Project Orion: A discussion of Science and Science Fiction

[kerbiloid]

Spoiler

 

[wumpus]

2 hours ago, Shpaget said:

What exactly do you think is the main purpose of the pusher plate in Orion?

The acceleration profile would probably have a sawtooth component, depending on the spring constant.

You could adjust the spring profile to get a smoother acceleration profile, but expect it to always want to revert to closer to a sawtooth.  Don't forget that on an Orion, some of the efficiency (energy to momentum conversion) scales up as the pusher plate mass increases.  Orion can have a reasonably constant acceleration, but I'm sure you'd notice the difference.  Might wind up being similar to being at sea (and get more and more stable as larger and larger Orions are built).

[MKI]

I can't help but shake the idea that unless it was perfectly handled, it would get some people very motion sick in a way that isn't really possible on Earth.

The ground itself would feel like its in motion... dear god.

[Nuke]

my concern is that after the initial burn to put you on course, the engine has to lie dormant for north of a hundred years and then fire up flawlessly for the declaration burn.  i have concerns if the shock absorbers will work and not liquify the crew on the first pulse unit. will it lose hydraulic fluid or cold weld during the voyage? then the long term storage of the pulse units themselves is also an issue. will your weapons grade plutonium still be weapons grade when you get there?

Edited April 22, 2021 by Nuke

[Spacescifi]

8 minutes ago, Nuke said:

my concern is that after the initial burn to put you on course, the engine has to lie dormant for north of a hundred years and then fire up flawlessly for the declaration burn.  i have concerns if the shock absorbers will work and not liquify the crew on the first pulse unit. will it lose hydraulic fluid or cold weld during the voyage? then the long term storage of the pulse units themselves is also an issue. will your weapons grade plutonium still be weapons grade when you get there?

 

Solar system only.

[cubinator]

Getting anything to last long enough to be part of an interstellar spaceship is a challenge. Perhaps we'd do better to spread our consciousness within the cosmic dust itself?

In any case, nuclear pulse is VERY tough to make comfortable.

Edited April 22, 2021 by cubinator

[sevenperforce]

1 hour ago, cubinator said:

Getting anything to last long enough to be part of an interstellar spaceship is a challenge. Perhaps we'd do better to spread our consciousness within the cosmic dust itself?

In any case, nuclear pulse is VERY tough to make comfortable.

If you're going interstellar then just bite the bullet and light up a NSWR.

[cubinator]

1 hour ago, sevenperforce said:

If you're going interstellar then just bite the bullet and light up a NSWR.

I agree. Test the damned thing as far away from Earth as you can, though.  

[Spica]

11 hours ago, wumpus said:

You could adjust the spring profile to get a smoother acceleration profile, but expect it to always want to revert to closer to a sawtooth.  Don't forget that on an Orion, some of the efficiency (energy to momentum conversion) scales up as the pusher plate mass increases.  Orion can have a reasonably constant acceleration, but I'm sure you'd notice the difference.  Might wind up being similar to being at sea (and get more and more stable as larger and larger Orions are built).

I know it runs counter to the "low tech starship" mythos around Orion, but I'm sure modern technology would let you use linear electric motors to smooth out the acceleration far better than any purely mechanical system would let you. I'd imagine the best case wouldn't be all that different from how it feels to drive on a bridge with multiple expansion joints, or ride a train over old rails.

Edited April 23, 2021 by Spica
clarity

[Spacescifi]

1 hour ago, Spica said:

I know it runs counter to the "low tech starship" mythos around Orion, but I'm sure modern technology would let you use linear electric motors to smooth out the acceleration far better than any purely mechanical system would let you. I'd imagine the best case wouldn't be all that different from how it feels to drive on a bridge with multiple expansion joints, or ride a train over old rails.

 

I have no issue with that.

 

For what it's worth...an Orion likes extra mass anyway so you could do that.

However at this point, you could launch it, but I doubt you could land it unless you separated it module by module.

 

That's a lot of modules to deorbit!

I know people say shuttles, but reentry is not the kind of thing any craft needs to do on the regular without taking it into the shop for repairs.

[kerbiloid]

Every 100 000 charges, at 2 per second rate = 50 000 s = 0.6 day

Just a day of horse riding.

You can't take millions of them, and iterstellar flights anyway require huge ships with magnetic reflection.

Nothing to worry about.

[magnemoe]

For use inside the solar system you would do hour long burns so bumping is not much of an issue. You want to reduce it but humans are not the most vulnerable to bumps anyway. 

For interstellar use, as I understand an interstellar orion is possible but it would need to be tens of kilometre in diameter and using some insane bombs. 
The medusa sail idea is probably the best way to do this and here you have an much easier time  softening the bumps 

[kerbiloid]

12 minutes ago, magnemoe said:

For interstellar use, as I understand an interstellar orion is possible but it would need to be tens of kilometre in diameter and using some insane bombs. 

A single push can't be high, same tens m/s.

And you can't have millions of nukes onboard, so total number of pulses is limited.
(I've read about 300 000 x 100 kt charges onboard, and this means just two days of acceleration).

The pistons also have their lifespan, and unlikely in billions of pushes.

So, the Orion-style acceleration can't last long.

17 minutes ago, magnemoe said:

The medusa sail idea is probably the best way to do this and here you have an much easier time  softening the bumps 

Medusa requires even more scifish solutions and materials than Orion.

Only magnetic mirror, only hardcore.

[Nothalogh]

On 4/22/2021 at 1:00 AM, Spacescifi said:

if you pulse every two seconds

The number I've always seen is twice per second

[sevenperforce]

8 hours ago, kerbiloid said:

Medusa requires even more scifish solutions and materials than Orion.

Not really. Medusa and Orion are about equally achievable.

[kerbiloid]

30 minutes ago, sevenperforce said:

Not really. Medusa and Orion are about equally achievable.

What's a problem in a huge sail, kilometer-long cables, and a sliding ring.

[kerbiloid]

Just a sudden thought.

The Orion crew should include a board dentist.

***

Also a common nickname for them is Nutcrackers.

Spoiler

 

Edited May 5, 2021 by kerbiloid

[Spacescifi]

 

10,000 kilometers?

According to quora even at thousand kilometers the gamma radiation could kill even though it is short lived compared to a nuke radiation.

https://www.quora.com/If-antimatter-bomb-did-exist-would-it-be-worse-than-thermonuclear-bomb

 

So if a civillization did AM orion launches, it would have to be in a desert very far away from civilzation.

And after a launch any persons in the area would need radiation protection or need to be inside a radiation shelter.

The launch: SSTO style. Boosts with bottom rockets, pusher plate is on top, flips in midair clear of launch area and engages the Orion drive. Crew is inside a gyoscopic hab-module that flips to orient with the direction of acceleration.

Edited June 18, 2021 by Spacescifi

[Starhelperdude]

do you mean an antimatter-catalyzed pulsed fission engine? I would suggest to use a magnetic nozzle and not a normal pusher plate since it can get very hot and stuff

and quora is just a question-answer website, I would suggest you to look on more serious websites

and also AM and atmosphere don't mix that well (aside from stuff like ''antimatter jet engines'')

and it's not that much of a problem in space

also, you use a small amount of antimatter, not large enough to rip a country apart or smth., everything beyond that would obliterate the spacecraft 

[Spacescifi]

1 hour ago, Starhelperdude said:

do you mean an antimatter-catalyzed pulsed fission engine? I would suggest to use a magnetic nozzle and not a normal pusher plate since it can get very hot and stuff

and quora is just a question-answer website, I would suggest you to look on more serious websites

and also AM and atmosphere don't mix that well (aside from stuff like ''antimatter jet engines'')

and it's not that much of a problem in space

also, you use a small amount of antimatter, not large enough to rip a country apart or smth., everything beyond that would obliterate the spacecraft 

 

1. No. Would have mentioned it, and I am familar with it too. I want pure AM detonation precisely because it does not leave long lasting radioactive mess around in it's wake.

2. Using only enough of AM and not too much is a given.

 

3. That's why I am here LOL!

Edited June 19, 2021 by Spacescifi

[wumpus]

Antimatter and pusher plates make zero sense.

And the real issue with the Orion isn't how much radiation comes off the launch going up (although you'd want to be a healthy distance away), it is what happens when the magnetosphere collects all the ionized heavy atoms and lets them fall to Earth.  Hint: launch from Antarctica and you can avoid this issue.

[magnemoe]

49 minutes ago, wumpus said:

Antimatter and pusher plates make zero sense.

And the real issue with the Orion isn't how much radiation comes off the launch going up (although you'd want to be a healthy distance away), it is what happens when the magnetosphere collects all the ionized heavy atoms and lets them fall to Earth.  Hint: launch from Antarctica and you can avoid this issue.

This, orion pulse nuclear makes sense because its the highest trust * ISP thing we can build but it  require the use of nuclear bombs who get less efficient as they get smaller. 
Antimatter is way better and as you say its no reason to pulse it, you probably pulse antimatter-catalyzed fission as its simpler but not an pure antimatter engine. 

Outside that the fact that the antimatter would react to the air  
So you might have to use charges anyway. It would be much less radioactive in the term of fallout than an nuke, instant radiation would be much the same as a nuke I think.  
However antimatter has the problem that is detonate on contact with matter so you need to keep the containment active at all time, any fail and the charge go off, this will make nearby charges to fail in an chain reaction. 
Nuclear bombs does not have that issue, yes you might detonate the chemical explosive on one with an micro meteorite or missile strike, this would become an dirty bomb releasing plenty of radiation but it will not detonate other bombs in the magazine. 

[Spacescifi]

10 minutes ago, magnemoe said:

This, orion pulse nuclear makes sense because its the highest trust * ISP thing we can build but it  require the use of nuclear bombs who get less efficient as they get smaller. 
Antimatter is way better and as you say its no reason to pulse it, you probably pulse antimatter-catalyzed fission as its simpler but not an pure antimatter engine. 

Outside that the fact that the antimatter would react to the air  
So you might have to use charges anyway. It would be much less radioactive in the term of fallout than an nuke, instant radiation would be much the same as a nuke I think.  
However antimatter has the problem that is detonate on contact with matter so you need to keep the containment active at all time, any fail and the charge go off, this will make nearby charges to fail in an chain reaction. 
Nuclear bombs does not have that issue, yes you might detonate the chemical explosive on one with an micro meteorite or missile strike, this would become an dirty bomb releasing plenty of radiation but it will not detonate other bombs in the magazine. 

 

Secret: It has the same energy yield of as AM but it is an engineered super fuel that is somewhat easier to handle than AM.

 

I did not mention it at first because the energy yield is EXACTLY the same. Either way the bomb is encased in nonreactive casing as it is ejected.

 

It won't react with the air at all, only the detonation of the super fuel will.

[kerbiloid]

Zero kilometers. It's non-viable and won't work. So, won't radiate the radiation. So, is absolutely safe.

Until gets warmed.

4 hours ago, Spacescifi said:

So if a civillization did AM orion launches

then the first one will be the last one.

They will realize their error on the very first pulse, and stop doing that.
 

4 hours ago, Spacescifi said:

The launch: SSTO style. Boosts with bottom rockets, pusher plate is on top, flips in midair clear of launch area and engages the Orion drive. Crew is inside a gyoscopic hab-module that flips to orient with the direction of acceleration.

Or just start with the pusher plate down, and don't flip. Then no gyroscopic hab is needed.

3 hours ago, Spacescifi said:

I want pure AM detonation precisely because it does not leave long lasting radioactive mess around in it's wake.

1. Nobody tried, but it should create radioactive isotopes due to the cocktail of short-living particlesm gamma-radiation, and local thermonuclear reactions.

2. It doesn't work this way, because AM has nothing common with the Orion drive.

[Scotius]

If you are on tech level that allows to produce and manipulate enough antimatter to get an Orion-sized ship to space... you don't need a damned Orion in the first place!

It only makes sense if your planet is dying, and you absolutely must launch as much as possible to space NOW! And you don't care anymore what you leave behind. Hint: It will be partially glassed radioactive wasteland. Also known as "What in the horseradish were you thinking, you colossal dum-dum?" idea.