Bob In Space

Once again the rumor mill is busily grinding away at all manner of oddball rumors, most of which are unlikely enough as to be downright stupid. The only thing dumber than some of these rumors is the alleged “people” (term used very lightly here) who create and start the spreading of such rumors. Though I suppose that those who believe them are probably dumber yet.

According to one of this latest batch, Bob (the gerbil pictured in the blog header) has discovered the space flight simulation program Kerbal Space Program and has, according to rumor, built a ship capable of reaching escape velocity and is on the way out of the Kerbol system.

The rumor continues by saying that this has apparently earned him some kind of trophy for achieving something truly epic that shouldn’t be possible.

The thing is that while it is entirely possible that Bob has discovered KSP, there is definitely no prizes for that particular accomplishment.

I say that because in KSP 0.16 it is possible, without mods of any kind, to build such a ship easily. All you need is the small one person capsule, a 400 liter fuel tank, and one aerospike engine.

The trick to accomplishing this feat is to keep the throttle setting as low as possible. Lift off from Kerbin at about 1/3 thrust and as you gain altitude and achieve orbit, keep adjusting the throttle setting downward until you are at the lowest setting possible that keeps the engine running.

Once you achieve orbit just turn the ship prograde and continue thrusting. The downside is that because you’ll be constantly thrusting you have to do this in real time because you cannot use time compression if you’re under acceleration.

I’ve done this myself just to see it work. The only thing I did differently in the ship design was to add a small MechJeb module to the side of the capsule so that I could get flight data and use it’s autopilot to hold the prograde attitude.

At mission elapsed time of 26 minutes and 46 seconds the ship had accelerated to 2.325 kilometers per second. Fast enough that the map view showed that it would reach “Kerbin Escape” in a touch over 16 hours.

Because at that time the ship still had 221.6 liters of fuel left I decided to leave the flight running, continuing to thrust prograde at minimum throttle.

I checked on it once in a while at at Mission Elapsed Time 2hrs 56min 33sec it had 173.5 liters of fuel left, had an orbital velocity of 16.620 kilometers per second, and the map view showed “Sun Escape” would occur in 68years 35days 3hrs.

Just for grins, I left it running. Currently the Mission Elapsed Time is 4hrs 52min 7sec and velocity is 32.497 kilometers per second and accelerating. There is 111.3 liters of fuel remaining which means this thing could easily take another two or three hours to run out of fuel, by which time it could well be moving at over 45 kilometers per second.

The reason this is possible at all is because of a fuel consumption bug in 0.16. From what I’ve read on the KSP forum this bug is fixed in 0.17 (not released yet as of this writing) and there is an “unofficial hotfix” that fixes it.

While it may be great to fly all over the system on almost no fuel I think it’s a much better idea to apply the hotfix and start redesigning ships so that they will work without the bug. Otherwise when 0.17 is released, all your ship designs will suddenly have to be scrapped because they won’t be able to do what they could in 0.16