clapanse

Escaping only requires that your eccentricity is greater than 1, regardless of how far the game considers the sphere of influence to be.

Absolutely. You'll find it's fairly difficult to get everything to work out properly though.

I'd be very curious to see how. I would have thought a rocket would be much better for this challenge.

From what I can tell, based on some experiments with prograde, retrograde, and polar flight paths with high speed jets, the engines really only care about speed relative to the air, and it doesn't seem that there are any high altitude winds (so basically, relative to the ground). Going retrograde makes it a bit easier to avoid accidentally going into orbit, but it also means you have to stay in the lower atmosphere, since you have to make more of the lift yourself, and I wasn't able to get any more speed going retrograde as compared to prograde.

Well, assuming mechjeb is allowed, here's my first at least vaguely competitive attempt: https://www.dropbox.com/s/3tw06hwry0pj99f/Attempt_1.PNG

Is mechjeb allowable? I have one that's looking really promising (it has 28min left in the top stage burn right now), but I can't fly it to orbit manually. EDIT: Well, this one isn't looking as promising as I thought, but the question still stands...

Yep - that's definitely the right config file and data. I tweaked it as shown here: And this was the result: https://www.dropbox.com/s/x0lk0opl3wrutuk/cfg_edit.PNG (No other changes from the previous post were made, and that is exactly the same craft) Actually, given that the hard upper limit in stock KSP is definitely 2400, some of the results are impressively close to the maximum.

Here's a 2288m/s manned plane, all stock except for MechJeb (kind of a basic, generic, high-speed design). It could probably do 2300+, but I'm not patient enough. https://www.dropbox.com/s/mykcialhhltuxfn/2288_takeoff.PNG https://www.dropbox.com/s/fmuuwv47f0c0ys4/2288_inflight.PNG https://www.dropbox.com/s/4ihpholzwepnuum/2288_summary.PNG Also, I took a look in the config files, and I'm pretty sure mach 7+ is not possible. This bit of code is in the part.cfg file for the turbojet: I would tend to interpret that as stating that the engine makes 0 thrust at 2400 m/s (relative to atmosphere), which is somewhat corroborated by the seeming upper limit of 2300 and a bit seen in the results above.

I present the Hopeless Triangle Thing: https://www.dropbox.com/s/4cygnjzfksaqm0k/OnRunway_1inlet.PNG It's pretty much impossible to fly by hand, so only MechJeb makes it possible, but it will do 2 km/s on completely stock parts (aside from MechJeb) with only one engine and one inlet. It makes a pretty nice fireball too... https://www.dropbox.com/s/t8rg9do2q8odzhq/inflight_1inlet.PNG https://www.dropbox.com/s/d88iinknomqo8ic/flight_summary_1inlet.PNG Sadly, it's about 25 m/s short of the mach 6 club - I may try to squeeze a bit more performance out of it at some point, but it's not too bad for now...

Hmm. It'll take some more tweaking to be competitive with some of the designs here, but here's a 22,222 shot (with 28 stages of the short solids): https://www.dropbox.com/s/o19jjmtbtvemk7q/3rd%20attempt.PNG (I love the fireball it's engulfed in though...)

Update: Still haven't managed a handflown circumnavigation (it's pretty well behaved at low speeds and altitudes, but it's a bit touchy at full cruise), but it's definitely possible to do a double circumnavigation that is fully within the rules (since the only disqualifying part about this flight was the autopilot): https://www.dropbox.com/sh/4kq6uus7e49spyp/Kssz_drewE It landed with 25.80 fuel left, which is actually several hundred kilometers of margin, so I think it could be handflown to a double circumnavigation. It would be kind of touchy though - the fuel efficiency is fairly sensitive to altitude, and this flight was flown (by the autopilot) pretty much 100% between 24,700 and 24,950. It's also interesting to see the speed build as fuel is burned off - initial cruising speed was around 1350-1400 m/s, but near the end, it was up well over 1700.

Here's a slight refinement - this is the best I can get for the moment. I don't know how 25km would be possible (though I'm sure someone will prove me wrong...) https://www.dropbox.com/s/mi66rh60d742cdm/2nd%20attempt.PNG https://www.dropbox.com/s/en4ljbzjzbjlod7/2nd%20attempt%20spacecraft.PNG

Here's my first quick, off-the-cuff attempt: https://www.dropbox.com/s/33sard3nqsdodh3/1st_attempt.PNG

Well... I haven't handflown it yet (mostly because I keep screwing it up, but I'll keep trying - it isn't that hard to handfly, but I have no patience), and I know mechjeb disqualifies the submission, but here's a design that can definitely do it (and I suspect that, if flown perfectly, it could make 2 circumnavigations unrefuelled at <25km). The cruising speed is pretty excellent too On this particular flight, it ran out of fuel just past 3/4 of the way around on the second circumnavigation, but I think it wasn't flying at its most efficient for the first time around (I didn't start really paying attention to fuel usage until half an hour in or so). https://www.dropbox.com/sh/hqj87rv5aixdiua/0GdWqsyiMs#f:InFlight2.PNG