KSP vs Apollo Program?

[Daze]

It's been a while that i've a question: why on KSP is more efficient to do a Direct Launch to Mun than doing a Lunar Orbit Rendezvous like the Apollo Program? Shouldn't be all "scaled" down, also the "efficience"?

Edited February 24, 2014 by Daze

[Brotoro]

I don't think direct is more fuel efficient than Munar Orbit Rendezvous. Although if you ignore the "realities" of reentry back at Kerbin and just land your guys in a lander can instead of a properly heat-shielded capsule, maybe you could do something direct that's more fuel efficient. Otherwise, I can't see how it would be more fuel efficient to carry you heavy return capsule and fuel down to the Mün.

Direct is certainly EASIER to do, so people use it a lot in KSP.

[ScallopPotato]

This is mostly because of how little fuel it takes to return from the munar surface to Kerbin. Apollo style is popular for missions to other planets due to the differences between the nuclear engine and other engines. Transit to a body with the efficient but low thrust nuclear engine, land with a less efficient but higher thrust engine.

Then there's a whole other reason why separate ascent/descent stages are rare for munar missions.

[Pecan]

The Kerbol's system isn't the same as Sol's system. Things aren't all to the same scale and aren't just 'scaled down' versions of the real thing. Specifically; the liquid fuel + oxidiser to rendezvous in LMO + monopropellant to dock + two docking ports outweighs the fuel to orbit and escape from the Mun. Therefore a Mun lander that just has the fuel and none of the other things beats an Apollo CM/Lander pair that do have them.

@ Brotoro: instead of re-entering with a lander can I usually land with a capsule ^^ anyway. If not my crew are probably only coming back to a space-station and there'll be a taxi ready when they want to re-enter :-)

[Rhomphaia]

The direct approach is more efficient, because in KSP, all command pods are pretty much equal. they are all pretty heavy and can all survive atmospheric reentry, so there isn't much point in taking more than one. and since the return from Munar orbit to Kerbin is the smallest part of the journey in terms of deltaV requirement , there is not much point in leaving the fuel for that in orbit.

[Daze]

So the main problem is that there's no reentry damage and that is not all perfectly scaled down exactly?

[robopilot99]

Also the command module had to Cary the heavy life support systems to keep all 3 of the astronauts alive for several days

[Pecan]

It's not a problem, just different. (This forum led me to Orbiter when I want 'real world')

[TimMartland]

I actually often rendezvous 2 or more modules in LKO or LMO before trying to capture/land. It is more difficult and less efficient yes, but it lets me bring lots of hardware and life support to the surface so I can stay for about a week to do science.

[Vanamonde]

The issue is that the parts are not scaled to the celestial bodies. A real-world Lunar lander carrying enough fuel to return directly to earth would have been the size of a high school gymnasium.

[LethalDose]

I think in both cases (IRL and KSP) its more efficient to do a direct landing than to enter a M/Lunar orbit and then land because in the direct landing, the rendezvous and landing are combined into a single maneuver.

The true is the same for the return flight: It is more efficient to return directly than to rendezvous with another ship.

However, it's probably *safer* to do an apollo-style mission, but with quicksaves, that's less of an issue.

Also, players are probably doing Mun landings before they've unlocked docking clamps... so they HAVE to go back directly.

[SkyHook]

In general, I don't do Apollo-style missions in Kerbin's SOI. It's a waste of time. I also use the dragon, though. If I don't use a craft with a heatshield, then I go and get a craft with a heatshield.

[jwenting]

bleh, and many people can't dock and never will be able to, however much others belittle them for that by saying "it's easy, just do it".

[SkyRender]

bleh, and many people can't dock and never will be able to, however much others belittle them for that by saying "it's easy, just do it".

I've been on both sides of the docking fence before, and I can tell you, once it clicks you have a hard time believing you ever had trouble with it. But before you've gotten over that hurdle, yeah, it seems pretty impossible and you can't help but feel that the people who can do it are mocking you with their explanations that make perfect sense to them yet don't even compute for you. Best advice I can give is, don't give up. Alter your technique in crazy ways and just try out things that seem crazy. You have the ability to quicksave and quickload, so you can make the most of it and keep doing things differently each attempt until it all starts to make sense. The best teacher is experience.

[Corw]

Also the command module had to Cary the heavy life support systems to keep all 3 of the astronauts alive for several days

I think this is the right answer. This has significant impact on total weight and currently all you need is engines and fuel. Remember that Apollo was cutting down to as little as possible in both weight required and complexity of the mission. Imagine how much weight did the direct ascent add to a mission if they decided that increasing complexity of the mission with LEM docking to service module on return from surface is better solution. Docking also required additional weight of its own too.

[Specialist290]

A few months ago I helped someone proofread a tutorial, and one section in particular ran the numbers for a real-world lunar direct ascent as a comparison to a KSP one in the context of a discussion of when a separate lander might be worth it compared to a direct-ascent profile in KSP. The particulars are on that page, but it basically boils down to the fact that in KSP, the scales of both the solar system and the craft parts involved are such that it's often more efficient to send one command pod / lander can to the Mun than two, whereas in the real world this turned out not to be the case.