My first experience with KSP: Stranded pilot, rescue attempts, rescuing the rescuers

[tfabris]

Half an hour with the KSP demo was all I needed to be convinced it was worth the purchase. After installing the full version and skimming the Wiki sections about getting to orbit and making a Munshot, I decided I was ready for the task. Sure I was! The following account is what I did during last weekend.

I sent a Kerbal to the Mun in a single-seat rocket of my own design. His name was Jebediah Kerman. After many aborted attempts and rocket redesigns, he finally made it. He landed successfully, and planted a flag, which I named "Tranquilizer base". He had a tiny bit of fuel left, but I was pretty sure his fuel wouldn't get him into Mun orbit, let alone back home. So there he sat, watching eclipse after eclipse, wondering whether his toes would ever feel Kerbal soil again.

I resolved to rescue him. I built a larger, three-seat rocket. Again, it took many tries at the design and many aborted attempts. I sent the three-seater up, with two guys onboard and an empty seat for Jebediah. Rescue Rocket successfully landed on the Mun! And only 3km from Jebediah! I was so excited.

Instead of making Jebediah walk the 3km to the rescue site, I thought it would be fun to have his lander, with its tiny bit of fuel left, jet over to meet the rescuers. The only problem is that I forgot to turn on RCS and SAS before taking off, and the lander was hard to control, and the lander flipped over on its side in about 1 second. The lander and Jebediah survived, but he'd only made it about 100 yards. Sigh. So he hoofed it (well, jetpacked it) over to the rescue site. He was very happy to see his fellow Kermen, he looked so excited and had a big grin. The three of them boarded Rescue Rocket and took off for Kerbal.

But Rescue Rocket was being very unstable on takeoff. I only realized after it was too late, that the instability was because I'd again forgotten to turn on RCS and SAS before takeoff. I wasted a lot of fuel over-correcting and getting it back on track to reach Mun orbit.

Finally we made it to orbit, I'd at some point figured out that RCS and SAS needed to be on, and we made our Kerbal Insertion Burn. It worked, I executed it correctly (having read the Mun Landing section of the Wiki), but we ran out of fuel before I could complete the burn. We escaped the Mun orbit and were back in Kerbal's sphere of influence, but only just barely. Now I had three guys stranded in Kerbal orbit, just barely inside the Mun orbit.

And as I contemplated another rescue rocket to rescue the rescuers, I realized the folly of my ways: I should have left TWO seats empty on Rescue Rocket at launch time, because now, I've gotta rescue THREE guys! Since the capsules seat three max, this means that now, if I want to rescue all three of the stranded people, I need TWO MORE rescue rockets!

Construction and testing of "Rescue 2: Electric Boogaloo" went swiftly because I discovered the SYMMETRY button in the vehicle assembly building. Suddenly I was able to do everything much faster, and the idea of adding six radial booster rockets wasn't as daunting a task as I'd originally thought.

Rescue 2 launched (with one pilot and two free seats because I'd learned my lesson now) and I had a devil of a time getting him to intercept the stranded rocket. I was learning how to do a Hohmann transfer by the seat of my pants, without reading that particular section of the wiki. I was amazed at how close I got. I got within a few kilometers, and I even sent Jebediah out with his jetpack, thinking it would be easy to jet out to Rescue 2. Boy was I wrong, the speed differential between the two rockets was crazy. Jeb watched Rescue 2 zoom by at an impossible speed and leave him behind. I only barely got Jebediah jetpacked back into his capsule. I deorbited Rescue 2 and resolved to try again.

Rescue 3 made a much better interception, and I finally understood some useful things about Hohmann transfers (after reading the relevant section of the wiki). Turns out that, in order to do a rendezvous, it's not enough to get the two spaceships to pass each other closely. One rocket on an elliptical orbit and one rocket on a circular orbit might pass each other, but the nature of their orbits means they'll be at radically different speeds. In order to rendezvous, they also need to have nearly identical orbits in shape, speed position, etc. The wiki had good information which I found fascinating and useful:

- Burn Prograde at Apogee to circularize your orbit while making the orbit bigger.

- Burn Retrograde at Apogee to circularize your orbit while making the orbit smaller.

- Do the same things at Perigee to ellipticalize your orbit while making it bigger or smaller.

- Burn sideways at the climbing/descending nodes (little green marks on your orbit screen) to adjust your eccliptic plane and make it line up with your target's eccliptic plane.

- To make your target "catch up to you" burn prograde ("speed up") to shift you to a bigger orbit, and he'll pass under you, since his narrower orbit is faster.

- To make you "catch up to your target", burn retrograde ("slow down") to shift you to a lower orbit, and you'll pass under him, strangely, faster. This is very counter-intuitive, but it works.

Through all of this, I was amazed at how little thrust was required to make massive changes in the orbit. A tiny amount of thrust in the right spot means thousands of kilometers difference on the other side of the orbit. Amazing.

Armed with this knowledge I got Rescue 3 pretty close, within a few Km of the stranded capsule, and the speed differential wasn't that bad. I thought it was time to go for it: Jebediah went out for EVA with his jetpack, and... Ran out of jetpack fuel trying to get to Rescue 3. So now poor Jeb was floating in space, no jetpack fuel, unable to get to the new rescue ship, and unable to get back to his original, stranded rescue ship. Wow, sucks to be him.

So it was time to bring the mountain to the man. I took Rescue 3 and figured out how to thrust over carefully to Jeb. And we made it! It took a few passes before I could finally get them together at a slow enough speed. But finally Jeb grabbed on and entered the Rescue 3 capsule. I learned the hard way this time that you can only grab onto ladders, and the orientation of your capsule is important in these situations. You gotta turn the ladder side towards the stranded astronaut.

With Jeb safely in custody, rescue 3 began his deorbit burn and was on track to land on Kerbal. Success! But there were still two people stranded out there. And then... something scary happened. I noticed that the stranded rescue ship was going to re-intercept the Mun's sphere of influence in just a few days. This meant that if I didn't rescue them soon, they would get wrapped up in the Mun's orbit!

It was time for fast action! While rescue 3 was still on its way homeward, I prepared and launched Rescue 4, this time with more ladders wisely attached to the fuselage, to make EVA grabs easier.

While Rescue 4 was waiting for an apogee burn, I watched rescue 3 re-enter, and deployed its parachute. Jeb was finally home!

I started to get really good at Hohmann transfer maneuvers. with much fiddling of orbit thrusts, Rescue 4 was able to get within a few meters of the stranded capsule. With the moon starting to loom large in the sky, I carefully thruster-nudged Rescue 4 up very close to the stranded capsule, and the remaining two crewmen jetted over with little trouble. A final deorbit burn and they were finally home! All my Kerbals were safe on their home planet again!

And good thing, too, because only a few days later, the stranded (now empty) capsule was snagged by the Mun's gravity and, after two swings around the Mun, slammed into its surface at incredible speed and vaporized.

I saluted as I watched it plummet.

Space travel is a troublesome business, I tell you.