# Fusion Ramjet

Discussion in 'Physics & Math' started by Hevene, Dec 8, 2001.

1. ### Janus58Valued Senior Member

Messages:
2,369
This is somewhat of of an old thread to bring back to life, but...

The fusion ramjet has limitations on its top velocity. At a certain point, drag caused by collecting the fuel equals the thrust one can get from fusing the fuel. This limiting velocity has been estimated to be around 10% of c.

3. ### eburacum45Valued Senior Member

Messages:
1,297
That's right;
From here
http://en.wikipedia.org/wiki/Bussard_ramjet#Discussions_of_feasibility
But some alternate designs might work; see David Darling's page on the subject
http://www.daviddarling.info/encyclopedia/I/interstellar_ramjet.html

5. ### FungezoidBannedBanned

Messages:
213
The drag force and max. velocity of the fusion ramjet is all well and good, but what about the rotating orbital accellerator idea? Do you thinkit would be viable? If so, then, and only then will I spend time on calculating the max. velocity. What do you think?

7. ### Janus58Valued Senior Member

Messages:
2,369
It seems wastefull and redundant. The amount of fuel/energy needed to spin it up would be more than you would have used if you had just mounted engines on the ramjet and boosted it up to speed directly.
Then you have to waste even more fuel spinning it back down so you could attach another ship.

8. ### FungezoidBannedBanned

Messages:
213
Ok then... Let's try out this idea. What if we put a cylindrical ship inside a giant orbital accellerator that uses electromagnetic pulses to accelerate a projectile using electromagnetic repulsion. Bit in this case, the ship would have its own electromagnet-studded shell, and the ship's electromagnets would be of the opposite force, so the ship would shoot out of the barrel. There are already accellerators like this--
(google magnetic accelleration and get the first one thast comes up)
SO why not apply that technology to shooting a ship? The massive power needs for so amny huge electromagnets in the big accelerator would be provided by a antimatter reactor (detonating antimatter in a controlled condition and converting the heat and light (along with the kinectic force) )?
So, is this any more feasible?

Messages:
1,297
10. ### XeliosWe're setting you adrift idiotRegistered Senior Member

Messages:
2,447
It's really strange to read a post I made 6 years ago...

11. ### draqonBannedBanned

Messages:
35,006
lifetime will pass and you will see your own words here 30 years ago and you will wish to be that you, but time is not to be controlled for such is life pitiful and desolate. The sentences will freeze in a moment of forever and will leave a mark of your existence, and than someday the server will erase that memory as well...as though nothing, not even you, have ever existed.

12. ### NasorValued Senior Member

Messages:
6,231
Actually a fusion ramjet is probably a better choice than antimatter for fast interstellar travel, even ignoring the problems of antimatter production. If you wanted to accelerate a ship up to near the speed of light and then slow back down, you would need over twice the mass of your ship in antimatter and an equal mass of normal matter to react it with. The beauty of a fusion ramjet is that you can collect your fuel as you go, so you only need to start with enough fuel to get you moving.

13. ### FungezoidBannedBanned

Messages:
213
Of course the fusion ramjet is abetter idea. But there JUST ISN'T ENOUGH FUEL OUT THERE! Instead of having that rediculous scoop idea, just carry enough fuel! It is soooooooo simple!

14. ### FungezoidBannedBanned

Messages:
213
And by the way, isn't this supposed to be about space exploration, not looking back on your own past!?

15. ### NasorValued Senior Member

Messages:
6,231
Making a huge magnetic trap for hydrogen doesn't seem any more far-fetched to me than making thousands of tons of antimatter. Who knows which once will be practical first?

16. ### eburacum45Valued Senior Member

Messages:
1,297
If you read the page written by David Darling you will see that we might need both a dumpster full of antimatter and big magnetic scoops to make the ramscoop concept work. Without antimatter the scoop just acts as a big brake.
That isn't to say a brake isn't useful; a magnetic braking effect would be useful for any hypothetical interstellar ship you might care to design, especially as it doen't require on-board propellant.

17. ### FungezoidBannedBanned

Messages:
213
How 'bout we use the magnetic accellerator tube idea? And I don't mean the dumb "spacetime manipulation" sci-fi thing, but my idea of magnetic repulsion to shoot a ship out like a cork out of the proverbial bottle.

18. ### temurman of no wordsRegistered Senior Member

Messages:
1,330
You don't need to stop the spinning to attach another ship. Just connect the ship to the fixed end of the rotating arm and then move the ship slowly towards the other end.

19. ### Janus58Valued Senior Member

Messages:
2,369
To what purpose? As the ship moves outward, the structure transfers momentum to the ship at the cost of its own. Once the ship releases, the structure will be rotating slighty slower than it was before. Now either you need to spin the structure back up to its original speed, or accept each successive ship will be launched at a slower speed.
Eventually, the launch speed will drop below a practical value and you will have to spin the structure back up. And doing so will take just as much effort as it would have taken to accelerate each ship up to its "launch" speed on its own.

20. ### temurman of no wordsRegistered Senior Member

Messages:
1,330
Well, IMHO the only good thing is that near the fixed end the velocity will be low, so you don't need to be moving very fast to achieve high velocity at the other end. But you need to push with enormous force, and the arm material should be incredibly strong.

21. ### PeteIt's not rocket surgeryRegistered Senior Member

Messages:
10,167
An orbital accelerator could be useful for storing energy and momentum. Build up speed slowly over weeks or months (perhaps from solar wind), then deliver it quickly (hours) for launch.

Messages:
1,330
Nice idea.

23. ### nx-2418Registered Member

Messages:
1
Bussard papers

Hello everyone.

New Here. Sure you are spelling Robert's name right? If not, it is spelt Bussard
and I have two articles for you jen, if you are interested.

Email me at s_troi@yahoo.com with your email address or b&m address and I can get you some of my Star Trek research information from my notebook on starship research including his warp drive which discusses the collectors breifly.

My suggestion is that you look under the heading FTL travel or FFTL travel, Warp Drive, Bussard warp drive or the like.