How do I get home ?

[Mozza]

Hi all

I'm happy, I've managed my first completely successfull orbit, I'm currently at 244 km at 2045 m/s and all is well with the intrepid trio.

Now - I know how to get back to Kearth, but how do I aim to get back near to the KSC - I know that these are marked on my artificial horizon - but what is the general idea / aim in order to give my Kerbanauts the smallest walk home ?

Thanks

Mozza

[CannotIntoSpace]

I hope you still have fuel.

aim your thrusters the opposite direction of where you're going. Slow down, and wait.

[Mozza]

Yep - still got about quarter of a tank for the de-orbit burn, so I know about slowing down to return - the question is how do I get as near as possible to the Kerbal Space Centre.

[CannotIntoSpace]

you need to time it perfectly. hopefully your orbit passes right over the space center. Just slow down, and hope to drop in somewhere near.

there is a reason why astronauts have preferred to drop in near a huge body of water. the method is not precise at all.

if you still have a quarter tank, you'll probably have to finish that off to slow down, so you must not fail. You need more than just a quarter tank to make minor adjustments while dropping down.

if you're not anywhere near the space center when you hit the atmosphere, you probably can't make it anywhere near home.

[Mozza]

Ok - thanks

I'll give it a few more orbits and then fire up the engine , wish me luck ;D

[CannotIntoSpace]

good luck.

the best way of doing it is by designing a rocket with tons of spare fuel.

you'd want to go 0 m/s right at the top of the pink reticle, preferably before you hit the atmosphere. Reserve some fuel just before hitting the ground for some minor corrections.

[Entroper]

It is possible to 'aim' your re-entry point. Try doing a transfer orbit to 34 400 m. Initiate your transfer orbit when you are exactly 180 degrees around the planet from KSC. It takes exactly one-half a revolution to complete a transfer orbit, so you should be entering the atmosphere just over KSC.

[Mozza]

Thanks chaps

seems with a bit more practive my orbits are getting better and better, I seem to average around 55k now with more and more fuel left over for the retrograde burn, all is good

I can get pretty close to the Space Centre now, just with a nice long burn as soon as the Space Centre comes into view over the horizon, its a bit trial and error but my last attempt got within swimming distance of the base so I was partucularly chuffed with that one 8)

[Tim_Barrett]

Getting back to the launch pad matters allll the way back to which way you launched.

[lujz]

It is possible to 'aim' your re-entry point. Try doing a transfer orbit to 34 400 m. Initiate your transfer orbit when you are exactly 180 degrees around the planet from KSC. It takes exactly one-half a revolution to complete a transfer orbit, so you should be entering the atmosphere just over KSC.

I tried this approach with almost circular orbit at 44k and landed way earlier than expected.

My guess it's because when you hit the 34k wall you start falling fast.

So in order to compensate for early atmosphere, I did the deorbit burn at T/2+T/4 from the base,

T being the orbital period. I think the dV for the burn was around -10 m/s.

This approach got me a few km past the base.

I imagine T/2+T/8 from the base would bring me even closer.

[Douglasdtlltd]

I feel like an idiot after reading all this. I just got done doing a hour orbit. But i forgot one thing, MY ENGINE. I need to rethink my rocket design.

[rdfox]

there is a reason why astronauts have preferred to drop in near a huge body of water. the method is not precise at all.

That, or, in the case of the Russians and Chinese, vast empty wastelands (Siberian steppes and the Gobi Desert, respectively). The two really big reasons that the US has always preferred water landings for capsules are:

1) Even under the parachutes, you're still coming down at about 20 mph/35 kph. Anyone who's ever been in a car crash knows how 'gentle' an impact that is; a water landing cushions the blow quite a bit. (The Soyuz, and, presumably, the Chinese Shenzou derived from it both use a braking rocket on the parachute harness that fires about ten meters off the ground to slow the descent at the last moment.)

2) American spacecraft, if they have a launch abort, are going to land in the water off Florida, so they have to be designed for water landings anyway--if you're gonna put the weight in for a water landing design, you might as well go ahead and use it as your primary landing zone, too.

[cjameshuff]

there is a reason why astronauts have preferred to drop in near a huge body of water. the method is not precise at all.

Real capsules carrying humans have better instruments and actually fly aerodynamically on reentry, adjusting angle of attack to control their trajectory. Or at least, are intended to...some Soyuz capsules have come in purely ballistic due to loss of active control, resulting in rougher reentry forces and landing off target. (Still, preferable to getting scattered across the countryside...)

Anyway, it's not actually that inaccurate with good instrumentation and control. The later Apollo missions came down within 1.85 km of their targets, and SpaceX's Dragon splashed down within 800 meters of its target on its first flight. They also plan to come down on land, using rocket propulsion for final braking and perhaps maneuvering before touchdown...it's possible they'll be able to reliably hit a specific landing field.

[Moach]

the most advisable way to do this, is to use the orbital calculator posted in the sticky atop the how-to page and figure out a trajectory that would lead you down to hit the 34.5K mark just as the KSC comes up on the horizon (which i have guesstimated to be roughy the travel necessary to stop given a 2km/s velocity)

there's no way to go rocket-scientist with this right now... KSP still lacks some rather basic flight instruments that would allow you to figure this out with, well... -any- precision -- so yoou gotta do it 'kerbal style' which is, blast away and try to think happy thoughts ;D

[cray]

there is a reason why astronauts have preferred to drop in near a huge body of water. the method is not precise at all.

Well, actually, capsule landings became quite precise in the Gemini and Apollo programs. After Gemini 5, most US splashdowns - even Apollo 13 - were within a few kilometers of their targets.

http://en.wikipedia.org/wiki/Splashdown_(spacecraft_landing)#Locations_of_splashdowns

Kerbal Space Program? Not so much. I'm lucky to hit the same hemisphere twice running.