Project Orion: Exploring a Nuclear-Powered Spacecraft

[quetzalcoatl9]

http://en.wikipedia.org/wiki/Project_Orion

What do you guys think, is it time we start looking at options such as Orion again? Most of the necessary pieces of the project had/have been developed, and it is tempting to know that the first planned flight for an Orion-based spacecraft was to make a lap around the Solar System on a timescale of less than a year!

http://www.bbc.co.uk/bbcfour/documentaries/features/mars-a-bomb.shtml

 

[Astronuc]

No! . . . .

 

[quetzalcoatl9]

No! . . . .

any particular reason?

if it is over fallout/pollution, what about the potential solutions to the problem that the wikpedia article mentions?

and even if they still cannot be overcome, why not assemble in orbit and blast off nukes to our hearts content outside of the Earth's atmosphere?

 

[theCandyman]

The whole project sounds very science fiction. In fact, I am reminded of the recent movie "The Core". The section talking about the problems mentions the fallout from using this technique, I do not think doing this in orbit would be any safer.

 

[quetzalcoatl9]

The whole project sounds very science fiction. In fact, I am reminded of the recent movie "The Core". The section talking about the problems mentions the fallout from using this technique, I do not think doing this in orbit would be any safer.

...and yet the project was very real. Experiments were done to test the concept.

As far as doing it from outside the atmosphere (note: not necessarily from orbit), isn't there radiation out in space anyway? Wouldn't the radiation increase vs. background gamma radiation be a pittance? It would be like urinating in the ocean and calling it "pollution".

 

[russ_watters]

No! . . . .

Ditto.

...and yet the project was very real. Experiments were done to test the concept.

Depends on how you define "real" - from what I have seen it wasn't much more than some very theoretical back-of-the-envelope calculations. I would actually be curious to know what the total budget was and how many engineers they had working on it. edit: it says in the second link that it went from 1958 to 1965, but that doesn't really tell us how big it was... Considering that to really get such a craft off the ground would be a project perhaps an order of magnitude larger than the Apollo program (which was the most expensive and complicated engineering program ever), that doesn't say too much for what was really done.

But maybe I'm getting ahead of myself - I think Orion was fatally flawed in three very basic ways: I don't think such a thing would be feasible from an engineering standpoint, an economic standpoint, or an environmental standpoint.

re:building it in orbit -
Building one in orbit eliminates virtually all of the economic benefit.

 

[quetzalcoatl9]

True. Orion was never quite moved out of R&D phase to actual production, despite Werner von Braun's approval.

As for the engineering challenges...when is this not the case when space travel is involved? It is imaginable that there would be considerable difficulties in making an orion spacecraft work, but the question is: is it worth it?

Which brings up the point you mentioned, economics. In terms of economics, what could be worse than chemical rockets? Given the massive nuclear arsenal of 'overkill' that countries like USA and former-USSR possess, the main arguments for Orion were that you could move a great amount of mass more cheaply than with chemical rockets.

It also makes current pipe-dreams like a manned mission to Mars and Jupiter a reality, if the technology were to work. The constraints imposed by the orbital periods of these planets with respect to the Earth would be alleviated. Astronauts could travel in large groups, in relative comfort, in a large ship capable of real travel around the Solar System...

would these potential benefits be worth the effort nowadays? I myself am not entirely convinced, but at the same time I see a lot of R&D going into alternative propulsion mechanisms again so it is relevant to bring up the topic once more, IMHO.

 

[Astronuc]

My terse answer is all that Orion deserves in my opinion.

I share Russ's opinion on the matter.

I advocate the economic, safe and responsible use of nuclear energy.

Certainly Orion is unthinkable (and unconscionable) within the Earth's atmosphere.

As for experiments, there was a scale model using chemical explosives. It's not the same thing full scale for a number of reasons.

 

[quetzalcoatl9]

re:building it in orbit -
Building one in orbit eliminates virtually all of the economic benefit.

that depends...let's say we want to send a manned mission to Saturn. Let's say that for reasons related to human physiology, we need to restrict the total time for our astronauts in space to be a maximum of 1 year.

Assuming that the orbital mechanics allow for a 6 month trip in each direction, how could we possibly do this with chemical rockets? We couldn't.

So if we wanted to do it, constructing an orion craft from some place outside of our atmosphere (say, the L2 point of the moon-earth system) and launching from there could possibly work. Other alternative methods of propulsion for such a trip (ion drives, etc.) face all of the engineering concerns as orion plus more, since at this point we at least we have some idea of how nuclear explosions work, whereas alternate propulsion methods are at least equally unproven.

you would agree, that putting things like satellites in orbit in an economically feasible way, is not the point of orion. the point would be that we could do things that are currently impossible given the state of propulsion.

i am willing to conceed that launching an orion from the surface of the Earth is not a good idea. but i have yet to hear an argument why we should not at least consider the idea for interplanetary travel.

 

[russ_watters]

that depends...let's say we want to send a manned mission to Saturn...

...and the USA had a GDP of $100 trillion.

Not a realistic scenario.

edit: put another way, when the time comes when we need to send a man to Saturn, then maybe it would be time to have another look at Orion.

 

[quetzalcoatl9]

...and the USA had a GDP of $100 trillion.

Well, at the current GDP of $11 trillion and 4.4% growth (assuming growth to hold constant) it will be ~53 years from now, hopefully in my lifetime.

I guess interplanetary travel is completely out of the question then for the next 50 years.

I appreciate all of your input (everyone). Thank you.

 

[theCandyman]

GDP growth of 4.4%? It has only been over four a few quarters in the past several years, I have had to study it for the past week in economics: http://www.bea.gov/briefrm/gdp.htm. That is very optimistic, and I think that is russ' point; he does not rule it out, it is just beyond realistic.

 

[russ_watters]

Well, at the current GDP of $11 trillion and 4.4% growth (assuming growth to hold constant) it will be ~53 years from now, hopefully in my lifetime.

I guess interplanetary travel is completely out of the question then for the next 50 years.

I appreciate all of your input (everyone). Thank you.

Sorry to be such a downer - I'd love to see massive spaceships carrying explorers to the outer planets in my lifetime too (I'm 29). We'll just have to see of course, but it very well may be 50 years before this becomes feasible - and then we still need to have the motivation to do it...

 

[Art]

GDP growth of 4.4%? It has only been over four a few quarters in the past several years, I have had to study it for the past week in economics: http://www.bea.gov/briefrm/gdp.htm. That is very optimistic, and I think that is russ' point; he does not rule it out, it is just beyond realistic.

I can see where he obtained the 4.4% figure he quoted

GDP - real growth rate:
4.4% (2004 est.)

http://www.cia.gov/cia/publications/factbook/geos/us.html#Econ
Anyone know what NASA's annual budget is? I'm wondering how it compares with America's military budget of $370+ billion (which accounts for 47% of the world's military expenditure)

 

[Astronuc]

I can see where he obtained the 4.4% figure he quoted http://www.cia.gov/cia/publications/factbook/geos/us.html#Econ
Anyone know what NASA's annual budget is? I'm wondering how it compares with America's military budget of $370+ billion (which accounts for 47% of the world's military expenditure)

http://www.nasa.gov/about/budget/index.html

Last year -

President Bush's $16.2 billion NASA budget proposal envisions annual lunar missions, by humans and robots, as mere steppingstones to exploring Mars and beyond.

for FY2005, according to RedNova.com and other sources.

 

[Astronuc]

Back in the mid 80's, some colleagues and I did some scoping studies for manned missions to Mars. We should have been there by now, but . . . .

So now we have Project Prometheus, the latest space nuclear redux to consider the application of nuclear energy for space exploration, both as surface power source and spacecraft propulsion. Well the program has already changed priorities.

JIMO was to be the first application with Nuclear Electric Propulsion, however due to uncertainties about the technology, that mission has been postponed, and the program re-prioritized. The priorities are:

1. Surface nuclear power system (to be demonstrated on the Moon)
2. Nuclear Thermal Propulsion system
3. Nuclear Electric Propulsion system (this was first priority until recently)

JIMO and exploration of Saturn's moons are important because they will provide materials in support of a human presence out near Jupiter or Saturn, if ever that happens.

An ORION is not under serious consideration.

I'd love to see massive spaceships carrying explorers to the outer planets in my lifetime too (I'm 29). We'll just have to see of course, but it very well may be 50 years before this becomes feasible - and then we still need to have the motivation to do it...

That's one of the problems - massive spaceships - which need lots of energy.

Designers have to look at the mass to power ratio (inverse of specific power), kg/kW. A figure of merit is about 1 kg/kW. JIMO at 200 kWe with a mass of 15,000 kg's (of which payload is about 1500 kgs) would have a ratio of 75 kg/kWe. It's more complicated than that.

The problem with ORION is the mass (pusher plate) as compared to the propulsive energy recovered from the nuclear detonation. Then one has to consider how many nuclear propulsive units (each perhaps several 100 kgs). There is a lot of physics to consider and ultimately the actual Isp.

 

[quetzalcoatl9]

Back in the mid 80's, some colleagues and I did some scoping studies for manned missions to Mars. We should have been there by now, but . . . .

Awesome, this sounds very interesting, I would be grateful to hear any cool stories you may have.

The problem with ORION is the mass (pusher plate) as compared to the propulsive energy recovered from the nuclear detonation. Then one has to consider how many nuclear propulsive units (each perhaps several 100 kgs). There is a lot of physics to consider and ultimately the actual Isp.

It was my understanding that as you increase the mass of the Orion craft, your Isp actually goes up..Is this not true? The highest estimate I have seen was around 10,000 Isp for a very massive ship.

 

[hitssquad]

Orion's Isp calculations

The problem with ORION is the mass (pusher plate) as compared to the propulsive energy recovered from the nuclear detonation.

It might seem strange for a problem with ORION to be the mass of the pusher plate, given that favorable-seeming Isp's have been calculated.

Then one has to consider how many nuclear propulsive units (each perhaps several 100 kgs). There is a lot of physics to consider and ultimately the actual Isp.

Calcuation of Isp is generally simple arithmetic. Where does complicated physics enter in the case of the Orion?

 

[Astronuc]

It might seem strange for a problem with ORION to be the mass of the pusher plate, given that favorable-seeming Isp's have been calculated.

Calcuation of Isp is generally simple arithmetic. Where does complicated physics enter in the case of the Orion?

It's not complicated hitssquad. Rather as you say it is quite simple. However, thrust divided by mass (also a simple principle) yields very low acceleration (a problem with high Isp systems which also have high masses). Very low acceleration means long times to get to particularly high velocities.

The other point - "Favorable Isp's have been calculated" - but not demonstrated.

 

[kurushio95]

It wouldn't work. The only reason nukes have shockwaves here on Earth is because explosions cause sudden and violent air compressions. And in case you haven't noticed yet, there is no air in space. The only use I see for it is a literal interstellar ark to save the human race. If Earth was on the verge of becoming uninhabitable, we could build maybe twenty of the "super" Orions and launch them all at the same time. The whole reason would be to relocate to another planet with an Earth-like atmosphere.

 

[quetzalcoatl9]

kurushio, before you interject you may want to research the matter a little.

i don't think that you really understand the principle behind nuclear pulse propulsion. the point of the fission detonation is to turn a disc of polymer propellant into plasma, which will strike the pressure plate with a high velocity, thus delivering energy to the spacecraft after passing through a shock absorbing system.

See Freeman Dyson's "Physic's Today" article on interstellar travel by way of a "Super Orion" for details. Another (slightly different) variation was Project Daedalus, which was planned to use a laser-initiated fusion reaction to reach a star 5 l.y. away.

 

[hitssquad]

Rockets cannot work in space

It wouldn't work. The only reason nukes have shockwaves here on Earth is because explosions cause sudden and violent air compressions. [...] there is no air in space.

There are particles and photons in nuclear explosions, so a lack of particles in space is not an issue. If you need more particles, you can place an accelerant disk (a disk designed to disintigrate) between the bomblet and the pusher plate.

The issue of having no atmosphere to push on was raised prior to the age of space rocketry. The issue is the same for the Orion rocket as for any other type of rocket, and the problem of having no atmosphere to push on has been shown by repeated spaceflight experience to be a non-problem.

 

[quetzalcoatl9]

here's a NASA paper from the 70's:

page 1
http://www.projectrho.com/rocket/orionisp1.jpg

page 2
http://www.projectrho.com/rocket/orionisp2.jpg

their theoretical calculations show that the Isp continue to grow as a function of the pusher plate diameter and mass. Optimal values can theoretically achieve 15,000 Isp with high thrust (as compared with ion-propulsion which have high Isps - although not as high as 15,000 - and low thrust).

 

[kurushio95]

Didn't know that. Next time I'll keep my nose out of things I don't know.