Orion drive and related physics

[NuclearNut]

On 2/22/2016 at 4:54 PM, SomeGuy123 said:

So you need 9300 m/s to reach orbit.  At 2 Gs, that's 20 m/s gained per second.  At an average of 2.5 blasts per second (you might adjust the number used depending on altitude), it's 1163 nuclear explosions.  Per launch.  

It's kind of ironic that instead of being crazy, this is one of the most level headed, practical methods of reaching space with a lot of stuff anyone can actually build...

Let's see : the W48 supposedly cost 1.25 million each, with 1 million of that being the plutonium.  Let's say that is 1970 dollars.  So 6 million today.  And call it 12 million per pulse unit.    So 14 billion per launch in fuel.

Which sounds like a lot, but you're lifting thousands of times the mass of a falcon heavy all the way to orbit every launch...

Well, there could be various things done to make the pulse units cheaper than conventional nuclear weapons.  Considering mass if far less a concern here than with nuclear weaponry, we could use larger reflector units around the pit, something that the W48 did not have due to it's microscopic size.  This would allow us to shrink the quantity of plutonium needed significantly, cutting down the cost some more.  

We could potentially, if we are willing, use a N reactor type reactor to produce nuclear energy while producing weapons grade plutonium.  This, unlike a conventional civilian nuclear powerstation, would have an extremely short fuel cycle and low burnup during operation.  This could be improved by making the unit a special fast reactor, capable of online refueling, thus allowing for both high utilization for our uranium resources and weapons grade plutonium production, but again, it would have to be a fast reactor designed specifically for this purpose, an S PRISM will not do.  This again could cut down the cost of our plutonium quite a bit by making our facility dual use.

And lastly the cost could be expected to decline due tho the size of the production of nuclear weapons, 1163 nuclear bombs is about a fifth of the size of the present US arsenal.  Because I am not privy to the actual design of nuclear weapons, I can only make broad guesses about the quantities of plutonium, but I would say that it is probably likewise a fifth of the US weapons grade plutonium tied up in nuclear weapons as larger nuclear weapons would presumably have reflectors and other such plutonium saving devices to ensure a minimum cost.   As you can see, an orion would not be a simple thing to just throw about, and a significant number of orion launches would require a physics package production capacity the likes of which the world has never seen before and would likely never see again should orions cease to be launched.  This would imply that the production of such devices would reduce in cost over time as the industry grows, though these gains are likely to be quite small in comparison to the previously mentioned options.

[lobe]

On 3/2/2016 at 9:38 PM, Aghanim said:

May I hijack this thread for a while? I want to talk about all pulse drive, including Orion drive and inertial confinement fusion drive. How can I calculate the parameters of an pulse drive, including thrust, ISP and waste heat? I'm assuming sufficiently advanced technology to be able to induce a laser driven inertial confinement fusion inside a helium-3 gas flow inside the magnetic nozzle, so that the firing frequency isn't limited to how fast can the pellet gun can fire. If my drive can fire in 1 kHz frequency, how much thrust and heat will be produced? Please point me to the right direction so I can calculate this myself

 

Don't worry, it is not hijacking. This thread is meant to be a cover-all thread for the physics related to the Orion drive. To answer your question, wouldn't the thrust just be the average acceleration/force over the period of detonation? Heat is kind of relative, heating the pusher plate or the heat of the exhaust gas?

On 3/1/2016 at 4:32 PM, sal_vager said:

Nice thread @lobe, I'm pinning this for March

OHMYGODOHMYGODIMPOPULR!!!

[Emperor of the Titan Squid]

This topic was being heavily discussed on the nova thread, but that is extremely out of place. FYI this is not about the current orion spacecraft

[Spaceception]

23 minutes ago, Emperor of the Titan Squid said:

This topic was being heavily discussed on the nova thread, but that is extremely out of place. FYI this is not about the current orion spacecraft

The search tool is your best friend

Pick one and go to it

[PB666]

14 minutes ago, Spaceception said:

The search tool is your best friend

Pick one and go to it

Right-oh, some many threads.