InterPlanetary

[snow25699]

Are there any tips and techniques for designing any rockets that are capable of interplanetary flight? The delivery to the target is possible for me, but the launcher seems to be a major problem...

Would like tips for the delivery system as well...

[EndlessWaves]

Keep it lightweight, for many of the planets you don't need much more than you need for the mun lander-wise and for under 20 tons of lander a 1600L tank and single nuclear engine is sufficient for interplanetary transfer.

Where are you going? The requirements will differ tremendously depending on whether this is an eve return mission or a one way expedition to Duna.

[snow25699]

My main goal is to reach duna. I have a good moon rocket(link in my signature). Could it make to duna and back with some modifications?

[EndlessWaves]

Your lander has a huge thrust to weight ratio and plenty of fuel (sufficient to get into kerbin orbit) so that should have no problem landing on Duna and the rest of your rocket is almost there. Swap the 400L tank above the LV-N for a 1600L one and swap the booster stacks from 4x to 6x symmetry and that should be sufficient for a one way trip to duna (I start from a 75km kerbin orbit, you may need a little more on the first stage if you want to go up to 100km).

It might even make it back, I haven't been down to duna yet so I'm not sure how much effort it takes to get down and back up,

[snow25699]

I also head into a orbit around 70km. In a failed interplanetary mission in which I tried modifying this rocket, the lander appeared to have enough fuel to get back, but i could not intercept duna. I also intend to go down on parachutes(I guess that saves fuel and is easier). I had no idea that my lander has so much thrust.

On my failed mission, I increased the symmetry and added a tank or two for the boosters, and one more tank for the nuclear rocket.

Thanks for the advice, a ton. I will try the modifications tomorrow if I can, and will tell the result. I have another version of my moon rocket with 3 sunbeam lasers on the landing fuel tanks to clear up debris on the way. It adds a weight of 1.5 to my rocket. Is it worth is or shall i leave the lasers?

[EndlessWaves]

It depends on how ambitious you're feeling, every bit of extra weight will require you to enlarge the rocket further.

You definitely want to dump the weight as soon as possible though. Hopefully you'll be able to use the interplantary stage to start your deorbit burn so it crashes into duna so you could mount the lasers on the interplanetary stage. Your only debris would be in orbit around kerbin so wouldn't require much fuel to rendezvous with on a future mission though. Parachutes do retain their full weight even after use so I've lately taken to mounting them on top of stack decouplers and putting sepratrons on the decouplers so I can fire them off after landing giving me less to haul back up to orbit (they work on radial decouplers too, but they're weaker/more weight).

[snow25699]

I flew the rock yesterday with the modifications you suggested.

I had to change the booster symmetry to 8, and I changed the 400l tank to 1600l tank above the nuclear rocket, and added parachutes with decouplers. I managed to make it to a 70x70 km orbit, but I miscalculated the take off time and ended up waiting for 10 days in orbit(I used the maximum time warp possible) for proper alignment. I was using protractor addon to determine the burn location.

Finally I started the burn using remaining fuel in the launch stage(I had half a tank left) and when the fuel ran out I was prepared to decouple and engage the interplanetary stage, but the game crashed and I ended up using task manager to kill the program. I guess it was because of the excessive use of time warp. Will try again today... Jeb was on board, so it must have been a big let down for him...

[draeath]

70km is terribly close to the atmosphere. I'd suggest 71km at minimum.

[snow25699]

I too realised that. After 10 days in orbit, the apogee lowered by 5m. I again launched the mission, only to encounter the same crash... will jettison the launch stage before continuing... I also found Jeb still in orbit, and I guess bob will still be orbiting too...

[EndlessWaves]

70km is terribly close to the atmosphere. I'd suggest 71km at minimum.

The atmosphere ends at 69km (well, 77m above that) so you're already almost a kilometre clear.

[draeath]

Yes, but that's so close that RCS maneuvering might just nudge your peri into the atmosphere. Give yourself some space. Doesn't take much ÃŽâ€v for that last kilometer.

[Tauge]

The atmosphere ends at 69km (well, 77m above that) so you're already almost a kilometre clear.

Yes, but that's assuming that the entire orbit is above 69km. A 70km orbit may only be 70km on one side. I just find that a 75km orbit is best for me. Not too much fuel burn to get up there, no real risk of accidental reentry, and still a good amount of extra velocity from the Oberth Effect.

[Elladril]

How are you guys able to properly judge the ejection angle for your transfer burn when orbiting that low? With my lander, which uses a NERVA engine, my rocket would probably move through 100+ degrees...

I've always launched up to 300km or so, so that the ejection angle changes little during the burn.

[RoboRay]

How are you guys able to properly judge the ejection angle for your transfer burn when orbiting that low? With my lander, which uses a NERVA engine, my rocket would probably move through 100+ degrees....

The Protractor mod gives a "running" display of the current angles.

For interplanetary flights, I set my parking orbit at 80km. Any higher and I'm just wasting fuel to circularize the other side.

[snow25699]

I guess with the half a tank of fuel left in the ascent stage, I can reach a safer orbit then...

[snow25699]

Dropped the idea of manned flight to duna. will instead land a rover, and have already created a good model which can land on Kerbin.. Also, how to ensure an intercept without timing the burn for a direct intercept? I don't like to wait that long....

[Vanamonde]

I learned from experience: if you don't wait for a good transfer window, you waste even more time at high warp, trying to bring your ship and the planet together. It can be done, and it was my prefered method, until I just got tired of all that wasted time and realized the methodical way is best even for impatient people like me.

[snow25699]

Oh... ok... the major prob is that the rocket falls apart on the pad after time warp....

[EndlessWaves]

Oh... ok... the major prob is that the rocket falls apart on the pad after time warp....

That's just a bug caused by stopping high warp abruptly, going down to 5x first should fix it.

[AmpsterMan]

I too am interested in interplanetary transfers. So far I have been able to make it to Duna, but I always end up in some extremely weird, polar Orbit.

[dimovski]

i tried getting to eve 5-6 times, each time i start burning exactly at the ejection angle , the phase angle is just right, and still i get closer to duna then to eve...

[Qumefox]

Using protractor? I haven't had much of an issue, but remember you still have to adjust your inclination mid flight.

Though, when i've done kerbin-eve transfers, my orbits have come nowhere near duna.. the transfer orbit doesn't even extend past kerbin orbit at the slightest.

[EndlessWaves]

I too am interested in interplanetary transfers. So far I have been able to make it to Duna, but I always end up in some extremely weird, polar Orbit.

Yeah, you will do unless you're very precise due to the different inclinations of the two orbits. Don't worry about it, a polar orbit is no harder to land from (arguably easier because it passes over all parts of the planets giving you a wider choice of landing locations).

[RoboRay]

I too am interested in interplanetary transfers. So far I have been able to make it to Duna, but I always end up in some extremely weird, polar Orbit.

Polar orbits are actually preferred, as you can easily reach any point on the surface without having to expend extra fuel by waiting for the rotation of the planet to bring your landing-zone under your flight path.

They are also better if you're mapping or just scouting the surface for future landing sites, as you're not restricted to just the equatorial regions.

But your inclination after making orbit is entirely up to you. When arriving (unless from way out of the plane of the ecliptic), whatever latitude of the planet you position your periapsis over is going to basically become your orbital inclination. So, if you aim right at the equator, you'll have an equatorial orbit. If you aim toward the poles, you're setting up a polar orbit.

Edited October 16, 2012 by RoboRay

[Rickenbacker]

So far I've been unable to reach Duna. I use the protractor mod, and burn when the angles match, but no intercept... is there a good way to judge your orbital inclination? I could be off by a few degrees, but it looks close enough visually...