Talk:Bussard ramjet

Ram Scoops Separate Article

Why does the ram scoop concept have a separate article? It seems to me that it is essentially the same concept. Plus, the ram scoop article is terribly short and uninformative. Why not merge it with this one? <~Zebraic/talkedits> 20:48, 26 December 2007 (UTC)

I agree entirely. "Ram scoop" should be merged into this one. DanielCristofani (talk) 10:03, 28 July 2008 (UTC)

Fusion Reactions

Those fusion reactions on the page are completely fudged. D-D Fusion is NOT 17MeV, it's around 3. And that's by far the most likely operating mechanism of this design. Tritium is rare on earth, it's needle-in-a-haystack in the interstellar medium. —Preceding unsigned comment added by 76.174.13.182 (talk) 05:18, 19 March 2010 (UTC)

Ramjets

anybody want to talk about ramjets? —The preceding unsigned comment was added by Tmayes1999 (talk • contribs) on 09:34, 12 June 2005.

Ramjet speed

I have a question about ramjets: In the section about the example ramjet design the solar wind velocity relative to the ramjet scoop in interstellar space is said to be 50km/s. But what about when the ramjet exceeds this speed? How can a ramjet approach the speed of light if it keeps getting pushed back by the interstellar medium? Can someone put up an example of what would happen if the ramjet was travelling at, say, 0.9c? Felix Dance 04:20, 9 November 2005 (UTC)

Calculation of drag

"The typical velocity of the solar wind within the solar system is 500 km/s."

In the article this is taken as drag. Now, since we still are within the solar system at the time, then this should be taken as draw (or push), instead of drag. The solar wind is outwards, which also is the direction of the spaceship.

Thus, when still within the solar system, it can enjoy capturing a solar wind of 500km/s, and thrusting its ions back to the same direction, "winning both ways", so to speak. —The preceding unsigned comment was added by 80.186.145.218 (talk • contribs) on 00:17, 17 December 2005.

Drag

Ignoring the velocity of the solar wind, does drag not scale as velocity squared, whilst thrust scales as velocity? Take limits for VMax? —The preceding unsigned comment was added by 155.198.10.247 (talk • contribs) on 12:31, 8 January 2006. If the drag is from the electrostatic force of the particles being drawn in, do those particles not give an equal and opposite force to the device which generates the electrostatic field? That is, is not the "drag" actually somehow pulling the vessel forward, since you are charging particles only forward? Or at worst, a net wash in force, at least at low speeds, as particles behind the ship drawn in would slow it, and particles in front would pull it? however, once you start to clear a wake, that will no longer be the case, as you will be travelling through a region cleared of material by the scoop.

That is, it seems to me that the drag is not in accordance with the properties of physics as I know it.

Jonathan Schattke

The obvious problem

I wouldn't edit the main article directly, I just made this account, but I *am* an astrophysicist.

Now, the whole idea of a scoop fails miserable because particles hitting the collector at an angle (to be scooped up) will either 1) go right through, or 2) bounce back again at an angle depending on the shape of the scoop. The point is that it is not trivial to get the particles that hit the scoop concentrated in to the engine. In fact, you might as well ditch the scoop all together.

When an electrostatic field is used for ion collection the electrostatic attraction force of the charged grid on the ions will prevent scooped ions from bouncing out of the ramscooop. Tmayes1965

The effective area of the scoop will never be larger than the size of your engine. You would be riding a giant cylinder and I'm afraid the time needed to build up any appreciable acceleration would be too long for any practical purposes.

Odegard 05:01, 12 February 2006 (UTC)

To see why anyone thought it was a good idea, I believe that a useful way of looking at the ramjet idea is to think of it as something similar to an (open-ended) magnetic mirror. You're interested in material within the loss cone (ions that have an angle of incidence such that they pass through the aperture at the point where the field pinches, instead of being deflected). The idea is that this concentrates some fraction of the incoming plasma. The problem is that in order to get sufficient compression for fusion, you need a very tight pinch with a ridiculously small loss cone, and almost all incident ions are deflected. My understanding is that the drag from deflected ions was overlooked in the original analysis. To add insult to injury, of the atoms that do make it into the pinch, only the deuterium has any hope of fusing, so the work done compressing light hydrogen is wasted. --Christopher Thomas 08:03, 8 June 2006 (UTC)

The kind of compression that nuclear fusion uses is the Teller Ulam-radiation implosion of the fusion fuel plasma. In a magnetic fusion reactor this compression is provided by the axial, or toroidial electromagnetic field deflecting the plasma toward the center of the field . Also not all versions of the ramjet try to induce nuclear fusion in the scooped hydrogen . Some versions just use it as reaction mass. tmayes1965

A good ramjet scoop design can use an electrostatic field to attract the incoming ions, and thus draw them inside the ramjet engine. The magnetic field merely deflects the ions, and thus makes the ions follow a helical spiral path around the field lines. —The preceding unsigned comment was added by Tmayes1965 (talk • contribs) on 05:42, 24 May 2006.

The article is completely missing any theoretical treatment of the workings of the electromagnetic fields, their sources, energy balances, control schemes, etc.; likewise for the so-called 'ion scoop', as if ion scoops were common, everyday appliances everybody is familiar with. The article itself has more a Sci-Fi flavor rather than that of a hard science article; and please remember: Robert Bussard was a scientist. Another issue: I changed the obviously wrong "Environment" Wikiproject header. --AVM (talk) 16:46, 31 October 2008 (UTC)

Not enough hydrogen

There are some well known calculations that show there is not enough intersteller hydrogen for the ramjet to work. That seems to be the primary issue of feasability. DonPMitchell 04:25, 15 March 2006 (UTC)

-That depends on what speed the ramjet reaches on internal fuel before attempting to initiate ram collection. Obviously the thinner the density of hydrogen in interstellar space, the higher velocity you need to be at to collect enough to maintain sufficient fuel supply. It is also obvious that any ramjet vessel will begin its journey inside a solar system where hydrogen densities are much higher from solar wind. The real question is that as the vessel gains speed and exits the solar system, whether the declining hydrogen density is sufficient at the higher velocity to maintain fusion. Also note that if hydrogen is less dense, this also means that drag would also be lower.75.67.80.68 (talk) 01:46, 22 May 2009 (UTC)

Interstellar space contains about 1 hydrogen atom per cubic centimeter. This means the total swept out volume of 1 light-year by 1 square kilometer contains only about 10 kilograms of hydrogen. DonPMitchell (talk) 00:13, 27 September 2012 (UTC)

Something is off

I'm neither a mathematician nor an astrophysicist, but there seem to be a couple of things off in the calculation that don't conform to normal rules regarding drag and energy calculatons.

The first is the actual "stopping power" of the shield. As you speed would increase, the relative speed of the ions woul increase as well. At some point you shield would need to be abe to stop and funnel to the engine particles at very, very high speeds. My guess is that this alone will cause a hard cut-off point in your speed. Unless the engine is the same size as you disc, which seems imposible from an engineering point of view.

The second problem is that your drag will increase with your speed as well. If your engine exhaust speed is 500.000m/s, then this seems to be your maximum speed in deep space (when the effect of positive solar winds are trivial). Since you captured ions will hit you shield at 500.000m/s, and you also spit them out at the same speed. I've seen nothing in the description about the initial impact speed of the ion being preserved and te exhaust speed being added to it, so I must assume that the exhaust speed is the maximum speed.The ions will exit the ramjet engine at a much higher velocity, then the velocity at which the ions enter the scoop because the ramjet engine accelerates the ions .tmayes1965

The third problems is that the system still seems to require a lot of fuel just to get started and get it past a speed where enough ions are collected to power the shield, the engine and any power overhead some of the suggested might require (a fussion reactor requires a lot of initial energy).Nuclear fission can also power ramjets. It does not have to be nuclear fusion to power them.tmayes1965

Janbart

Non-ramjet material removed

I've removed this material --

" It could also be an inertial confinement fusion reactor in which pellets of lithium 6, or lithium 7 deuteride, undergo Teller-Ulam radiation implosion by high energy laser beams, maser beams, or proton or antiproton particle beams. This will heat and compress the fusion fuel pellet until its temperature is more than 100,000,000 degrees Celsius, and increase the density of the fusion plasma by up to 30 times. This will ignite nuclear fusion in the fusion fuel pellet.

-- because it isn't about ramjets, and maser beams and antiproton particle beams aren't among the plausible ways to ignite inertial confinement fusion reactions. 67.117.145.211 03:58, 27 December 2006 (UTC) Your wrong about that . Go learn about the Aimstar project at the nuclear engineering department of pennsylvania state university . tmayes1965

I deleted this paragraph about electrostatic scoops because it seemed unclear:

The flux of the interstellar galactic electric field is 1.6 * 10^ -19 electron volts. This means that an electric ion ram scoop field will have an ion collection radius that is the square root of 10¹³ times (about three million times) greater than the ion collection radius of the electromagnetic ion ramscoop.

First, fields are not measured in electron volts. Second, there is not enough information to determine how the author does an apple-to-apples comparison of electrostatic scoops to electromagnetic scoops. Third, there's no citation. Is this an original calculation by the author of the section, or is there a reference for this calculation? Geoffrey.landis 21:00, 27 June 2007 (UTC)

Deceleration

I'm no astrophysicist, but i'm wondering how a bussard ramjet travelling to another star system would decelerate as it arrives. If it is travelling (presumably) at fractions of light speed, how could the magnetic funnel retrieve enough H to power the engines when the spacecraft was travelling in reverse relative to its motion? Unless the engines were reoriented i suppose. Perhaps this could be included in the article. Dallas 15:35, 14 July 2007 (UTC)

Another problem...

Ok, assume a working ramjet is designed and several are built for intra-system exploration - travel to the other planets, asteroid mining and whatnot. Wouldn't space around Earth quickly become depleted of viable fuel? Or would galactic rotation ensure that there is always a fresh supply? Applejuicefool (talk) 21:37, 15 January 2008 (UTC)

Antimatter

Article needs to have calculations for using stored antimatter onboard as a power source when combined with scooped matter. —Preceding unsigned comment added by 72.200.76.139 (talk) 03:19, 1 August 2008 (UTC)

• I think this should actually be under "antimatter rocket" I may add it later. Having done some "back of the envelope" calculations my finding is that for a 137.00 metric ton spaceship to reach 30.000% of celeritus and then decelerate to rest - assuming an antimatter powered pion/photon rocket with a 70.000% propulsive efficiency - it needs to take 22.377 ton of antimatter and 22.377 ton of matter. If it takes only antimatter and scoops the matter from the interstellar medium it needs "only" 18.144 ton of antimatter. A definite improvement in efficiency considering the cost of antimatter fuel - but this implies a very long flight path (several light years) to intercept enough matter. Aksel89 (talk) 03:36, 18 February 2009 (UTC)

Just to make that clear, the ship mass is 137.00 ton without including the fuel, total mass before launch would be 181.75 ton for a non ramjet and 155.144 ton for a ramjet.

More useful to know is that for acceleration to 30.000% lightspeed and back the ship needs to be 12.312% antimatter by mass if all fuel is caried onboard or 11.695% antimatter if it is a ramjet design collecting matter. All values stated to 5 sig figs.

Also I choose 30.000% lightspeed because travelling faster is extremely energetically costly; just to accelerate to 40.000% lightspeed the ship would need to carry 11.613% of its mass as antimatter fuel (for a non ramjet) - nearly as much as for the entire voyage at 30.000% lightspeed!

Unless there are more comments, I will add this to the antimatter rocket article and include a link on the ramjet page.Aksel89 (talk) 08:27, 18 February 2009 (UTC)

Ramjet

This thing sounds somewhat like a perpetuum mobile. Is it? If it accelerate by collecting fuel from 'empty' space, and traverse increasingly more of space as acceleration increase, then fuel intake should increase as well, leading to yet higher acceleration, resulting in yet more traversal of space, resulting in yet more fuel, and hence yet more acceleration, ad infinitum (or maybe rather 'ad lightspeed'). I don't think the article is very clear on this effect, if it covers it at all. —Preceding unsigned comment added by 83.89.0.118 (talk) 18:40, 14 August 2008 (UTC)

It's no more a perpetuum mobile than something propelled through water by a water-jet--like, say, a squid. Admittedly, the ramscoop has to do more with its fuel than just squirt it out the back (it has to fuse it first), but there's no physical law being violated. Nagakura shin8 (talk) 10:51, 6 March 2009 (UTC)

It is more like a motorboat that can run forever because it is traveling in a sea of gasoline. Sure there is drag from scooping the gasoline into the engine, but you get a lot more power from burning the gasoline than you lose from the drag of siphoning it into your engine. It is the stored energy in the hydrogen atoms that is unlocked by fusion that prevents anything like perpetual motion. It actually does expend the fuel, it is theoretically possible to deplete the free hydrogen in the interstellar medium, but practically impossible because there is just so damned much of it. 128.97.68.15 (talk) 21:24, 17 October 2012 (UTC)

WHO'S THE IDIOT!

Who';s the MORON who redirected "Bussard Collector" into "Bussard Ramjet?!?!?!?!?!?!

Whoever did it needs to be backhanded for doing things backwards! If you're going to redirect, it should be Ramjet into Collector!

Fix your goof or take a hike!

75.8.36.225 (talk) 23:34, 19 January 2009 (UTC)

Of course...a real concept theorized, and used in science fiction, since 1960, ought to redirect to the article on a piece of Star Trek (first aired 1966) trivia. Makes perfect sense to me. As everyone knows, real astrophysics is defined by Star Trek, not the reverse; to think that articles on real concepts ought to take precedence over Star Trek, is, as you say, doing things backwards. Did it ever occur to you that they probably got the idea for the Enterprise's Bussard collectors (added, I believe, in TNG) from the ramscoop? Probably, I'd say, direct from Niven.

Nice manners, by the way. Nagakura shin8 (talk) 11:08, 6 March 2009 (UTC)

Just noticed "Consider also the case of a wessel leaving a star system", once more a star trek reference leaks into a "science" article —Preceding unsigned comment added by 94.194.42.49 (talk) 22:30, 26 April 2009 (UTC)

Oh, John Timberlake

lol @ "It is the title of John Timberlake's book[6] where he addresses notions of realism and fiction in photography and their proximity to constructions of utopias/dystopias. Interweaved with his images and bearing on 9/11, fusion-theory and space travel, John Timberlake’s compelling, three part narrative weaves Sci-Fi with contemporary realism to counter tarnished and myopic notions of 'future' civilisation and landscape." —Preceding unsigned comment added by 67.85.36.128 (talk) 05:11, 20 April 2010 (UTC)

Where is the original paper ?

Why is not Robert Bussard, “Galactic Matter and Interstellar Flight,” Astronautica Acta Vol. 6 (1960), pp. 179–94 not referenced? aajacksoniv (talk) 22:29, 3 September 2012 (UTC)

Separate 'Cultural References' section?

It may be a good idea to move the cultural references from the first paragraph to their own section. This would allow for a clearer distinction between the scientific issues and the portrayal of the technology in science fiction works as well as easier integration of other cultural reference not currently included in this article. (e.g. The vessel Red Dwarf in the Brittish sci-fi sitcom of the same name was intended as a ramjet - link)

Prosthetic Head (talk) 19:10, 11 November 2012 (UTC)

Speed Limit

This section has no references. aajacksoniv (talk) 14:53, 13 January 2013 (UTC) Neglected is miss spelled. aajacksoniv (talk) 14:54, 13 January 2013 (UTC)

Still didn't six months later so I deleted it. Pure WP:OR 202.81.243.196 (talk) 15:09, 25 July 2013 (UTC)