Project Phoebus. Apollo replica with both realism and low part count in mind!

[Rune]

Hello there! Yes, I know, there are a gazillion of these out there. But have I already told you this beauty is only 230 parts on the pad?

The new lander jumped the part number a bit from the previous 200 parts. (I'm that OCD), but it is still very manageable for slow computers. The thing is, I've always liked Apollo replicas. But since I saw Munbug for the first time, I thought I had nothing better to offer people. Since then however, not only has Munbug become wildly popular (first ship that gets stickied and all that), it has also become a lag monster with about 1000 parts. What happens to people with potato computers, they can't get nice toys to play with? Well here I am to change that! But I also wanted the high fidelity and attention to detail that the Munbug family had, of course. And the building tricks! So a few weeks back, in a fit of inspiration, I put all the ideas together, and set about to create an Apollo replica with a tight budget in every way. I think I succeeded! And believe me, I was the first surprised when I noticed this thing actually worked as intended.

We warned, this ship is for players that know their stuff, and has tight margins all around. Just like the real thing! If you find yourself failing with a maneuver, you have probably already have and will have to abort the mission and start thinking up ways to save your kerbals. But now that that's out of the way, the nerdy details. First off, I knew this would be a mass-limited thing. I just couldn't afford more than 10 first stage tanks if I had to keep part count low. So, I had my first inspired idea of the day, and used the skippers as F-1 equivalents. That meant poodles for J-2's, and they actually fit the part quite well. With that, I just had 11 tanks with 11 engines for the whole booster, and I could even afford some fairing eye-candiness. However, a small rocket means a light payload. Then again, NASA also struggled to fit a lunar mission inside the Saturn's V fairing . But by keeping things light and simple (and very tight margins on the lander), we made do, and not one bit of realism suffered for it: as an example, the CM hangs from the fairing, and is not connected to the lander in any way, just like the real thing.

Then of course I came up with a very stupid-looking lander, but some time off the project, a look at the various other apollo replicas out there, and a fit of inspiration about how to put things together, and a newer and much more sexy lander came about:

Now, I must confess to a slight inaccuracy. Turns out the fuel doesn't fit 100% perfect with an Apollo flight profile: The S-IVb should have about half/one third of the CM's fuel. I know, tiny detail, but make sure you do two things: first off, the coast to apoapsis is a very nice time to perform the lander retrieval. You will ditch the upper part of the fairing, keeping space clean, which is always nice, and also you will save precious delta-v for TMI. Mind you, you could also dispose of the fairings after TMI along with the S-IVb, to keep it even more accurate and have time to do the fancy docking maneuvers, but then the decouplers may push the fairings away from a free return trajectory and into the garbage category. Second, before TMI, make sure to top off the S-IVb tank with fuel from the CM. You won't need all of that, but it's always nice to not have the maneuver interrupted because you miscalculated. If it happens anyway don't worry, you have a lot of emergency fuel on the SM, just transfer some more. Call that the checkout Apollo crews had to perform before TMI.

Of course, to comply with the clean space act, the S-IVb is left on a crash course with the Mun, and the mission continues with a stack that would run on a wristwatch:

Other than that, the missions keeps on following (obviously) and Apollo-like profile. I performed the Munar sortie from a 10kmx50km parking orbit, but then again, I managed to land on dry tanks. That actually happened, running out of fuel less than five meters from the surface, and on both test missions, with the new and the old lander. Because of math, and science! It was an effficient-ish landing with low T/W, so you might want to go slightly lower and never higher, and know your stuff to do good suicide burns.

I hit some snags during development, like landing legs that got lost to the kraken, and a parachute that continued to get ripped apart no matter what. But in the end, thanks to F9 and a bit of ingenuity, all kerbals managed to complete all test missions, and the bugs were ironed out without loss of green. A hugely succesful (and funny!) development program!

The full two test missions are commented somewhat in the album, so you can see the whole development program if you want (the version in the download with the sexy LEM and the thinner fairing is first), and a bonus download: the S-V replica as a two stage perfect subassembly. You know, for the Phoebus Applications Program (soon!).

IMGUR ALBUM:

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DOWNLOAD:

Project Phoebus - Apollo-like Munar Mission

V rocket - Perfect subassembly

Rune. We choose to go to Mun, not the easy way, but the hard way!

Edited November 11, 2013 by Rune

[Whirligig Girl]

but... I named my apollo spacecraft phoebus

[Rune]

but... I named my apollo spacecraft phoebus

Boop! I didn't know that! Sorry! Mind sharing the name? I thought it awfully clever, it taking me five minutes googling wikipedia and all that... ^^'

[Urban_K]

Deorbiting LM with CM exhaust is neat. I hadn't thought it really would work, now I'll have to try it!

[blurrr 2]

This is awesome!

Just a thought: You would probably be able to save a significant amount of dV by using a 1m decoupler on the CM. It wouldn't look as good, but would probably help new players.

[Sovek]

Note, those legs you have are heavy, use the smaller, more LEM like legs, should increase ÃŽâ€V margins on the lander, and if you use those savings to shave even more weight (in the form of fuel) off, this should increase your ÃŽâ€V margins on the rest of the rocket as well.

[Rune]

Deorbiting LM with CM exhaust is neat. I hadn't thought it really would work, now I'll have to try it!

Actually, that was a bit of an over-statement. You can perhaps give it 1-10m/s and a nice tumble before it gets out of range, but unless you plan very, very carefully, that won't do. I lowered the CM's orbit to a suborbital arc to rendezvous with the LM, then did the Munar escape burn (in a very inefficient way, but the CM has like 5 times the necessary amount of fuel)

This is awesome!

Just a thought: You would probably be able to save a significant amount of dV by using a 1m decoupler on the CM. It wouldn't look as good, but would probably help new players.

Actually, I couldn't. The whole rocket hangs from that decoupler through the fairing, and substituting it would mess up the fairing, which would require a complete redesign, increase the part count... But I have half-thought a lighter LM that would greatly increase the total delta-v for the S-IVb and allow a true apollo-like flight without unrealistic fuel transfers... and perhaps take care of that slight bulging in the fairing (actually, it's built already... but I really don't want to mess with that fairing ^^').

Note, those legs you have are heavy, use the smaller, more LEM like legs, should increase ÃŽâ€V margins on the lander, and if you use those savings to shave even more weight (in the form of fuel) off, this should increase your ÃŽâ€V margins on the rest of the rocket as well.

Yup, my thoughts exactly, which is why that was the test version (good thing I tested, the second stage decoupler on the LM was clipped and trying to lift off from Mun resulted in a small explosion and a long wait for rescue). In the one actually released, I increased Delta-v margins a bit (so you can be sure it can be done, even with a heavier vehicle), and switched the legs to the small ones. Then I forgot them extended while switching ships, and the kraken decided to steal them. Good eye catching that!

Rune. This is getting some bug ironing before going to my thread. I want it perfect. We'll see what we get.

[Rune]

Update! the new lander has finally been tested, and found excitingly close to what can't be landed on the Mun. This is finally at a point where I'm happy with it

Rune. Project Phoebus is succesfully completed!

[Wayfare]

Congrats Rune! Building a successful Apollo-style Mun rocket is one of those things you just gotta do