Permanently Parking a Lander in Orbit

[CrashyMcCrashFace]

I always think I'm the first one to come up with something then it almost always turns out it's been done forever or maybe is just a really bad idea. Anyway, I'm about to get past direct missions (I can dock now. Go me!) and thought instead of taking a lander on every trip to just park one in orbit of the destination. Then when I need to go there I just take a little extra fuel, dock, etc. Then just leave it in orbit and head home. I'm thinking this might lend itself to a larger lander or mule to get fuel/supplies/science on/off the surface. I play both sandbox and career mode and not sure which it would be better for. Good idea, bad idea, thoughts?

Edited April 9, 2018 by CrashyMcCrashFace
Spelling

[Superfluous J]

It's a fine idea and you're not the first to have it

The main problem is, there are not a ton of reasons to land the same basic lander on a world multiple times on separate visits, other than maybe Mun and Minmus. And they're so cheap to get to it's not worth the trouble.

Edited April 9, 2018 by 5thHorseman

[RizzoTheRat]

Thats what I usually do for Mun/Minmus/Duna.  The lander acts as a tug to drag a fuel dump out, and I include a small return capsule.  Future missions carry a bit extra fuel which they leave in fuel dump.

In practice though its never as useful as I think as I find my lander has a couple of shortcomming so I send another one with the next mission... 

 

ETA after seeing 5thHorsemans reply...

Agree about reasons to land, usually after the first landing or 2 on Duna I've completed the science tree, and contracts want me to mine or haul ore, which need different designs.  However having a lander in orbit is great for training crews, you can send a basic capsule craft on a grand tour and use local landers to get them down the surface to plant flags.

Edited April 9, 2018 by RizzoTheRat

[Greenfire32]

It's not a bad idea at all, but it does usually lead down a specific path.

At first, you'll have the lander in orbit (lets say of the Mun) and you'll use it as you're intending to. Problem is, you'll need to pack extra fuel. Enough so that it can both land, ascend, reach orbit, and dock with the "transfer" craft. This becomes an issue if you burn too much fuel on the transfer craft and have to dip into the lander's reserves, because remember, the transfer craft also needs enough fuel to get there, dock, and get back.

So then, in response to that problem, you might come up with a self sufficient lander than can gather ore to refine into fuel. That's not a bad idea either. But then you'll need something to actually refine it, so now your lander in orbit becomes a refinery station in orbit with a lander. Still no big deal, but now your lander becomes a bit bigger and a bit heavier and bit harder to maneuver to and from the surface. Also, instead of docking to a lander in orbit with the transfer craft, now you're docking to an entire station.

So then in response to that problem, you might just end up taking the easiest route and come up with a small, light lander that you can take with you on each mission. No busing back and forth, no ISRU, just flag and splash down.

There's nothing wrong with playing the game the way you've outlined, but it almost always ends up the way I've described

[CrashyMcCrashFace]

Thanks for the input. I just thought I could put a relay antenna and probe core and have it pull double-duty. Which means it will probably end up just being an overly-large/expensive/unnecessary relay. Just like Greenfire32 said, it's already getting larger and I haven't even built anything yet. Still doing it.

BTW, I love the "play the game the way you want" attitude here.

Edited April 9, 2018 by CrashyMcCrashFace

[Daveroski]

In my career games, I always build stations around each body I visit. Each station has a coms array, science bay, ISRU and a lander. I still gather the science even when the tree is maxed out.

Deep into a game, it's good sometimes to visit a world you have been neglecting and go down to do some science.

My landers are specialized for the world they are parked around but they are also the command module for the Ore Harvesting Module. This is a module which the lander docks with using  a Senior port on it's base. It then has extra fuel capacity, ore capacity and more powerful thrust as required.

On some of my stations I have started adding Crew Modules for the lander so that crew excursions can be performed.

The science module is also a separate module as it is generally surplus to requirements when going to mine ore.

The basic lander is great for flag planting missions and rescues in the orbit of their world.

 

[Zhetaan]

I do not wish to impugn @Greenfire32's experience, but I think compounding the lander into a self-sufficient flying base to stave off fuel shortages is evidence of a solution in search of a problem--by that I mean to say that if the original issue is bad piloting which dips too far into the lander fuel reserves, then isn't it a lot cheaper to learn better piloting skills?

In fairness, I make use of the permanent on-station lander method, but I also use reduced science gains in a modded tech tree to make it a lot more difficult to acquire science in the first place.  I also use LS, and the advantage of needing to take only small amounts of LS supplies to the surface while the transfer vehicle carries the supplies needed to keep everyone fed for a few weeks is a worthy one.

Therefore, I'll say that it is useful, but that it is perhaps more a novelty in stock.  It definitely has a place when exploring the Mun (it is a cousin to the popular 'biome-hopper' styles of landers) because of the Mun's variety of biomes, but for explorations of the polar regions where you need a polar orbit, it's both cheaper and easier to get a polar orbit on transfer rather than after arrival--but a polar orbit can interfere with your mission planning in a number of ways, not the least of which is that it compounds the transfer window problem.

Of course, if you want to visit a number of places on multiple trips, a different-but-equally-viable method is to take a rover, land it once, and then ensure that it is parked somewhere relatively flat.  Then you can take your lander to it, rove wherever you wish to go, and return.  If you want to be really creative, you can land on the rover and take your lander with you, or attach wheels to the lander and let it be a rover as well.  Unless you're using fuel cells (which is a valid method) or an engine alternator (which is also a valid method, but it's expensive), it doesn't cost delta-V to run electric rover wheels.

To more properly address fuel shortage concerns--as I said, I have no desire to insult @Greenfire32--if running out of transfer fuel is a possibility and piloting skills are not up to the task of cheap and efficient rendezvous, you can always calculate the amount of fuel that will be required to return to Kerbin, load that amount, and then lock the tank until you are ready to return.  Then there will never be a need to dip into the lander's reserves unless you make a deliberate choice to do so, and in that case, on thine own head be it.

With that said, there are distinct disadvantages to having a permanent lander on station.  @RizzoTheRat as much as said that designs iterate over time:  the lander with weak engines and fixed solar panels that you could afford as soon as you had the parts to build it was probably only just good enough for the job, but once you unlock good vacuum engines, better electrics, and decent landing legs, you may feel the need to upgrade.  Modular building mitigates that a bit but eventually you'll feel a need to actually use some of the parts that you're spending all this time getting the Science to unlock.

Unlocking new science experiments poses a problem if you don't have a means to attach them to the lander.  I took a single-seat lander with a docking port on top and added a two-seat can on top of it (it was a modded part, not the ungodly heavy Lander Can Mk. II) that had docking ports on either end and my new science experiments attached to the sides.  It's ugly, but I designed the lander to handle the mass (I had the future in mind when I made it--it now serves for crew transfer as well).  Once you unlock the tech tree, however, the acquisition of Science becomes academic (apologies for that) and since most base and station contracts require new vessels, the only continuing use of such landers is for flag-planting missions and communications relays--though a couple of mine do see service as station tugs and crew transfer vehicles when I'm somewhere far enough away (Jool or farther) that sending a dedicated crew tug is far more prohibitive than the parasitic mass of the never-to-be-used-again landing legs on the vehicle that is there right now.

Edited April 9, 2018 by Zhetaan

[Daveroski]

16 minutes ago, Zhetaan said:

...the parasitic mass of the never-to-be-used-again landing legs on the vehicle that is there right now.

My landers are "the ungodly heavy Lander Can Mk. II"

One of those with a senior port on the bottom and a regular port on the top and 4 RCS thrusters.

Everything else is a module.

 

[Laie]

3 hours ago, CrashyMcCrashFace said:

and thought instead of taking a lander on every trip to just park one in orbit of the destination.

Never really worked for me. The next time I went to visit the body, there were different mission requirements so the original lander wasn't exactly suitable.

However, I'm the kind of guy whose gameplay is 90% VAB -- I have more fun designing new vessels rather than flying old ones again and again.

[CrashyMcCrashFace]

Off work now and been playing with some designs and something I didn't think of. I noticed I was building a lander exactly how I want without having to compromise. I've been designing only direct accent vehicles up until now so maybe this is normal when bring a lander every time. In any case, I like it.

I went all mono-propellant.

Edited April 9, 2018 by CrashyMcCrashFace

[Greenfire32]

2 hours ago, Zhetaan said:

-snip-

All valid points and no offense taken. Pilot-error is definitely a factor that can make or break a good ship design. Getting better at the game will absolutely 100% increase your odds of success in any given mission.

However, not all of us have those skills or desire those skills. I myself am a fairly good pilot (haven't lost a single Kerbal ever, been playing since 2011-2012), but I'm no Poe Dameron either.

[Zeiss Ikon]

One thing to consider with leaving a lander in orbit is that there won't be anyone aboard to stabilize the lander for docking.  That means you'll either need to be confident enough at docking to dock with a potentially tumbling lander (which I've done, twice, and would prefer to avoid for the future), okay with using time-warp to stop the tumble between attempt, or you'll need to have a probe core with SAS capability and enough comm range to control it "from the ground" (controlling a probe from a vessel in flight requires a high tech antenna).

OTOH, if you bring a fresh lander with you each flight, you can launch it already docked to the crew module, or (if you want to play Apollo) do a transposition and docking while the lander is still attached to the transfer stage, hence much more resistant to tumbling just due to inertia.

[DerekL1963]

1 hour ago, Zeiss Ikon said:

One thing to consider with leaving a lander in orbit is that there won't be anyone aboard to stabilize the lander for docking.

 
Codswallop.  The presence or absence of a stabilizing system is a choice left to the designer - not a law of nature.
 

1 hour ago, Zeiss Ikon said:

or you'll need to have a probe core with SAS capability and enough comm range to control it "from the ground" (controlling a probe from a vessel in flight requires a high tech antenna).

Mostly correct.   You don't need enough range to reach KSC from the lander if you have the appropriately ranged relay antenna on the the approaching vessel.  (Or a seperate communications relay bird.)

[CrashyMcCrashFace]

Yeah, I have a relay network already setup with 99.9% coverage. Of course I somehow hit that 0.1% all the time in the most critical moments.

I ran through the whole thing tonight in sandbox on the Mun before implementing in career mode. Having the relay network + SAS module made it pretty easy to send a scientist to the surface since I rely on most of the SAS modes pretty often. I'm not exactly sure how I'm going to implement this setup for getting science though.

One thing I didn't like was setting up a parking/rendezvous orbit over 25km. I normally go between 10-15km for Mun but you can't get over 10x warp that low so the rendezvous would get painfully long. I know most people can do it pretty quick but I'm new and slow.

One more thing I want to figure out is if going all mono-propellant is better than a mix of mono and liquid-ox. Fuel planning was easier but it seemed like the "puff" engines used a lot.

Edited April 10, 2018 by CrashyMcCrashFace

[Scarecrow]

In one of my saves I actually parked a station around Kerbin, Mun, Minmus, Duna and Jool.  The Mun and Minmus stations had landers permanently attached for visits to the surface, and were fairly basic.  The Duna station had a lander capable of both landing on Duna or making a visit to land on Ike and return.  At Jool, the lander assigned to the station there was intended for making excursions to Val, Bop and Pol, though I think I updated to a newer version of KSP before actually using that lander in anger.

[FlyingPete]

I thing the 'reusable' method only really works if you have some space station infrastructure in place. So you can have Duna Station equipped with power, fuel storage, a science lab, crew facilities and a lander or two. Thus gets left behind for future missions to use.You could even leave a permanent science/mining crew behind and rotate them out with arriving/departing crews if you want to play that way.

If you bring an improved lander with some future mission, the original can be relegated to use as a spare or an orbital shuttle.

Whether this makes sense vs bringing expendable craft with each mission depends on how much exploration you plan to do and the dV requirements to get it there.

Edited April 10, 2018 by FlyingPete

[DerekL1963]

18 hours ago, CrashyMcCrashFace said:

One thing I didn't like was setting up a parking/rendezvous orbit over 25km. I normally go between 10-15km for Mun but you can't get over 10x warp that low so the rendezvous would get painfully long. I know most people can do it pretty quick but I'm new and slow.

You can leave your parking orbit low if the craft performing the rendezvous goes high (enough for a faster warp).   You don't have to rendezvous from underneath.

[CrashyMcCrashFace]

18 minutes ago, DerekL1963 said:

You can leave your parking orbit low if the craft performing the rendezvous goes high (enough for a faster warp).   You don't have to rendezvous from underneath.

Ah. Very helpful tip. Thanks. This whole thing has become very long and tedious. Getting it done a little faster is nice.

[RizzoTheRat]

On ‎10‎/‎04‎/‎2018 at 7:31 PM, Scarecrow said:

In one of my saves I actually parked a station around Kerbin, Mun, Minmus, Duna and Jool. 

I once took the same station to Kerbin, Mun, Minmus and Duna.  4 separate contract with the same vessel netted me a fortune and delivered a station in to Duna orbit with comms, parking but not a lot of fuel left

[Zhetaan]

On 4/9/2018 at 3:22 PM, Daveroski said:

My landers are "the ungodly heavy Lander Can Mk. II"

One of those with a senior port on the bottom and a regular port on the top and 4 RCS thrusters.

Everything else is a module.

I agree; that's about as modular as it is possible to be with just the stock parts.  It's not at all how I play, and for my trouble, I'd prefer to have a solar panel or six on the can, but otherwise I can see the appeal.  On the other hand, mission planning also means shipping the various modules that you might need and supplying storage for the modules you're not using right now, so I can see how this solution can balloon quickly into a logistical nightmare--but since you're in the habit of building stations around everything, I suppose that's not so much a problem for you.

 

On 4/9/2018 at 11:55 PM, CrashyMcCrashFace said:

One more thing I want to figure out is if going all mono-propellant is better than a mix of mono and liquid-ox. Fuel planning was easier but it seemed like the "puff" engines used a lot.

Monopropellant is not so efficient as LFO.  The Twitch and Spark are the nearest comparable LFO engines (they have roughly the same thrust, mass, and size), and the comparison breaks down as follows:

	Puff	Spark	Twitch
Thrust	20.0 kN	20.0 kN	16.0 kN
Isp (vexh )	250 s (2451.7 m/s)	320 s (3138.1 m/s)	290 s (2843.9 m/s)
Fuel Flow	8.16 kg/s	6.37 kg/s	5.63 kg/s

I_sp is specific impulse, the measure of engine efficiency available in the game (it's given in seconds), and v_exh is exhaust velocity, a different measure of engine efficiency (given in metres per second) that is more directly useful to the comparison.  For double-checking purposes, v_exh is calculated by multiplying I_sp by g₀ (one standard gravity, set in-game and real-life as 9.80665 m/s²), though in reality, I_sp is calculated from v_exh and not the other way round.  Thrust is measured in kilonewtons, a measure of force (one newton is equal to 1 kg*m/s²), and is equal to exhaust velocity times fuel flow.

For the most part, the differences are in the engine design (one could, for example, configure a monopropellant engine that uses .00001 kg/s of fuel--it's just a number in a computer file) but it is meant to reflect reality:  monopropellant, in general, cannot effectively store or release so much energy as a bipropellant system.  The chief advantages of monopropellant are in the simplicity of the fuel delivery system (no mixing ratios), reliability of the engine (run it over a catalyst and it blows up; there are no ignition problems), and stability of the fuel (most bipropellants have at least one cryogenic component; most monopropropellants are stable at high temperature).

In-game, monopropellant is less effective because it is less dense:  LFO (LF and O have the same density) is 5 kg/L; monopropellant is 4 kg/L.  Therefore, in addition to the mass of fuel being dribbled out of the engine at lower velocity (which reduces efficiency), it takes more units of that fuel to reach that mass.  Translating to units of fuel consumed per second (which is what you see on the resource tab), the Twitch takes 1.13 units/s (.51 LF and .62 O), the Spark takes 1.27 units/s (.57 LF and .70 O), and the Puff takes 2.04 units/s (all 2.04 Mono).  Part of what you see is an illusion; the LFO engines consume fuel from two bars on the resource tab, so each bar drops at approximately half the total rate (45% LF and 55% O), but the monopropellant engine still takes almost twice as much fuel after accounting for that.

If we were to create an LFO engine with the exact same efficiency as the Puff, it would also have a fuel flow of 8.16 kg/s, but that would translate to 1.63 units/s (.73 LF and .90 O) solely because of the 25% greater fuel density than monopropellant.

All taken together, this means that to get the same effect from monopropellant, you need to take more of it.  The main advantages to using monopropellant are that you don't need to be concerned with tank arrangement, placement, and plumbing, that the tanks available (especially the radial tanks) can be fit into many small or otherwise wasted spaces on a vessel, and that (especially if you already need it for docking) you can save on complexity by using only one fuel for everything.  The main disadvantages are that it is less effective, more expensive (.3 Funds/kg versus .2 Funds/kg for LFO), and lacks good high-volume tankage solutions.

 

On 4/10/2018 at 1:31 PM, Scarecrow said:

In one of my saves I actually parked a station around Kerbin, Mun, Minmus, Duna and Jool.

 

On 4/10/2018 at 2:19 PM, FlyingPete said:

I thing the 'reusable' method only really works if you have some space station infrastructure in place.

At least at first, I tend to take a lander to the Mun or Minmus (or both), leave it in orbit, and then bring the station later.  Of course, that's usually because I need to go to the Mun and Minmus to get both the science and the money to afford decent station parts--my original forays into reusable landers came of the need to leave off mass in order to have a cheaper ride home.  Since it was already there, the next mission was made cheaper by my only needing to take extra fuel rather than an extra lander, but I freely admit that that had more to do with my hard-mode game settings than it did any especial advantage of the method.

[CrashyMcCrashFace]

3 hours ago, Zhetaan said:

Monopropellant is not so efficient as LFO.  The Twitch and Spark are the nearest comparable LFO engines (they have roughly the same thrust, mass, and size), and the comparison breaks down as follows:

Thanks for the detailed explanation. It's nice to learn why my design didn't work out. I ended up changing to the Spark and it required only about 2/3 the total fuel (liquid and mono). I want to try different things but the Spark just seems like the go-to engine for this type of thing. I was playing with the Twitch and was able to get a lower center of gravity on my design. I'll try to actually put it into use next time.

[Tyko]

I use this approach for all of my Mun/Minmus missions. Usually after the first tentative landings I want to explore the moons in earnest and re-using the lander is great. I'll cycle through crews so everyone gets the experience of landing on both moons.

[radonek]

I also do this all the time, but it need a bit more infrastructure and planning to use effectively.

1. As mentioned, early landers are bound to get obsolete. So do not bother with reuasble desing for few early landfalls. Instead, use them to gather less accessible science (from poles, will come to that).
2. Take your time with design. If it's to be reused, it worth to take time perfecting stability, CoM alignment, RCS placement… IMO key part here is the engine - reusing also gives you chance to perfect your landing technique, and decent TWR is key to that.
3. Go wide. Wide base is great for lander stability, but people tend to avoid it because it's harder to pull up from kerbin. However, if you are after reuse, it is definitely worth it to invest into it, event if it means tricky and inefficient launch.
4. Once you can build a reasonably good lander, put up support station with the lab, bunks and fuel at low orbit.  And because you taken care of poles already, you can place it at equatorial orbit to make rendezvous easier. Have it at decent height so that phasing from low parking orbit does not take forewer and you can use higher warps. About 30km worked well for me at Mun.
5. Lab is not strictly needed if you have scientist in crew to reset experiments, but I have it anyway.
6. Do not go overboard with spare fuel - hauling in more is easier then flying in modules. Be generous with docking ports - in long term, mun/minmus station needs one for fuel tanker, one for crew rotation vehicle, at least two spares for future expansion and of course something for the lander. Be careful where you put them, they will see a lot of traffic, so putting them close to delicate equipment is not a good idea.
7. Have a relay antena or pilot on station. If you are quick, descent and most of ascent can be made with direct visibility to station. This may not help much routing the connection, but it can help a lot with early low-power antenas.
8. I also find it useful to have one tiny fuel tank for precise dosage  when transfering small ammounts of fuel, ie. to deorbit useless parts.
9. Deploying a new lander is a chance to visit places… add some additional drop tanks to visit biomes that require larger inclination changes.
10. Obviously, you will need a tanker ship to top up fuel. It begs to do this as carefuly as others, but in my experience is not worth it. With all precious science invested into lander,  you will want to upgrade it's design anyway.
11. While it's perfectly reasonable to offload surplus fuel prior to departure, resist temptation to combine the crew rotation vehicle with full-blown tanker.

Yes, space stations have other uses then just contract targets. This way, you can easily harvest a lot of science, train a crew and practice rendezvous/docking in stable scenario.  Downside is that it moves from more complicated navigation (direct polar missions) to simpler ones (ascent to equatorial orbit).

[Tyko]

Here's an example of my fav reusable setup... I launched the vertical component Core with partial fuel - enough to circularize in Lunar orbit and as much extra as I could carry with an early tech 1.875m stack. Next I sent up the lander with transfer stage including a fuel tank and engine. The transfer stage docked to my Core first and transferred all of it's remaining fuel before de-orbiting. After that the lander docked.

From there it was just a matter of sending crews with some extra fuel on each trip. Later I actually added two additional modules to allow for research and longer term stays around the moon - essentially becoming my first small lunar station.