What I did this 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 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 orbit 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.

I was interested enough in KSP to install the demo this weekend, but I didn't get a chance to play it.

After reading this, I think I am going to have to play it this evening and most likely, preorder.

I have to admit, the first time I read that it felt like the final sentence was going to be along the lines of:

"We need you to transfer 2000 USD to initiate the rescue mission, once safely rescued you'll be rewarded with a cheque for 20M USD."

I thought you'd gone all 419 for a minute there Tony.

When you play the demo, keep in mind that it's from a much older code base. There are a lot of bugs in the demo version that don't exist in the full version. And limitations too, but you expect that with a demo. For instance there are many more parts available for building spaceships in the full version. Full version is totally worth it.

After posting that, I checked the price and realized that it was on sale for 3.5 hours, so I purchased the full version.

If nothing else, it will be a great opportunity to go post-traumatic from my orbital mechanics classes if nothing else . I'm looking forward to it.

Viking space program, funny video's with kerbal:

http://www.youtube.com/playlist?list=PLD1262982675D497A

Hilarious!

My timing is awful! I paid 22.99 for mine, and now it's on sale for 13.79. On the other hand, either of those prices is a bargain for something so entertaining, and I'm glad I can support the developers.

I've just been playing the demo. A couple of launchpad disasters; a perfect sub-orbital flight marred slightly by forgetting to deploy the parachute on re-entry; an attempt to circularise orbit while pointing directly at the ground (that didn't work too well); and one successful orbit of the planet, followed by aero-braking to land (periapsis inside atmosphere), because I ran out of fuel.

I think I'm ready to purchase this thing.

That is first rate story telling, Tony!

Saw your Steam icon pop up for it yesterday. Figured that would be the way of things.

Had a similar experience with my friend Tod (EmpegBBS handle: CommOri) who I've been mostly out of touch with for years. As I was playing Kerbal last weekend, I kept seeing his Steam popup: CommOri is playing Planetside, CommOri is playing Planetside, CommOri is playing Planetside, and I have to assume he was seeing my popups on his system too. Then a couple days later, I see the popup: CommOri is playing Kerbal Space Program Demo... I had a big laugh just then. I later confirmed that yes, after his coworkers had been nagging him to try it, my popups pushed him over the edge.



Yeah, the whole orbital mechanics thing is interesting. So much of it is very unintuitive. You'd think, for example, that burning your engines while pointing at the ground would be the efficiant way to deorbit, but it's not.

More playing around with Hohmann transfers has led me to figure out some good rules of thumb about orbital burns:

- Burning prograde or retrograde (i.e., exactly with or exactly against your travel direction, i.e., the yellow pips on your navball) always gets you the best fuel efficiency in terms of the change in your orbit shape.

- Burning pro/retrograde at any point in your orbit will change the altitude of every part of the orbit except the point you're at. In other words: if you think of your orbit as having four "quadrants", and you've managed to line yourself up with another object (such as a ship/planet/station you want to intercept) but you're only touching their orbit in one quadrant and the other three quadrants don't line up, then wait until you're sitting in the touching quadrant (at the touching point) to do your burn. Then to get the other three quadrants to line up, burn retrograde to ensmallen the rest of your orbit, or prograde to embiggen the rest of your orbit. Using this technique you can, by repeating it at various points along the orbit, get your orbit to exactly match the target's orbit without expending very much fuel at all.

- Burning prograde at perigee is the most fuel-efficient way to gain orbit altitude at the expense of making your orbit very elliptical. Burning prograde at perigee gets you the most elliptical orbit.



Been there done that. Ran out of fuel before I'd quite gotten the reentry angle I wanted, so I had to sit through a few orbits as the ship aerobraked. Fun stuff. Note: I think there's a bug in the game where, if your perigee is inside the atmosphere, but you are at your orbit map and you crank up the timewarp, it'll zip right through the atmosphere as if it hadn't aerobraked at all. If you want to make sure to get the aerobrake to work, you have to use a slower timewarp (1x to be sure) and view from the piloting/staging screen.

Thank you! :-)

Sandbox games can frequently be boring to talk about, but this one really manages to set you up for some interesting adventures.

Last night I discovered an alien artifact on the Mun, a giant stone archway a hundred stories tall. I saw it when I was on approach with a lander. I wasted a bunch of fuel trying to change my landing site to be closer to it. (I later checked the wiki, and it says the Kerbal solar system is full of easter eggs like that.)

Not as dramatic, but I just successfully put an ion-powered probe (for Science!) in a polar orbit around Eve on my first attempt.

It's currently in an almost-perfect circular orbit (apoapsis ~= periapsis ~= 38,500 km). Gonna see if I can sort out the inclination and then drop it down to synchronous orbit next...

I've found that learning how to use the "Add Maneuver" node helps significantly in setting up and executing changes in orbital inclination.

First, find what they call the "Ascending node" or "Descending node" in your orbit. For a circular orbit, these will be the half way points between the apogee and perigee, I seem to recall. If you have a "set target" then the ascending/descending nodes appear automatically on the screen as green markers.

Add a maneuver marker on either the ascending or descending node point, then drag the purple handles on the maneuver marker to line up the orbit plane the way you want it. It'll give you a readout of the length of the burn required, next to your navball. Then you just point at the new target marker on your navball (dark blue target symbol) and execute the burn. This target marker will be at a point on the horizon "sideways" from your direction of travel, the maneuver node is what helps you remember which side. Remember to delete the maneuver node after you're done with the burn. More details here.

If you've got an ion-powered space probe with low thrust, you might not be able to get the job done with one burn. Inclination changes are most efficient at the ascending and descending nodes, and if you spend a lot of time burning at points away from those nodes, your orbit will do other things you didn't intend. So you might need to burn a bit, then wait till you come round to the next node, then burn some more, etc.

So how different is it from the demo - after a few hours I got entirely disillusioned with the demo and uninstalled.

Couldn't get close to an orbit - spaceships would either fall to pieces at speed or not get off the pad as they were too heavy (with all the struts I used to hold them together)

There were some bugs in the demo that made it genuinely difficult to create a working spaceship. Though I *was* able to get to orbit in the demo.

It's a simulator, so getting a working spacecraft and learning how to fly it is something that's going to involve some work and some trial and error. I don't recall if the demo had a tutorial section or not, I know the full version of the game has a tutorial section. I completely skipped the tutorial and did fine, but I'm told that the tutorial contained important information, such as, you have to press T to turn on the SAS system to keep the spaceship from spinning out of control and breaking apart. Also, looking at the tutorial sections on the KSP wiki can help.

The full version is quite advanced even though it's still at only alpha 0.22 at this time. The full version has many more parts available to build spaceships with, and entirely new sections to the game. But if you were frustrated by the demo, I don't think the full version will help that.

The demo cinched it for me because I like the idea of tinkering with a spaceship design, and having to correct design flaws that make the ship fail, and have to start over again. I like that. Some people would find that frustrating, and I get that. I don't think this game is for that category of folk. You might possibly be in that category.

I figured you skipped the tutorial when you said you found the symmetry button and it made adding the engines less daunting of a task

A funny thing happened last night:

I was trying out the new Career Mode they implemented in 0.22. In this mode, you must perform science experiments to earn science points to climb a tech tree to get a wider variety of rocket parts.

I'd gotten enough parts to make it to the Mun, and I managed to collect a ton of science points on the trip. You get significant bonuses for certain science experiments if you are able to return the experiment modules back to Kerbin (as opposed to just transmitting them back by radio), so I was keen to do that. I was able to fly the ship back from the Mun successfully, but just barely. I ran out of fuel with my Kerbin perigee pointed at 50k altitude.

50k is fine for a return to Kerbin, because the atmosphere starts at about 70k, so it means that I was aerobraking on each orbit and would eventually reach Kerbin. The problem was, the air at 50k is so thin that it was taking far too many orbits to get any serious amount of altitude reduction. Pass after pass, and my altitude would only decrease a small amount each time. It was taking forever.

My ship had no rocket fuel left, and no RCS thrusters because I hadn't gotten that far in the tech tree yet. So I couldn't use direct thrust to get my perigee any lower.

So I tried something that I wasn't sure if it would work: I got out and pushed.

I'm not making this up. Jeb has a jet pack which resets to 100 percent fuel each time you leave the capsule. I pointed the ship in the retrograde direction at apogee, did an EVA, jetted around the to tail end, bumped up against the engine nozzle, and just thrusted forward with the jetpack.

It did take me a few tries of going back into the capsule, checking my perigee, then going back out again. Also at one point I had pressed CTRL-ESC so that I could get back to the Windows desktop, and this left me with a stuck CTRL key in the game, and since CTRL is jetpack-thrust-down, it made Jeb shoot away from the capsule at high speed. It was a tense moment getting him back to the capsule, but I made it.

In the end, it worked. Just a few rounds of jetpack thrusting at apogee and I had reduced the altitude at perigee a few K, enough so that the aerobraking had some bite to it, and I reentered normally and landed safely with parachutes.

It only worked, though, because I was already on a reentry orbit path that was good, and all I needed was a slight tweak to the overall orbit. And small speed changes at apogee result in big altitude differences at perigee, and vice-versa. Still, it made me think of Leia chiding Han in TESB: "Would it help if I got out and pushed?" "It might!"

So, I guess that any landing you can walk away from is a good one...



It's not a "great" landing, though.

Hey, everybody's smiling. That's the important thing!

Yeah, provided that you're on your home planet where they can come get you with relative ease. Walking away from a "landing" on another celestial body can be a more problematic situation.

Got your rescue mission en route yet?

I've been trying the career mode, and it's a lot of fun trying to scour Kerbin and the Mun for different biomes to get science to purchase part upgrades. I've done several missions around Kerbin just to test out rocket designs and incidentally collect science points. The two Mun landings I've done netted me 900 science points on the first run, and I'm in the middle of the second run and it's netted me 1400 science points so far because I had a rover loaded with science experiments, a transmitter, batteries and solar panels. I've traveled scores of kilometers in that rover so far.

Yeah, *cough*, so it turns out that (1) I need to practice my landings, and (2) my rescue mission needs rescuing

I forgot to tell you: For rescue missions, use a remote-controlled* craft and make sure it's empty of personnel before launch.

*There are remote control modules available in the same place you pick your command capsules. All you have to do is make a spaceship like you normally would make it, with a command capsule and everything, but just clip on an extra remote control module. This allows the ship to either be remotely controlled with an empty capsule, or, be controlled by Kerbals in the capsule.

And one thing I've found that helps landings: Wider spread of landing legs with a lower center of gravity. Can accomplish this with girders and such. My main Duna lander is actually a wide flat circle of small fuel tanks with landing legs on its outer edges, for the widest possible spread of landing legs.

Kerbal Space Program - $13.56 or about 50% off.

Forgot to update this -- I haven't played KSP for a couple of weeks now -- but I finally managed to retrieve everyone from the Mun. Longest stay was about 3 years MET.

It turns out that I didn't have enough delta-V to get the rescue mission out of Mun orbit, so I also had to send another craft over with some spare fuel...

Heh. Yeah, real-life rocket scientists calculate their craft's delta V before launching. I think that KSP deliberately does not display any information about the delta V of a craft because they want to encourage the very adventures we're getting ourselves into by not knowing our own delta V. I know that you can get a craft's delta V to display with mods, though.

Achievement Unlocked: This.

Turns out that aerobraking into Kerbin at 48km isn't low enough. Cue Bill Kerman getting out and pushing at Apoapsis.