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  1. Hello! I'm working with @FreeThinker of the Interstellar Extended mod to try and get his antimatter engine spacecrafts to be more accurate. Primarily, we want to make sure we have the correct exhaust ISP and reactor output for an antimatter reactor. We're looking at beam-core specifically, but while we are at it, looking ant anti-matter catalyzed fusion or being open to even more efficient alternatives would be great. Here is the mod forum link (you can find the mod itself on CKAN) Now, there are a few designs out there in existence which we can reference as-is. However, many of these have specific mission parameters in place at the get go. They also include a surplus of mass for use as shielding against gamma rays generated from the use of the antimatter. That goes way beyond what is necessary in Kerbal, modelling shielding from gamma rays would be a a lot of work. Also, depending on the configuration of the reactor, that shielding might already be in place. Different Physics than Tsiolkovsky The first and most important thing to realize is that the traditional rocket equation no longer holds. Some of your mass wet mass is literally annihilated and converted into energy. This means that you can reach substantially higher delta-V than simply calculated from your Isp. You can read more detail from this source, but here are the basic eqs. The problem for KSP is that once you take the derivative of this to model the fuel loss, you can't solve it symbolically for the total Isp. Ship Designs There are a few different designs out there, some in the VERY early stages of NASA Tech Readiness Level, others are far ahead in fiction alone. Here's a list from Orion's Arm which I summarize below as well, and add ACF. Antimatter Catalyzed Fusion Uses antimatter reaction to trigger D-D or D-T fusion ICAN-II: A study by Penn State Picture by my friend Seth Pulsed Explosions AIMStar Solid Core - (ISP = 1000 s) high energy conversion efficiency, but very high thrust and low ISP - little thermal decay Gas Core (ISP = 2000 s) Plasma Core (ISP = 10^5 s) Beam Core (ISP = 10^7 s) Project Valkerie Project Frisbee Gamma Ray Photon Rocket Right now the mod is focused on Beam Core, Gamma Ray photon rockets are well beyond the scope of any serious study right now. Here's two charts which show the propellent/dry mass and antimatter/dry mass ratios. Beam Core is the best, hands down. For every 1 mT of dry mass, to reach 33% light-speed, you'd only need roughly 2 mT of fuel, or 4 mT for acceleration and decelleration. For Anti-Matter, for 1000 kg dry mass reaching 33%, you'd roughly hit parity. You'd want an amount of antimatter nearly equal to your dry mass. Or twice that if you need to decelerate too. Or seen this way at just direct mass 10^6 g is 1 mT Antimatter Storage Density and Energy Requirements So first, we should look at mechanisms for storing antimatter - it needs to be tight. Generating antimatter is important as well, but the mods that @FreeThinker has does a great job at that. We actually do have antimatter stuck in the Van Allen Belt, and so does Jupiter. It can be harvested. And it's already used, it occurs naturally in lightnight strikes, and PET Scans used in hospitals are actually generating positrons from isotope decay to track gamma rays being generated inside your body. Insane right? Antimatter is NOT for energy production, it's for energy transport. It is the most efficient fuel known to physics. Antimatter can be stored in a number of ways, but here are the most prominent. Antimatter can be an anti-proton, a positron, or anti-hydrogen. Conceivably you could have heavier anti-particles, or exotic anti-particles, but those are for another time. Some of those particles though, pions, are created and destroyed during the annhilation process of larger particles. Positrons might end up being easier to store, but they have much less mass-energy than an anti-proton. Positrons are 0.5 MeV, Anti-Protons are 938 MeV. Ultimately, a LOT of your dry mass will end up being just the components necessary to house the stored anti-matter. Penning Traps - generally pretty large and energy demanding, but can hold large amounts of either anti-protons or positrons. These get a lot better with superconductors. These could potentially scale up into larger electromagnetic holding cells - but it's still pretty risky to keep it all in one place. Micro-Trap Arrays (source)- "Atom chips are now being proposed for trapping antiprotons, positrons and antihydrogen." - Source Intended for positrons at the moment, but microtrap arrays are also used in Quantum Computing and a lot of solid matter physics experiments. You can trap heavy ions in these things, it happens all the time, and these microarrays are far safer. If one fails, you might have an explosion, but not necessarily a chain reaction. A microtrap array would probably be much heavier than a large penning trap, but it could still remain relatively small since you can arrange the traps in 3 dimmensions. It's hard to get a good estimate on possibly storage limits, because most of the time these traps are used in QC where you are trying to have only one atom per trap, not several. But - if you include "cooling lasers" to the mix, it might be possible to scale things up pretty large. There are no listed numbers available for max storage capacity for Microtraps in a serious large scale use - however - "It was computationally shown that each microtrap with 50 µm radius stored positrons with a density (1.6 × 10^11 cm−3 ) even higher than that in conventional Penning-Malmberg traps (≈ 10^11 cm−3 ) while the confinement voltage was only 10 V" Source Since microtraps are basically tiny coils on a wafer, once can see how these could easily scale up. Taking the mass of a positron at 9.1e-31 kg, and the number of positrons at 10V, which is 10^8, you get 1.45e-20 kg/trap. Each trap takes up 50 micron radius, which gets you to a number of 1.47e-9 kg per square meter. So the surface area required to reach 1mT of antimatter is... 6.76e11 m^2 So that's still a lot, and mostly because positrons are so tiny, but you could fold a lot of surface area into a tiny volume if you wanted to. If you stacked all of those traps linearly, you would be 41,000 km long, but only 50 nm wide. Now... I think I did my math right, but I wouldn't mind being checked. You could possibly fold that 41,000 km into thin sheets that were 100m x 100m - assuming that EVERY microtrap has a spacing of 50 nm, I calculated that you could fit the entire aparatus into a box which is 100m x 100m x 164m, or roughly a box that is 117m^3 - again, that's for 1 mT of Antimatter Bump that up to 120m^3 for posterity, and you get a figure that says you have 5.7e-4 kg/m^3 of antimatter, or 0.57 g/m^3 Now, let's say that you bump up the potential from that 5-10 V to something more like 100 V, you now would have 12 KG/m^3, because storage scales logarthimically AND folded arrays scale cubic. You also could possibly shrink the trap size but retain a similar positron count. Realistically, you probably will want more space between the cells - but you'll run things at a somewhat higher voltage because otherwise you can't store enough. The "dry weight" here would probably be comparable to an average data center, but I'll have to calc that out when I have more time. Buckyball, CNT, Physical Binding- more coming soon. Neutral Molecular Binding - look up positron dynamics, this is a very promising technique too, definately a hell of lot easier to create en-masse than a 3D circuit of microtraps that is ~100m in diameter. Here is the chart @FreeThinker put together for his storage estimates on his antimatter tanks. - I will review tomorrow - but I think splitting tank types might be a good idea, since tech level will determine storage capacity. Diameter 0.625m 1.25 m 2.5 m 5.0 m 10 m 20 m Antimatter (mg) 1695 13192,25 105538 844304 6754432 54035456 432283648 Antimatter (kg) 0,013 0,1 0,84 6,75 54 432 Tank Mass (kg) 25 50 100 200 400 800 1600 Tank Mass (ton) 0,025 0,05 0,1 0,2 0,4 0,8 1,6 Antimatter Beam Core Reactor Energy More to come on this soon - will try to derive from the charts above. Help appreciated. Magnetic Nozzle Exhaust Velocities I will expand on this soon. Basically though, it's variable based on what reactor you use, but enough sources out there claim an upper limit of about 10,000,000 ISP, while some only predict 100,000. ISP, Exhause Velocity and Delta V are again related, but not via the traditional ratios of the rocket equations. See above. ALRIGHT - this is my first draft - I'll update this first post with relevant information as we revise things. Also - I'll probably post another thread for the MagScoop Sail too - since that can handle the bulk of deceleration (interstellar 'wind' drag) andthus cut your fuel needs down by nearly half.