A lander that stays in space?

[pondweed]

Hi all

so iv done a return trip to minnimus (w/ sciency stuff), and am looking to go further out (ike).

iv encountered snafu with lander designs.

in the past iv attached return fuel tanks underneath. works okay but im left with a very, very long lander that, upon landing, has to balance upright or lay on its side (risky).

so im trying to design a lander, that is very short in length, with fuel tanks stacking outwards (x4). kinda like a giant space starfish.
getting it into orbit for EVERY far-bound mission is costly due to 'fat' aerodynamics. so i was thinking of keeping it in kerbin orbit, with the refueling station.
than having a separate science module + crew-pod which can detach and come back down to kerbin by itself.

anyone done this sort of thing before? any pics/vids?

one potential issue i though off was, when coming back from far out missions, i wont the able to do much with using atmosphere to airbrake.
with just science kit + crew-pod, i can come in steep, at high speeds. nice little heat shield protects compact unit.
but doing that with a fat lander that i want to put back in kerbin orbit? will it survive the heat?

thanks
PW

[Venusgate]

Why yes, I have :)

[imgur]Qk4l0[/imgur]

[sdj64]

Like Venusgate's design it might be best to go with a separate lander and transfer/refueling ship. That way the lander stays small and manageable but the big transfer ship can contain fuel for many landings. At the end you can either de-orbit and land like you have been doing, or send up another ship with fuel and a change of crew so the transfer ship and lander can be used again on another mission.

[HoloYolo]

I've always found it cheaper to just launch landers after every mission than to keep one up and launch fuel stations. Think about it. A 100k fuel station launched every 5 missions+50k lander means 150k for the first fuel station. You can complete 3 missions with separate landers for the same cost.

[Geschosskopf]

[quote name='pondweed']so im trying to design a lander, that is very short in length, with fuel tanks stacking outwards (x4). kinda like a giant space starfish.
getting it into orbit for EVERY far-bound mission is costly due to 'fat' aerodynamics. so i was thinking of keeping it in kerbin orbit, with the refueling station.
than having a separate science module + crew-pod which can detach and come back down to kerbin by itself.

anyone done this sort of thing before? any pics/vids?[/QUOTE]

Yeah, and there are qutie a few ways to do it. In all of them, however, the lander is as short and wide as possible. Not only does this provide better stability when landing on steep slopes, but it also facilitates giving it balanced RCS thrusters if the mission involves docking the lander to anything. And docking is more likely needed at other planets.

When building short, wide landers, it's never necessary to go all "starfish" with the tanks arranged like wheel spokes. First, they don't like being attached that way (they much prefer to be parallel with the central stack). Second, if you don't think several parallel tanks are wide enough, you can always put the landing legs out on outriggers made of structural I-beams or box girders to widen their stance. This doens't seem to create enough extra aerodynamic drag to worry about.

So really, the 1st step is to determine what, if anything, you intend to return to the surface of Kerbin. Given that you can EVA, grab all the data from experiments, and stuff them in the capsule, there's no real need to return anything except the capsule unless you just want to recover more parts for their scrap value. This is especially useful if you send a scientist because he can reload the Goo and Materials experiments for use in multiple biomes per trip. And as long as you've got the OKTO probe core unlocked, you don't need a pilot to use SAS, so 1 scientist + 1 OKTO is the most cost-effective science-grabbing crew available.

Anyway, desing and buld whatever will end up on Kerbin's surface at the end of the mission. Capsule, parachute(s), heat shield, plus anything else you think is too expensive to abandon. Then design the whole rest of the mission and the necessary rockets around that. Just remember, the more mass you bring back, the more chutes it will need, so the heavier it is, which means it needs more rocket to get anywhere, which makes the whole thing more expensive, and outweighs the savings on a few small parts attached to the capsule at the end.

Note that it's quite possible to put radial decouplers between the central, recoverable stack and the radial fuel/engine/leg modules. That way, the last job of the lander engines is the de-orbit burn, after which you dump them and just land the central core. This works great for short trips to Mun and Minmus.

However, there's no sense at all in bringing a whole lander all the way home from another planet. Even if you do intend to make further use of it (which is rare), why burn the fuel to move it back and forth? Much better to leave it where it's useful, at the planet it was designed for. This leads to the overall mission concept of the mothership. In this scheme, you have 2 separate components that dock together: a lander specific to the target planet and a crew transport. The general idea is, the crew transport takes the crew there and back. At some point in the trip, the lander docks with the crew transport to pick up crew, lands on the planet, and returns to the transport with the crew and data. The data and crew go back into the transport, the lander is left behind, and the transport returns to Kerbin.

So there you have 3 general options for a landing-and-return mission to another planet:

1. Scaled-Up Mun Rocket
No docking. You have just 1 vehicle, a rocket with a lander on top. However, having a multi-stage lander is desirable, so you don't have to lift the legs and such from the surface again, you just fly home in the lander's upper stage(s). Simple mission but you have a much bigger, heavier lander than the other options, which means a bigger, more expensive rocket. Still, quite workable.

2. The Mothership
Here you dock the lander to the crew transport in LKO and send them out as 1 unit. Lander only has to get down, back up, and rendezvou, so is pretty small and light. However, the crew transport is bigger and more expensive than necessary because it has to get both itself and the lander out there (although only itself home).

3. The Flotilla
Here you have a lander as in #2 but a crew transport only big enough to move itself. They go out separately and rendezvous at the destination prior to landing. Somewhat cheaper than the mothership concept, plus a lot easier to maneuver and you have fewer parts in the same place most of the time. And if you can handle sending multiple ships to the same place at once, which isn't difficult at all (see link in my sig for a flotilla tutorial), you can send a dozen or more. Full constellation of satellites, a whole ISRU set-up, permanent colonists, you name it.

[Temstar]

[quote]
2. The Mothership
Here you dock the lander to the crew transport in LKO and send them out as 1 unit. Lander only has to get down, back up, and rendezvou, so is pretty small and light. However, the crew transport is bigger and more expensive than necessary because it has to get both itself and the lander out there (although only itself home).
[/quote]

This concept is not necessarily bigger than the flotilla concept because of one very important reason - the Mothership can be optimized for deep space only operation and lander can be optimized for landing/takeoff only. For example an Eve lander by necessity needs high TWR and engines that can work under high atmospheric pressure. Sure you could use such engines to make an interplanetary trip but they are not optimized for it. If instead you send the Eve lander to Eve with a nuclear thermal rocket powered mothership then you no longer need to refuel the lander before landing on Eve or need to build an integrated interplanetary stage to the lander.

Also another important factor: once you designate your interplanetary mothership as "deep space only" this opens up the option of reuseability. Just like how the mothership remains in orbit while the landers land in the outward part of the trip, upon returning to Kerbin you can elect to park the Mothership in low Kerbin orbit. The crew and the data can return to KSC via SSTO space shuttles and the Mothership refueled by your orbital infrastructure and be prepared for the next trip.

Also, for target worlds were SSTO landers are possible (so basically all of them except Eve and Tylo), once the landing is complete you simply leave the lander back in orbit and have the crew move to the mothership on the return leg of the trip. This means on the next trip to that world you already have a lander waiting in orbit and all the mothership have to do is bring fuel to refuel the lander for another landing.

Here are some images of my interplanetary trips using this mothership-lander architecture:

Duna + Ike double landing
[img]http://i50.tinypic.com/2hzh4oz.jpg[/img]

Landing on all four moons of Jool (Pol didn't exist back when I did this mission)
[img]http://i42.tinypic.com/m8zhn9.jpg[/img]

Eve + Gilly double landing, including an Eve rover for driving to the ocean
[img]http://108.imagebam.com/download/pDGNiG6An__Fltu2YmOYJw/25596/255950333/screenshot1124.jpg[/img]

[MaxL_1023]

I usually just put an ISRU and mining drill + ore tank on any lander intended for another planet. You only need one small tank (you can just use the ore and re-fill it) and the weight is not that big of an issue as you basically half your fuel requirements for non-atmospheric bodies.

When it comes to launch, I just make it as draggy as I want, and launch it nearly straight up at a low TWR to start. This minimizes drag losses and only takes a moderate investment in extra delta-v.

[Xavven]

[quote name='Temstar']
Eve + Gilly double landing, including an Eve rover for driving to the ocean
[/QUOTE]

Side note: I really like your use of the plane tails as mounts for the LV-Ns, Temstar. It looks nice!

@Pondweed, the fascinating thing about your question is that engineers and scientists at NASA struggled with a similar concept when designing the mission mode for the Apollo moon landings. I highly recommend reading the section entitled "Apollo Mission mode selection" on this wikipedia page: [url]https://en.wikipedia.org/wiki/Lunar_orbit_rendezvous[/url]

The mission mode you propose isn't quite "direct ascent" because your lander wouldn't return to the [I]surface [/I]of Kerbin per se, but you have already identified some of the main drawbacks of your mission mode -- the lander has to carry fuel for the return trip to Kerbin. It has to haul this fuel to the surface of your destination celestial body and back to orbit. This not only makes the lander heavier and and rather ungainly (as you have mentioned), but it also expends a great deal more [I]total[/I] fuel for the entire mission than if you designed the lander to only return to orbit around the destination celestial body, not Kerbin, and used a "mothership" or Command Module to do the returning.

Furthermore, in my experience playing KSP so far, I estimate that one can use a single lander design that is sufficient (but not optimal) for about 60% of the moons and planets in KSP. Each of the other 40% of the bodies in KSP require their own, individualized, dedicated landers with special planning and often at least 2 stages. So your lander probably isn't reusable for a little less than half the stuff anyway. While we're on the subject of reusability and efficiency, you're going to gain more by leaving your lander in orbit around a given celestial body for future visitors than by expending fuel shipping that lander back and forth between planetary systems.

All that said, it is an interesting design challenge to keep your mission mode idea. I'd love to see what you come up with! Not everything in this game is about "conform to this rule because it is the most efficient. Assimilate or die!"

[Kaiser82]

Sort of like a mobile home, that never went anywhere. Hmm.

[Pthigrivi]

Yeah I actually love this play-style. I try to re-use [I]everything[/I]. Its just so expensive to get this stuff up there, it seems crazy to de-orbit anything useful. Also once you have a good mining set-up there's really no reason to bring anything but dry modules to LKO and maximize everything they do. There have been good suggestions all around here, but I like running a number specialized re-useable modules almost entirely on Nervas.

- LKO station with fuel tank and science lab
- Re-usable lander with science set-up capable of aerobrake back to LKO
- SSTO shuttle for crew transport to LKO
- SSTO cargo lifter to LKO
- Minmus mining rig
- Aerobraking tanker for returning fuel to LKO
- Kerbin SOI tug for transporting modules, Oberth assist

It does make for some tricky engineering, especially in 1.0.5. Making something really efficient and light that wont flip around or overheat when aerobraking can be tough.

[Geschosskopf]

[quote name='Temstar']This concept is not necessarily bigger than the flotilla concept because of one very important reason - the Mothership can be optimized for deep space only operation and lander can be optimized for landing/takeoff only.[/QUOTE]

Actually, the motherships is ALWAYS bigger. I've done it both ways enough times to know :).

The ONLY small, negligible benefit to doing it mothership-style is only having to manage 1 ship. Everything else is in favor of flotillas.

Whether you do a mothership or a flotilla, the lander is equally optimized for its job so that's a wash. But with the mothership, the crew transport is compromised by having to be big enough to move not only itself but also the lander out to the destination. This increased size of the crew transport means a bigger lifter, and the cost of rockets increases faster than the masses of their payloads, so you always spend more doing a mothership than a flotilla. And it gets even worse if there are multiple destinations (say a planet and its moon). The Jool 5 Challenge is completely the wrong way to do things because you have to lug the entire mass around instead of sending small, specialized units to each moon.

And the case for flotillas beomces even stronger if you're doing more than just a 1-shot landing. What if you want to land in every biome on both Duna and Ike? You'll certainly need to refuel the lander multiple times for that. Which means you'll need to map both bodies. Are you going to make the mothership go from polar to equatorial orbits at both places? That was be insane. No, you'll send probes for that. Plus something to get ore, turn it into fuel, and deliver it to your other ships. Thus, you'll be sending 4-5 ships just to suppor the main mission, so there's no reason not to split the main mission up into its component parts as well. If you can fly 2 ships at once, you can fly 20.

[Temstar]

Yeah but each lander has to leave LKO and get onto the interplanetary trajectory somehow, how do you propose to do that in a flotilla? If the answer is "integrated interplanetary transfer stage" for each lander then the mass of those stages have to be included. And if these are nuke stages which you then drop that's a lot of nuke engines that you are throwing away. Putting all those engines onto a mothership means they can be reused on later trips and there won't be any hot reactors flowing around Kerbol.

When I did my Jool 4 mission the mission architecture was:

1. Launch mothership into LKO
2. Launch Bop lander to LKO, dock with mothership
3. Launch Tylo lander to LKO, dock with mothership
4. Launch Laythe/Vall double lander to LKO, dock with Mothership
5. Launch tanker rocket to refuel the entire stack
6. Mothership + 3 landers make a burn for Jool SOI using mothership's nuke engine cluster
7. Upon entering Jool SOI, Mothership makes trajectory adjustment for Jool aerocapture pass, after aerocapture AP is now at Tylo orbit
8. Tylo lander undock from mothership and adjust orbit for Tylo SOI encounter
9. Bop lander undock from mothership and adjust orbit to raise PE above Jool's atmosphere, then at PE it fires its engine again to raise AP to Bop orbit
9. Mothership adjust orbit to raise PE, so that after another aerobraking pass it's AP will change to Laythe orbit
10. Tylo lander enter Tylo SOI at its Jool orbit AP, fire engine to enter Tylo orbit
11. Mothership + Laythe/Vall lander enter Laythe SOI, adjust PE for Laythe aerocapture
12. Bop lander enter Bop SOI, fire engine to enter Bop orbit
13. Mothership + Laythe/Vall lander now in Laythe orbit after aerocapture pass
14. Tylo lander lands on Tylo surface, jettisoning orbital maneuvering fuel tanks in the process (no engine, only fuel for orbit change and deorbit burn)
15. Bop lander lands on Bop surface (polar orbit landing to visit Kraken)
16. Laythe lander undock from mothership and land on Laythe surface
17. Laythe lander jettison descent stage shortly after lift off, the ascent stage returns to the orbiting Mothership with empty tanks. The ascent stage now becomes Vall SSTO lander
18. Vall lander refuel from Mothership fuel reserve
19. Vall lander make a moon-to-moon tranfer burn, leaving Laythe for Vall
20. Mothership makes an ejection burn to leave Laythe SOI, pass through upper Jool atmosphere for aerobraking pass and settles down in Low Jool Orbit
21. Vall lander enter orbit around Vall, then lands on Vall surface
22. Bop lander launch from Bop surface, makes an ejection burn for Jool aerobraking pass
23. Tylo lander launch from Tylo surface, jettison ascent stage and makes an ejection burn for Jool aerobraking pass
24. Vall lander launch from Vall surface, makes an ejection burn for Jool aerobraking pass
25. The remaining sections of all three landers make aerobraking pass through Jools atmosphere and settle into Low Jool Orbit and dock with the Mothership.
26. Service modules of all three landers and jettisoned, leaving only the capsules attached to the mothership. Service modules deorbited into Jool's atmosphere for science
27. Mothership + capsules fires nuke engine cluster for interplanetary trip back to Kerbin
28. Mothership + capsules make aerocapture pass through Kerbin atmosphere and settles into LKO.
29. Shuttles bring crew and data back down to Kerbin, fuel tankers refuel Mothership to prepare for next trip.

You're not suppose to take the Mothership everywhere, the Mothership is only responsible for carrying the landers to the parent body SOI, the landers then all undock and go onto complete their individual missions before rejoining the Mothership for the trip back. In my case my Mothership also pulled double duty bringing fuel for the Laythe/Vall lander. I considered this extra leg acceptable since you can aerocapture both ways between Jool and Laythe. Edited November 24, 2015 by Temstar

[problemecium]

What I usually do is build a small reusable lander with a docking port and set up a station around wherever I'm exploring, so that I can land, ascend, dock, send the crew on their way and add new ones as necessary, and repeat.

[Wanderfound]

[quote name='Kaboom!']I've always found it cheaper to just launch landers after every mission than to keep one up and launch fuel stations. Think about it. A 100k fuel station launched every 5 missions+50k lander means 150k for the first fuel station. You can complete 3 missions with separate landers for the same cost.[/QUOTE]

Which is why you don't launch multiple 100k fuel stations. Launch one fuel station (cheaper and easier if you use its fuel capacity during the launch), then fill it with SSTO spaceplane tankers. Once you account for recovered vehicle funds on the tankers, the cost per unit of fuel is tiny.

Having the fuel supply up there also converts most of your LKO ships into interplanetary vessels; if you can hit LKO with enough tank capacity for a few thousand ΔV once refuelled, you can go anywhere.

[Pthigrivi]

This is also incidentally part of the reason I think kerbals shouldn't have to return to kerbin to level up, or at least a way aught to be available to level up without it. I get wanting to encourage return missions but a leveled up kerbal stuck on the surface of Eve isn't of much use anyway. Edited November 24, 2015 by Pthigrivi

[Thanny]

A lot depends on what techs you have available. Provided you have docking ports, you lander only needs enough fuel to get down and back up again. The rest stays in the transport ship that you re-attach to after leaving. Of course, if you're trying to maximize the amount of science you get, you can still have a monstrous lander. An asparagus hopper for Minmus is a good way to get a chunk of science once you've unlocked decouplers and fuel lines. And if you want to get the most out of your science, you don't transmit, but return it to Kerbin. That throws re-usability out the window, unless you get fancy with where the instruments are attached, or stick with capsule data that can be transferred (basically reports and surface samples).

For me, a big part of the fun of the game is figuring out how to get [URL="http://oi68.tinypic.com/1yvm07.jpg"]particular monstrosities[/URL] into orbit, so I'm always coming up with something new for future missions. Quite beyond that, landers are hardly universal. A lander suitable for Minmus isn't going to be worth a damn on Duna.

As a general rule, worry more about weight than aerodynamics. You'll want a fuel depot in low orbit to fill up large interplanetary craft that you launch empty, with a launch stage that has just enough fuel to get it to the depot.

[magnemoe]

My standard design for an light lander on minor moons is 4 45 liter tanks around an MK1 landing can, you can also use an material lab in bottom, or use 90 liter tanks.
909 or 48-7s engine.

This is the type of landers I leave at destination for later science missions, can also be used to return kerbals to base for later pickup.
difference from an early mun or minmus lander is the lack of decoplers.

[Warzouz]

I also wanted to build a reusable lander able to refuel and do other trip down quickly. So I've worked with space station

I came to that design : [url]http://forum.kerbalspaceprogram.com/threads/132464[/url]

The station is fully refuellable from it's parent body or a nearby object. Lander is generic and validated for most bodies (except Eve, Tylo and Laythe - you could land but not come back) but it could host dedicated reusable landers (for Laythe or Tylo). The miner is also the engine section of the station so it can move easily (as did my Joolian mission).

The lander and miner have been tested on high slopes (27° for the miner on Bop)

Typpical mission is sending the station and lander there with a return vehicle. 6 crew goes there and 3 return. Then I plan crew rotations.


[CENTER][url=http://tof.canardpc.com/view/052d05b8-a4cd-4bd4-bd64-f92bd0bde15c.jpg][img]http://tof.canardpc.com/preview/052d05b8-a4cd-4bd4-bd64-f92bd0bde15c.jpg[/img][/url] [url=http://tof.canardpc.com/view/8c5413fc-2ba4-48c0-b0d9-ef602c9d33ec.jpg][img]http://tof.canardpc.com/preview/8c5413fc-2ba4-48c0-b0d9-ef602c9d33ec.jpg[/img][/url] [url=http://tof.canardpc.com/view/e4402384-66b4-4982-9cff-b9ec6edb33ce.jpg][img]http://tof.canardpc.com/preview/e4402384-66b4-4982-9cff-b9ec6edb33ce.jpg[/img][/url]
[SIZE=1]Station orbiting Vall / Vaccum lander on Dres / Miner landing on Eeloo[/SIZE][/CENTER]

Beware that wasn't fully recheck for 1.0.5. I'm waiting for 1.1 Edited November 24, 2015 by Warzouz

[FlyingPete]

On missions to Mun and Minmus, I like to put a station in orbit of the two moons. A lander is based at the station and is used multiple times. The lander uses fuel from stocks at the space station, and the crew then only need to bring fuel with them to replace that used by the lander. If you have a space station around Kerbin as well, you can have a reusable shuttle that transfers between LKO and Mun/Minmus orbits, rather than launching a new vehicle each time. A much smaller craft is needed for each flight which just brings the crews to the station in LKO.

Once you have ISRU equipment, exploration of Minmus can support itself. A tanker can shuttle between the surface and the station, either bringing ore (if you do the refining on the station) or fuel (if you refine on the ground.) The science lander and the station-to-station shuttles can be refuelled at Minmus, and Kerbin only needs to supply the launch/reentry vehicle.

[Warzouz]

And don't hesitate to pack a lot of fuel. You'll be able to do multiple hops and finally use less fuel than a smaller ship that needs to refuel more often from space. My default lander has 3000m/s with only one small Rockamax tank and one terrier.

BUT the new lighter ISRU may change that...

[Landge]

Not a starfish shape but close. These bases are both stock.

Early 0.18 I think. Before rover wheels were invented...


After jettisoning the rovers...

Here is how I attached the Hitchhicker to the center stack...


My current version was to have 4 wings but it became real laggy after 3...



The Hab Hub is the center piece that links all wings together.
Not technically stock. I made a copy of the HubMax Multi-port Connector and supersized it by editing stationHub.cfg file to stationHubXL with a rescaleFactor =2.


It took 4 launches total to build plus a lot of rocket hopping, time, and sweat to get the docking ports to connect. The largest base I ever want to make.
You have to have suspension of belief due to the hitchhikers being on their sides. I would love to see Squad make a different IVA for horizontal builds.

Edited August 2, 2016 by Landge

[Warzouz]

@Landge : very nice base

[cantab]

Back to the original question, why not keep the lander in Minmus orbit? You can then have a science and fuelling station to support it. With a lab on the station over time you can get considerable bonus science points. In career mode do try and level up your scientists or the research will be super slow, and you'll want to have unlocked fuel transfer by upgrading R&D I think too.

If you'd prefer a simpler approach, consider making a lander that launches "sideways", that lets you get a nice stable lander that fits in a slim fairing for launch.

My science station: [url]https://flic.kr/p/yxSxUs[/url] As you can see I needed extra solar power, the lab is an electricity hog. I used a tall lander, seen docked to the far side, but no reason I couldn't have gone for a wider one. The return ship is docked to the near side, and doubles as a backup lander in case I need to rescue a Kerbal (which happened once).

A "sideways" lander: [url]https://flic.kr/p/rbNWMd[/url] that's a probe, but no reason it couldn't work for Kerbals too. Just be sure to add a probe core facing up to control from or the navball will be screwy.

[vixr]

All of my landers are true spacecraft, they are born on Kerbin, but never go back there. They all have a command module to push them into low orbit of the planet or moon and then return them to the station they are assigned to. I undock the lander from the command module and dock both ships to the station...I can't begin to explain how cool it is to park the CM/LM near the station and then dock both. I have made tugs that tow the station and CM/LM to where I want to explore next. Its been fairly successful. Some of my designs are wobbly (depending on the size of the docking ports) and hard to fly but I always seem to get where I'm going. Edited November 24, 2015 by vixr

[pondweed]

whaaa! wicked stuff guys. thanks for all the great info. lots to play around with here