AeroGav

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  1. What about a pod that has an asymmetrically attached wing part and spins down like a sycamore seed ? Might be a bit hard to predict landing point, but i've created such things inadvertently before, usually mid air, from what was once a symmetrical, intact aircraft with the same number of wings on each side....
  2. I got home from work tonight and used hyperedit to put it orbit of dres, then forced a kerbin encounter by dumb retro burning from full tanks, ended up going into kerbin at 4700. A more realsitic encounter would have lower speeds, jool return is normally 3800 to 4000 and i normally need to retro burn 500 or more dv on a mk3 Now, the more you retro burn and slow down before hitting the atmosphere, the lower your periapsis can be and not blow up , which in turn means you can brake more. So retro burn before aero brake. I kept save scumming till i found the max speed that enables me to get captured by the kerbin system with a velocity of 3700 m/s when entering the atmosphere, i could go no lower than 48.6km and after passing through the atmosphere, we were still on an escape trajectory from kerbin. At 3600, we could drop down to 47km and the drag built up and built up, holding radial out with max roll to spin stabilize us , we ended up with a 3 million km apoapsis in the kerbin system after the aerobrake. So your options would be 1. Add an inline clamp o tron to refuel the ship in orbit before setting out for Dres, ans do the needed retro burn 2. Do a clever gravity assist off Duna or the Mun. This is beyond my skill and could add many years to the mission 3. Accept you wont capture kerbin system on 1st pass, orbit the sun a few times and the next encounter with Kerbin will be easier. This also takes a lot of skill and can add decades to the mission 4. Put a 1.25m heat shield between the nose cone and the cockpit, and a decoupler in front of the heat shield. When re-entry is your goal, decouple the nose cone, exposing the heat shield, and come in prograde, let the heat shield do its job Just realised this won't work. The wings will still explode. In short term, high intensity heat scenarios like this, they aren't much tougher than the cockpit. - it's down to the max skin heat. The mk1 crew parts have low tolerance for internal heat, which is due to prelonged, less intense exposure. To be honest i never considered you'd want to go to Dres. I just built this as a demo of what's possible with this tech level. In my career games i'm usually still on minmus at this point. A craft like this might get used for Going to the Mun and driving over the surface biomes Visiting Mun and Minmus in same mission - some tourists ask for this Gilly Duna, this craft is VERY suited to flying around there and getting thermometer / barometer readings from the biomes in its lower atmosphere. If you unlock stronger landing gear, perhaps some verner lift thrusters or some drag chutes, you could actually land with this plane EDIT - On second thoughts, are you wanting me to design a mk2 cargo bay spaceplane based off panther and nerv tech ? How many cargo bays long does it need to be, if you'd prefer to use it to lob a capsule at places like Dres instead?
  3. @sturmhauke @4x4cheesecake I did a rocket powered horizontal launch once and was thinking of trying a rocket sled launch with recovery chutes for the sled after the failure of my latest vertical launchold vid - As for jet engines I guess the problem is that in the real world you don't get a sufficient fraction of orbital peed out of them (real scale orbit is mach 21) to justify their weight. I have built many craft with dispoable jets however - those jet pods on top of the wings come off at mach 2.5, then it's got 3 nervs. Wing loading and TWR are similar in both modes so it's fairly easy to control, unlike a shuttle stack in the atmosphere.. You could say "jets ok sol long as you launch vertically", but then i'd just use a cluster of fleas to throw me to 200m , then level out and fly the rest of the climb like an airplane.
  4. Is there any clarification on the rules of this thing, as to what precisely constitutes a "space shuttle"? I feel as though i should make it resemble the historic system as much as possible, but there's three things i always struggled with 1. vertical launch.. is it ok to take off horizontally instead, that way you don't need your highest twr right when your vessel is at it's heaviest (Partially solved with an ungodly huge cluster of Fleas and Thumpers for a "stage minus one" , that only gets you to 100 m/s . 2. no jet engines on launch (jets for landing are ok ) ... is that right? Makes for ginormous rocket fuel tanks 3. does it have to have external tank underneath and boosters either side of the external tank.. or is it ok go with more symmetrical layouts clustered around the fuselage :-) Would love to do the Duna challenge someday :-)
  5. Alright, I'm in a much better mood now that the damn thing is finally finished than I was after two days of editing CFG files in Notepad and reloading KSP every time the game bugged out. If you think this thread should be moved, let's tag a mod and get it done. I'm wondering what to try next. Non nuclear looks like it's pretty high on the list. So, no cryogens in wings, and I want to avoid nasty hypergolics that made the space shuttle so expensive to service (all the technicians having to wear space suits just like the astronauts). Should the fuselage tanks be allowed cryogens? Unless we have Kero/HTP at 250 seconds as our sole fuel, i guess we'd have to allow that. Ice hitting the wings and causing another Columbia disaster ? Well, I suppose it could have been designed out with enough effort,. More robust materials on vulnerable TPS sections even if they require active cooling as a result. Or better tank insulation /warmed skin layer to inhibit ice formation. Also, SpaceX seem to consider Methane and Oxygen to be storable propellants now. So - 1. Kerosene in wings, Methalox in fuselage , boosters of whatever. Have kerolox and methalox engines on orbiter, the kero ones providing a bit of extra slam down on the deck Or 2. Hydrolox fuselage with Kerosene wings. Not all the Kerosene gets used on launch, some (and some LOX) is kept behind for use in orbit as OMS - also verner thrusters can run off this stuff. What about my objection to Hydrolox on account of density? Well the thing is , hypersonic lift/drag ratio is no longer important. In KSP, wings can assist ascent using low TWR NTR and jet engines. But since we're using neither, its easier to just have a high TWR and get out of the atmosphere ASAP. Only unlike the original shuttle, this one does not need to crossrange glide on re-entry to land back in USA after being in an inclined orbit over enemy territory to deploy a spy satellite . I suppose we''ll keep the wings so we can still call it a shuttle. Given all this, might as well have an external tank... but i don't think i can handle the off-axis thrust this comes with, atmosphere or no. So I'm tending towards 1) if we can get by on Methalox ISP..
  6. Alright, fair enough. I'm probably being too thin skinned or too much of a "snowflake" here. I posted in this section of the forum hoping for more info on certain propellants than i might get in SpaceCraft Exchange or on the Shuttle Challenges and Mission Ideas thread. So, this is where I am, and if someone wants to criticise the entire concept and tell me i shouldn't undertake it at all that's part of the deal. People who don't like the Space Shuttle, don't like space planes, and who don't like nuclear propulsion in the ascent to orbit are a lot more likely to be of that opinion. I felt as though some of the comments were "cheap shots" and were just derailing the discussion, but in the end it's only my opinion and I need to man up and learn to take it. As regards vacuum nozzles.. well, the real STS has them as will the SLS so if its a mistake i'm not the first person to do that. Though the boosters provide most of the thrust up to 10km or so anyway, by which point vacuum nozzles are outperforming sea level ones, and by that point it still has a very long way to go till orbit velocity. Why do i insist on building these annoying winged craft that fire their nuclear engines within the atmosphere ? Because otherwise I don't see us ever having mostly SSTO or mostly reusable vehicles. Also I just like building these kind of craft, but because of the forum i'm in as you point out i can't hide behind that shield. Flyback boosters or just learning to mass produce really cheap expendable launchers might be the better approach, perhaps yourself and @wumpus and @Xd the great think along those lines? I had a similar thread concerning Lunar Oxygen harvesting, someone kept posting one line objections. He eventually declared his own position - that he was against visits to any celestial body, that we should focus on space stations and orbiting power arrays, which made his earlier postings more understandable from my point of view. Everyone's entitled to their own dreams and opinions, though if you insist on having the last word you could shoot back with "this thread is about your idea, mine are not up for discussion" and " opinions got nothing to do with it, it's about cold hard facts " (the facts back me up AND YOU;RE WRONG being strongly implied :-)
  7. Well, here's the config i finally settled upon - , ISP of 520 in NTR mode, SL 300 (assumed similar nozzle to RS25), thrust of 110kn, mass 0.85T Yes one large engine makes more sense an am not sure you can put a critical mass of reactor together that small, but it looks really silly unless you can mod something like a Rhino visual model on and i don't know how to do that. Maybe all 3 turbopump/bell nozzles are running off the same reactor? Thrust is 196kn in HTP Afterburner mode, Vac ISP 420 and SL to 330. I made an assumption that the extra mass flow and reheating effect of the combustion would make it less overexpanded. NH3 flow rate is about the same in both modes. I had a big rethink about the flow ratios for HTP afterburner. Running an fuel : oxidizer ratio of 4:1 meant i was running out of liquid ammonia in the fuselage way before the wings were out of HTP, even if i stayed in afterburner mode the whole flight. HTP is about twice as dense as Ammonia. Thinking about it, in a hydrolox engine the air fuel ratio is 2:1 and each oxygen atom combusting is heating products with a total atomic weight of 20 by 3200k. Assuming an NTR core temp of 2750K and stuff losing another 500 or 600 K from expansion by the time it hits the afterburner, a small amount of LOX is able to bring the exhaust stream up to temp in LANTR. But the exhaust products of a NH3 / HTP rocket have much greater atomic weight, so i came up with a mixture that's only 60% rich of Stoich for the afterburner.Some small Kerolox boosters help us up to mach 1.5 or so. Reliant engines are barely enough for a vertical launch - it comes off the pad like a Saturn V. The modded NERVs also lack Gimbal, but TBH it's not such an issue when you don't have the off - axis thrust the real orbiter did This kind of ascent is even worse for heating than re-entry, because you are heavy with fuel, and operating at a lower angle of attack (because you are trying to minimise rather than maximise drag). But , the propellant heading to the engines go through a heat exchanger for some kind of cooling loop, an option that's not available on re-entry. At least you're getting some heating of the fuel in exchange for all the friction. Science Lab in orbit , yay. Now do that on a real scale solar system... :-o
  8. You have over a thousand posts so I am sure you must know this by now, but in case any person reads this and gets the wrong idea.. The exhaust of a solid core nuclear thermal rocket is not radioactive. The fuel and the byproducts of the reaction stay inside the reactor, unless it has a meltdown It's going to emit x rays and gamma rays when operating because for weight reasons it's probably only shielded on the side that faces the crew module. You don't want to get closer to a mile to this thing when the engine is firing, for that reason. But X rays and Gamma rays are not persistent, as soon as the ship leaves the area or cuts its engine they are gone. What the general public fears about nuclear power is persistent stuff, ie. when the environment gets contaminated with atoms of radioactive fuel or waste from a containment breach. These atoms are unstable and each one will, after a random period of time, undergo fission and when that happens, and X ray or Gamma ray is kicked out, hence the ticking geiger counters. This is bad if it happens to be inside your body at the time, because the contamination got into your water supply. In terms of a launch vehicle with an NTR, there is obviously the risk of launch failure. Apparently the reactor itself is built of very strong stuff and can be made to survive a terminal velocity fall to the ground (that's why they are so heavy) but obviously any cooling systems will have been destroyed, even shut down reactors produce residual decay heat as the reaction byproducts under go further decay to their final products. The level of decay heat is dependent on how long the reactor has been run for and at what power level. The reactors in a power station operate for months on end at high output, so decay heat can be substantial after an emergency shutdown, which is why Fukushima melted down after the cooling system failed even though the reactor was shut down as soon as the earthquake hit. Would i be having to fend off arguments like this if the thread was in "The Spacecraft Exchange?" I am trying to build a mod shuttle system because all the stock ones i could come up with have been awful to fly and made no sense with the game mechanics. The Role Play / Science Fiction aspects of this are just a bit of fun
  9. I got my figures from this site, http://www.projectrho.com/public_html/rocket/enginelist.php#ntrsolidcore it mentions 3000k, and quotes Exhaust velocity (H2) 8,093 m/s Exhaust velocity (CH4) 6,318 m/s Exhaust velocity (NH3) 5,101 m/s Exhaust velocity (H2O) 4,042 m/s BTW, don't go to that site unless you don't mind losing an afternoon. When you divide those exhaust velocities by 9.8m/s this converts into an ISP of 825 for Hydrogen, 644 for Methane and 520 for Ammonia. I'm all for low balling the numbers a bit and playing it safe, not only is this thing carrying people, it's going in an atmosphere and is meant to be re-usable. However Project Timberwind in 1991 supposedly had 1000 ISP from hydrogen. Regarding LANTR's afterburner, it is correct that adding even one eighth of the amount of oxygen as required to burn the Hydrogen stoichiometrically doubles the mass flow, because oxygen is so much denser than H2. However, is that the ONLY factor? Bear in mind, the oxygen never goes through the reactor, it is dumped into an afterburner at the top of the nozzle. The combustion of the hydrogen and oxygen must raise the temperature of the gases , promoting greater expansion. I mean, if combustion of 4KG liquid oxygen with 1KG liquid oxygen is able to take these materials from cryogenic to hotter than the core of an NTR, even though half the hydrogen is not reacting because we're pig-rich, then if we're starting with gases that are already at 2700k from passing through a reactor, then they're going to end up even hotter surely?
  10. AeroGav

    [1.3] Real Fuels v12.2.3 July 30

    Good work... that's so much more readable too than how it looks in Notepad. My justification for thrust and ISP values are in this post HTP is an Oxidizer and NH3 is a fuel, apparently it gets about 260 seconds impulse at sea level. I did some dodgy extrapolation from the LANTR project, the performance charts showed that if you add enough LOX to burn about one eighth of the Hydrogen flow, you double the thrust whilst losing one third of the ISP advantage that LH2 NTR has over Hydrolox. Of course it may well be that a litre of HTP results in a lot less energy release than a lire of LOX as used per LANTR... feel free to share your thoughts on a better estimate. My main doubt is thrust. I based the thrust values off the TWR achieved by project Timberwind, but that's likely far too high for stock scale KSP .
  11. AeroGav

    [1.3] Real Fuels v12.2.3 July 30

    Damn, the original file as seen in Notepad looks like everything is on the same line, but putting an [ENTER] between the two fixed that error. Looks like Notepad is screwing things up by hiding the formatting characters, causing extra ones to be added or removed from the file without fessing up? I did look at your spreadsheet , but couldn't figure out how to use it, especially for a bi modal engine like this. Unfortunately, I'm still having issues with the modded engine. The ISP values are wrong in pure NTR mode, the Vacuum ISP is too high and the Sea Level ISP lower than I specified. Parameters I was trying to get - Mass 0.75T NTR Mode Fuel LqdAmmonia Ratio 1.0 Thrust 200kn Vac ISP 520, Atm 300 (observed values of 925 and 286!) Afterburner Mode Liquid Ammonia Ratio 1.16 HTP Ratio 0.1 Thrust 400kn Vac ISP 450, Atm 360 (observed Vac ISP of 620?!, sea level ISP correct) Here's the butchered file - https://www.dropbox.com/s/nsoob4svbflvxhi/Squad_NTR_modularEngines.cfg?dl=0 ... and this is the file before i started hacking it (from the stockalike engine pack) https://www.dropbox.com/s/yhcb9gh4ovq1vup/Squad_NTR_modularEngines.zip?dl=0
  12. Derek, there's a couple of ways of reading this statement. Hostile reading "you are not aware of the limitations of the game" "this is not a worthwhile exercise so you should cease and desist" because "this kind of fanboyish garbage is annoying " More liberal interpretation : That you also think Ferram is not perfect and the issue I identified with hypersonic aerodynamics is a show stopper in your opinion. Or something like that. The thing is there is not much actual information in your post which makes it more likely to be read as a put down than something constructive. Also, from our previous dealings with each other, If you had anything to say about this project, it wouldn't be positive ! I'm struggling with modding engine config files anyway. Might take another look at this next week, if i decide it's worth it.
  13. Before anyone shouts at us, remember it is NOT an SSTO - the jet engines are on decouplers, and the value of the discarded components comes to 7150 Kerbucks, though he orbiter itself still has a value of 52,819 Kerbucks after staging and empty of fuel. As regards re-entry, if you leave SAS set to Prograde in surface mode it will, because of high lift drag ratio, keep skipping off the atmosphere and will end up much further downrange than you think. In fact if you retro burn to an AP of 35km you are likely to come down at this point - after gliding round the entire planet one more time. To get back in a reasonable timeframe (and without cooking our Kerbals unnecessarily) , i'd say use the desert on the continent west of the space centre as your aim point, and retro burn until the blue trajectory line shows you will impact the ground in the middle of the desert. Come in with the nose pitched at 5 degrees above prograde, and watch your trajectory from the map mode screen (but keep the navball visible so you can see if the plane is doing anything silly). As you get down below 45km the atmosphere should start to bite and the blue line moves downrange. If you think you might be undershooting, go to prograde hold mode for a better glide rate, if you think you're overshooting, pitch up aggressively. Of course you can also use the engines but that's cheating.
  14. He's giving a sea level rating of 380 to LH2 LOX, so just under 310 in Vacuum?
  15. I'm starting to mess around with modded KSP again, and am brainstorming for a near future, Space Shuttle 2.0 concept. To this end I've installed Ferram Aerospace and Real Fuels. The orbiter is going to have liquid ammonia tanks in the fuselage feeding a nuclear thermal rocket. The TWR can be below one as it will use wings for lift in the upper atmosphere, and I'm proficient at doing these "wave rider" style ascents. Why Liquid Ammonia , and not Hydrogen ? It is storable, so this can double as our OMS system. It is liquid at room temperature with a modestly pressurized tank, which is a good thing given that the Columbia disaster was precipitated by a chunk of ice breaking off a cryo tank. Relatively non toxic, at least compared to the hypergols Unlike Methane, it won't leave carbon deposits sticking to the inside of the reactor. Scraping those off is a job for someone you don't like. It is much denser than liquid hydrogen. This is important because Ferram does not model compression lift, so lifting body designs like Skylon that have plenty of internal volume and reasonably good hypersonic lift/drag ratio aren't possible. The fuselage needs to be slender like on a conventional supersonic jet. FWIW, NTR are commonly quoted as giving the following ISP with different propellants - Liquid Hydrogen - 900 Methane - 640 Ammonia - 520 . However, we've also got some liquid volume in our wing tanks, what to put there ? Due to icing, cryogens are out of the question. Ammonia also appears to be out - the pressures to keep it liquid at room temperature are not large, but too high to make a mass efficient non-cylindrical tank. One option was Kerosene. Combined with a bit of LOX tankage in the fuselage, we could run a Kerolox engine to assist the NTR during the early part of the ascent, when the craft is most heavy with fuel. However, we could fill them will High Test Peroxide instead. This could be injected into the Ammonia stream that's just been heated by the reactor as an "Afterburner", rather like the LANTR proposal, again during the early part of the ascent. 2NH3 + 3H2O2 = 2N2 + 3H2O Any idea what kind of ISP, propellant ratios and thrust i can expect in this config ? Stoichiometric hydrogen/oxygen has a propellant ratio of 1KG hydrogen being burned with 8KG liquid oxygen. Actual rocket engines run rich, to take advantage of he lower molar mass of hydrogen, ratio of 5:1 or 6:1 . LANTR could run richer still, 3 to 1 or less, because combustion does not have to supply all the heat to expand the products, thanks to the reactor. According to this PDF, https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930085381.pdf page 41, the ISP of this combo when burned as a chemical rocket is rather low , 253 seconds, but same source quotes hydrolox as about 345, which also seems low ball - are these sea level ratings?. Unlike most fuels, Stoich gives best ISP, with Ammonia about 42% of the propellant by mass. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950005290.pdf As regards the afterburner, i'm wondering if we can meaningfully extrapolate anything from the LANTR data - TWR doubles at a mixture ratio of one (an oxidizer volume only 20% of that which gives best ISP in chemical hydrolox), while ISP only drops a third of the difference between the hydrogen NTR value and the chemical hydrolox value. So, dodgy guesstimation time - NTR (Ammonia) ISP - 520 Ammonia / Peroxide ISP - 330 Afterburner ISP - 460 ish Not bad for relatively dense, room temperature propellants (the alternative are hypergolics). What about TWR ? The in-game NERV engine appears to be based on 1960s technology, with a mass of 3 Tons and 60kn of thrust. If we look at its late 80s counterpart, Project Timberwind, it does slightly better - https://en.wikipedia.org/wiki/Project_Timberwind (nothing to with Justin Timberlake) Timberwind 45 has half the mass (1.5 tons) and thrust has improved just a bit, to 441kn That's still only half the TWR of the Space Shuttle Main engine, and the Merlin 1D (nothing to do with boy band One Direction) that SpaceX use on their Falcon series, has a TWR 50% higher than the SSME. But still, Timberwind is nowhere near the lead sled that is NERV. On the other hand, Orbital Velocity in stock KSP is only 1/3 real life, so we don't want our engine too overpowered. Why not install real scale solar system ? Well, then you run into FAR's inability to model compression lift and before you're halfway to orbit, you'll be seeing lift to drag ratio below unity. One major "known unknown" (thanks, Donald Rumsfeld) is the combustion speed of ammonia / HTP mixtures. LANTR injects oxygen after the throat, at the start of the bell nozzle itself, so as not to cause back pressure/choke problems for the reactor which is optimised for pure NTR operation. But, flow in the bell nozzle is supersonic, so not a lot of time for combustion. If combustion takes too long, the mixture will have travelled some distance down the nozzle before reacting, and thus will not get to expand as much as it should before exiting the nozzle.