Mun and Minmus- expendable vs reusable

[FlyingPete]

Pre-1.0, I'd always 'done the Mun and Minmus by having a reusable shuttle which went from a station in LKO to another station in orbit around either moon. This worked out quite cheaply as aerobraking meant the return costs from Minmal orbit, were er, minimal. The ship remained in orbit, and only fuel supplies and a launch/crew return vehicle needed to be sent from Kerbin to the station in LKO. With the atmospheric heating introduced in 1.0, direct aerobraking from a Minmus-Kerbin transfer gets pretty hot, and so realistically engine burns are needed (I know you can make multiple passes, but it's not very convenient in terms of time.) This means hauling more fuel along for the whole trip and so makes the craft larger as well as needing more refuelling. Heat shields help, but they'd be depleted after a couple of trips.

So, what's everyone's preferred way to get Kerbals to and from the Kerbin system's moons? I think a single-use capsule would be simpler as it could make a direct re-entry from the transfer orbit, protected by a heat shield. I'm using expendable launch vehicles anyway, so it just means the capsule goes to Minmus rather than staying at the LKO station. 

Once I've developed ISRU, established a mine on Minmus, and engineered some decent spaceplanes (or SSTO rockets) then perhaps reusable craft would be more viable- it would only need enough fuel for the outbound trip. Any fuel left in the tanks on returning to LKO would offset the refuelling costs for the next trip. Heat shields would have to be replaceable using the large docking ports, and a stack of them stored in orbit.

[Pecan]

Same way you used to do it - but then I have developed SSTO rockets and planes as body-specific landers.  My space-only vehicles never land, so they are very cheap.  On the other hand, you are also right that a simple one-shot ship for a simple one-shot mission is simpler - that's why Apollo did it that way, even though resuable 'shuttle-type' plans were available right from the start (to paraphrase XKCD: it works in Race Into Space).

I don't bother with Kerbin-SOI ISRU though; SSTO launches from Kerbin are cheap enough for me.

[nosirrbro]

Preferred way? Depends on what I'm taking there. If im not taking as much science as possible, an expendable and efficient mk1 lander can is my favorite, but semi reusable lander shuttles with ISRUs if possible are my favorite for taking loads of science

[Mitchz95]

I just use an expendable booster to send my crew directly to land at my Minmus base. Once their tour of duty is finished, they take off again and go for a direct re-entry. Don't even need a heat shield since the (mostly) empty fuel tank and engine block more than enough of the heat.

[LordKael]

Personally, I have a rather expansive station in a 500Km orbit around Kerbin, and it has a shuttle designed to get from the station to either moon or to the planet. Usually, if it goes to the planet, I take a very shallow reentry angle, then fly it to the runway at KSC, which takes between 10 and 15 mins real time depending on where the station was in orbit. No heat shield required for that design, just a modicum of flying ability from the person behind the keyboard. It has a tiny little lander attached to it, which is capable of VTOL on either the Mun or Minmus, which is how my crew gets to the surface. Kinda low on Delta-V, so its pretty limited in use, but gets the job done.

[justidutch]

My preferred way is also to use stations in orbit around each body, with a transfer vehicle or two.  By the time such creations are possible in my career I've made enough kash to do it that way and don't worry too much about cutting every single corner.  I find going from station to station, docking, cycling crew members around a fun way to do things.  But, early on in career doing single mission specific ships is the thing that makes most sense to me.

[OhioBob]

I use single-use expendable spacecraft and rockets.  I always do a direct reentry on my return from Mun/Minmus.

 

Edited December 17, 2015 by OhioBob
spelling

[FlyingPete]

I have a station in orbit of Minmus now, with an attached lander that will do the actual landing and science gathering. So the transfer ship from Kerbin is really just a bus. I figure that by bypassing the LKO station and just going directly to/from Minmal orbit with the crew bus, less fuel will be used as a one-shot heat shield can make maximum use of aerobraking- so the ship itself is smaller too. The expense of using expendable vehicles for each transfer would be offset by not having to send refuelling missions to supply a reusable transfer ship.

I've just collected six crew from operations at Minmus with a Mk2 fuselage-based design, and during a direct aerobraking 'simulation' most of the small parts (RCS thrusters etc) decided to separate from the ship in an explosive manner. Not ideal for something intended to be reusable.A shallower approach needed considerable engine braking to do anything useful. As long as I'm using expendable launch vehicles to get the crew to and from Kerbin itself, I think it makes sense to just use the same ship to get them to Minmus station.

ISRU around Minmus would change things somewhat. By refuelling at Minmus, I could skip aerobraking entirely and just fire the engines out in space to get back to LKO. The ship itself wouldn't need to be any larger than one intended for aerobraking as it would only need to carry fuel for the outbound trip. So by staying out of atmo completely, there's no concerns with aerodynamic heating. It only makes sense to do this if the crew launch vehicle is also reusable,

[GoSlash27]

I'm scouring the Mun and Minmus early in my career, so I have kind of a hybrid system for that.

 I have reusable landers to shuttle the crew and instruments between the munar surface and orbit. The station in Munar orbit has plenty of fuel and monoprop for the landers.

I use a disposable system to get my crew to the station in low munar orbit and back. It's a good compromise between ease of use and cheapness.

Best,

-Slashy

[AbacusWizard]

I usually use either a spaceplane or an traditional multi-stage rocket to get crew up to Starbase Alpha in low Kerbin orbit, then use a four-seat atomic-powered orbital skiff to move them back and forth between there and Mun Orbital Command or Minmus Orbital Command (each of which has a dedicated lander). When they need to return to the surface, they get back in the spaceplane or rocket, re-enter the atmosphere, and parachute back to home. (Thanks to Arthur C. Clarke's magnificent nonfiction book The Exploration of Space for the general idea.)

 

Once the infrastructure's in place, everything's re-usable except for the occasional surface-to-orbit rocket. The only cost beyond that is sending up an occasional fuel depot, and if I bother making a refinery on Minmus, that becomes free too.

[bewing]

The way I see it, the Mun/Minimus are the trees, not the forest. If you look beyond the immediate goal, you really want everything that is already in orbit (including "debris" of every sort) to be reusable in space -- unless a contract specifies that you must bring it down. Stations with dedicated fuel transports, space tugs, landers, ore extraction, etc. In the real world, it takes so much money/fuel/deltaV to get stuff up there that bringing it back down is a crime.

 

[DunaRocketeer]

Wow, there's some extensive infrastructure you people have in place, I'd love to see some pics

I'm not nearly as frugal. My Mun and Minmus flights feature spacecraft that are displosable. The transfer stage gets destroyed through impact on the Mun/Minmus. The rover (if applicable) is left behind on the surface. The lander, with all its expensive equipment, gets destroyed on Kerbin re-entry. The only thing that gets recovered is the capsule/heatshield/parachute. Very Apollo, very wasteful .

My one saving grace is the launcher, which is partially reusable: The disposable upper stage is made to be as basic and cheap as possible.

[GoSlash27]

DunaRocketeer,

 There really isn't much to see in my case.

Just a big ol' fuel tank with solar panels/ docking ports and a couple reusable landers.

The disposable part runs about the same way as yours; booster stage never reaches orbit, TMI stage impacts the surface, and SM stage burns up on reentry. I hate leaving debris in orbit...

Best,

-Slashy

 

[Geschosskopf]

On ‎12‎/‎17‎/‎2015‎ ‎11‎:‎29‎:‎23‎, FlyingPete said:

So, what's everyone's preferred way to get Kerbals to and from the Kerbin system's moons? I think a single-use capsule would be simpler as it could make a direct re-entry from the transfer orbit, protected by a heat shield. I'm using expendable launch vehicles anyway, so it just means the capsule goes to Minmus rather than staying at the LKO station.

Well, the ultimate goals of my space program always lie far, far beyond Kerbin's SOI so I view Minmus and especially Mun as merely the 1st steps on the long road to elsewhere.  Thus, I raid them for their Science! as quickly and easily as possible, then never bother with them again unless a particularly juicy contract involves them.  Ideally, I can get the Science! I need from Minmus (because 1) it's worth more, and 2) it costs way less dV to hop biomes on it). with only doing 1 Mun landing (simply for the money to "Explore Mun").

So, I usually make a 1-shot Mun lander first due to contracts.  What returns to Kerbin is the capsule filled with the data from all the experiment parts that were jettisoned somewhere along the route home.  Then I make a Minmus biome-hopper.  This has a 1-seat capsule for a scientist, an OKTO probe core for SAS, every Science! experiment I currently own, and enough fuel so that it will have somewhere between 3500-4000m/s dV left in the tanks once it's on the ground the 1st time at Minmus.  This ship is capable of hopping around all 9 of Minmus' biomes and returning to Kerbin with bit of a safety margin, although it will require several aerobraking passes prior to landing.  Again, all that returns to Kerbin is the capsule full of dozens of data sets, the scientist, and the probe core.  But it brings in many thousands of Science! points and a lot of money from milestones (plus maybe a few contracts).  There is now no longer any point in going back to Minmus and usually no reason to go to Mun again, either.

[Fearless Son]

On 12/17/2015, 9:29:23, FlyingPete said:

Heat shields help, but they'd be depleted after a couple of trips.

Have you considered using a sub-assembly with a heat shield attached to a docking port?  Send your reusable craft with one of those attached and do the aggressive aerobreaking.  Then when the heat shield is depleted beyond its usefulness, detach that docking port and attach a fresh one in its place.  You could dock several of them at a single station and then change them over during your lander's regular rendezvous.  Maybe have docking ports on each side of the heat shield so you can transport and hold them all in a "stack" and attach from both sides.  Then just attach your lander to one side, detach the other, and off you go.  Sure the external hatch will burn up in the atmosphere, but the sub-assemblies are supposed to be expendable anyway.  Just detach the old worn one before you do your corrective burn after aerobreaking and it will fall into Kerbin's atmosphere on its next pass and deorbit, clearing out the debris.  

[Wanderfound]

On 17 December 2015 at 4:29 AM, FlyingPete said:

Pre-1.0, I'd always 'done the Mun and Minmus by having a reusable shuttle which went from a station in LKO to another station in orbit around either moon. This worked out quite cheaply as aerobraking meant the return costs from Minmal orbit, were er, minimal. The ship remained in orbit, and only fuel supplies and a launch/crew return vehicle needed to be sent from Kerbin to the station in LKO. With the atmospheric heating introduced in 1.0, direct aerobraking from a Minmus-Kerbin transfer gets pretty hot, and so realistically engine burns are needed (I know you can make multiple passes, but it's not very convenient in terms of time.) This means hauling more fuel along for the whole trip and so makes the craft larger as well as needing more refuelling. Heat shields help, but they'd be depleted after a couple of trips.

So, what's everyone's preferred way to get Kerbals to and from the Kerbin system's moons? I think a single-use capsule would be simpler as it could make a direct re-entry from the transfer orbit, protected by a heat shield. I'm using expendable launch vehicles anyway, so it just means the capsule goes to Minmus rather than staying at the LKO station. 

Once I've developed ISRU, established a mine on Minmus, and engineered some decent spaceplanes (or SSTO rockets) then perhaps reusable craft would be more viable- it would only need enough fuel for the outbound trip. Any fuel left in the tanks on returning to LKO would offset the refuelling costs for the next trip. Heat shields would have to be replaceable using the large docking ports, and a stack of them stored in orbit.

These days I try to get the Mun and Minmus cleaned up in a couple of high-ΔV multi-biome disposable launches. Like this:

OTOH, if I get a "base on Minmus" type mission, I'll usually do that by packing a nuke-equipped spaceplane with a dozen kerbals and doing a sightseeing visit. It's a handy way to make some money while training up a large crew

[cantab]

Bear in mind I'm in a modded system, so some delta-V needs and aerobrake speeds are different to stock. I'm also in science mode, so not worrying about funds.

Most of my landings were one-offs with expendable vehicles. I did though put a space station in Mun orbit. For that I then used expendable capsules to take crew to the station and back to Kerbin, along with a reusable lander to make Mun landings in various biomes and bring science back up for the lab on the station. This seemed to work pretty well. I sent the space station out with a bunch of fuel, but tech tree permitting I could have done ISRU to fill it up.

Since pictures are being requested, this is said station

Delivery of our new solar array by cantab314, on Flickr

The orbiter is on the near side, the Mun lander on the other side, and the solar array is being brought up - science labs are power hungry! The half orange tank was enough to support five landings, and I sent four orbiters to visit (though one was destroyed being used to rescue Jeb from the Mun's surface after he got stuck on a mountain with no EVA fuel).