paul_c

I managed an insertion at 127deg for Minmus, there was a satellite contract for 300 x 360km, 180deg inclination. However, obviously the speeds at Minmus are a different kettle of fish. The strategy was to do a trans-Minmus burn to aim directly at the moon (no Pe shown), then do a normal/antinormal at the midpoint. Of course, if you lose comms at the midpoint.....

I've looked at combining missions where they fit nicely together. About 70% of the time I do the career stuff, the other time its my own personal curiousity. Here's an interesting one....is it possible to get a gravity assist off the Mun the "wrong way", ie approach it from further forwards then, figuratively speaking, "turn right" (if looking from above N pole)? I've never done it like that but I don't know if its simply not possible physically, or its just that the normal direction of entering the Mun occurs say 95% of the time. The reason being, I have this: Ap: 14,661,033m Pe: 3,393,304m Inclination: 180deg Argument of Periapsis: 357deg I don't fancy the fuel bill for going "the wrong way" then going uphill A LOT!

ETA the other issue was CofG when flying stage 2, I had to have a few goes. First time it did a loop the loop, I recovered but it was too late, I squeaked into low orbit but with a bunch of fuel not there. So I had to spend a bit longer rearranging where everything fitted together to get a nicely flying rocket too.

Phew! The other aspect of the trip, landing on the Mun, has been done. It was an unmanned basic lander but with a service bay and some scientific instruments - and a big fuel tank. I need to decide if I'll risk another T/O and landing on the Mun or just come home. The little satellite's contract is also fulfilled now, here's the total dV spent: Inclination change, 90% of the way to Polar: 181dV(Extra burn needed on Mun lander to lower its Pe to 15km: 55dV) Raise Pe: 144dV Inclination change #2: 66dV Pe adjustment (down! I should have remembered, an inclination change tends to circularise the orbit...): 9dV Ap adjustment: 15dV TOTAL 415dV (could/might have been 397dV) Of course, there's the extra rocket fuel and size for its additional weight piggybacking - in total this satellite weighed 520kg. I had loads of fuel too, I could have probably 1/8 filled the tank (instead of 3/4 filling the small doughnut one) and gotten its weight down a bit more. But I had no idea what the requirements would have been.

Do you mean using solar panels to provide the power (every satellite contract I've seen has a requirement to generate electricity) or something else? Normally I've put 1 or 2 (depending on equipment installed and loads) fold-out panels. In this case, I was going ultra-cheap so used the small flat panel and made a mental note to keep it facing the sun.

Yes, its one of those funny assignments - I don't know if anything like that would be asked for in real life. I'm flying the mission now, and its a bit brain-wracking managing the both at once (the small Polar sat has 1 panel for cost/weight saving, the Mun lander has fixed panels covering 4 sides because extended ones could be damaged in a rough landing). Fortunately I stuck the upgrade aerial on the probe, since its 38Mm away at the moment. Didn't want to risk it on the Mun lander so it has 4x basic ones, fortunately I have 3 relays orbiting Mun but I need to keep track of it, especially since I chose to launch at new moon. I could always park it and wait for full moon though, to play it safe. So far, its certainly been a "cheap" launch: Inclination change, 90% of the way to Polar: 181dV Extra burn needed on Mun lander to lower its Pe to 15km: 55dV I still need to jiggle around the orbit the hard work is done now, its just tweaks.

Its a Kerbin orbit. I've come up with a better idea - I've stripped down the satellite to the bare minimum. However, building a rocket cheap/small to just about do it is proving a bit more tricky. I tried SSTO (to save on coupling, another engine, etc) but it didn't work. And then I tried a more conventional 3 stage (1st to about 10000m, 2nd to low orbit, 3rd on the sat itself) but that proved to be twitchy to drive so although I can get it into space, getting it nicely onto a low orbit is proving troublesome. So.....since the satellite is only about 300kg I'll piggyback it onto the next big rocket going to the Mun. I'll need to do some deft switching of control to juggle the both; or I could just detach it at any point in between the Mun mid-course alignment burn and the Mun retro capture burn, to send it onto an eccentric Kerbin orbit. I will do it earlier than later, then do a tweak of some kind at some point, so it doesn't keep re-encountering the Mun and throwing it off or possibly crashing it into Mun or Kerbin.

Here are the contract specs: (have a thermometer and an acceleratometer) Ap: 30,390,457m Pe: 30,278,764m inc: 90deg LAN: 195.3deg If it were an equatorial (or near) inclination, I know the below would work out good. But it being a Polar orbit, normally the thing to do would be to launch to the North straight away. I have no idea of how to (precisely, or even vaguely) calculate the delta V requirements of a satellite launch. All I know for now is, the approx dV to get to LKO; to get to the Mun; and to get to Minmus. But things in between, not so sure of. So, the idea is: 1. Launch to LKO, try get inclination 0.0deg on the way up (to save fuel later setting it; or to mean I can aim for the Mun at any point rather than restricted to ascending/descending node). 2. Aim at the Mun, but don't aim for a low Pe, instead look to achieve a sufficient gravity assist to give a large eccentric Kerbin orbit upon Mun escape. As large as possible. 3. Once at Ap, perform the inclination change and also burn pro/retro as needed to 'set' the Pe to 30Mm 4. At the Pe, perform a retro burn to set the Ap to 30Mm I (think I) know the 'cost' in dV of launching Polar - you lose the benefit of the eastwards launch, by the speed of an object (that object being the launch pad of KSC) on the surface of Kerbin - I'd need to look up the number. And I think 2-4 of the above is basically a bi-elliptic transfer, albeit the initial elliptical orbit powered by (the gravity of) the Mun, instead of rocket power. But its all a bit relative?

I think that will be my strategy for now. I tried the "aim for the centre, Pe isn't even there" and all it meant was a fair mid-course burn. I figure the best way, is to get a tight as Pe as terrain will allow, straight from the prograde burn from Kerbin, then do the minimal retro burn to capture the Minmus orbit, then once at the top, do any gross correction of inclination there. Then once at Pe again, circularise to a lowish orbit ready for a landing try.

That's a handy tip! I gave up on the aerial in the end (there's the one on the controller and the cockpit for other non-science comms) and the science is in the storage box which is coming with me all the way to the surface of Kerbin.

Next problem.....I thought this might come up.....is it possible to configure something during the build, to indicate that the engine is downwards (well..it was sideways in the VAB) mounted? The nav ball isn't giving the correct indications, I had a job getting into a stable orbit with the wonky controls but the RCS saved the day and I used it instead, to stop my brain hurting. But I need to get out of Minmus' orbit and home and I don't fancy doing those burns the wrong way! I guess I can try little blips of the throttle at different positions and suss it out. It wasn't such an issue during the landing because I was able to visually orientate myself, and in any case I'd put the mothership into a low orbit so there wasn't too much to do orbitally, it was a pretty quick transition to level (well, controlled slowing down and descending) flight.

No mods installed (yet). Forgot to mention too, the horizontal low slung concept worked! Just a few tweaks needed really. Landed at an angle on an almost 30 degree slope..... Many thanks for the replies

Aaaah there's no hope then! At least not for today. Oh well, I'll put the little fella back on his feet - strangely, in my quest for weight saving I didn't think to fit solar panels on the underside.....and the top extended one broke off. Also I broke the aerial (it WAS fitted to the underside, for protection) but my no stars engineer can't fix it, is that the way it is until he gets a gold star or two? Lucky I've not constructed and put into orbit 7 space stations all with the docking port fitted the wrong way round......

Ok I know its not orthodox but the guy who sold me them said there were powerful magnets which should dock them together. The science lab space station fell over during landing but is otherwise undamaged; and in fact seems to work better for crew access etc on its side. The horizontal lander is a bit unusual, in that it has a centre-mounted, downwards facing engine and also it can safely roll over onto its back to offer various different height with which to mate to other craft. I think they're close enough - have I fitted the docking connectors properly (eg not backwards??) Do I need to target one with the other, or anything like that? Are my angles okay??

I suspect there is a relationship between approach speed (which would be higher from an eccentric orbit ie distant place/Ap) and ideal Pe. We are fortunate, KSP is quite forgiving (on Kerbin at least....don't know about the other planets yet) with it and there's a wide envelope which will "get you home" - and the Time Warp, to make 2+ orbits okay. The Apollo crew didn't have that luxury, they had limited power and CO2 filters etc etc....but that's the difference between real life and the game! Also, I dare say an orbit in outer space is somewhat predictable due to the vacuum, while an atmospheric re-entry on a real planet needs to deal with variations in the upper (and lower) atmosphere weather and many other considerations, like not landing over populated areas etc. Its all fun! Anyway, just a quickie, I've now landed my contraption on Minmus but I can only transfer certain and not other experiments - I can't transfer the Science Jr and Seismometer results (but have transmitted them). I know there's some experiments which it won't store, are these some of them?

Update: I tried a "test" scenario. I built up a basic design rocket which I knew would make it into at least low-Kerbin orbit; and configured a command capsule + heatshield then Science Jr + heatshield, and added a few modules to it (goo, temp, pressure) and a chute. I figured, with the dV I had spare - around 600m/s - I could take it out at least part-way to the Mun, to simulate a much faster-than-from-LKO re-entry. Test 1: at Apoapsis, I did a small re-entry burn to lower the Periapsis to ~35,000m. The capsule went 2 1/2 orbits round ( I didn't monitor it closely though, I was looking at the debris/other parts) and made it back safely. The Science Jr and instruments burnt up, the only remaining part was the chute itself which went 2 1/2 orbits and landed safely - it deployed at 5000m and came down at 2.5m/s. The rocket stage survived the first encounter with the atmosphere and went round again, then survived the re-entry but was destroyed upon impacting the surface at ~280m/s, unsurprisingly. Test 2: As above but I went for 65km entry. Interestingly, I noticed the decoupling (at apoapsis) itself lowered the periapsis by 5k - something to be aware of! The science module 'bounced off the top of' the atmosphere, and went for another orbit...and another...and another. In all, 12 orbits were made, each time a little lower on the Ap (but not really the Pe) until last time round, its speed was low enough to drag the Ap below 70km and it made a safe re-entry - science recovered too. the capsule...is still orbiting....... Possible additional tests * Put some RCS onto the command module, so it doesn't make multiple long orbits round. * Work out if the extra fuel needed to carry the Science Jr (plus other instruments) 'home' from Mun, offsets the extra fuel/size (in all components) in having to carry the Science Storage Box in addition to everything else. I suspect its very much worth using the Storage Box and leaving the instruments behind on Mun. The good thing is, in my KSP Career I'd not observed the outer space around Kerbin so I gained +32.7 science points from my tests!

Aaaaah cool, I vaguely remember something similar from my boating days. Its something to do with the distance between the centre of gravity and the centre of buoyancy. When a ship rolls, it has a righting force due to the buoyancy 'pushing it back upright'. There is a metacentre and a metacentric height. And it linked to how "tender" or how "stiff" it feels. Obviously this is aerodynamics stuff, not boating, I'll need to research a bit more!

I've done plenty of flights with a mk1 crew capsule and 2-pax cabin coming down in front of the heatshield, the cabin alone is very stable (I suspect they made it so, otherwise the game would be somewhat inaccessible until you understood the navball and controlling retro position thru descent, which can be hairy). In my in-game career any new pilot with no stars usually does an orbital sightseeing thing to gain their first star and the prograde/retrograde buttons. I tried 2x2pax cabins, ie 5 all in, but personally I couldn't control it well enough. It might be possible if I understood the physics a bit more.

I'll fire up sandbox mode and do a test tomorrow, I'm quite interested if my theory is right or not now! Also I'm not 100% sure if there's a smaller parachute available in the game, I remember a smaller heatshield I think. I am in career mode now and been quite conservative with my trading in of science points for the availability of more goodies (I need to work out how to use the stuff I have so far!) I believe its how a lot of the science data in the early days of space was recovered back to earth (little boxes which were de-orbited and dropped) and weather balloons do it too.

I thought aerodynamics (or a Kerbin Space Program tweak for gameplay) tended to flip it ablator-side down, and it had a little stability in that position? With something light and not too thin/long, it should be okay? In any case, with the science storage box I can incorporate that into the return stage and leave the Science Jr and all other instruments on the Mun. Even the expensive ones.

I'll be doing a bunch of research/discovery/testing on what exactly all the parts do - or rather continuing, since I am still discovering new things as the game career goes on and so far I've been adding bits without 100% knowing what they do. Or....not adding parts then wondering why it doesn't work! The one that still gets me is the little 909 engine doesn't have an alternator, so any trip of more than a few minutes once undocked requires a decent solar setup. And solar is somewhat "breakable" on an uncontrolled landing! Also need to start looking at electrical power, transmission date rate/power draw, etc etc more methodically. One of my ambitions is to do a "powered return" of a 1st rocket stage/booster or something like that, similar to how SpaceX do it so well. Of course, with the above restriction and there being no auto-pilot (in the standard game) it means I'd need to either set up the onwards stage(s) to do their job on their own (eg reach orbit on a constant throttle and heading setting) or sacrifice it for the purposes of the ambition. All the bits are there in KSP to do it, so I bet someone has already, but it would be fun to nail it.

That's food for thought. I've tended to put 2 parachutes on any lander anyway, for redundancy. Perhaps, one on the science module, one on the cabin. If the cabin one breaks off, I'm committed to bringing the science module home. If the science one breaks off, I have a choice of trying to slow down a descent (aerobraking, 1.5 or 2.5 orbits round, etc) or just transmitting and ditching (or maybe docking with a science lab on a space station, but that has its own challenges). If both chutes are still with me, the design could have 2 heatshields (extra weight) and I can recover the Kerbal and/or science independently. Their salaries are getting expensive now, I'm running out of them! I am warming to the idea of having the science module and strategically using it, I like the fact that it mounts end-on-end but is slimmer than the fuselage, it means components can be mounted on it and are crash protected. Somewhat like I have mounted a bunch of essentials onto the hexagon in the screenshot above. I seem to be developing a Volvo Lander!

ETA (just seen other reply too) I'm now on Mk3 or whatever of my idea of what a lander might be like. Instead of lashing it together in an hour, I'm going to spend a number of days tweaking everything - engine performance, fuel liquid vs mono etc etc. A good summary to the approach might be "only take with you what you need to". So, aiming to make full use of asparagus-staged external fuel tanks, leaving whatever batteries, solar and comms behind that might be considered excess, maybe even leaving the liquid engine and fuel tanks on the Mun and planning on mono and RCS for the trip home? All the while, giving due consideration to crash survivability and redundancy. I created a save point and did 4-5 landings, some were complete failure but some were what you'd call a partial success, with bits broken off but that were only needed to get there. And that's with a basically uncontrolled crash at 30-40m/s into the Mun. It can right itself too. And the design 'kneels' on the landing struts, thus saving a ladder. Crashed and tumbled at about 30m/s. Science Jr broken off rear, a other bits damaged but in theory still usable. 5th time lucky! No damage Now, the challenge is to make the exposed parts the ones I don't want to return, hopefully break them off, or if not use a decoupler to drop them in one 'pack'!

Indeed, that's part of the problem, but also part of the fun. The challenge is you need to set the module off on its own trajectory, knowing in advance how the physics broadly works. Then possibly do some testing, for example send a same-spec module up into LKO, set it off then jump back to the tracking station to look at the performance of the 'debris'.

I'm designing a new/improved lander, mainly for the Mun, possibly for Ike and beyond later on. I think I have this right....this is manned, so obviously my last stage is a cockpit/crew bit with a heatshield and a parachute. If I do this: * Make my last-but-one stage a Science Jr module with a bunch of science instruments (eg temp, pressure etc), a parachute and a heatshield, and control these two last stages into a return trajectory to Kerbin with a periopsis of (for example) 69,000m - possibly keeping the liquid fuel engine and tanks (but jettisoning them at some point to save re-entry weight on the chute) * then using the last gasps of monopropellant and a couple of RCS vents which were at the front anyway, lower my cockpit's periopsis to (say) 30,000m Will the cockpit come back in one piece okay, AND the science module possibly do another orbit or two of Kerbin, but each time lowering so eventually it comes down safely all the way? It can be recovered maybe in a week or two. I guess I can arrange to stage the science module's chute alongside its release, but it won't deploy until eg pressure 0.04 and altitude 5000 (so I can be sure to clear terrain)? Also what's the value/purpose of the science storage box? In the above scenario, I am aiming to return the Science Jr & instruments & chute & HS & decoupler are 0.84ton all in. Could I simply attach a science storage box to my final stage, do a transfer before take off off of Mun, which would save weight and thus improve dV, then I can leave that 0.8ton behind me (I'll need a decoupler) It seems the trend in KSP is to return a 'last stage' all-in or almost all in; but in real life, when they went to the moon they even used separate descent and ascent engines, but the ascent module of the LEM was really very small (but then had to dock).