Talk:Antimatter rocket

Please permit me to post this, for purposes of eliciting discussion, as I really want to know:

http://www.scienceforums.net/forum/showpost.php?p=550954&postcount=11

Many thanks !! 24.143.68.216 (talk) 08:19, 18 March 2010 (UTC)

photons collected from starlight or sunlight & hydrogen extraction from space as hydrogen is sparingly available in space — Preceding unsigned comment added by 121.217.53.133 (talk) 09:05, 27 June 2013 (UTC)

Maybe an "antimatter rockets in fiction" section could be added.

One such example is Peter F. Hamilton's Sci-fi space-opera "Nights Dawn Trilogy", in which Antimatter is outlawed, but used by rogue space captains with AM drives in thier spacecraft.

Loeffe 20:05, 6 April 2006 (UTC)

Peter F. Hamilton's space ships aren't really Antimatter rockets as described in this article, but ships that use an antimatter reactor to power a "warp-drive" type fictional FTL drive. 131.113.17.20 —Preceding unsigned comment added by 131.113.17.20 (talk) 06:21, 11 September 2007 (UTC)

Or from Avatar, the ship that brought them to Pandora was an Antimatter ship. (The physicist01 (talk) 04:40, 9 January 2015 (UTC))

:Has already its own article at Project Valkyrie. Mightyname (talk) 19:20, 23 November 2015 (UTC)

I've finished doing a major rewrite of the article to make it better-organized and to make it better reflect its source material. At least two more references need to be added:

• The Scientific American article on interstellar flight that ran in (I think) the 1990s. This mentioned beamed-core antimatter drives, as well as things like AIMStar and gas-core nuclear drives.
• A decent Brookhaven National Laboratory article describing the Valkyrie craft proposals. The link that was in the article doesn't cut it as a reliable source for a scientific article, in my opinion, and a better one should be easily available.

--Christopher Thomas 04:39, 2 April 2007 (UTC)

I've expanded the article covering pretty much everything, and added some of the requested citations. I'm not too sure about the sources of all the old parts, though. I've organized the sections according to newer papers and classifications namely some term changes. Since this field is being researched in all directions many of the presented "solution" are becoming outdated to some degree. This mostly affects papers relying on older papers which are using older data. I suggest to add only principles, concepts and formulas. Coming this far the articles needs some images showing the various concepts visually. Mightyname (talk) 00:55, 8 May 2014 (UTC)

I've read the paper by Frisbee (ref 2), and one problem he ignores is the heat flux through the radiation shield. In his design the heat from the shield is transferred to the 500 km radiator and dumped in space. however, the heat first has to pass through the shield itself, and with a flux of 200000 TW (more than the total energy the earth receives from the sun) through a 20 m diameter Tungsten shield, that requires a temperature gradient of 10¹⁰ °K per mm. Frisbee only hints at this problem in the very last sentence.

Are there any papers that discuss this particular aspect? Ssscienccce (talk) 10:06, 3 August 2015 (UTC)

:Nothing even relatively comparable afaik is available. It's a complicated problem with many possible (combination of) solutions with possible serious impact on the ship's total mass but not impossible. It is certainly a challenging technical engineering problem. If the shield can take the heat flux then it is possible to deal with it. For example the simplest solution is via simple Thermal conduction e.g. a cone shaped rod mass, as large as the shield in diameter, along the whole length of the radiators in the length-axis to transfer the heat. The radiators could have a rectangle or triangle shape depending on the transfer rate at a distance. It's a very large mass solution, hence, it overshadows any other smart Thermodynamics solution e.g. Steady Flow Energy Equation as in high volume slow fan pump + high pressure pipes. This can be used as the upper limit for estimations. Mightyname (talk) 18:56, 23 November 2015 (UTC)

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= Request for comment =

There is currently a debate on deleting an article about the Vacuum to Antimatter-Rocket: https://en.wikipedia.org/wiki/Wikipedia:Articles_for_deletion/Vacuum_to_Antimatter-Rocket

:I have suggested keeping it because:

:I believe it's the only spacecraft proposal on using Schwinger pair production for uncrewed interstellar travel.

:JBIS is one of the most prestigious journals on interstellar tavel: https://www.jbis.org.uk/paper/2011.64.378

:Centauri Dreams (https://www.centauri-dreams.org/2016/08/02/the-evolution-of-antimatter-propulsion/) is written by Paul Gilster, an expert on interstellar travel: https://www.planetary.org/profiles/paul-gilster

:Space.com and Interesting Engineering and reliable secondary sources as far as I'm concerned.

:Cheers. ExoEditor 03:36, 26 February 2021 (UTC)

= Formula uses Isp but it's not Isp =

Hi,

The section https://en.wikipedia.org/wiki/Antimatter_rocket#Modified_relativistic_rocket_equation is much appreciated and the source document the formula comes from was very helpful in my research (and I'm really happy the Archived page was added to the citation!).

However, there's a point of confusion originating in that source that should be clarified in this article - maybe?

The formula in the article exactly matches the source, no problem there. However, the formula uses the term "Isp" when it does not mean Isp as generally used nor as defined within the elsewhere within the source (nor as defined on Wikipedia). Isp gets misused frequently, so this is not entirely surprising.

The first reason I believe that Isp in the formula is something other than Isp is this quote from the source: "(For convenience, we have assumed that Isp is in velocity units compatible with AV.)" Given Isp is in seconds and delta-V is in m/s (usually), this is a big deal. The only way (I know) to make Isp compatible units with delta-V is to multiply Isp by g(0), which is exactly how to compute the exhaust velocity (ve).

Second reason is the source speaks of Isp values like 0.33c. To get from Isp to ve requires multiplying by g(0), which at 9.8 would give a ve of >> speed of light. In fact, there's a line in the source where the author refers to an Isp of 10 million, using the correct Isp units, followed by "or 0.33c"; indeed, converting an Isp of 10M to ve gives 0.33c, but the author made them appear to be equivalent values for the same thing, Isp - which they're obviously not.

Finally, I spreadsheeted the formula. I then changed the "a" term (fraction of propellant remaining after annihilation) from the value listed in the source's table (.22) to 1.0, which means I was comparing the source formula with the standard rocket equation (and used delta-v and ve values insignificant to the speed of light). I got the exact same mass ratios with both formulas when inputting ve for both: ve in the normal rocket equation and "Isp" in this article's formula.

All that said: I am NOT suggesting changing the formula - it is cited correctly. I do think adding some form of clarification to the article would save the next person my effort to figure out the confusion. Perhaps something like:

:The source document treats Isp (specific impulse) as ve (exhaust velocity) for the purposes of this formula.

Thanks for your patience!

Mauricef (talk) 03:34, 28 June 2021 (UTC)