January 31, 2014

A Weekend on Minmus, Part Two

Hello again, ladies and gentlekerbs, this is Jebediah Kerman, along with Bob, Calfrod, Philmon, Desberry and Hersey Kerman, coming to you live from orbit above the green plains of Minmus.


Shortly our initial crew of five arrived here with the combined Keptune lander, orbital laboratory and transfer vehicle arrived here at Minmus, we planned our initial landing.  We decided to get the one likely to use the most fuel out of the way first, and Bob, Philmon and Calfrod headed for the north pole of Minmus.

Bob, Philmon and Calford Kerman near the North Pole of Minmus

With a nice flat plain to land on, and the low gravity and small size of Minmus, they had no problem putting themselves into a polar orbit and then landing near the North Pole.  They conducted all the scheduled experiments, and then launched back into space, maneuvering themselves back into an equatorial orbit, followed by rendezvous and docking with the laboratory, all conducted flawlessly.

Unfortunately, as we were refueling the lander for the next trip, we discovered that our estimates of how much fuel the lander would use on each trip and how many times we could refuel it from the fuel onboard the laboratory were just slightly overoptimistic.  We were hoping to land on Minmus as many as nine times, and it seemed clear that we were only going to get two, maybe three landings before we'd have to return home to Kerbin, or risk not having the fuel to do so.

This not being a good way to get all the science we wanted, not to mention all the experience and practice in operating landers, making orbital rendezvous, and docking that we need, it was decided that we would continue the mission, and a fuel resupply vessel would be sent out to us.

Kexxon Valdez on the pad

The engineers back at the Kerbal Space Center quickly threw together a resupply ship they christened the "Kexxon Valdez."  It's not very elegant, but it carries a lot of fuel, and is capable of carrying that fuel all the way out to the lab in orbit above Minmus.

Kexxon Valdez launch

Hersey Kerman was selected as the pilot for this mission, and launched on his way to bring us more fuel shortly thereafter.  In the hurry to get fuel to us, the relative position of Kerbin, the Mun, and Minmus was not adequately considered, and Hersey had the dubious pleasure of finding that he couldn't plot a transfer orbit to Minmus that didn't intersect the Mun on the way out.  He ended up plotting a Mun encounter, and then using that to slingshot himself out the rest of the way to Minmus.  We'll have to run some simulations later, but we think he actually got to us on less fuel than he would have otherwise.

Kexxon Valdez passing close by the Mun

Once Hersey arrived at Minmus in the Kexxon Valdez, we had to consider how to arrange the docking.  Our Keptune space lab only has two docking ports, both of which were already occupied.  We decided to undock the lander, let the Kexxon Valdez have that docking port, and then the lander could dock to the side of the Kexxon Valdez.

Keptune lab with Kexxon Valdez added on

With the extra fuel now available, we continued our mission to explore Minmus.  Over the course of the mission, we made a total of nine descents to Minmus.  Each time the lander returned, Calfrod was kept busy servicing the instruments of the lander and ferrying data between the lander and the laboratory.

Calfrod ferrying data from the lander

We had a bit of a scare on the return of the lander after the next mission, as docking set up a nasty oscillation in the combined station that our reaction control systems could not damp.  After a minute of progressively more violent swings, we decided to undock and separate all four vessels, stabilize things, then dock everything back together, taking care not to impart any large jolts in the process.  This worked, and we were careful not to repeat the problem on the remaining dockings.

The ninth and final landing on Minmus was the most hazardous: a landing on the slopes above the great flats.  By this time in the mission Bob had gained quite a lot of experience with the Keptune lander and landings on Minmus.  Even so, the slope chosen was so steep that the lander rolled as soon as the rockets were turned off.  Luckily, Bob was able to right and stabilize the lander with only minimal non-critical damage.  Truly an impressive bit of flying!

Last Minmus landing, on the slopes

With our exploration of Minmus now complete, Hersey, Desberry and Calfrod Kerman entered the capsule of the Kexxon Valdez and set course back to Kerbin.

Kexxon Valdez departs Minmus

The damaged Keptune lander was left adrift on an hyperbolic orbit that will eventually crash it into the surface of Minmus.

Kexxon capsule returns to Kerbin

The Kexxon left with about one fifth of it's fuel capacity, which was more than sufficient to get Hersey, Desberry, and Calfrod safely back to Minmus.

After their capsule was safely down and recovered, Bob, Philmon and I entered the capsule of the original Keptune transfer vehicle.  We placed the space lab on it's own impact trajectory with Minmus, then undocked and set course back to Kerbin.

Keptune tansfer vehicle departs Minmus

With our tanks having been topped off by the Kexxon Valdez before it departed, we had massively more fuel available than necessary for a simple transfer back to Kerbin.  I decided to test the limits of the vehicle, and see if I could manage a powered landing on Kerbin.

Attempting a powered landing on Kerbin

The vehicle almost proved capable of a powered landing, we were down to a velocity of only 70 meters per second when the fuel ran out a few kilometers above the surface.  We actually had enough fuel in the actual return vehicle to have made it a safe landing, but there wasn't time to perform a transfer, and the return vehicle itself lacked the thrust for a powered landing attempt, so I jettisoned both and we deployed our parachutes for landing.

Final Keptune landing

The entire Keptune mission encompassed four launches from Kerbin, nine landings on the surface of Minmus, Sixteen orbital rendezvous and docking manuevers, hours of EVA operations, and two return landings on Kerbin.  All of the astronauts involved delivered an outstanding performance, and we've made great strides in developing the skills and techniques we will need when it comes time to perform this kind of evolution above Eve.

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