January 06, 2014

Answering Ancient Questions

Ever since the first Kerbal trained a telescope to the skies and looked at Kerbin's second moon, Minmus, a question has remained unanswered: is Minmus really made of green slurpee goo, and if so, is it as tasty as it looks?


I am Jebediah Kerman, and today I plan to find out.

Merkerby-Kerbysseus on the Launchpad prepared for a trip to Minmus
The Kerbysseus capsule that the Royal Squirrel Patrol Space Force has used explore the Mun has served us well, and there is no need for any great change on this mission.  However, in consultation with we astronauts, the engineers have made some minor improvements, giving us the Kerbyssues II capsule.

The Kerbysseus II Capsule

There are a variety of minor improvements not obviously visible: some things have been moved around for easier access or better balance.  There are a few additional scientific instruments.  But most notably, the capsule now has lights, so it's much safer to land in the shadow of a mountain or crater wall, or even on the dark side of the Mun.  Hopefully this will also prevent a repetition of the unfortunate, though hilarious, episode where Bill Kerman spent ten minutes trying to climb up the wrong side of the capsule since he couldn't see that there was no ladder on his side.

The Ikerbus launch vehicle likewise has served us well going to the Mun, but speaking honestly, it was just barely up to that task.  To go to Minmus, we need something a bit more robust.  With this flight, we roll out the Merkerby launcher.

Merkerby transfer stage

The transfer stage, shown above, is quite simple.  Our engineers have simply taken an Ikerbus transfer stage, doubled it's length, and then strapped it to two more rockets just like it.  This transfer stage packs almost the same average thrust to weight ratio as it's predecessor, but can keep it up for much longer, enabling us to perform far more significant transfer maneuvers.

Merkerby boost stage

The boost stage maintains that simplicity of concept.  We begin with a duplicate of the transfer stage, and then each of the three rockets that compose it has another two matching rockets added on the outside, for a total of nine rockets.  

Merkerby-Kerbyssues

Finally, we strap three large solid rocket boosters to the apexes of the triangle.  These boosters come to us courtesy of a new vendor, KW Rocketry.  KWR assures us that these boosters will provide us far more thrust than the Rockomax boosters we've used previously, and their three segment design will allow them to burn almost all the way to the gravity turn.  They also look quite stylish, which is not to be discounted.

On our way to space

Our flight profile to Minmus doesn't require any particular launch window, so at the request of the publicity staff, we launched in the late morning when the lighting was good for photography.  The three Globe SR-2 boosters and 9 KWR Wildcat engines make for quite the exhaust plume as I rise into space.  The rocket was quite stable, in comparison to the rocking and shaking of the Ikerbus, the Merkerby just vibrates soothingly.  In fact, I very nearly fell asleep.

Burn to change Inclination

Unlike the Mun, Minmus does not orbit Kerbin in alignment with the equator.  It has an orbital inclination of 6 degrees.  I considered launching at a 6 degree inclination to begin with, but that would have required extreme precision to line up the resulting inclined orbit with Minmus, so instead I opted to go for a normal equatorial launch and correct afterwards.  Fortunately there is plenty of fuel in the transfer stage for this.

Hohmann transfer to Minmus

Having matched inclination with Minmus, I then set up a simple Hohmann transfer orbit.  Fortunately the Mun was on the opposite side of Kerbin at the time so I didn't have to dodge it on the way past.

Transfer burn

The transfer burn was moderately lengthy, allowing me to send out a camera probe for this nice shot of the transfer stage during boost with the Mun silhouetted against the milky way in the background.

After the burn, it was time for a long boring coast to Minmus.  I caught up on my sleep, then awoke to this nice view of Minmus appearing ahead.

Approaching Minmus

After a nice breakfast, it was time to get some work done and stretch my legs a bit.  As our initial course brought us past Minmus, I popped outside to take some readings from the science instruments.  This was far from my first EVA, but somehow knowing that a million kilometers from home with enough velocity that if I didn't get back to the ship I'd never come near Kerbin again added a little excitement to things.  I did take a moment to get a good look down at Minmus.  From here I still can't tell if it's green slurpee or not.

EVA over Minmus

Once safely back inside the capsule, I burn to kill off that velocity and put me in a close orbit around Minmus.  The engineers have done well, I've still got a significant reserve of fuel available when I shut down the transfer stage.

In orbit around Minmus

As I approach a suitable place to land, I use the transfer stage for a de-orbit burn.  That will put the transfer stage on course to impact on Minmus, making sure it's not a navigation hazard for the next astronaut to come this way.

Detached for landing

With my lander detached and on a slow fall towards the surface, it's time to pick my landing spot.  I plan to make an initial landing on a flat spot in the midlands, not far from the lowland sea.

Lander over Minmus

After using the transfer stage for me de-orbit burn, I had very little lateral velocity, and the gravity of Minmus is minor, so the only difficulty on landing was simply keeping my fingers light on the throttle so I don't end up over correcting and heading back up into space.  A few minutes after I start on my way down, the lander makes a nice soft landing in the midlands.  Time for another photo-op!

Jeb on Minmus

The lander lights are a welcome addition, the sun isn't very bright here.  Kerbin looks very small.  The surface does indeed seem much like green slurpee, but unfortunately it's not actually very tasty.

Low gravity is fun

My first attempt to get back into the lander was actually a bit difficult, I didn't expect a light jump to go quite so high.  However, it did make bouncing down to the lowland sea surface for another sample quite easy.

After getting my samples, taking some photographs and logging the data from the instruments, I conducted a few interviews with fans back home, then prepared for my return trip.  Given my recent experience with how light the gravity was, I made sure to keep the throttles quite low, and achieved a Minmus orbit within a matter of seconds.  The hard part here was just keeping the lander oriented so that the orbit was in the proper plane for a return to Kerbin.

Leaving Minmus

I used the bare minimum thrust to put me on a return trajectory, so there was another long transfer to wait through.  I read a few chapters of The Mun is a Harsh Mistress, then got some sleep so I'd be well rested for my final maneuvers.  I woke up in time to get this nifty photograph as I passed between the Mun and Kerbin.

Between the Mun and Kerbin

Since the Kerbysseus lander was designed to be able to land and return from the Mun, we had way more delta-v than necessary for Minmus' lighter gravity.  That's probably a good thing, as my return velocity was pretty respectable, and I didn't really feel like seeing if the capsule materials were up to that much aero-braking.  I burned off the rest of the fuel over the ocean, curving me towards a nice tropical landing spot and pulling my velocity down to something more reasonable.

Slowing down over Kerbin

It's probably a good thing I did slow down a bit, as the plasma display during aero-braking was pretty intense.  I understand Bob Kerman is talking to the engineers to see if they can rig a spit to roast hot-dogs and marshmallows for his flight.

Aerobraking

A few peaceful minutes of floating under my array of parachutes later, I'm afloat in the warm tropical seas of Kerbin.  With the fuel tanks empty, the lander is nicely buoyant.  I'm happy with that, as I just saw a distressingly large shadow pass under me, and I'd hate to come back from Minmus just to become shark food!

Afloat on the seas of Kerbin

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