Kerbin Circumnavigation 1.0.4/1.0.5 - Aviator Challenge Continuation

[Xannari Ferrows]

Basically insurance, plus the extra fuel. Don't wanna be getting asymmetric thrust now, do we?

[nicky4096]

not saying there's anything wrong with nacelles, but... the pre-cooler also has 40 lqd. fuel and also has 0.5 intakeair.

[Xannari Ferrows]

Well, there's no difference in that case. I guess it just gives the plane a more unique look, and it looks more fitting when mounted under a wing.

[nicky4096]

xannari, what you could probably do to improve your time further is to use the mk1 command pod. it has less drag and weighs less. i'm managing 1717 m/s with a single engine at half fuel load using this.

[HelmutK]

This is very hard to beat. Respect!!

I tried some prototypes, but the last craft is currently my fastest.

[Xannari Ferrows]

It'd be interesting to find out the fastest possible circumnavigation time. It'd rely on a number of factors, but I may be able to find something like that.

I mean, 3.896 [approx] megameters is a long way to go.

[nicky4096]

well, i think i'm pretty close to the limit with 1 engine - getting nearly 1715 m/s 2 minutes in.

some things i've done:

- you should use an RC-001S and a Z-1k battery instead of a command pod. they are both inline and combined weigh 0.15t. ideally, you would use the OKTO2 and an RTG, but they both have an unusable heat tolerance.

- no tailplane! those are for wimps!

- reversing the shock cone gives the least drag

[Xannari Ferrows]

The limit is 0:29:33

[nicky4096]

why?

[Xannari Ferrows]

It is the fastest possible circumnavigation.

[nicky4096]

based on heat tolerance at 30km?

[Xannari Ferrows]

That's one factor.

[MunGazer]

The limit is 0:29:33

To clarify, is that limit for circumnavigations that are done without exceeding 30 kilometers altitude? Assuming the circumference of Kerbin is approximately 3,769,911.1843077518861551720599354 meters based on the equatorial radius of 600,000 meters, and that 29:33 = 1,773 seconds, that would give an average speed of 2,126.2894440540055759476435758237 meters per second to achieve said circumnavigation time, not including effects of traveling prograde or retrograde. Of course, this estimation is based on the simple geometry of a circle and doesn't account for deviations for changes in terrain or altitude in a flight trajectory.

[nicky4096]

can you explain how you calculated it? :3

[Xannari Ferrows]

Well, assuming a cruising altitude of my favorite height, 20100 meters, the smallest distance you would have to travel is about 3.8962 megameters. A compilation of the lowest drag parts [only necessary], enough fuel, and perfect balancing as well as flying, can make the RAPIER achieve a maximum speed of 2197.5 m/s. This assumes more than perfect piloting, as well as finding a way to make it take off and get up there. It would also be super hard because the whole thing would be incredibly sensitive to applied lift forces, and a single millionth of a degree off will cause the whole thing to flop around like a crazy floppy thing.

EDIT: This is also assuming optimal ascent path that equates to a distance slightly less than the required distance, but the times would balance out. And I guess overheating is an issue, but you can exploit the cooling properties of those necessary parts we talked about earlier. Those really need to be fixed.

Edited July 11, 2015 by Xannari Ferrows

[nicky4096]

interesting!

[MunGazer]

Assuming a sidereal rotational velocity of 174.53 m/s would simply be subtracted from that average speed to give a better figure for the average speed required in a retrograde circumnavigation, (2,126.2894440540055759476435758237) - (174.53) = 1,951.7594440540055759476435758237 m/s. Again, this is the "average" speed; the actual cruising speeds needed to compensate for acceleration, deceleration and other things would be even higher.

Edit: just now saw your replies. Yeah, I guess our figures are very close xannari for what average speeds would be needed; the major difference I suppose is just that you're looking at a slightly larger circle to account for altitude, which makes sense because that's where you spend the majority of your flight. But time spent accelerating and decelerating will likely push the top speed seen in a limit approaching craft significantly above our average speed figures.

- - - Updated - - -

can you explain how you calculated it? :3

Not sure if you were asking me or xannari, but my calculation was (circumference of kerbin in meters / time in seconds of a hypothetical navigation ) = average speed in meters per second for circumnav.

However, xannari's approach for looking at the circumference at a given altitude is more accurate, since of course no one will be doing mach 6 at sea level. My figures were just purposely being extremely conservative, at the limits based on known data and the simplest, non adjusted geometry.

Edited July 11, 2015 by MunGazer

[nicky4096]

anyway, while not a record, i managed 39:30 in a 1 engine plane and will try to improve that.

i was managing what would have been 39:15 landings but the wheelbase is to narrow so it kept tipping over and getting destroyed...

Javascript is disabled. View full album

and i filmed the ascent!: https://vid.me/Olr7 (youtube sucks, so vid-me it is! )

no descent vid though, took at least 50 tries.

anyway, it doesn't beat my PB but i just wanted to show it

[Xannari Ferrows]

That's an interesting design. I might have to "borrow" it for some tests.

[nicky4096]

i think it's as good as you can get with 1 engine.

[Xannari Ferrows]

I don't know. A few minutes in the hangar can do wonder.

I must ask though, where's the crew?

[nicky4096]

there is none. it's an RC-001S and a Z-1k!

edit: also, i think it can go faster...

edit: yep, 1719 with 250 fuel...

Edited July 11, 2015 by nicky4096

[HelmutK]

OK, next try.

Not a new record, but with some modifikations it is maybe possible to come under 39.

It is fast, but I had to fly high in order to save fuel.

I ran out of fuel schortly before the mountains.

@nicky4096

39:30 with single, nice:)

[PanzerAce]

Ok, learned two things today in my speed attempt:

1) Plant a flag at KSC so that you can find it easily on the way back

2) My piloting skills leave much to be desired. I got ~2/3-3/4 of the way around Kerbin before I discovered I was robbing myself of ~300m/s of ground speed due to my poor piloting.

Attempt 2 will happen later tonight with 33% more thrust, a flag to mark my spot, and....airbrakes. Hard to slow down from 1700m/s without them.

[nicky4096]

ahhh, i just realized that unmanned flights are banned. nooooo...