Still Flying: Fueling Station-1

So another revision (0.25), another game.  I've been trying to get into the habit of playing more regularly so that Nathan gets used to the idea of playing games.  He also likes watching me play, since I do different things than he does.

I've also been experimenting with recording my game play sessions.  I've been using Open Broadcasting System, and having a hit-and-miss record with it.  Several sessions ended up being black screens with the audio.  After some fiddling around I seem to have a sequence of actions to do in order to end up with a recorded session, although I have no idea if the changes/updates I made ended up making any difference or if the sequence of starting things up is necessary.  The photos in this article are still screenshots, rather than video stills.  I don't know how I'm going to end up dealing with the video.  There are some good sequences but there are hours of crap, I could probably do a 30-second highlights reel but since large periods of time went by with no video at all it would be pretty disjointed.

Previously to this set of posts I launched a space station core.  It ended up in orbit, although a pretty eccentric one (96x131 km).  So the next step was to launch a brown fuel tank and then fill it, and use that station as a base for further exploration.

This was my first idea:

Tanker-1

Launch a tank of fuel on top of a ridiculously over-powered lifter arrangement, then put a tug-type ship on top of that.  For efficiency, since the tug wasn't expected to return to the surface, the tug has a nuclear engine on it.  For extra style points there is no engine underneath the brown fuel tank.  Once the boost stage is exhausted, the tug has to perform an Apollo-style separation-and-reconnect maneuver and then guide the tank to the station.

The weakness in this design is that the boost stage isn't enough to get us into orbit, and the nuclear engine isn't powerful enough to push the full tank into orbit after doing the separate/flip/dock/orient dance to get everything pointed in the right direction.  I tried this three times before giving up.

Tanker-2 series flights were more straight forward:

Tanker-2 Boogey Woogey

I put an engine on the bottom of the brown tank to get us into orbit.  It also has a self-guided RCS-box called a 'bot on the nose.  This configuration is extremely wobbly and it took three flights to get into orbit.  Eventually I hit on the strategy of basically going straight up with the lift and boost stages before gravity turning on the brown-tank stage.  This isn't efficient but it does have the benefit of actually working.

Once I made orbit, I finally got Tanker-2c to the space station.  Note that the capsule at the left end with no drive section was there because of an accident during staging.

Before

You can also see that the 'bot is on the nose of the brown tanker module -- this was the entire point of the 'bot, to manuever around the various components once they are delivered into the space station's general area.

Finally, you'll note that the picture is labelled as "Before".  That is, as in "Before The Next Staging Accident".

After

So now I have two crews up there and no return modules.  I also have a second Tanker-2 nearby the space station, which I tried multiple times to dock with no success.

So this leads us to the Tanker-3 series.

Mandatory Glamour Shot:
This way to space

Tanker 3 is the same as Tanker-2 with two small differences:

Two docking ports at the base of the brown tank.  This means that you can dock a 'bot to each side.  And once you do that, the tank is much more manueverable.  

In this configuration, docking is a doodle, even with a half-full tank.  And with this tool, I could do teh following dance:

• Dock with Station 1, dump all fuel from Tanker-3 into Station-1
• Send Tanker-3 to rendevous with Tanker-2d, and drain all its fuel except for a small amount needed to return Tanker 2-d back to Kerbin



Space Is Really Big:
Tanker-3 shuttling fuel back to Station-1

This picture is pretty because it shows Tanker-3 in the middle, Station-1 above it, and Tanker-2d just on the lower horizon.  I like pictures that show the emptiness of space.

• Send Tanker 3 back to the station, and top-up the fuel there
• Detach Tanker 3
• Have Tanker-2d dump its brown tank module, redezvous with one of the orphaned capsules, and return to Kerbin



Synchronized Landings

The secret of synchronized landings is to have the two capsules docked for the entry and descent configurations, then undock at about 15000 meters, just before the parachutes open.



Eh, pretty close

• Use the engine on the base of Station-1's brown tank to lift it it into a 150km-by-150km orbit (actually a 152x148 or so, but still acceptably better and easier to catch than was the 96x131 orbit I was dealing with up until now)



Tanker-3 catches Station-1 for the last time

• Send Tanker-3 after Station-1 in its new orbit and top up the fuel

Which is what I did.  Most of those items were single game sessions lasting up to an hour each.  So I've logged a bunch of time in the game over the last three weeks or so.

The end result of all this:

Look at all that fuel in orbit

So that's where I've left it.  Right now I have something like 3km/s of delta-V in Station-1 so I could probably send it to Jool if I really wanted to.  Tanker-3 has a full load of fuel in the capsule, plus more in the brown tank.  I really don't want to throw expensive fuel away by de-orbiting it, so I have to keep Tanker-3 present for now.

The only real liability that I've got in orbit is a lack of RCS -- I have four big tanks, but only enough propellant for one and a bit.  I guess shuffling that big tank around is expensive as far as RCS goes.

My current missions list:

In the immediate term, I want to send up a RCS refueling tanker so that the 'bots can all be recharged.

In the medium term, I want to get rid of the Tanker-2 series fuel tank and replace it with the Tanker-3 tank, mostly so I can free up the third 'bot for shuffling duties.  There's also a 'bot in an eccentric orbit that has to be recovered and returned to Kerbin.  I might also send up a proper "tug" module that uses the nuclear engines for efficiency.

Finally, I want to launch some probes to the Mun so we can practice landing, which sets the stage for a manned Mun mission.

I doubt I'll get to all that, but it's been interesting anyways.