multi stage vs single stage.

[Sidoz11]

I tend to use the Apollo technique, two-stage lander on the ground and the Command Module stays in orbit ready for a rendezvous

[MarvinKitFox]

I very often use a 2-stage *lander*.

As in, the retroburn and initial descent is handled by one stage (usually the same stage that did my orbital insertion/circularisation in the first place), but this stage uses space engines, not really suited for landing.

When approaching 30s-1min from touchdown, it is staged off and the final single-stage lander touches down. This same stage will later ascend, in one piece. (possibly jettisoning landing legs..)

A trivial side-effect of this style is that the debris of the dropped descent stage makes for handy range-to-ground-surface indicators!!

[Red Iron Crown]

I would say it's one stage, with drop tanks (and drop science modules). It's not the most authoritative source, but according to Wiki, "A multistage (or multi-stage) rocket is a rocket that uses two or more stages, each of which contains its own engines and propellant." So dropping a part that is just a fuel tank, just an engine, or neither a tank nor an engine doesn't count as true staging. Though the early Atlas rockets, which dropped engines but not tanks, were sometimes described as "stage-and-a-half".

I would consider anything dropped or jettisoned a stage, so it would be two stages in my book. I guess we're back to razark's point that it depends on how you define "stage".

[pauix]

I've never needed a multi-stage lander, so I haven't built one (to be honest, I land the whole ship down, lift it up and return it to Kerbin without landers ).

[Kasuha]

Regarding staging, there are two definitions.

A Wikipedia one:

A multistage (or multi-stage) rocket is a rocket that uses two or more stages, each of which contains its own engines and propellant.

And a NASA one:

In order to lighten the weight of the vehicle to achieve orbital velocity, most launchers discard a portion of the vehicle in a process called staging.

The NASA definition is closer to my heart. Staging for me is an event when the ship decreases its (dry) mass to improve performance of the remaining part.

Mind you, stages of space shuttle ascent are launch, SRB separation, fuel tank separation, and orbit.

Even Wikipedia mentions space shuttle as "two-stage with boosters" category of three-stages-to-orbit vehicles although on space shuttle page it talks about it as a two-stage ship, boosters and orbiter+tank.

Personally I use both. I greatly enjoyed single-stage landers but then I tried apollo style with leaving the descent stage on the ground and it was fun, too. The only thing that's not fun are landers which leave a lot of debris, such as Eve lander with each leg and parachute on a decoupler. It's too annoying to clean these things up from tracking station afterwards (although the huge explosion at launch is almost worth it).

Edited May 13, 2014 by Kasuha

[KerbMav]

I started out single staged, then went Apollo, now I use both methods on a case by case basis, especially a lander on a multiple landings trip will be single staged.

But I tend to leave landers back in orbit whenever I leave for Kerbin - missing out on the "landed on" bonus - will have to design a flight recorder of some kind.

.

No need to be ashamed, this is actually difficult in its own way - although I gather you are trying to avoid docking this way?

[Speijker]

I always use a descent-stage, with an aesthetically pleasing design, which is left on the surface to mark landing-sites with something more than just a flag to look at (probably comes from before we had flags).

Besides, designing seperate landing- and ascent-stages is more fun and challenging.

[pauix]

although I gather you are trying to avoid docking this way?

More or less. I accidentally landed the ship once, and since nothing broke apart I decided I wouldn't bother with docking as long as I could get the job done with what I already had.

[SelectHalfling0]

I have built an atmospheric lander that uses 4 drop tanks in asparagus staging. Can reach orbit at all atmospheric planets (except eve) and most non-atmospheric planets.

[Concentric]

I don't think I've ever tried a multi-stage lander on a non-atmospheric body, so I can't say for sure how I feel about them. And the only bodies with atmosphere that I've managed a descent-ascent on so far are Kerbin and Duna - and I needed to stage off bits there. I've also only twice left an orbiter up and rendezvous'd the lander with it for the return journey. It was interesting, but its another stage of complexity that I don't often consider. I guess I'll try the separate descent/ascent stages sometime.

[Godot]

It depends ...

one use landers are designed dual or triple stage (at the extreme: 1. stage = fuel for stopping the orbit and fall straight down, 2nd stage: fuel and legs for descent, 3rd stage: legs and outlying fuel tanks are left on the ground, with the remaining spaceship = engine + fuel + RCS fuel to rendezvous with the orbiting spaceship ... if dual stage, it just corresponds to stage 2 and 3)

For Kerbins Moons however I nowadays use multiple use landers which are single stage and get refilled at an orbiting spacestation

[bsalis]

I use single stage landers,

, since they are re-usable.

[Kerbonautical]

I've never actually thought of building a multi stage lander before :/ I don't know why it never occurred to me. Honestly though it seems like a bad idea in reality and I'm surprised it was actually used by NASA. That's a really expensive bit of gear to just leave on the surface of the Moon forever

[Godot]

I've never actually thought of building a multi stage lander before :/ I don't know why it never occurred to me. Honestly though it seems like a bad idea in reality and I'm surprised it was actually used by NASA. That's a really expensive bit of gear to just leave on the surface of the Moon forever

Well, actually for the Moon Landers it didn´t make any difference ... the one part was left on the surface of Moon, the other part was (AFAIK) left orbiting moon ...

no part of the moon lander returned back to earth to be reused (which would actually have been difficult, considering the method of return (i.e. capsule via parachute).

Maybe a mission where the lander would return to earth would even be more expensive/difficult than the acutal moon mission ...

and one in which the lander remains (as a single piece) in orbit in order to get refilled and reused might, on the other hand,

pose the difficulty of the landers systems detoriating during the wait for the next astronauts to use it

(making subsequent missions rather risky)

[EdFred]

Depends on the body.

Moho - I basically used the core of my Eve lander, and it ended up being 3 stages. 1 stage used as descent, but the empty tanks had landing legs on them so they had to stay until touchdown.

Eve - SSTO (yeah right). Eve was like a 7 stage ascent. But nothing used on descent because of atmosphere

Mun/Minmus - single stage. So little dV needed. Same with Gilly.

Duna - dV is pretty low and you can use chutes for 98% of the descent, also single stage.

Laythe is the only other body I've landed on, and that was done single stage.

[Zad Fnark]

I've grown fond of a 1.5 stage technique. I'll strap on a short tank with a Poodle to the bottom of the lander to de-orbit and do most of the slowing down of the lander, dumping it within 1,000 m or so. This will leave a mostly fully fueled lander ready to go.

ZF-

[zarakon]

I usually have a set of 2-4 drop-tanks on the outside of the lander, and I put the landing legs on those. This allows me to have a wide base to make landing easier, and I can dump the landing gear along with the empty tanks for my ascent.

[Paul Kingtiger]

I did some calculations and testing on this a while back. Because KSP engines are heavy and because the Mun is smaller than the Moon, a single stage lander is more efficient (lower total mass for the required DV) than a separate decent/ascent stage. However that's only true if each stage has a separate engine.

If you used a single engine but left some fuel tanks and the legs behind it becomes a question of which is lighter, 2 tanks and a decoupler, vs 1 tank, no decoupler, but taking the legs back up. Even then I was struggling and now use single stage for all my Mun missions.

[costermonger]

I usually build a single stage lander (for low gravity moons anyway) but I've taken to placing my lander on top of a compact, high TWR/low dV stage that acts as an LES if needed, and if everything goes well it's got enough dV to perform some (or all, if at Minmus) of the de-orbit burn for landing. The KW solid rocket ullage motors are perfect for this.

I usually aim for the LES stage to have a TWR rating 1.0+ higher than the highest generated by the lower stages, and seem to get 200-300 dV.

[TerLoki]

I tried out an Apollo-style two-stage Mun lander for a few missions, but compared to the usual single-stage landers I use it turned out to be a bit of a mess. It took four tries to get one that actually worked AND let me get all the science. I may stay with that design if I ever do any more one rocket there and back Mun missions, but otherwise I'll stick with a reusable lander and space station combo.

[undercoveryankee]

My single-use landers are two-stage so I have a clear separation between descent delta-v and ascent delta-v.

It's easier to remember "As long as I have this stage I have enough delta-v to make orbit" than "If I let the fuel bar go below this percentage, I have to abort."

[Scottiths]

I simply like leaving landmarks next to my flags

[bartekkru99]

That's my typical Mun/Minimus mission:

1. Lift off.

2. In middle atmosphere detach two liquid fuel boosters.

3. When in high atmo. (50km) detach other two boosters.

4. 1st stage main engine separation (sub-orbital).

5. Achieving the orbit with 2nd (transfer) stage.

6. Burning to Mun/Minimus.

7. Achieving stable orbit.

8. Lowering the orbit.

9. Separating (finally) the transfer stage at about 100m (With some fuel left).

10. Landing.

11. Lift off.

12. Sub-orbital filight.

13. Landing again to collect science from somewhere else

14. Eventually repeating 11, 12 and 13 one more time.

15. Achieving stable orbit.

16. Burning retrograde relative to moon's (not ours,) orbit. You can save a lot of fuel doing that because you'll end instantaneously on sub-orbital around Kerbin without

adjusting periapsis.

17. Landing with parachutes and engines.

And how my vehicle looks like:

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[razark]

Honestly though it seems like a bad idea in reality and I'm surprised it was actually used by NASA. That's a really expensive bit of gear to just leave on the surface of the Moon forever

Well, once that bit of gear has done it's job, you don't need it. Any extra stuff you don't need to lift back to lunar orbit would be a waste of fuel. Also, if something were to go wrong during the landing, the crew could use the ascent stage as an abort. Build everything in one stage, and you don't have that option.

[R0cketC0der]

I've never actually thought of building a multi stage lander before :/ I don't know why it never occurred to me. Honestly though it seems like a bad idea in reality and I'm surprised it was actually used by NASA. That's a really expensive bit of gear to just leave on the surface of the Moon forever

What would be the difference? The ascent module was also dumped. The only part of the entire Saturn V that was recovered was the capsule and on some launches also cameras.