once up to "cruising" speed you could switch over to Bussard mode.
That way the amount of fuel needed to get to say, Alpha Centauri, would be a lot less.

 

[gunsandrockets]

I recommend renaming this thread. "Orion Tweaks" can be easily misunderstood as referring to the Orion spacecraft from NASA's project Constellation. Perhaps "Orion nuclear pulse drive tweaks" would be better?