ArcFurnace

You could turn the resistojet into a high-ISP RCS port. Sadly linear only since multi-nozzle bipropellant RCS doesn't work in stock, but the current model only has one nozzle anyway. You might have to shrink it a bit, of course. EDIT: Found an issue, the mass ratio of the FS-L 0.625m LFO tanks is off. The stock fuel tanks have all been normalized to have a mass ratio of 9 (8 tons fuel:1 ton tank). The FS-L tanks have a mass ratio of 81 (80 tons fuel:1 ton tank) - e.g. the FS-L50 carries 1.2 tons of fuel with a tank mass of 0.015 tons, compared to the FL-T200 that carries 1 ton of fuel with a tank mass of 0.125 tons. I think you misplaced a decimal point somewhere. I checked the rest of the tanks to be sure, and they all look fine (identical or close to stock). The FS-L10T is a smidge low, but I think you knew that (and the stock toroidal tank is also lower than the others).

That's looking pretty good. I would also add a comparison with the O-10 "Puff", which is 0.0 Ec/s, 250s, 20 kN, 0.09t, TWR 22.65, Precision Propulsion (t5). Clearly the high-TWR, low-ISP option for monopropellant.

I'm not sure if you can really call the Project Pluto design a "jet" in the sense of a manned aircraft useful for anything other than destruction. It was unmanned, had no radiation shielding at all and had radioactive reactor-core dust as part of the exhaust stream, and I doubt you can eliminate those without reducing the performance substantially. Radiation shielding to keep crew and passengers healthy is heavy, and if you don't want bits of the reactor core coming out the exhaust you have to run it at lower temperatures and/or without supersonic airflow through the heat exchanger (making it a jet instead of a ramjet) and thus giving lower exhaust velocity. The Aircraft Nuclear Propulsion project was a lot more sane, and they wound up abandoning it after studying shielding requirements for an active nuclear reactor in an aircraft. However, the ability to operate in non-oxygen-containing atmospheres might be enough of an advantage to make it worthwhile.

Acceleration can be measured by an accelerometer. Taking the time integral of the acceleration gets you the change in velocity, although you have to be careful (if the accelerometer is off by a little, integrating over time will result in increasing levels of error in your measured velocity). See also inertial navigation system, which is a more detailed discussion of that procedure. A star tracker can give you your attitude (the direction you're facing), although I'm not sure if it's possible to get velocity from those. If you have access to a ground station, you can send radio signals back and forth and track how long it takes for them to be transmitted and received, which will give you position and velocity (see also here). A theoretical technique is to use pulsars of known locations and frequencies as beacons to determine location (and measurement of your location over time can give your velocity).

Also, specify which dev build you're using, by version number or similar - "most recent" works at the time you post it, but it's possible that Ferram could push another update before he sees your report, in which case confusion might result if you don't clearly specify the version.

I actually couldn't find numbers for Merlin 1D-Vacuum sea level ISP anywhere, presumably because nobody bothered to calculate them (as it would never be used). I did find this webpage, which states that while the Merlin 1D has a chamber pressure of 97 bar (9.7 MPa) and an expansion ratio of 16, the Merlin 1D-Vacuum has the same chamber pressure and an expansion ratio of over 117! Even more annoyingly, I couldn't find equations that would let me take the chamber pressure and expansion ratio and calculate the exhaust pressure at the nozzle, but I bet it's a lot lower than 1 atm, which would indeed make it effectively unusable at sea level due to massive thrust loss and/or flow instability due to gross overexpansion.

Basically, with the stock system, a certain amount of heat flux (from the shock compression plasma) is applied to parts. However, in the stock system a single part is modeled as having a single temperature throughout that part, and the entire mass of the part contributes to its thermal mass (how much energy you need to add to raise its temperature by a certain amount). This means that for, say, a big heavy fuel tank, it takes quite a lot of heat to heat it up to the point where it explodes from overheating. This isn't really realistic. The superheated air is only touching the very outside of a part, and it takes time for that heat to work its way inwards. As such, initially only the very outside of a part heats up, and since only a tiny fraction of the part's mass is involved, it heats up a lot faster (same energy into less mass equals more temperature increase). DeadlyReentry models this by splitting a part into "skin" and "core" sections, with the skin being 10% of the part's mass by default (correct me on this if I'm wrong, Starwaster). Then, if the skin of the part heats up above the part's MaxTemp, you get the superheated plasma burning its way through the skin and destroying the fragile insides. This ends up being a lot closer to how things work in the real world. It also eliminates one of the oddities you can get in the stock system, namely that you can heat up, say, a crew cabin to 1500 °C throughout its entire mass without converting the passengers into piles of ash. Instead, the insulating skin gets hot but the insides stay cool (if everything is functioning correctly). I believe Starwaster also dramatically increased the rate of heat transfer from the atmosphere to parts to get something that more closely approximates the heat loads you would see in Earth reentry (~11km/s) despite Kerbin reentry's much lower velocities (~2km/s for orbital, somewhat more for Mun/Minmus return or interplanetary but almost never anywhere near Earth reentry velocity). This makes reentry much more, well, deadly. However, the heatshield parts were similarly buffed to ensure this can be survivable.

So, reading Claw's post there, it seems the major reason why the air feels so "soupy" is that pointy shapes (nosecones and such) that OUGHT to cut through the air easily are actually modeled as being much more drag-inducing - and since the majority of drag comes from the front face of the craft, this makes drag seem excessive overall. My other comment is that, currently, reentry heating doesn't do much due to craft slowing down rapidly enough that nothing overheats (I had a craft turn out to be reentry-unstable and flip so that all the parachutes were facing forward, but it made it through the atmosphere just fine). This doesn't seem right, but there's more than one way to adjust things so that heat shields are necessary.

I agree that electric propellers would be nice. Would either need a workaround or an adjustment to the stock engine module, though- the current version requires an ISP value and at least one propellant that has mass (ElectricCharge does not), which is why you have things like the Firespitter electric propellers generating "FSCoolant" from ElectricCharge and then using that inside the engine module. Squad being in control of the game's code, they are in the best position of anyone to make this workable without using such a workaround.

Material is the most relevant for maxTemp values, shape could affect heat loading during reentry but would not really alter maxTemp. Very few materials meet the dual criteria of (a) structural strength at high temperatures and ( low weight. The Space Shuttle thermal protection system gives several examples of high-temperature materials. One of the highest real-world values is the reinforced carbon-carbon leading edges on the Shuttle, which are structural and rated for up to 1,500 °C, although RCC can be very brittle. RCC may even be able to go higher than 1,500 °C. A lower-temperature but tougher material is titanium metal, which can maintain structural strength at 600-800 °C (600° is the safe end, 800° is pushing it pretty hard and may lower lifetime). Stainless steel can do a similar temperature range as titanium but is generally too heavy for aerospace uses. The Shuttle actually used an aluminum structure that could not go above 175 °C without failure, plus lots of lightweight non-structural insulation to keep the heat away from the aluminum. The "high-temperature reusable surface insulation" tiles (rigid silica-fiber foam, 94% empty space) are ultra-lightweight and can tolerate up to 1250 °C, but are very delicate with respect to mechanical impact. The "flexible insulation blanket" is a lightweight silica-fiber cloth that can handle up to 650 °C, probably a good minimum value for part maxTemp unless it's something explicitly never intended to handle reentry. Easier to work with and less likely to shatter than the tiles. Short summary: Reinforced carbon-carbon = 1,500 °C or higher, titanium 600-800 °C, other structural materials rely on insulation rather than inherent temperature tolerance. Space Shuttle silica fiber foam tile insulation = 1,250 °C, silica fiber cloth insulation = 650 °C. Probably no part that one would reasonably expect to be exposed to the air should be much less than 650 °C, although delicate bits could be less (science gadgets, unshielded solar panels, etc. that are shielded by fairings or external heat shields instead).

You seem to be conflating "procedural fairings" (non-predefined-shape fairings) with Procedural Fairings (the mod). In Procedural Fairings you just place a fairing base and a fairing panel, and it automagically reshapes itself to fit the payload- am I right that you feel that this is "cheating"/"too easy" since it requires no effort from the player to ensure that the payload fits in the fairing? The actual description of how the fairings work by HarvesteR seems to imply that this is not the case for their implementation. I see nothing in there about automatic fairing shaping, and several things about manual fairing shaping. If your desire is for fairings that are manually shaped by the player, you seem to be getting your wish.

That is looking pretty good to me, Nertea! I like that it now has a separate niche of wide-load (plenty of room for extra surface-mounted bits on the sides of a 2.5m fuselage) or rover deployment with that flat bottom and the tail ramp, making it nicely distinct from the stock Mk3, which is a bit more of a snug fit on 2.5m cargo and can't really do rovers (outside of maybe dropping them from an inverted cargo bay).

So when you say "Mach effects," do you mean the visual effects (similar to what we already get when moving at high speeds at low altitudes), or a sudden increase in drag as you approach the sound barrier?

Yes, precisely. The one that tells you part count/mass. It's in the AppLauncher (the stock toolbar), so it's an app.

If that's what is supposed to happen, then something's bugged, because pressing Launch to Rendezvous doesn't update the launch inclination for me (tried this multiple times). It can still manage a decent intercept even with the wrong inclination. Launch into Plane of Target works perfectly, automatically updating the inclination of the launch autopilot to match the target and correctly timing the launch. This is 0.90 KSP with Mechjeb dev#393, no other mods installed. Reproduction steps (at least for me) are basically "have a target craft in an inclined orbit, manually set the launch autopilot to 0° inclination, target the inclined-orbit craft and hit Launch to Rendezvous, observe that the launch inclination is not altered". If you do the launch-and-revert thing it can still manage a decent intercept with the target, but it won't change the launch inclination without you either manually doing so or hitting Launch into Plane of Target and then aborting as a workaround. I would honestly be okay either way with you fixing this or just declaring it intended behavior, LtR has the previously-mentioned issues with inclined orbits (namely that even if it matches the target's orbital inclination, it probably won't match the target's orbital plane, which makes the inclination matching slightly pointless). If you can't reproduce this yourself/want more details, just ask.