sevenperforce

Without a specific lander design, it's hard to do much math to determine the most efficient solution.

Me too; that's why I set out to figure it out a few weeks ago. By MECO-1, I meant booster engine cutoff. BECO?

I heard that proposed, but not by anyone connected. Yep!

In the real world, it is customary that each stage deliver about the same proportion of dV to orbit. But everything others here have said is true.

I have not attempted midcourse inclination corrections before...I understand the principle, of course, but how do I plan the first maneuvering node without targeting an actual intercept?

I'm currently thinking of going from Minmus to Kerbin flyby to Eve flyby to Gilly, then refuel. Gilly to Eve flyby to Duna, then refuel. Duna to Ike, then refuel. Ike to Duna flyby to Dres, then refuel. Dres to Jool system, hit all the moons I can, refuel. Jool to Eeloo, refuel, then head home. I can't do direct entry at Kerbin since I don't have chutes or heat shields, so that last bit might be tricky. Sorry, I don't understand what you mean by "biggest margin for capture". Most remaining dV. In case I fudge something up, or can't find a capture assist.

Well, it's never been done.

The Zenit boosters for Energia used pyros for joint separation, then used a second set of pyros to separate from each others, then used a drogue on the tail to re-enter nose-first, then cut the drogue and popped mains at the empty CoM, then deployed landing legs and fired a third set of pyros to brake at horizontal touchdown. Probably the most complex solution for sep and recovery, but surprisingly error-proof. I recently did strap-on boosters with liquid retrothrusters near the CoM. Used action groups to fire the retrothrusters for separation, then switched back to the main engines for a boostback burn to KSC, then cut the engines, popped drogues, popped mains, deployed landing legs, and fired the retrothrusters again for soft touchdown.

Perfect! This is what I needed. Just so I understand it properly: if the gate orbit is near or above a given moon, you shouldn't drop; if the gate orbit is substantially below a given moon, you should drop? What's going to give me the biggest margin for capture at Jool: Gilly-Eve-Jool, Minmus-Kerbin-Jool, or Ike-Duna-Jool? Given that all three recommend drops. Also, what's the gate orbit for Jool to Eeloo? Should I try to go direct from a Joolian moon to Eeloo, or would I be better off leaving from Dres or Ike and getting a Jool assist?

In a sense, the Shuttle SRBs were actively controlled post-sep, since they were tracked and chuted down, but the sep mechanism was single-use, they used pyros, and the SRBs were essentially inert cylinders all the way to splashdown, so it's not really comparable. The Soyuz boosters vent the LOX ullage pressure from the nose of each booster, nudging them away from the core. As far as we know, sep will take place post-MECO-1, so the engines on the boosters will not aid in separation. The cold-gas thrusters on the top of the boosters can push them away from the core, but the primary concern is that the CoM will be high enough that this would cause rotation, potentially slamming the engine cluster into the core before it can clear. Two possibilities exist: one, that the lower attachment points have a rotational degree of freedom, allowing the upper attachments to be released first so that the boosters yaw away from the core before the lower attachments are released. The other, that the lower attachments have pneumatic pushers to shove the octawebs apart with enough force to counteract thruster-induced rotation.

From an Oberth/dV-efficiency standpoint, there are quite a few different options. The Merlin's lower isp and higher thrust is beast for getting off the ground and into orbit, but it's less useful for getting beyond LEO. However, when the alternative is a non-cryo hypergolic with even poorer isp, it's a good idea to make the most use of it, especially if you can do the TLI straight off the pad. Then again, one option would be to use an inverted version of the Earth-Lunar-Orbit Rendezvous planned with Constellation. Constellation had the man-rated Ares I lifting Orion into LEO, then using Ares V to lift Altair into LEO for a rendezvous. After docking, the Ares V upper stage would send the whole stack to a free-return, after which the Altair's descent engines would perform the lunar orbit insertion burn. Using the lander's engine for the insertion burn is slightly more efficient than going the Apollo route (using the CSM's engine), since you get to drop those tanks on your landing. The inverted version of the Constellation architecture would be to send a prop-heavy lander up to LEO on the first Falcon Heavy, then send up a Dragon 2 (with kick stage in the trunk) and dock to the lander in LEO, with the Falcon Heavy upper stage still attached to the Dragon 2. That stage then fires for the TLI, rather than the lander's terminal stage as in the Constellation plan. This allows the whole mission to make optimal use of the two equally-sized LVs rather than using one gigantic HLV and a smaller man-rated launcher. I haven't crunched all the numbers, but one very interesting option would hinge on whether the Falcon 9 upper stage can be easily modified for extended-lifetime restarts. That's where things get really interesting, because you could dock both stacks in LEO, use the Dragon 2's ascent stage for the TLI, and then use the lander's ascent stage in cislunar orbit to perform the insertion burn. Dry mass does start to pile up a bit, in that scenario, but you make the best use of the MVac's higher isp relative to storables, and you have the smallest cislunar mission stack, which means less dev cost. JLOR is good, but it means your Dragon 2's kick stage needs to carry enough fuel for both lunar insertion and for the Earth return burn, and I'm not sure exactly how much dV you can realistically cram into that trunk.

Is Minmus-to-Jool-via-Kerbin a better option than Ike-to-Jool-via-Duna or Gilly-to-Jool-via-Eve? I plan on going to Gilly, Ike, and Duna anyway, so I'm not losing anything by picking the most efficient one. Duna has less of a gravity well for Oberth assistance, and I lose more dV getting off Ike than I would getting off Minmus, but the actual Jool transfer burn is smaller. In contrast, Eve has the nicest gravity well of the three, and getting off Gilly is essentially free, but the Jool transfer burn is much larger there.

No.

Indeed, look at videos of failed landings.

Should I burn for Jool from Gilly, from Minmus, or from Ike? Or even from Dres?

In-game time is no object. Player time...well, I don't want to spend TOO long. By my numbers, I should be able to get to Duna (2,550 m/s) and from there to Ike, without needing a gravity assist. However, I wouldn't even know where to begin to try and do a semi-grand tour of anywhere else. With 2.9 km/s of dV, I know that Laythe, Tylo, and Moho are out of the question, but I don't know about Dres or Eeloo. I should be able to do Gilly easily enough, but I don't know whether I should try to use it for anything else. If I get into the Jool system, I can hit Pol, Bop, and Vall easily enough, but I don't know whether I can actually make it there.

I'm currently on Minmus in an ISRU-capable lander with 2942 m/s of dV, in year 1, day 75. It has a single drogue for landing on Duna. How far can I go? I'm not so great with gravity assists.

For all my Mun-SOI missions, I take basically the same steps, assuming that I start from a roughly circular, low-or-no-inclination orbit. Create a maneuver node that won't take you anywhere near the moon, and tug on the prograde marker until your apoapse just touches the Mun's orbital path. Grab the node and tug it around your orbital path until you get the kind of Mun encounter you want (prograde for normal landing or gravity assist; retrograde for free-return). Pull back on the retrograde marker until you get your trajectory as low as possible. ??? Profit!

Allow any engine to be used as a vernier.

That was after optimizing the ascent profile. Anyhow, I ended up dropping the Junos, dropping the wing engines, and just clustering six Sparks on the tail inside a clipped fairing. Aaaaaand it flies itself into orbit with nothing but trim adjustments.

It's not actually false. Falcon Heavy can throw about 20 tonnes to TLI. The whole integrated Apollo stack, including CSM and LM, came in at 44 tonnes. Storables would not be able to get as good of isp as the MVac, so if you're doing TLI it's far more efficient to go straight from the pad to TLI on the Falcon Heavy and simply use a smaller payload. Methalox or hydrolox would be better, of course, but then you have to deal with mounting a cryogenic fuel tank and engine on top of Falcon Heavy, which would be tough to do with the LM and impossible to do with the crew-carrying CSM. Your first Falcon Heavy launch would send the lunar descent and ascent modules to TLI. Use the descent-module engine to brake into lunar orbit, like the plans for Altair. Once your lunar module is in orbit, send up a Falcon Heavy with Dragon 2, but put a few Dracos in the trunk along with a nice big fuel tank. That goes to TLI on the Falcon Heavy alone, after which the Dracos in the trunk perform the lunar orbit insertion. Joint Lunar Orbit Rendezvous, flags and footprints, and you're done.

Tried again with a Mk1 form factor and just 4 Sparks and 4 Junos, and I'm just 93 m/s short of orbit. Going to ditch the Junos and see what happens.

You know, in his original 2011 unveiling of Falcon Heavy, Elon posited that two FH launches is all it would take to drop astronauts on the moon and bring them back.

I'm not one to suggest adding a whole bunch of new planets or anything, but there are a few things the Kerbol system is definitely missing: An ice giant A moon or moons in retrograde orbit Rings A planet with high axial tilt One new planet could take care of all that.

I was going to say, "When are you staging your nukes? If you're not staging them until late, try a little earlier so they are burning in parallel with the ramjets." But clearly I was beaten to the point.