foamyesque

If you're willing to throw dV away, you can do these all in one burn, but a better choice is probably going to be grabbing a small chemical engine and tank -- Ant, Spider, maybe Twitch or Spark depending on the size of your satellites -- and use their higher TWR. With small objects and low dVs, which it sounds like is true in this application, they can wind up being more mass efficient than ions are since you can seriously cut down on your electrical infrastructure and they have better tank MRs and engine TWRs.

This actually got me experimenting and I have a proof-of-concept for the ascent; I hyperedited it to Eve and did a flying start at ~90m/s & 1.5km altitude to avoid having to deal with landing stress. (Note: KER is not processing the drop tank dV correctly. Dunno why) Working out how to land it, get it through entry, get it to Eve, or remove the rover once in orbit are left as an exercise for the student.

Send up a spar with a claw on one end and a docking zone at the other, stick it onto the main miner at an angle, so that one end is where the rover is, and the other on the ground. Then dock everything to that spar instead.

If I wanted to, I think *could* build something to return the rovers -- it's already returning 4 dudes --, but no, once they're on Eve they're on Eve forever. They aren't necessarily going to be in the *same place* on Eve, though; the idea's to biome-hop via ISRUing a big rocketplane. A prior iteration had the ISRU integrated into a bomb-bay style of cargo bay, which would be jettisoned in-flight on the final liftoff, but cost in aerodynamics for opening the bay and flying near-level long enough to get the thing out the doors is harsh and it also made taking off more difficult. The idea behind the rover approach is to be able to wheel the thing off beforehand and avoid all those issues. The undocking/redocking thing is because I'd like to have my non-ISRU rovers be able to bomb around wherever I land, then reattach for travel to the next stop.

I'm kind of surprised the wheelbase you've got on that thing doesn't catch on cargo ramps or bay walls, @XLjedi. Maybe I can widen mine. Otherwise, you've certainly given me some very interesting ideas -- I *really like* the interchangeable overhead gantry system. Have you tried it on Eve, specifically? Does the higher gravity impact anything?

Hm. I usually wind up building my pods as close to centerline as possible, and running a strut from nose in to the body, as well as one or two struts to interlink the wing sections so's they don't flop around. The drag penalty's atrocious, but I got my building habits in the days before autostrut; I always wind up spacetaping things, even when it's not the best choice. To tell the truth, I don't even know how to turn auto-strut on Totally feel you on the thrust torque though. Like you, I have an action group, but in my case I use it to terminate all the RAPIERs; orbital manouvering's done either on RCS vernors (which also maintain attitude control as the aerodynamics fail & the CoM shift increases in the upper atmo, as with you) or on a single Thud, whose huge vector range and extreme-rear placement allow it to work regardless. Nothing quite like doing your circularization burn with a <0.1 TWR

Interesting idea, underslinging it like that. I would have expected ground clearance to be an issue, but evidently not. I'm a bit surprised those pods don't warp your wings, though; it's always been a problem for my high-thrust planes.

I'd be interested in that mobile ISRU design, if you could post a picture. It's one of the things I'm working on; my current build looks like this: The canted drills allow it to thread the eye of the needle of a cargo ramp, getting down to ground level w/o clipping through bits. That way it can still operate whilst docked in the cargo bay. Gotta be careful when roving, though. Likes to roll :v

@GoSlash27: You can use planes to transfer cargo without using cargo bays, you know. I posted an example upthread. Of course, that means you need to work out an alternate means to streamline things, but that's by no means impossible.

@Brikoleur:I'd be interested in seeing those heavy-duty spaceplane designs. Also, a question: When you say 'payload', is that counting all the miscellanceous hardware in the launcher (wing, engines, etc) or is it mission gear -- passenger modules, deployable craft (satellites, spaceport modules, etc), left-over-fuel if you're doing refuel runs...?

No, primarily because I need fuel flow, and as far as I recall the Klaw does not allow that. It's also a bit bulky.

The real killer is the gravity losses that the atmosphere necessitates. Drag losses themselves are reasonably small on an efficient ascent, especially with larger/lower-TWR rockets, but keeping them small and/or avoiding thermal implosion means you need to do a lot more climbing than otherwise, while avoiding sharp turns and staying prograde-- so you end up thrusting against gravity for a much longer period than you would otherwise.

I've been fiddling with the docking port positions for some time and haven't yet been able to produce one that will allow a dock/undock sequence. Unfortunately using rockets to adjust height, or non-cargobay solutions, aren't going to work for this particular mission, since it's headed to Eve. The ports can have the wheels visibly clear of the floor of the bay in build mode (and decouple from initial construction without issue), but after redocking to them, and then undocking... boom. Occurs even if I have spring strength cranked to minimum, too.

So I'm poking at KSP again for the first time in a while, and it seems there's been some changes to either wheel physics or docking packing that's made a lot of my old cargo-bay rover systems break. In general the idea is that there'd be a docking port at one end of a Mk3 bay that a rover would nose on-to to clamp on to a mothership of some sort, which would then fly the rover somewhere else for it to deploy, rinse and repeat. However, on undocking from the ports now, it appears the spring in the wheel suspensions go absolutely batty and blow apart not only the rover but potentially the ship that's supposed to carry it around. I've seen wonky wheels launch stuff weighing substantial amounts hundreds of metres into the air on deployment. Has anyone else tried a similar architecture or have some tips on how to do this? I'd really like to be able to use a rover in more than one spot.

Just as an example of the kind of plane I'm talking about: This needs to get up to around 700m/s before a climb of more than 5 degrees is feasible, at which point it's already at the altitude where you'd want to be flattening out for a speed run anyway. Delivers 180t pure payload to orbit (the piggy-backed modules), and another 80t or so in the carrier's dry mass + leftover fuel.

Fire-in-the-hole staging was pretty awesome, but it's pretty difficult to do reliably with the larger thermal tolerances of parts these days. Doing Node 0 rockets (which meant no decouplers) and using solid boosters to detonate the solid booster underneath 'em was oodles of fun. You could get to the Mun that way

Dihedral and anhedralling wings do affect your stability, yes.

That's true, but it is, in practical terms, often much easier to get the airspeed feedback loop going first, when you're low down, because even if the engine's pressure curve says it can operate more efficiently higher up (on a thrust/drag basis), as you get higher up it has to compensate for the loss of lift (hence flying at higher AoAs and/or requiring higher control deflections, both of which are murder on your drag profile, and can cause cosine losses and impact your intakes as well). This is in my experience particularly noticeable with planes with relatively low liftoff TWRs, i.e ~0.3.

That's trivially obvious -- so obvious, in fact, that I assumed it to be implicitly understood that the comparison involved equivalent masses: the same burn being performed by the same ship, with the only difference being the ship's original velocity when executing the burn. Because that's the useful thing to think about; you're looking really hard for things to argue about here instead of trying to understand what people're telling you. At this point I'm not sure what to say. EDIT: Also, in a non-relativistic system, which KSP is, deltaV is independent of reference frame and will always be equal viewed by all observers.

Good luck!

High AoA certainly can, but the other factor here is that to really beat thrust-per-drag you need to *already be going fast*.

A fair number of my planes *can't* climb worth a damn unless they're supersonic. The big reason to go supercruise early is because, if you're using RAPIERs (and to a lesser extent, Whiplashes) you can use the positive feedback on the thrust curve to reach your top speeds much easier. After about the 10km mark I want to be doing around 1km/s, with approximately an additional 100m/s per 1 km of altitude up to the point where the jets can't make the thing go any faster. Also, I often find it tricky to get the thrust and lift needed to go supersonic at the altitudes you are unless I'm already thoroughly supersonic; between the Mach wall, the reduced thrust, and needing to have a significant AoA just to maintain level flight, the engines just can't overcome the drag. Something carrying more engines or wing would have less trouble, I suppose.

Fundamentally, what Oberth does is not change how much dV you get from your propellant, but how much dV is needed to accomplish something. Look at it through energy methods: If you want to transition between two different energy states (in this case, trajectories, which may or may not be orbits), and since gravity is a conserving force and will neither add nor remove energy, you need to supply or remove the difference. However, because kinetic energy has a squared function in it, the same amount of change in velocity can produce different amounts of change in energy, which depends on what the original velocity was. The higher it is, the larger the change in energy achieved by changing the velocity by a fixed amount becomes. Because rockets in vacuum always produce the same change in velocity for the same amount of propellant regardless of their velocity, they can get more energy change for the same dV and propellant use if they're going faster. This 'extra' energy comes from the stored kinetic energy of the propellant itself, for anyone worrying about CoE.

The fact that it burns the same amount of propellant is the even the whole reason the Oberth effect works.

Especially on small rockets, drag is murder. I've gone to orbit on a pair of OSCAR-Bs and trust me it was not pleasant :v