Anquietas314

Going by the 21.43 tonnes of ship, and the fact xenon only comes in 400 and 700 quantities (assuming you launch with full tanks - why wouldn't you), I'd say the number OP stated was correct. To save OP the effort (and messing up the calculation): deltaV = 9.82 * 4200 (ISP) * ln(21.43 / (21.43 - 2.720)) = 5598m/s give or take. Note that the constant in KSP is 9.82, not 9.81 as in Tsiolkovsky's equation. It has nothing to do with gravity though.

You're going to need more than 8 jet engines here, especially with the added mass of dedicated rockets. The spaceplane I built was a similar size to yours and used at total of 12 turbojets plus I think a skipper as the main rocket engine. It could lift an orange tank and the big RCS tank at the same time, full (but it didn't quite remain stable after dropping off the payload :/ problem was mass distribution). if it's taking you 3/4 of the runway to reach 90m/s, you don't have enough thrust. You do however have plenty of lift - too much even - which is why you can take off with the payload at what is quite a low takeoff speed. Ditching some of the wings will increase minimum takeoff velocity, but also decrease drag. If you have enough thrust you should still be able to take off. Also remember that high up, you're moving much faster, which means drag is significantly higher, even in spite of the thinner atmosphere. This tails off above ~30km; by 40-50km it's almost nonexistent, which allows you to maintain a low throttle (to ensure you get out of the atmosphere) and keep accelerating using turbojets if you have enough intakes. Your payload fraction is probably fine. As I said, my spaceplane was a similar size and could lift a payload of around 40 tonnes (orange tank + rcs + 2x large docking ports). Your main issue is insufficient thrust/intakes.

Blame the outdated KSP planner I had to use for that. Apparently the skipper was buffed in 0.24. Still, the result there is sensitive to the command pod used (and thus payload fraction). The previous 5 posts could have been avoided if you just posted the specs of the test rocket as asked. Please do that. Even a screenshot will do.

This would be fine, if you did indeed build a rocket that fits this specification; you have so far provided no evidence of that, since your description was "a Skipper and with MechJeb set to limit to terminal velocity", which says nothing of the deltaV capacity of that rocket, what fuel tank was used, etc. For example, say you had just enough fuel to hit 10km. Using a mk1 command pod as the control part, a single Rockomax X200-8 would be just about enough fuel, and of course you can set the TWR via the thrust limiter. That makes your "payload fraction" at 10km, including engine/tank, is 4.5/9.3 = 48%, or in other words fuel is 52% of your launch mass. That means your TWR increase is approximately 108% - much more than your estimate.

Two things: 1) If you're going to use turbojets anyway, you'll quite possibly be better off ditching the RAPIERs entirely and using only turbojets to get to space, then using a high-ISP engine (nukes, poodle, etc) once you get there. Turbos have higher thrust than RAPIERs. 2) You don't really have enough thrust for the mass of that plane; that's most likely the reason you need such a high AoA between 1.5 and 15km. Roughly speaking you need a minimum of one engine per 13 tonnes of aircraft, which you have, but you want more than that to make it fuel efficient for getting to space and easier to fly. When you say it gets off the runway, does it lift off while still on the runway, or go flying off the end of it, but stay in the air afterwards? You should probably balance your intakes better too; right now the turbojets are getting a decent bit more than the RAPIERs, assuming intake and engine placement was done using the ordering trick and the intakes nearest the engines are for those engines. Also, 26km isn't really high enough to be switching to rockets. You want to be doing that at more like 36-40km if you're using RAPIERs. If you use only turbojets, you can actually just get out of the atmosphere using those and not switch to rockets at all until you're in space. This probably means you need to add a few intakes

The option is at the bottom of the page when you're posting a new thread. It might be available editing the OP too, but given I haven't posted many new threads, I'm not sure about that. EDIT: Checked one of the few threads I have started; nope, can't add polls to existing threads.

You are quite correct - I've had this issue quite a few times in 0.90. The problem is that, at least some of the time, the game doesn't add an invisible "extra" stage before the one at the bottom of the list; it used to. Instead, just add a blank stage at the end. When you stage it everything else should behave normally. Note that you can't always rely on VAB staging; consider ships constructed in orbit via docking.

There is an alternative solution, which incidentally is handy if you use B9 and don't want all of its colossal memory footprint: Procedural Dynamics, AKA Procedural Wings AKA pWing . It is however a bit more complicated to use than normal parts, but I found it very effective for building a Mk3 spaceplane that could lift a full orange tank (and a bit more) to orbit. Sadly I don't have a screenshot of it to show you (unless Pecan wants to dig it out of his inbox - sent items never seems to work and my gaming machine is broken atm ).

Aside from ctrl+z or just putting the part back correctly (may not have desired results if you have intakes/jets), sorry no . Unless of course you saved shortly beforehand, in which case you can just re-load it .

Normally I would agree, but if having to fix the config of a few simple things manually prevents having to deal with a crash or otherwise useless/broken craft file, I think that's a small price to pay . Fuel would have to be something you'd reset anyway since some of it will have been used in the persistence file (unless it's sitting on the launchpad/runway of course). There is also the small technicality that if you don't write a blanket solution, then you will need to have a list of things that you should reset just to make it function, so really it's a question of which approach is the least problematic.

Except you're only testing a rocket to 10km, which can easily be a very small rocket that's incapable of going further, so it does matter. EDIT: The reason it matters is because, with rockets with a larger payload fraction, the TWR will increase much more slowly, which means you'll spend longer far below terminal velocity, meaning gravity losses are much more significant. This is also ignoring the gravity losses from performing your gravity turn, where drag losses become more and more irrelevant as you ascend. Depending on TWR in this phase, you may or may not be able to perform it efficiently while maintaining an ascent (demonstrated by OP's rocket).

That's an awesome shuttle - easily one of the best (prettiest) I've seen, I see why you were so determined to keep it . Everyone? I didn't even help ; you should leave me off that list .

I'm not sure if this is possible via KSP's API, but could you not reset all parts' err... tweakables? extra data? ... whatever it's called, to the defaults? I assume you mean things like activating reaction wheels or other stuff that can be changed in flight but not in the editor. It seems like that would solve the problem if it were possible, though it might mess up stuff like procedural parts. Nice work though

You've actually got that backwards If you increase your orbit (by which I assume you mean increase apoapsis or periapsis or both), you do initially go faster, but as your orbit carries you outwards, you slow down - so much so that things below you (either on the surface, or in orbit) can catch up!. But yes, in your case increasing the orbit is probably the best way to do it.

Heh, that's a relief Well, the mistake was slightly more than an extra zero...

Hmm, okay. What was the payload fraction of that rocket? If you just stuck a fuel tank to a capsule/probe and added the skipper, TWR would increase quickly enough that the difference would indeed be small.

Turning 90 degrees would be a bad idea - it needs to be about 45 degrees to miss all the panels, assuming they're still an issue while retracted.

First, horizontal ascents are more efficient than vertical ones due to Oberth effect and a few other details; think of the model as a sort of lower bound on deltaV and upper bound on efficiency losses. As I said earlier, you can directly compare the gravity and drag losses between low and high TWR using MechJeb. I would myself, but alas, gaming machine is broken . In the atmosphere, a "high" TWR is anything over 2. We're talking about a rocket with a TWR significantly less than 2, and you really won't reach terminal velocity (or even near it) at all in that situation (follows pretty much from its definition). EDIT: I will add that, with FAR (and IRL), a significant part of the reason lower TWR rockets perform almost as well is due to the lifting body effect and starting the gravity turn much earlier than you do in stock. I suspect this may be part of the confusion here. /EDIT As for the first 10km, you are aware that pretty much half of the deltaV spent to get to orbit is done so during this part of the ascent, in the optimal case? Low TWR means large inefficiencies due to gravity losses in this stage; in my experience that can be as much as 50-60% of the deltaV spent with a very low TWR rocket. The excessive drag losses can be avoided by throttle control; KER is especially helpful for that, mostly due to the atmospheric efficiency and terminal velocity readouts, which of course will also tell you how much you're losing due to gravity losses.

Psst. Your browser has this thing called zoom. The shortcuts are typically ctrl - to zoom out, ctrl = to zoom in, ctrl+0 to reset. If you look closely you can see that the two symmetrical things are basically identical landers. They seem to be independent of each other seeing as they're both attached at the back end using docking ports, and there's nothing visible connecting them otherwise. It's not a great camera angle, granted.

Look closer. The engines are the tiny little rockomax radial engines. It's not massive amounts of thrust, but those engines are powerful enough to get off Duna no question. I'm concerned about the amount of fuel though.

True, but the exhaust might be close enough for it to still be a problem even with them retracted. Gigantors stick out quite a bit

On closer inspection, the LV-Ns are mounted on IR servos - the placement seems a bit weird, but it might be possible to turn them around. You'll need to undock and rotate the engine section though - it would currently be firing them at the solar panels which causes all sorts of nasty . If that doesn't work you could try undocking the big decoupler and just docking the engine section the other way round. I'm guessing you have the decoupler as an "emergency" measure or something, but it's really not necessary given docking ports serve the same function

Yeah, but you can always use the nukes at low throttle. It'll take forever but it won't matter too much for total deltaV cost.

Well, it looks like it has enough fuel to get there and back . You'd be better off making it a puller rather than a pusher though, but it should be perfectly usable as is. Ditch the big engine at the back though - it'll just waste fuel and make the thing wobble like crazy. I'm not sure from your screenshot if the lander design is able to launch from duna though; it's a fair bit smaller than one I would build, but it should be adequate for Ike .

It's much more than 300m/s. From the model I linked, that 70% is (roughly) 70% of the total to get to orbit. For kerbin that's about 3,500 m/s, give or take, assuming SSTO as mentioned above. Granted a lot of that is unavoidable due to gravity turn/atmosphere etc, but a decent chunk (roughly a third?) of it is.