Best way to get to the Mun in early career mode?

[computerFan]

I am currently about to go to the Mun in career mode. I have placed a restriction upon myself that I should use a lander can for landing and any other command pod for orbital maneuvers. My question is should I use Apollo-style, Direct-Ascent, or Kerbin Orbit rendezvous. Thanks in advance.

[Aegolius13]

Apollo style is probably going to be the easiest one of those; there's no particular disadvantage to launching the command pod and lander together,  and this will save you time and fuel not having to do the first rendezvous.   

By direct ascent, do you mean not getting into a circular orbit around Kerbin before burning for the Mun?  You might save a tiny bit of delta v this way, but it might be a little tricky to get the timing just right.   So I'd suggest getting into a stable orbit first unless you're specifically looking for that added challenge. 

[Cunjo Carl]

7 hours ago, computerFan said:

 My question is should I use Apollo-style, Direct-Ascent, or Kerbin Orbit rendezvous.

I'm a big fan of direct ascent, especially in early career when orbital maneuver nodes aren't available yet anyways. Doing your burn at 30-40km only saves a little fuel (150-250m/s is what it feels like), but a trip to and from the Mun is an extremely deltaV intensive proposition early game. For me, every little bit counts and it's worth the extra difficulty during launch. That said, they're both good approaches!

Let us know if anything further would be handy. Best of luck on your trip!

[Human Person]

9 hours ago, Aegolius13 said:

By direct ascent, do you mean not getting into a circular orbit around Kerbin before burning for the Mun?

That's not what Direct Ascent is. Direct Ascent means no docking in lunar orbit. In the stock game, this is by far the easiest way of doing it, as the other two require docking and make the mission more complicated. Of course, Apollo style is more efficient, but it doesn't make a huge difference in the stock game (in real life it does).

[computerFan]

Thanks everyone, I will be sure to use your advice and will let you know how it goes.

[mk1980]

using a single command pod or lander can and no rendezvous is by far the easiest solution. adding a rendezvous in mun orbit or a second launch and both a rendezvous in kerbin and mun orbit makes the mission needlessly complicated. 

[Cunjo Carl]

8 hours ago, computerFan said:

Thanks everyone, I will be sure to use your advice and will let you know how it goes.

Have fun! I just realized something. If you have a lander can, it'll explode if you try to do your burn to the Mun while still in the atmosphere. In this light, my advice may not be the best

 

8 hours ago, Physics Student said:

That's not what Direct Ascent is. Direct Ascent means no docking in lunar orbit. In the stock game, this is by far the easiest way of doing it, as the other two require docking and make the mission more complicated. Of course, Apollo style is more efficient, but it doesn't make a huge difference in the stock game (in real life it does).

Wait, maybe I'm confused on this, too. I thought direct ascent referred to not entering LEO before doing the Mun Moon transit injection burn, but is it actually referring to not entering LLO before the return burn?

Edited September 10, 2017 by Cunjo Carl

[Human Person]

2 hours ago, Cunjo Carl said:

I thought direct ascent referred to not entering LEO before doing the Mun Moon transit injection burn, but is it actually referring to not entering LLO before the return burn?

Now I'm confused *looking it up*. Now I'm even more confused. Wikipedia says your version here, but why would not entering a LEO parking orbit result in a much bigger rocket? It's a bit

contradictory

Then it shows the proposed Gemini lunar lander, wich was meant to fly a mission without a (lunar) rendezvous. 

 

I think it all about not having to do rendezvous and docking maneuvers, and the thing about the LEO parking orbit is humbug. Please correct me if I'm wrong.

Edited September 10, 2017 by Physics Student

[Cunjo Carl]

@Physics Student As long as we're beset with pandemonium and confusion, we can tell we're hot on the trail to good science! I wonder if anyone in the industry actually uses the term? That could explain the contradiction.

[N_Molson]

Strict Direct Ascent or not, I do think that landing the Mk1 pod without entering lunar orbit is one of the best recipes (as a mix of tech available early, cost-efficiency and mission design simplicity). Skipping the Parking Orbit and going straight up is an interesting idea, but it sure requires to a very accurate launch window and ascent trajectory. The ideal munar landing is achieved performing a "suicide burn" ; which means engaging full thrust at the very last moment. It requires some maths unless you use autopilot mods. It was successfully performed by the Surveyor lunar probes in real life (to make things even worse, they used a solid rocket motor for that !).

[computerFan]

18 hours ago, mk1980 said:

using a single command pod or lander can and no rendezvous is by far the easiest solution. adding a rendezvous in mun orbit or a second launch and both a rendezvous in kerbin and mun orbit makes the mission needlessly complicated. 

I have done Mun missions with only one command pod before, but I am trying to do it either like Apollo or Constellation hence my need for multiple pods.

[mk1980]

yeah ok. in that case, i guess an Apollo-like mission profile would be the most reasonable. you have to push both pieces (lander & orbiter) to the mun anyway, so i don't really see much point in splitting them up before they are on a trajectory to the mun.

at that point, you could split them up and set the lander can on an impact trajectory and the pod on a flyby (and then capture burn into mun orbit). or you keep them combined until after the capture burn and then descend from mun orbit. i guess the latter would be easier to do.

if you split them up while they are in transfer, you might end up in a situation where you'd have to control the capture burn of the pod and the suicide burn of the lander can at the same time.

[computerFan]

39 minutes ago, mk1980 said:

yeah ok. in that case, i guess an Apollo-like mission profile would be the most reasonable. you have to push both pieces (lander & orbiter) to the mun anyway, so i don't really see much point in splitting them up before they are on a trajectory to the mun.

at that point, you could split them up and set the lander can on an impact trajectory and the pod on a flyby (and then capture burn into mun orbit). or you keep them combined until after the capture burn and then descend from mun orbit. i guess the latter would be easier to do.

if you split them up while they are in transfer, you might end up in a situation where you'd have to control the capture burn of the pod and the suicide burn of the lander can at the same time.

Yeah one time I sent four probes to Minmus and they all arrived within 20 minutes of each other. I had to switch between each ship after I did anything with the others. It was not fun

[Zhetaan]

@computerFan:

Not to unnecessarily add to the confusion, but I understand direct ascent as meaning a well-timed burn that shoots straight up from Kerbin's surface to the Mun.  It's doable, but your margins for error are rather thin.  If what you're referring to is using the same pod to do the orbiting and landing, I don't know any specific industry term for it but I know that it has been occasionally referred to as a single-vehicle mission (or single-vehicle launch-land-return for the especially pedantic).

However, if you're restricting yourself to a lander can for landing and an orbital pod for orbiting, then you wouldn't be using either direct ascent or a single-vehicle mission anyway.

There is another option, which is to send an autonomous lander to Mun orbit and rendezvous with it there, but it has all of the problems as a two-launch orbital rendezvous and none of the advantages, plus the cost of a second transfer stage and remote control apparatus, as well--it's better to save that stuff for station launches and the like.

On the other hand, if you leave your Mun lander in orbit there, then it saves you the cost of bringing it back to Kerbin.  If your lander is a Mun SSTO rather than the Apollo two-stage design, you can use it for future missions and the only expense for those missions would be more fuel.  If you ever build an orbital station at the Mun, the lander then could become a Mun landing shuttle.  Or you could replace it with something better-built, but don't be too quick to give up on the old-but-good landers that you've already paid to put in the sky.

Anyway, to get to the original question, the Apollo-style launch requires a larger launch vehicle, but it's cheaper in the long run because, even putting aside the changed efficiency and delta-V requirements of launch, that larger launch vehicle is less than the sum of the two you would need for Kerbin-orbit rendezvous.  For example, let's say that your launcher needs a reaction wheel.  Maybe the smallest effective wheel is still overpowered, so the combined launcher can use something less than two reaction wheels.  Maybe both launchers require fairings:  though the fairing on the combined launcher would be twice as tall, it wouldn't require two decouplers or two top cones.  And so forth.

[Tyko]

1 hour ago, Zhetaan said:

On the other hand, if you leave your Mun lander in orbit there, then it saves you the cost of bringing it back to Kerbin.  If your lander is a Mun SSTO rather than the Apollo two-stage design, you can use it for future missions and the only expense for those missions would be more fuel.  If you ever build an orbital station at the Mun, the lander then could become a Mun landing shuttle.  Or you could replace it with something better-built, but don't be too quick to give up on the old-but-good landers that you've already paid to put in the sky.

This is a great solution because only your first flight needs to take a lander. The follow-on missions take spare lander fuel instead and keep reusing the same lander.

[FlyingTexan]

If you're in early career mode I'd advise against it. I found once you do something all your good contracts revolve around that. I'd suggest just getting to orbit then picking up a lot of pax missions. Then after building up some cash hit the mun orbit and do pax missions for that. I'd take 24 pax at a time and get over $2mil a pop.

[sevenperforce]

The Wikipedia article on Direct Ascent is just flatly wrong.

There were actually five competing designs for getting to the Moon and back:

• Direct Ascent (Nova). Stack an Earth-entry command module on top of a transfer stage on top of a moon-ascent stage on top of a moon landing stage on top of a moon capture stage on top of a TLI transfer stage on top of a ginormous lift vehicle. This approach is the easiest thing to do in KSP, since the dV requirements aren't really very high and you can combine stages.
• Earth Orbit Rendezvous (Saturn C1). Use separate launches to orbit an Earth entry command module, a transfer stage, a moon-ascent stage, a moon landing stage, a moon capture stage, and a TLI transfer stage, then dock them together in LEO and proceed from there. This approach is overkill for the Mun in KSP but can work well for Duna missions.
• Lunar Orbit Rendezvous (Saturn V, N1). Launch a command module and a separate landing module, together, directly to the moon using a very large lift vehicle; use the landing module to descend to the moon and then return, and then come back to Earth in the command module. This approach matches the Apollo missions and is a LOT of fun to fly but isn't much more efficient than Direct Ascent (at least, not in KSP). It's great for Eve missions, though.
• Joint Lunar Orbit Rendezvous (Gemini to the Moon). Launch an unmanned landing module directly to the moon, then launch a manned command module directly to the moon. Dock them in lunar orbit, climb out of the command module and into the landing module, then proceed as in the Lunar Orbit Rendezvous approach. This is good if you have a large launch vehicle but not one quite large enough to throw a full-size LOR mission at the moon. Not recommended for anything outside Kerbin's SOI, due to the need for multiple transfer windows.
• Double Orbit Rendezvous. Do a Lunar Orbit Rendezvous mission, but assemble it using multiple launches in Low Earth Orbit. This is the most time-consuming and requires a LOT of docking, but it can be good practice and is excellent for when you have a very small launch vehicle.

"Direct Ascent" never means launching pure-radial. This is a really ridiculously bad idea; you're fighting gravity drag virtually all the way and no one would ever do it in real life. Always, always do a gravity turn.

There is a form of "direct ascent" where you time your launch such that you continue on to a trans-munar injection while you are completing your gravity turn, so your periapsis never actually comes above the atmosphere. This is just slightly more efficient than circularizing before your TMI, but the difference is really, really minimal. And this wasn't the difference between the competing moon mission architectures; the "direct ascent" architecture meant the astronauts went straight from the lunar surface back to Earth, rather than docking with a command module in lunar orbit.

[computerFan]

20 hours ago, sevenperforce said:

The Wikipedia article on Direct Ascent is just flatly wrong.

There were actually five competing designs for getting to the Moon and back:

• Direct Ascent (Nova). Stack an Earth-entry command module on top of a transfer stage on top of a moon-ascent stage on top of a moon landing stage on top of a moon capture stage on top of a TLI transfer stage on top of a ginormous lift vehicle. This approach is the easiest thing to do in KSP, since the dV requirements aren't really very high and you can combine stages.
• Earth Orbit Rendezvous (Saturn C1). Use separate launches to orbit an Earth entry command module, a transfer stage, a moon-ascent stage, a moon landing stage, a moon capture stage, and a TLI transfer stage, then dock them together in LEO and proceed from there. This approach is overkill for the Mun in KSP but can work well for Duna missions.
• Lunar Orbit Rendezvous (Saturn V, N1). Launch a command module and a separate landing module, together, directly to the moon using a very large lift vehicle; use the landing module to descend to the moon and then return, and then come back to Earth in the command module. This approach matches the Apollo missions and is a LOT of fun to fly but isn't much more efficient than Direct Ascent (at least, not in KSP). It's great for Eve missions, though.
• Joint Lunar Orbit Rendezvous (Gemini to the Moon). Launch an unmanned landing module directly to the moon, then launch a manned command module directly to the moon. Dock them in lunar orbit, climb out of the command module and into the landing module, then proceed as in the Lunar Orbit Rendezvous approach. This is good if you have a large launch vehicle but not one quite large enough to throw a full-size LOR mission at the moon. Not recommended for anything outside Kerbin's SOI, due to the need for multiple transfer windows.
• Double Orbit Rendezvous. Do a Lunar Orbit Rendezvous mission, but assemble it using multiple launches in Low Earth Orbit. This is the most time-consuming and requires a LOT of docking, but it can be good practice and is excellent for when you have a very small launch vehicle.

"Direct Ascent" never means launching pure-radial. This is a really ridiculously bad idea; you're fighting gravity drag virtually all the way and no one would ever do it in real life. Always, always do a gravity turn.

There is a form of "direct ascent" where you time your launch such that you continue on to a trans-munar injection while you are completing your gravity turn, so your periapsis never actually comes above the atmosphere. This is just slightly more efficient than circularizing before your TMI, but the difference is really, really minimal. And this wasn't the difference between the competing moon mission architectures; the "direct ascent" architecture meant the astronauts went straight from the lunar surface back to Earth, rather than docking with a command module in lunar orbit.

Ok I just have one more question. What angle should the Mun be at compared to the KSC if I am doing direct ascent?

[sevenperforce]

5 minutes ago, computerFan said:

Ok I just have one more question. What angle should the Mun be at compared to the KSC if I am doing direct ascent?

It should roughly be completely behind the planet. That is, if you set the Mun as your target, the "antitarget" marker should be right above your head, if you have targeting in your career yet. At launch, you will be going directly away from the Moon, globally speaking.

Of course, you will go into an eastward gravity turn immediately. There will be some variance based on what your ascent profile looks like.

[computerFan]

Thank you all so much for helping me. Soon I will begin the mission and post it in mission reports. You can check it out there if you like.

[Palaceviking]

Do it your way.

Except the launch for which I absolutely recommended explosive decoupling. 

[Grand Ship Builder]

More boosters.

[Palaceviking]

On 25/09/2017 at 2:56 AM, Grand Ship Builder said:

More boosters.

And explosive decoupling! 

@Grand Ship Builder is it me or has ksp changed into something a bit too serious,  what happened to the more boosters approach?  Lithobraking techniques?  Enough srb's to give you 2fps? Bah humbug...

[Spricigo]

5 hours ago, Palaceviking said:

is it me or has ksp changed into something a bit too serious, 

hey! Game spaceship is serious business!!!

(well, at least that is what I learned while playing a different game.)

[Grand Ship Builder]

19 hours ago, Palaceviking said:

And explosive decoupling! 

@Grand Ship Builder is it me or has ksp changed into something a bit too serious,  what happened to the more boosters approach?  Lithobraking techniques?  Enough srb's to give you 2fps? Bah humbug...

Probably because Danny and Nexter are dead, the more serious KSP channels took over, and us non-serious people are slowly dying out.

 

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