shynung

Not unless you use the NPP system entirely as an orbit-to-orbit propulsion system, and you keep it away from LEO.

Nice to hear that. I agree, the fuel tank sharing would be quite a headache. I wonder, though, would separating the folder containing tankage from the engine folders reduce some complexity? Something like what you did with LH2, but applied to all tanks in general? I ask this because MIF, at least the MSNW design, requires light metals for propellant, not LH2, because the fusion process uses the propellant to induce fusion. You'd need to borrow the lithium tanks from NFT Propulsion if you plan to include MIF. Also, are you planning for FFT-NFT interdependence, or is it going to be a completely separate mod?

It's a magnetoplasma heatshield, really. How they managed to do that, I have no idea.

There's a fusion rocket being developed by MSNW LLC right now, funded by NASA. It is projected to have a specific impulse of 5000 seconds, yet has a power requirement of just over 200 kW. It promises an Earth-Mars trip time of 30 days.

MSNW LLC was recently putting forward that idea. Not shillin' or anything, just recently dug it out.

A compressor does increase the amount of air entering the engine. This it does by compressing the incoming air. Compressed air holds more masses of air than air at atmospheric pressure, hence more amounts of air. A turbojet combustion chamber is larger than the compressor because the chamber is meant to hold an expanding cloud of hot combustion gases. A compressor does not need that volume because it runs counter to the compressor's purpose: compressing intake air. Also, stator blades in compressors are meant to improve compression efficiency. A compressor without stators would simply increase the velocity of the fluid, without increasing much pressure. Stator blades convert the fluid velocity into pressure, while also redirecting the fluid to prepare for the next compressor stages. Without stators, compressors would act as ducted fans.

@TheDestroyer111 Because compressing the air enables the engine to burn more fuel for a given size of combustion chamber. Rocket engines typically burn their fuel with pure oxygen, in liquid form, often referred to as LOX. This liquid is quite dense, so we don't need much of it, in terms of volume, to burn a given quantity of fuel. In stark contrast, atmospheric air not only contains 1/5th oxygen rather than the pure version used in rockets, it's also in the gaseous form, which is at a much lower density. This means less oxygen is available for combustion at its current state, which is why a compressor is used to compress the atmospheric air to gather enough oxygen to support combustion. As a comparison, this is an acetylene welding torch before the oxygen line is opened (burning with atmospheric oxygen): And this is the same torch, after the oxygen line has been opened (burning with compressed pure oxygen gas): The blue flame indicates higher temperatures, therefore more energetic combustion. The same principle applies in gas turbine engines.

How about coal-sourced synthetic Jet-A? It's not quite clean, but it's cheap, and the US alone have about 200 billion tons in her reserves, able to last for more than 2 centuries at current production rates.

The Atlas V rocket wasn't originally designed to have strap-on solid boosters, so the oxygen piping and control wires get in the way. That's why the SRB configurations has to be offset in some cases.

@K^2 I recall that you once mentioned nuclear isomer batteries somewhere?

@Northstar1989 Let me clarify that I don't, for a moment, doubt the effectiveness of microwave beamed power. We've used microwave for cooking, and microwave energy rectifier tech has been demonstrated. What I doubt is the feasibility of integrating the technology into our current aviation transport system, which already uses the microwave spectrum for other purposes. I agree that microwave beamed power would be very useful in space applications. Up there, we can communicate using methods that wouldn't be feasible on earth, such as laser communication systems, though maybe not for broadcasts. I was talking about biomass gasification and Fischer-Tropsch process, actually. The end result is very similar to crude oil, and can be processed with existing petrochemical technology. The gasification process can use carbon from almost any source, not just biomass. Nutzi Germany once processed coal in the same manner when it faced oil embargoes during WWII to supply themselves with energy and materials.

Something else to consider: airport radars used for ATC uses the microwave spectrum, and so does aircraft radios and transponders. Using microwaves to power the craft would throw a spanner to the workings of these equipment. Also, I'm not entirely convinced that microwave beamed power would be used at a large scale in the foreseeable future. I'm betting that we'll get the first fusion rocket spaceborne before microwave thermal rockets. Also, I think you played too much KSP Interstellar. Try Near Future Technology for a while.

@Nertea I suggest grouping the non-AM engines into later updates of Kerbal Atomics, since they're a bit closer to reality than AM power, and are indeed powered by the might of the Atom. They'd be somewhere between FFT and KA/NFT, in terms of game balance, overall performance, and power consumption. EDIT: On second thought, forget the suggestion. Also, how's your vacation?

@Bill Phil Regarding probes, I agree that we should start using nuclear-electric propulsion. Alternatively, we can also use radioisotope stirling generators to power the electric rocket motors, if a full-blown reactor is deemed too large. On larger vessels, I'd put my bet on either this motor (MIF), or its competitors VASIMR, gas-core NTR, or Zubrin's NSWR.

TWR issues, maybe? If it takes forever to get the ship going, then it can't use Oberth effects, and needs to use spiral trajectories that are much less efficient than straight-up Hohmann transfer trajectory. Also, naval reactors are floating in coolant. Sure, they can't exactly pipe seawater into the reactor cooling lines, but they don't have to carry big radiators, either. They're also optimized for power/volume ratio rather than power/mass ratio, so not an ideal choice for space applications. Of course, after we get through all the hoops, we do get impressive specific impulse out of electric thrusters. So that's that.

Fractional...dimensions?

Oh, I already got it; just recently got active in that thread for this reason. Doesn't have MIF yet (non-AM engines are limited to Z-pinch microfission/microfusion, and the NSWR), unfortunately, but still quite impressive nevertheless.

@Northstar1989 I'd hold back my expectation on microwave thermojets until there's a working full-scale prototype. We have quadcopter drones for a few years, but no full-scale versions have been developed today that are objectively better than the classic helicopter design. I do agree on microwave thermojet planes being more feasible than LH2, since we don't need to build new airports for them. I still think syncrude-derived jet fuel would be the less logistically-intensive alternative, though, since we don't have to refit/replace the airplane propulsion system for a new fuel/energy source, or the entire fuel supply infrastructure. We do need a reliable source for the carbon, however. There are far better uses for optical rectennas than flight, however.

We do have shock absorbers. Using them as part of the thrust structure seemed to be an obvious solution. These can be as simple as gas pistons separating the engine components and the rest of the ship. Combining fusion fuel and foil propellant would mean the compression ignition would be done purely with coils, which would raise energy requirements. The separate fuel-propellant scheme is set up to lessen the load on the coils by using the foil's kinetic energy. The lead was someone named Slough, actually. We don't even need break even fusion, because the generated energy goes wholly to propulsion. Fusion was simply a means to heat the propellant, which in this case was the metal foils.

For some of you, this might be old news. But I think it's worth discussing, if even for a little while. Back in the early 2010s, a paper was published about the rocket motor named as the title of this thread. The magneto inertial rocket was powered by fusion, using lithium as propellant. It works like this: fusion fuel (D/T, D/D, or D/He3) is turned into a blob of plasma in a field-reversed configuration, and injected into a chamber. Also injected into the chamber are metal foils, made out of lightweight metals such as lithium or aluminium. The foils and plasma injection is timed so that both converges at the chamber's end, inside the throat, at several km/sec. Aided by magnetic coils located strategically around the throat, the inertia of the metal foils compresses the plasma of fusion fuels to ignite the fusion reaction. Just after this happens, the plasma blob containing fusion products and what remains of the metal foils move into the magnetic nozzle diverging section, where it expands and converts its pressure into velocity, which ends up throwing the plasma out the back of the nozzle, generating thrust. Main advantages compared to more traditional nuclear thermal rockets are: - uses solid propellants, which have high density, lowering tankage mass for a given dV budget. - low thermal loads on motor components, since the plasma never touches the motor itself, confined by magnetic coils, reducing radiator mass. - fusion fuel is covered in foils at the moment of fusion, limiting emitted radiation. - lower energy requirements compared to other fusion methods, only need power to run the coils. The thrust generated isn't much - Atomic Rockets claimed a 13.8 kN thrust with pulses at 14 seconds interval - but it gets 5000 seconds of Isp. As a bonus, if the nozzle is replaced with a MHD generator, it effectively becomes a fusion power plant. What are your thoughts about the concept? Feasible? Foolish?

There are other concerns with the LH2 plane approach. As they're practically flying fuel tanks, an airplane fuel by LH2 with the capacity of a B777 or A340 would be humongous. They might be large enough to necessitate new infrastructure - wider/longer runways, larger aprons, larger hangars - which means these LH2 airplanes are limited to airports which can handle their size. Also, abandoning fossil fuels doesn't necessarily means abandoning Jet-A. We have ways to create synthetic equivalents of crude oil from solid carbon sources, such as coal or biomass.

That's the plane I meant. Reaction Engines called that plane the A2. Like you said, it's basically Skylon, minus the rocket mode. I don't think so. An older thread in this forum discussed about the feasibility of capturing CO2 from the air to create hydrocarbon-based fuels. The process itself is energy-hungry for sure, not least because of the generally low concentration of atmospheric CO2 compared to O2, but it could produce hydrocarbons. If the OP there considered using more concentrated forms of carbon, like coal or biomass, and avoiding burning some of the carbon feedstock for energy, we can improve the efficiency of the process. In the end, if cheap fusion power became a reality, I'd imagine these would fuel future jet airliners. LH2 would still be somewhat silly (flying fuel tanks), but microwave thermal jets? We don't even have a working prototype right now.

LH2? That thing needs really big fuel tanks, it has terrible density. Air travel still has to bother with aerodynamic resistance, so unless the planes start to look like Skylon (basically around 4/5 of the fuselage are propellant tanks), I don't think we'll see LH2 jumbo jets. Lighter hydrocarbon (C1-C4) fuels, I believe is still feasible.

A few points: - The Z-pinch engines hasn't had names yet. - The NSWR engine was named 'Heinlen'. Posting it here because you may have meant 'Heinlein'. - The NSWR engine consumes electricity. NSWRs in principle are nearly identical to hypergolic rockets, which simply release propellants into a reaction chamber. I don't see why the NSWR would need electricity, unless using a magnetic nozzle. Also, regarding this: I'd suggest to put in the ISRU components last. That way, you'd have a pretty good picture on what the ISRU processes need to produce, since the engines needing the refueling are done.

Just throwing the idea. I think I'd prefer a simpler implementation, too.