Author Topic: Kerbal Space Program or "Rocket science is harder than it looks"  (Read 372697 times)

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Offline Nuke

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
i had a little too much fun with very low munar orbits today. i really wasnt playing so much as wanting to test my freshly modeled mpd thruster (it doesnt even have textures beyond the uv template). anyway i wasnt equipped for landing on either kerbin or mun, had no chute, a weak (but efficient) engine, and an rcs gizmo. anyway after testing the engine out on a munar transfer, i figured it would be cool to play orbital limbo. got my apomun down to 642, and my perimun was around 300. so every time i reach perimun i tap my thrusters, until the perimun moves to the other side of the orbit. i was trying to get so close to the ground so that i could see my shadow, without ever making contact. low orbits are really creepy, your zooming a few hundred meters off the grond and theoretically you will never hit it, unless of course your orbit intersects a mountain. splat! thats 3 dead kerbonauts.
I can no longer sit back and allow communist infiltration, communist indoctrination, communist subversion, and the international communist conspiracy to sap and impurify all of our precious bodily fluids.

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Offline Rodo

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
I can't seem to land any kerbonauts safely on the mun. just 1 crew survived so far and only in exchange of the landing module.
horizontal velocity is proving to be a terrible foe, any tips about that guys?

el hombre vicio...

 

Offline MR_T3D

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
I can't seem to land any kerbonauts safely on the mun. just 1 crew survived so far and only in exchange of the landing module.
horizontal velocity is proving to be a terrible foe, any tips about that guys?



Sure.
aim at the reverse vector and do a forward burn to make your decent more vertical.
once you're close, aim directly upward and use RCS to make yourself totally vertical

 

Offline Bob-san

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Yeah--do your best to arrest your horizontal momentum. It's too tough to do it completely, though. When you come in for landing, use RCS to provide a little more thrust to better control your descent. Otherwise, I suggest you pick some altitude and aim for it. At that altitude, you kill your momentum and then fall back to the Mun again. I typically do it around 1000KM because that's when I decelerate directly from orbit to landing.
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Offline Pred the Penguin

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Finally circular orbit with this craft! Would have made a trans-munar orbit, too, if I hadn't messed up the timing.

 

Offline Rodo

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
thanks, I'll keep trying then.
el hombre vicio...

 

Offline Herra Tohtori

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Landing is simple. Keep an eye out on your pitch attitude, velocity relative to surface, and altitude. You first do a de-orbit burn to bring your trajectory down, so it takes you above your intended landing site.

When you are approaching landing site, you're falling lower so you're picking up speed. Obviously this is bad for the landing. So, you adjust your trajectory by keeping the nose retrograde (relative to surface) and adjust burn rate to control descent speed. You should be able to bring your ship to nearly vertical trajectory by this method, and then it's just a matter of keeping the ship upright and descending to very low altitude where you can make the final flare burn and touch down softly.

I think I'll make a youtube video of it with my shiny new PC stuffs. :)
There are three things that last forever: Abort, Retry, Fail - and the greatest of these is Fail.

 

Offline newman

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Having finally made a rocket that's both powerful and flyable enough to take a shot at a return moon trip, I decided to give it a try. This is the result:



Yay! Considering this was my first go, everything went without a hitch. I learned a great deal about planning a landing approach for vertical landing. What worked for me was, I established an elliptical orbit around the Mun, with periapsis on the far side (relative to Kerbin) and at some 3000m height. Apoapsis was "aimed" towards Kerbin and at some 70,000m. This gave me a nice elongated orbital ellipse, so once I reached apoapsis I began my braking burn. This maneuver "narrows" the ellipse the marks the orbit, as well as shortening it - I made it so that the descent trajectory crosses the Munar surface at almost a right angle. Once at 20,000m height, I just oriented myself so the artificial horizon shows that my nose is pointing straight "up", used SAS to lock that down, used the main descent engines to slow my descent and RCS translation controls to kill any horizontal velocity. The reason I wanted apoapsis aimed at Kerbin side was, that side was also pointed at the Sun, and it helps seeing what you're doing when descending. Seeing your shadow is helpful, too :) My descent stage actually allows for quite a big margin of error, there's plenty of surplus fuel, once I get the hang of landings I intend to bring less fuel and put a service module with some solar panels and a science package on the moon instead. Then detach and use the return stage for the trip home. This part is least problematic, as Kerbin's gravity does most of the work... and I find aerobraking a nice cheap way of reducing the apoapsis on my return trip. Quite like that trick. Even managed to land on water, smack in the middle of a nice bay, close to land. That would've been practical :)
« Last Edit: February 19, 2013, 09:00:31 am by newman »
You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here! - Jayne Cobb

 

Offline Rodo

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
kudos!
I've been busy with studies this week so no trip to the mun so far, but with all this intel being thrown lately I might pull it off.
el hombre vicio...

 

Offline newman

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
A lot of people seem to be using the main engine to kill horizontal velocity. While the main engine is great to do it roughly while still at a decent altitude, using it all the way down for controlling horizontal speed is impractical, unless you were very, very accurate and hit the approach vector at 90 degrees right off the bat. That might work for some people, but I'm the first to admit I'm nowhere near that accurate a pilot, and I find having to reorient the craft to do course corrections quite perilous at low altitudes.. which is why I used RCS translation controls to kill horizontal speed once I got close to the deck. I mean, this is what the system's there for. Ok, it's one of the things it's there for - might as well use it :)
I'm not one of those purists that only use the stock parts or else it's "cheating". I don't care as long as the parts I'm using aren't terribly unrealistic (warp nacelles are definitely out), as I want some options when designing the rocket stages. For instance, I really love the "landing" engine from Nova Silisko's pack. It's very weak, you would probably use it a as a blow dryer here on Earth. But on the Mun, away from Kerbin's powerful gravitational pull, it turns into a very useful rocket engine, that is also very small, very lightweight, and very fuel efficient. Weak engines that have fuel efficiency are just the ticket for landings / orbital correction burns. Once you've done your Munar Injection Burn, you no longer need powerful engines, but you do need something that's lightweight and doesn't burn through fuel like there's no tomorrow. Plus, most orbital maneuvers don't need long or powerful burns from this point on - it's amazing just how little fuel is needed to get back from the Mun, compared to what you need just to launch and get to orbit..
You know what the chain of command is? It's the chain I go get and beat you with 'til ya understand who's in ruttin' command here! - Jayne Cobb

 

Offline Retsof

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
I tried the C7 pack.  my "shuttle" flops around like a badly folded paper airplane before eventually crashing.  Also, what is the difference between the landing skids and the wheels?
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I can't help but hear a shotgun cocking with this.

 

Offline Commander Zane

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Flops around how? If it's the wings bending on turns then you need to place struts from the wing root to the fuselage, just two on my craft (Which is decently sized) hold the wings in place no matter how much I try to force them to break.

 

Offline Retsof

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
More that the back keeps trying to pass the front, and it like to be upside down for some reason.
:::PROUD VASUDAN RIGHTS SUPPORTER:::

"Get off my forum" -General Battuta
I can't help but hear a shotgun cocking with this.

 

Offline MR_T3D

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
I assume you're making a shuttle that looks like the shuttle, which IIRC has very bad aerodynamics.

Add some adjustable flaps, and maybe some canards, and use ASAS to keep it level

 

Offline Nuke

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
try angling up your wingtip segments up a notch. this raises the center of lift and adds more stability, sorta like folding up the wingtips on a paper airplane.
I can no longer sit back and allow communist infiltration, communist indoctrination, communist subversion, and the international communist conspiracy to sap and impurify all of our precious bodily fluids.

Nuke's Scripting SVN

  

Offline Pred the Penguin

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Is it possible to connect anything to radial decouplers aside from solid boosters?

 

Offline Rodo

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Is it possible to connect anything to radial decouplers aside from solid boosters?

other radial decouplers and wings?
el hombre vicio...

 

Offline Bob-san

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Is it possible to connect anything to radial decouplers aside from solid boosters?

other radial decouplers and wings?
RCS thrusters & struts. You can link a stack decoupler to the booster, too.
NGTM-1R: Currently considering spending the rest of the day in bed cuddling.
GTSVA: With who...?
Nuke: chewbacca?
Bob-san: The Rancor.

 

Offline Pred the Penguin

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Yeah, that's how I've been doing it so far. :blah: Ah well, time to take a more extensive look at extra parts maybe.

 

Offline Sushi

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Re: Kerbal Space Program or "Rocket science is harder than it looks"
Just managed my first round-trip mun mission, with vanilla parts no less!

The rocket:


The landing:


The mission went fairly routine, overall. The first landing site was far too steep, so I had to burn some gas for a retry. The second landing site turned out to be on a gently slope anyway, and apparently the mun is quite slippery: you'll notice in the second screenshot that I have 2.5 m/s of velocity as I slowly slide down the hill. This gradually increased, and I elected to go ahead and return to orbit before I tipped over.