Apollo-Style Munar Mission (yes, another one) with pics

[Dkmdlb]

Good morning everybody. I have accomplished a mission which I think is worth sharing. I set out to design an Apollo-style mission to the Mun, with two-stage lander, orbital rendezvous, etc. This is the rocket which was developed for the mission.

It features serial staging, a launch escape tower, a landing module stowed beneath the command module, and all kinds of other goodies.

It differs from the Saturn V in that the second and third stage have been merged into one stage on this rocket. It uses the second stage to achieve Kerbin orbit, then fires the same engine again for TMI. Craft file is attached.

Once the first stage is spent, the launch escape tower is jettisoned,

followed by stage separation a few seconds later.

Delta-v is a bit tight in the first two stages, but I was able to achieve LKO with enough delta-v left for TMI without too much trouble. I tested this extensively in various orbits of different altitudes and eccentricities and failed to make orbit with enough delta-v left to get to the moon on more than one occasion.

After a few orbits to run some tests and make preparations, mission control signed the permission slip for Jeb to fire up the second stage engine one more time for trans-munar injection.

After leaving Kerbin orbit, the CM was decoupled for transposition, docking, and extraction of the LM. I added a large RCS tank early on in the design, but when I realized I didn't need that much, I had already placed RCS ports and everything and I didn't want to redesign the whole thing so I just left it. The large RCS tank was scheduled to get swapped out for a smaller one because I was having trouble getting enough delta-v in the early stages to make orbit + TMI. But it turned out I didn't have to.

After successfully docking, the second stage was decoupled from the LM and, as on the later Apollo missions, left on a munar impact trajectory. The interstage was decoupled from the CM using a method mentioned in another thread which I can't find at the moment. The method is to place two stack seperators back to back, as can be seen in the below picture. To separate the CM from the LM, the first is decoupled. Then, the CM swings around to face the LM and the second is decoupled and the debris floats away. This procedure prevents it from getting in the way of docking and leaves the CM engine free for later.

After entering the munar SOI, the CM engine was fired retrograde for orbital insertion. Jeb settled on a 25km orbit, a little high for the Mun perhaps, but chosen because his normal 10km orbit could make docking with the LM ascent stage unnecessarily difficult do to the pronounced drift that would occur at rendezvous.

Two Kerbals EVAd to the LM to power it up and prepare for descent.

The LM solar panels were extended and the gear was lowered while still attached to the CM in case of malfunction. After completing the checklist, the LM was decoupled and moved away from the CM.

The descent engine was fired retrograde for long enough to point the LM in the direction of the munar regolith.

With landing lights illuminating the untouched munar surface, the LM entered final descent. The descent stage had plenty of fuel.

One small step for a Kerbal, one giant leap for Kerbalkind.

After stopping for a potty break, it was time to get back to work. The 4 ascent engines were fired and had plenty of power to quickly get the ascent module to orbit. Unlike the Apollo LM which had one ascent engine, this ascent module used 4 engines mounted radially. This gave a very high TWR, which gave it that classic ascent stage "pop" as it separated from the descent module.

The ascent module rendezvoused with the CM. The rendezvous was conducted entirely from the ascent module, which was highly maneuverable and had plenty of fuel. It probably wouldn't have had any trouble reaching a 40km orbit or more. Fuel was not a concern for the LM during this mission at all.

The kerbals EVAd back to the CM, undocked the LM ascent stage, and burned for Kerbin.

After a fiery reentry, the three intrepid kerbals were finally safe at home.

Debriefing notes:

The rocket was tested with mechjeb, and with the booster engines gimbal-locked and freed. There is a lot of wobble if they are freed, but the gravity turn is difficult if they are locked. I preferred to keep them free. Mechjeb can sometimes shake a rocket apart, but this rocket was able to withstand the shaking.

I had action groups set up for launch escape, gimbal locking, escape tower jettison, solar panel extension, stage decoupling, etc, and I preferred to use the actions groups instead of the space bar because I wasn't always sure what the staging was (all the docking and decoupling tends to screw that up).

Serial staging is extremely inefficient relative to asparagus. I had a really hard time getting enough DV in the lower stages to reach the Mun. Using the same basic plan with asparagus staging would have been a breeze to get out there.

The CM/LM with two-stage lander method is satisfyingly fuel efficient not including getting them both into orbit. But, given the ease of the CM direct descent method in KSP, it's not really worth doing except for the novelty of doing so.

This method generates a lot of debris compared to the direct descent method. There is the second stage, the descent stage, and ascent stage to worry about, plus the escape tower and CM/LM interstage. I like to keep everything nice and clean so this didn't make me very happy.

The craft file is here:

https://www.dropbox.com/s/qyg3z3oervmzu9r/Apollo.craft

Edited June 20, 2013 by Dkmdlb

[reenact12321]

I really liked your rocket. I have been wanting to tinker with the apollo style of docking etc, but wasn't sure how to work it into the stages and your way of doing it was really good I thought. I took it out for a flight without changing anything and noticed that you had merged the whole lifter stage into one pretty much, it works but I tried a rotary detachment (2 engines/tanks at a time) for a slightly more controlled (and I think, but am not sure) little more efficient take off. Either way, once in orbit, moving out to the moon was pretty friendly, I got into a moon orbit with plenty of leftover fuel (this could easily be a minimus rocket). I used a 20K orbit, I EVAd a kerbel down to the LM before hitting any of the stages to attach the two. I do have to ask how you got the two docking ports to dock in the design. Or was that done in a mod?

Other than the experiment with staged lift-off I really wouldn't change a thing. The lander actually had so much fuel left in it, I took the whole thing back up, it got me pretty close to the CM before I dumped it and then used the Ascent Moduel to get close. I buggered the rendevous (forgot to remove the escape tower) but I'm pretty sure it could have gotten back to earth without too much trouble. Heck, I'm pretty sure the lander could have made it back to earth on its own. I still can't figure out why your design overheats more than some of my own with lots of main sails. Does the weight actually affect the overheat?

Kudos on a really cool rocket. Thanks for sharing!

[Dkmdlb]

Staging it two tanks at a time with fuel lines is WAAAAAY more efficient, but I wanted to do it without that to keep it at a little more similar to Apollo.

Everything about it was stock, no mods. It can all be done in the VAB by rotating parts.

[reenact12321]

I like your rocket so much I even took it on my first successful trip to minmus! Thanks again. Only things I may tweak, a few more RCS points on the CM, it's a tad sluggish, though I do appreciate that being better than crazy movement. Thought about giving the LM RCS, but haven't decided. Oh, if you were to put the SAS module somewhere else, and the docking ports of the two modules were right up against each other, can you move the kerbals through? If not, I hope they add that eventually