(0.17) Stock 3-Man To-Duna Spacecraft (Not gigantic)

[Trebuchet-Launch]

Asparagus staging is your friend, people!

Here we are on the pad:

This is a fairly small vehicle but will do the job for three brave Kerbals. It uses asparagus staging and perigee kicks to get the mass down. Asparagus staging you're probably familiar with - multiple crossfed stages, if you don't - but perigee kicks are a new trick, I think, for people here.

NERVA stages are heavy. Putting tons of them on the vehicle forces you to lift them, which makes lower stages bigger, which tends to quickly make the rocket balloon in size. This uses a single NERVA engine to do the TDI burns, despite the low thrust-to-weight ratio. The bottom stages are capable of putting the trans-Duna injection stage in orbit. Now, to make an efficient boost out of Kerbin's sphere of influence, do the following: when the craft is near the 6PM terminator - sunset - in its orbit, burn. Once it gets away, stop and coast. This will put the perigee of the orbit around the terminator line. Each time you burn, gain more energy than if you did one big long burn due to the Oberth effect. After a few (I think three) orbits, you should be able to burn into Kerbin escape and be on the way to Duna. In fact, done correctly, you'll still have plenty of fuel - enough that you can use this stage to insert into Duna orbit and deorbit. The lander has parachutes to assist its landing, and the nuclear engines have enough gas to get you home.

"But Trebuchet, I don't want to learn about perigee kicks!" Fine, fine. In that case, bring the vehicle into the VAB and run fuel lines from the TDI stage to the two lander NERVAs. That should give you enough thrust to boost directly, if you want to be a bit wasteful.

Edited September 24, 2012 by Trebuchet-Launch
Dumb Oversight Fixed

[Trebuchet-Launch]

Here are a few shots in action:

Achieving orbit:

Landed on Duna:

Homeward bound:

(Note: The Eve-grazing return orbit was an accident - I had decided to sundive on the way back, and got an accidental intercept. Because of the crazy crossing velocity at Kerbin's orbit, the lander didn't have the oomph to slow down and capture. Use a minimum-energy transfer to safely return your Kerbals to Kerbin with this lander.)

[Carthaginian]

Do you have any construction tips for those of us looking to send small items in interplanetary missions using this kind of technique?

I'm trying to loft MapSats to all the rocky objects in the Kerbol System, and the interplanetary missions are killing me. Trying to put a nuclear rocket into orbit is not impossible; trying to put a nuclear rocket into orbit with any kind of usable payload (for me, anyway) is very nearly so. I have tried monstrosities that implode under their own weight, over-reinforced nightmares that slow a powerful graphics card to a crawl, and ultralights that almost- but not quite- make it into orbit.

The problem is that the nuclear engine seems to be constantly loosing speed during it's burns. I understand that until the thrust builds to a sufficient level that the mass of my spacecraft will slow me down... but can you recommend any solution to this kind of problem?

[thorfinn]

Nice craft you have there! I'm trying to do the same with a bigger ship: the Halfway to Anywhere N is bound to survey the whole Jool system, and come back... I'm sure it has quite enough delta-V for that. I tried not to look at pics of the Joolian bodies, I'd like to experience them first-hand.

First launch was aborted due to a stupid problem: the small hardpoints that are advertised as "fuel crossfeed capable", actually aren't....

No fuel lines on the first stage, though.... I kinda like it this big.

(Well, there are fuel lines technically: the center column feeds the four engine/tank stacks. I think that this "simulates" a bigger 1st stage with the parts we have. Asparagus is so efficient, I don't want to rely on it if possible)

Note: The Eve-grazing return orbit was an accident - I had decided to sundive on the way back, and got an accidental intercept. Because of the crazy crossing velocity at Kerbin's orbit, the lander didn't have the oomph to slow down and capture. Use a minimum-energy transfer to safely return your Kerbals to Kerbin with this lander.

Well, why didn't you just set a 15km periapsis and went to a straight-in reentry?

Edited September 24, 2012 by thorfinn

[Mindofscience3]

Do you have any construction tips for those of us looking to send small items in interplanetary missions using this kind of technique?

I'm trying to loft MapSats to all the rocky objects in the Kerbol System, and the interplanetary missions are killing me. Trying to put a nuclear rocket into orbit is not impossible; trying to put a nuclear rocket into orbit with any kind of usable payload (for me, anyway) is very nearly so. I have tried monstrosities that implode under their own weight, over-reinforced nightmares that slow a powerful graphics card to a crawl, and ultralights that almost- but not quite- make it into orbit.

The problem is that the nuclear engine seems to be constantly loosing speed during it's burns. I understand that until the thrust builds to a sufficient level that the mass of my spacecraft will slow me down... but can you recommend any solution to this kind of problem?

Check out my thread (http://kerbalspaceprogram.com/forum/showthread.php/20530-MoS-s-Stock-Space-Kit last post). I've got a great inter-planetary vehicle that can send you anywhere in the solar system. It's big but does not lag. It actually gets a large nuclear stage past duna-transfer with the base rocket. On top of the base rocket, it's got the nuclear stage, and the powered landing stage as well. The "payload" (nuclear stage + landing stage) is about 58 tons, and the delta v of the nuclear stage is approx 4250 m/s. The lander itself is 20.8 tons, so perhaps you could view that as the payload (your nav sats in this case). That should be more than enough .

Edited September 24, 2012 by Mindofscience3

[walia6]

Finally! A duna rocket that doesnt make my ksp cry! I'll try to use this! When i'm done ill post the pictures

[darkwolfpaw54]

does this work with mechjeb?

[Trebuchet-Launch]

To reply quickly in order:

Carthaginian, the nuclear rocket has low enough thrust that, for large stages, it will have a TWR less than one. Often significantly less than one. If you're aimed away from, say, Kerbin, what the rocket will do is make you fall more slowly. My rule is to only use nuclear engines in orbit or when taking off of low-gravity places (Duna or lighter).

Thorfinn, I didn't look at pictures of the moons before flying out there either. And as for why I was sundiving, I wanted to confirm it had enough delta-v to go home without twiddling my thumbs waiting for a minimum-energy return window. So I went sundiving and, what do you know, coincidental Kerbin capture! Between all the delta-v I'd expended to put the perapsis at Eve's orbit and the crazy crossing velocity at Kerbin, I didn't have enough gas in the tank to hit Kerbin's atmosphere.

Incidentally, if you get the crewtank mod, and send two ships, one a modified version of this with an extra crewtank added and the other straight vanilla, you can send an expedition to any Joolian moon save Tylo with this design. You have to be good at orbital rendezvous, though...

Walia, thank you! I put this up as sort of a how-to in minimal Duna missions. I saw no need for some of the overkill rockets I've been seeing.

darkwolfpaw, yes, it works with MechJeb. Put one of the pod types or something on it somewhere.

[Kadadj]

Ugh, it's so effing slow. After about an hour I just didn't even bother to try anymore. I'm more of a "build huge things that go fast without imploding in the process" kinda guy.

[Carthaginian]

Carthaginian, the nuclear rocket has low enough thrust that, for large stages, it will have a TWR less than one. Often significantly less than one. If you're aimed away from, say, Kerbin, what the rocket will do is make you fall more slowly. My rule is to only use nuclear engines in orbit or when taking off of low-gravity places (Duna or lighter).

I only use them in orbital or better stages, and then only in craft that I intend to try for interplanetary travel in.

The problem is that I wind up with the following scenario each time:

LAUNCH- no, wait, the ship was so massive it imploded or so wide that it contacted the tower and blew up.

*downsize*

LAUNCH- and the ship burns to a high-apex sub-orbital course. Upon leaving the atmosphere (80km or so) I start burning the NERVA- generally between 1000-1300m/s, depending on how well my rocket did in the thrust/weight department. At this point, my heart always sinks, because the NERVA starts burning balls out, but I slow down to between 800-850m/s or so before I ever see any thrust registering. OCCASIONALLY my ship achieves orbit- but I think it is because it forgets that Kerbal is below it and accidentally misses it when it falls, rather than actually achieving orbital velocity.

This is my biggest question: how high does my orbit need to be before the NERVA becomes a viable prime mover?

If necessary, I can detail my craft in general or specific terms, as I am using the same satellite (Probodobodyne parts pack, Dynasat parts pack & Mapsat parts pack) for every mission. In fact, I use the same stage for polar orbit transfer burns as well, so I can detail the entire craft that I plan to get to the target as it never changes. I figure that commonality will be a major boon in this situation, as I should be able to formulate my 'Maximum Rocket'- the one needed for the Joolian moon missions- and remove any unnecessary weight for closer targets- or even leave the entire assembly intact and have an appreciable safety margin (or even room for manned pods) on shorter duration missions.

[naloxone]

Can you expound on your kick burn timing. Burn until what "gets away"??

[Mindofscience3]

I only use them in orbital or better stages, and then only in craft that I intend to try for interplanetary travel in.

The problem is that I wind up with the following scenario each time:

LAUNCH- no, wait, the ship was so massive it imploded or so wide that it contacted the tower and blew up.

*downsize*

LAUNCH- and the ship burns to a high-apex sub-orbital course. Upon leaving the atmosphere (80km or so) I start burning the NERVA- generally between 1000-1300m/s, depending on how well my rocket did in the thrust/weight department. At this point, my heart always sinks, because the NERVA starts burning balls out, but I slow down to between 800-850m/s or so before I ever see any thrust registering. OCCASIONALLY my ship achieves orbit- but I think it is because it forgets that Kerbal is below it and accidentally misses it when it falls, rather than actually achieving orbital velocity.

This is my biggest question: how high does my orbit need to be before the NERVA becomes a viable prime mover?

If necessary, I can detail my craft in general or specific terms, as I am using the same satellite (Probodobodyne parts pack, Dynasat parts pack & Mapsat parts pack) for every mission. In fact, I use the same stage for polar orbit transfer burns as well, so I can detail the entire craft that I plan to get to the target as it never changes. I figure that commonality will be a major boon in this situation, as I should be able to formulate my 'Maximum Rocket'- the one needed for the Joolian moon missions- and remove any unnecessary weight for closer targets- or even leave the entire assembly intact and have an appreciable safety margin (or even room for manned pods) on shorter duration missions.

It's nice to have an orbit around kerbol when dealing with nuclear engines, but really, you want to be at least half way to the mun before they are effective. Interplanetary space is better of course. Thats why my rocket is designed to bring the nuclear and lander stages to kerbol orbit right away for best use of NERVA power!

[Fredonia]

OCCASIONALLY my ship achieves orbit- but I think it is because it forgets that Kerbal is below it and accidentally misses it when it falls, rather than actually achieving orbital velocity.

There is an art, or rather, a knack to flying.

The knack lies in learning how to throw yourself at the ground and miss.

To be on topic, I tried this last night and went kablooey on the launchpad... I guess I forgot to miss the ground so bad that the ship asploded in shame... I'll try it again later when I have more time. As idiot-proof as it it looks, I still managed to screw it up.

[Oggula]

The Stock Kerbal X craft can land on Duna if you move the launch clamps to the first stage and put the parachute before the last decoupler. You have to get a good interception though. This craft is pretty high power as well, I expect you could return with it if you wanted.

[walia6]

Walia, thank you! I put this up as sort of a how-to in minimal Duna missions. I saw no need for some of the overkill rockets I've been seeing.

Err... Damn this is harder then i thought XD.

Wheres that how-to duna missions you were talking about?

[Trebuchet-Launch]

Here it is.

[bradley101]

Not Gigancic This would turn some people away. Just saying.

[heath3777]

any idea as to why when I attempt to download the zip folder I just get a black page and nothing downloads?

[JebThePilot]

Whoa, whoa whoa. This is a MAJOR necro post. This has been dead for two years (and a few months) and it is SEVEN versions behind. It wouldn't work if you downloaded it, anyway!

[xoknight]

Holy timewarp, also yea this will probably not work anymore in this version. They're better rocket's now anyways.