iontom

Alright - adding some more -this paper is great http://www.deepspace.ucsb.edu/wp-content/uploads/2013/09/zhang_spie2015_SAIL-r815a.pdf It gives sail size based on max payload. So conversely - if you allow for multiple sizes of the sail - you could provide an estimated max payload. (of course you can discard your sail after it's used up too.) Which, we can solve for m_sail instead based on pre-set sail diameters. Also - how big can we make models in KSP? Is a 10km diameter sail possible once deployed? There's tons of other cool stuff on here. Anyway - I thought you might like this: http://www.deepspace.ucsb.edu/wp-content/uploads/2015/04/Laser-Propulsion-Classical-1D-Standalone.html If you view the page source, all the calculations are in there in the javascript, preformatted for you. Of course - the calculator doesn't seem to include anything about the beam dispersion - this is specifically for a phased array mission like the Breakthrough Starshot - and does NOT include the option for using a Collimating Lens - which would let you keep the laser active for probably more than 1000x longer. http://www.geoffreylandis.com/lightsail/Lightsail89.html

Yep! 2x the momentum! Here's a good article on it - http://muonray.blogspot.com/2016/06/the-spacecraft-that-requires-no-fuel.html The force itself is bundled up inside of "E" and is based on both the energy/freq of the photon and the work function of the metal that does the reflection - but for the most part that is assumed to be pretty high. ( between 0.88 to 0.9 reflective ) And technically this efficiency may change as you move since the photons reaching the sail will be more redshifted as the spacecraft moves faster - but that won't change by enough that it's worth modelling. Here's a good walkthrough! http://ffden-2.phys.uaf.edu/webproj/212_spring_2015/Robert_Miller/physics.html Perfect Sail: (theta is the angle between your light source and the normal vector of the sail) Realistic Sail: Now you just need to find F_0 For now we might assume that the reflectivity ( k ) is at a happy 0.9 The Beam Intensity (capital I) is not shown here - since this is a Solar Sail rather than a Laser Sail - (but don't forget to include the sun in the laser sail model - it will have a small but negligible force - and you could possibly break against other stars to decelerate) So, intensity for a star is measured in Watts/m^2 - and you probably have the Eqs for that in the existing solar sail mod you have. For lasers - the peak intensity is based on wavelength and something called the Optical Power - which is the factor where dispersion will come in. (w is the freq. P here is a the Optical Power, and is function of many different things including source distance) https://www.quora.com/Is-the-light-from-lasers-reduced-by-the-inverse-square-law-as-distance-grows-similar-to-other-light-sources (***NOTE*** Theta here is not the same as the Theta before. This Theta is the dispersion angle. ) What we need to find is the Optical Power and the Dispersion Angle Which - we may need to ask around for that - and/or scour the literature from the UCSB DEEP-IN Group that's working on laser sails because they do simulations on this stuff already. http://www.deepspace.ucsb.edu/projects/directed-energy-interstellar-precursors We also should assume that each lasing station will in-itself be functioning as a complete phased array - which make finding clean numbers a tad harrier - but they will be the same for each lasing station used. Once we find P and the Dispersion Angle, we'll have a good approximation of the force. The last step will just be adding the forces. And maybe we'll treat the collimator as it's own object. Which we can do the physics on later - but it will have the same dispersion and optical power traits as just the basic laser. F(total) = F(nearest star irradiance) + SUM(F_lasers(IS_TARGET, Laser_Position_3Vec, Laser_Wavelength, Laser_Optical_Power, Laser_Dispersion_Value=)) + SUM(F_collimator(SUM(Input_Lasers), NewDispersion, NewOpticalPower)

I think if we ask really nicely, I can get my friend Seth to make the model, although animating it might be way too complicated. In terms of the incidence angle - I'll try to get some more information in regards to laser driven sails - but for solar sails at least it's a pretty straightforward F=F_0*(cos2θ/R2) http://space.stackexchange.com/questions/2997/can-i-derive-a-combined-equation-for-velocity-of-solar-sail I'll do some more derivation later today though. What it will need however is some mechanism for calculating the beam direction from a laser station to the sailcraft. And you'd ideally want to use more than one beam station at a time. And even possibly a beam array from the surface of a body like the Mun. You could do it from the surface of Kerbin too - but you would have wavelength restrictions. We would also be assuming here that all of the lasing stations are capable of perfect beam orientation. So you would need to be able to get the directional vector, distance and atmospheric properties of a world to know the force your sail would receive, then your sailcraft force calculator would have to add all of those together and do simple force addition. Each beam station would have it's own incidence angle, but as you got further away from the Kerbol system, the difference in angle from each station would shrink, and all of the forces would be aligned. You also have the issue of placing a large collimating lens, which could be used to extend the usefulness of the beam. If you parked one of those in a "slow" hyperbolic orbit headed towards your destination - you could then have subsequent beamcraft ride the beam much further. From a programming perspective, I think you'd have to be able to "Set Target" for beaming stations while they are in Momentum Beaming Mode. THEN IF target = lightsail DO Add Sum(i=0, N){BeamingForce[Theta, R]} Return SailForceVector ELSE IF target = collimator DO Add CREATENEWBEAM[Sum(i=0, N){BeamingForce[Theta,R]}] Return StrongBeam So basically the Collimator would function just like a Beam Station, except that it would combine the forces of multiple other stations and it would have a much more effective force distance. I will start looking up what those force values will be - but essentially that's the architecture involved. Magbreaks would probably be programmatically easier to tackle since they would only be a function of a spacecraft's velocity. Cheers!

Totally agree, and you know exactly where to start with this Q That is the question - and I think you were able to answer the component that I wasn't sure on, which was how KSP calculates it. Which is that is uses STANDARD_GRAVITY = 9.80665f for g0 Where V_ex is the exit velocity. If the Isp calcs always just assume g0 to be zero, then it's not really a true ISP, but it's the I don't know the term... "Effective Isp" for Earth/Kerbin. In which case yes, your calc holds. 0.67c * 300.000.000 m/s * 55% efficiency / 9.81 = 11.269.113 s (periods instead of commas, you must be European!) Of course, that's not the Actual Isp, which to use that, you'd either use the gravitational force of the Sun, or of the galaxy itself in place of g_0 . Which, for interstellar flight is essentially worthless. You can solve for g_galaxy and get (6.67408e-11)*(5.8e11*1.989e30)/(5e20)^2 = 3.0797409e-10 but that's treating the galaxy like one big Keplerian system, which is totally false. It's just flat wrong, you need to derive Isp in some other way. http://www.relativitycalculator.com/rocket_equations.shtml Or more simply So, I guess you'd need to define "weight" without using g0 - and the only way I think you can do that would be to derive it from a change in relativistic kinetic energy....Which would be variable depending on whatever your current velocity was. And I'm NOT about to try to piece that out. Anyway - you don't need to worry about any of that, because for how KSP handles the physics your 11269113 s Isp sounds right on the mark. Isp is just a notation - so g0 doesn't really matter, still the value you came up with11 times higher than what the magnetic nozzle currently tops out at - which I think is closer to what makes sense from the NIAC dV charts I keep showing. Now since, I've got your attention, might I inquire your thoughts about laser-driven sails that might function like your Beamed Power network? Laser Sail Eqs. http://muonray.blogspot.com/2016/06/the-spacecraft-that-requires-no-fuel.html http://www.jsforum.or.jp/ISSS2017/papers/paper/17021_Paper_Bernd Dachwald.pdf Technically - photon sails work with solar incident rays and lasers - so you have two additive forces. This would probably be harder to model in Kerbal since it requires vector dot products and There's a lot of variables in there - but mostly it's just a function of: Sail area (A) Beam distance (because of dispersion) Incident angle Photon Energy - which wavelength The beam direction you might assume is just a straight line linking the beam source to the sailcraft - and leave it up to the player to figure out which direction to point so that they can either tack into or away from the incoming light. Still - I could see where that gets really tricky to model into KSP. Especially if you wanted to turn on multiple beams at once as part of a grid (you absolutely would). Magnetic Sail Eqs. Magnetic sails are a lot easier, at least if you only care about deceleration. Basically if you're going above 2000 km/s, turn on your magsail and you'll just simply lose velocity with a force strength dependent on your current velocity. http://www.academia.edu/28394236/Combining_Magnetic_and_Electric_Sails_for_Interstellar_Deceleration * Don't miss the radical up there ^(3/2) - also, m_p is usually just molecular hydrogen. I guess - you'd want to have the sail "deploy" once you're in space, because it's going to be huge and thin. And the radius you choose in the hangar would determine your speed. Also, depending on how you set it up - you would acquire interstellar hydrogen too - as you moved. What I'd like to find is an equation that would tell you how much hydrogen you gain as a function of velocity. It would also be slightly random, but within a set of parameters. You could mag-break down to 2000 km/s over about 10 years, and then have a nearly full tank of hydrogen from which you could do final deceleration/course correction. Hope some of that helps!

Hmm... What's the basis for the constraints on anti-matter storage? Penning Traps? Are Anti-Matter Catalyzed Fusion is supposed to have much steeper limits on max Delta-V because of the Tsiolkovsky problem. (AIM and ACMF shown here): Magnetic Nozzle Exhaust Velocity Also - I needed to hook up my Antimatter reactor to a Particle Generator - in order to get the magnetic nozzle to work - but shouldn't the reactor be generating charged particles already? From your description page: Magnetic Nozzles hooked up to a Beam Core reactor could potentially be expelled at close to 0.69 C http://newatlas.com/beamed-core-antimatter-propulsion/22654/ ANTIMATTER STORAGE There's groups like Positron Dynamics which are trying to commercialize a trend in positron confinement which actually uses special electron modes in simple neutral molecules. http://web.am.qub.ac.uk/users/g.gribakin/papers/p4541_1.pdf http://www.sciencedirect.com/science/article/pii/S0009261417302464 So there could potentially be more compact storage mechanisms for anti-matter as a more sophisticated tech. I think right now you're at around 1 kg / tank ? MICRO-LINEAR ACCELERATORS There's also currently development on small linear accelerators powered by lasers which could be used to transform any waste heat from either AntiMatter or a Fusion reactor into relativistic laser-accelerator nozzles. ( I'm still trying to find things like energy requirements for the lasers, but I think it's really low.) The ISP is going to be incredibly high, the thrust microscopic - but that might go up depending on whether this same miniaturization can work on higher mass ionized nuclei. You might even be able to push particles all the way up to iron if you wanted to. But really you'd probably end up using something like this to blast Oxygen that you will have a LOT of if you store your hydrogen or deuterium in water. https://www6.slac.stanford.edu/news/2013-09-27-accelerator-on-a-chip.aspx http://www.nature.com/nature/journal/v503/n7474/full/nature12664.html MAGNETIC SAILS Anyway - WAY more economic is Magnetic Sails for Breaking and Refueling - you basically get close to free deceleration - you just need enough energy to keep a small current in your super conducting loops. And you can actually hold onto the interstellar particles you capture - potentially for use later in your micro-accelerator nozzle. MagSail will work more efficient the faster you are moving, but becomes negligible under 2000 km/s https://www.semanticscholar.org/paper/Combining-Magnetic-and-Electric-Sails-for-Perakisa-Heinb/8278b9c81dd18c0a5dbea3b8e68b6ef25617c4d2 You also get extra deceleration from an E-sail too - which is a slightly different configuration and can break on a stellar wind as a spacecraft enters a system. How it might play out in Kerbal is just that if you have the magsail activated, it would slow your velocity until you hit the breaking limit. The E-Sail might work like the already existing solar sail - which also might do well as a conversion to a solar sail. Multi-stage spacecraft are a must for efficiency. Thanks for listening!

Hello, I've got a few suggestions that I wanted to toss in, but I don't know how flexible the codebase is, or how much time the developer has - but thanks for making such a great mod! Photon Sails: Update the "Solar Sail" into becoming a Photon Sail - such that it could receive "thrust" the same way that the beamed energy dishes receive energy. Laser Driven Photon Sails - like those being pioneered by the UCSB Deep-In and the Breakthrough Starshot project are one of the most feasible mechanisms of interstellar travel. Magnetic Sails/Scoops: Magnetic Sails actually can be used to Decelerate a spacecraft without using on-board propulsion. A magnetic sail can actually break against the solar wind, and it works better the faster you are moving. It can allow you to brake from any relativist speed down to about 2000 km/s; and more than that, you can actually scoop up interstellar gasses (mostly molecular hydrogen) as you are decelerating - which can then be used by other propulsion mechanism. Adjustments to Beam Core & Magnetic Nozzle: Essentially the beam core reactor should be able to produce particles that have velocities of upwards of 0.8c - which I'm not sure is accurately reflected in the impulse. I think it may be off by about a factor of ten. Also - allowing other fuels to react with the anti-matter would be significant. Water or Methane have a lot of hydrogen, and higher density than liquid hydrogen, without the need for super-cryogenic storage. While pure atomic hydrogen should stay pure inside the reaction chamber - other materials could be dumped into the plasma to contribute to the overall kinetic energy of the exhaust. This type of setup is ideal since L-H can boil off and tunnel out of containment. Metallic Hydrogen: has a density of 0.7 gm/cm3 (liquid H2 density is about 0.07 gm/cm3) - that ten-fold increase means a lot less dry mass for storage needs, and thus faster speeds. You probably could generate power from undergoing phase transition too - so you'd need a "Phase Converter" that produced energy that could be used for life support - all while acting as the primary feedstock into the Beam Core reactor. (*Notice the blue-line indicating the deceleration limit of a magnetic sail) Anyway, I recently made an interstellar trip in Kerbal using the beam core, I just had to cheat and Re-Up my fuel about 20x on LH and 200x on Anti-Matter (to reach speeds of about 0.3c) - anything slower than that will take days or weeks of time warp rather than hours. It 100 Kebin years (~25 earth years) in-game time to go 1 light year to reach the "Valentine" system. Overall I think it was between 2 and 4 hours of waiting, although I wasn't watching the clock super closely at first and I was trying not to cheat, but 1000+ Kerbin years was too long to wait. I think that people overuse the Warp Tech without appreciating the true challenges of interstellar flight. FTL might not even be possible. Now I know this is just a game, but I am trying to model this stuff for both fiction and non-fiction books - and there's no better way to explore a concept than to play. Basically - I imagine building a ship like the RAIR imagined by my friend Seth Pritchard. Except that the first stage of propulsion will be a photon sail, and the primary propulsion method will be Beam-Core rather than AM-Catalyzed fusion. Anyway - my first sortie into interstellar space (with cheats) - went well - and I least proved that interstellar trajectories are challenging but not impossible. Point and shoot works for 99% of the trip. Just bring a little extra fuel for final maneuvers. Here's the album, and yes, I feel sort of bad about cheating, but I wanted to know how long it would take in real time - which is about 3-4 hours if you can hit 0.25-0.3c for one light year. So plan accordingly!

Are there any mods out there for metallic hydrogen that would work well with this? A huge problem for doing Interstellar trips in Kerbal is that you can't really make your ships big enough without a lot of staging. And that makes maneuvers into a real drag. A metallic hydrogen to gas converter/reactor would significantly decrease the amount of storage volume needed and make maneuvers a lot nicer. You would have extra heat to deal with, and an additional energy source, but that's good news if you're powering say a habitat ring.