Why my spacecraft tumbling when i try to insert it on orbit

[Pawelk198604]

Thanks again :-)

I feel now like this :-)

[Pawelk198604]

i have also one question how to control craft without SAS i want to send lab and probe without kerbonaut i used subassembly of my older rocket

[fairytalefox]

i have also one question how to control craft without SAS i want to send lab and probe without kerbonaut i used subassembly of my older rocket

Oh, these Stayputniks. I'm afraid there's no answer to your question. They don't only are SASless, they don't have reaction wheels as well IIRC. Probably a bunch of fins will help you to establish a suborbital trajectory, grab a piece of low-orbit science and land on chutes. Even high-orbit science maybe, it's not that high actually. Just fly straight up till you're out of fuel.

[Pawelk198604]

Oh, these Stayputniks. I'm afraid there's no answer to your question. They don't only are SASless, they don't have reaction wheels as well IIRC. Probably a bunch of fins will help you to establish a suborbital trajectory, grab a piece of low-orbit science and land on chutes. Even high-orbit science maybe, it's not that high actually. Just fly straight up till you're out of fuel.

I just do some suboribital flights with Jeb and Val. i get 90 science and invested it in the probe core, i hoped that i can make flyby to mun but no :-( it's unstable

[fairytalefox]

I just do some suboribital flights with Jeb and Val. i get 90 science and invested it in the probe core, i hoped that i can make flyby to mun but no :-( it's unstable

Maybe a piloted Mun flyby will help. One command capsule, 4 Goo things, 2 Material bays and radial mounted chutes. You will probably have to upgrade some of your facilities if you didn't do it yet.

[kurja]

I just do some suboribital flights with Jeb and Val. i get 90 science and invested it in the probe core, i hoped that i can make flyby to mun but no :-( it's unstable

Did you try using your previously successful manned suborbital craft, just replace the capsule with the probe core (and maybe add batteries and solar panels if you have them)? If that doesn't work it's probably due to lack of control authority, try adding torque wheels or rcs?

[Pawelk198604]

Did you try using your previously successful manned suborbital craft, just replace the capsule with the probe core (and maybe add batteries and solar panels if you have them)? If that doesn't work it's probably due to lack of control authority, try adding torque wheels or rcs?

Yes it worked.

[Francesco]

Also note that drag increases significantly right around mach 1 (340 m/s)

What is the relationship between speed and drag?

Equations/pretty graphs...?

[cybersol]

What is the relationship between speed and drag?

Equations/pretty graphs...?

Not sure about the pretty part, but I posted some here.

[Pawelk198604]

Look at this :-)

Without NavNodes and any guidance OLDSHOOL :-)

Sadly i forgot to bring on it any scientific equipment

What a FACEPALM :-(

[Francesco]

Not sure about the pretty part, but I posted some here.

Thanks, very interesting!

So does that tell us if there's an altitude on Kerbin where it's "better" to cross the sound barrier?

You know, to push past 300+ m/s while not stressing the rocket too much and risk losing control?

[cybersol]

Look at this :-)

Sadly i forgot to bring on it any scientific equipment

What a FACEPALM :-(

Congrats on the fly by and orbit!

Thanks, very interesting!

So does that tell us if there's an altitude on Kerbin where it's "better" to cross the sound barrier?

You know, to push past 300+ m/s while not stressing the rocket too much and risk losing control?

No that would depend more on how drag decreases with altitude, instead of how it varies with speed. That said, I am the wrong person to ask about that topic because I have the belief that if you have to slow down a rocket with throttle then you are doing it wrong. A better designed rocket with more control authority will punch through transonic while maintaining control and end up saving fuel due to lower gravity losses.

[SanderB]

There isn't a "better altitude". You have to gain about 300-350m/s of vertical velocity and once you have obtained should not go above or below it until you have pitched almost horizontally. (KER is a mod that will allow you to monitor vertical velocity precisely.) Ideally continual 350m/s vertical velocity is held by going through a perfect gravity turn but it is safer to have a steep ascent, and reduce throttle in order to keep your vertical ascent/speed to 350m/s. Gravity losses are generally sustained by thrusting vertically in excess which is why reducing throttle can save you fuel and dV. A vertical velocity of about 350m/s is a happy medium for a fuel efficient ascent.

A swivel engine with 8 tons of fuel can easily orbit a 1t payload within a pointy fairing. This video is a swivel engine (set to 55% gimbal limit), 8 tons of fuel, 4 tailfins, a pointy 1.25m diameter fairing and a decoupler orbiting a 1.1t payload. With a trim ascent, fins on the back of your rocket and a bit of monitoring of what's going on during gravity turn, orbit is not so hard. Getting to orbit can be very seamless and easy looking in KSP. The rocket in the video had no SAS until much later in the video. Instead I once applied trim with one tap of Alt + D, set throttle to 100% and hit spacebar.

Using trim plus tail fins to ascend for your ascent to orbit takes a bit of practice but I think it is the most efficient way. To use trim, use Alt WASD and QE, to reset, press Alt X. Also, if your fins burn up you have to absolutely extend your finger to turn on SAS and activate stability control because your rocket will at that point be in danger of flipping. Otherwise getting to orbit can easily be a hands off experience from launchpad to your 70km apoapsis for any payload that allows your rocket to be stable through the use of fins.

Edited May 22, 2015 by SanderB

[cybersol]

Nice video SanderB! I am all for a fast and low profile to orbit, but yours might be a little too low. I suspect you could save a little fuel by being closer to 22.5* at around 24k, but of course the best values depend on your aero drag and TWR. In your case it would also likely prevent the overheating fins. I was also curious what mod gives the grid like overlay in your video?

[Pawelk198604]

What do you think about my mission to Mun

[SanderB]

cybersol, the ascent profile I use is just about the limit for how low you can go without losing more dV to drag than you do gravity, and the fins are just 25$ anyway, have served their purpose by the time they melt away and save mass for the orbit insertion burn. With trim-only there is always a random element that determines how fast you pitch over (if you stay hands-off until about 1km/s of velocity) so probably some manual corrections are always necessary and in my particular video this meant a very shallow ascent.

The lines on my screen are from Navhud mod.

Pawelk your mun vessel looks fine though a bit inefficient (my own first mun landers weren't very efficient either). Generally it is a lot more cost effective to use the least amount of engines possible, and that isn't done with the kind of asparagus staging you used and you didn't lead any fuel lines from the outer tanks into the main booster which made it even less efficient. For every 15 kN of thrust from a liquid engine you want about 1t of fuel on your booster whereas you had about 60kN of thrust for every 1t of fuel on your main booster stage. Your ascent profile was also quite steep. Ideally you want to pitch down about 10° for every 100m/s of surface velocity you have, until you're pitched up from the horizon by only 10-20° or so.

I think the most efficient way to get to the mun and back with a probe is as displayed in the video below. The exception is it should have 0.2t more fuel and a parachute to really get the final stage back in one piece. To get the mun encounter without maneuver nodes an Ap of about 10,800km above kerbin is reasonable.

Edited May 24, 2015 by SanderB

[Francesco]

SanderB, how do you build fairings as wide as the fairing base part?

The game won't let me do that :/ it forces me to place a wider cross section:

[Pawelk198604]

Does anyone have any suggestions which contracts choose what technology to invest in, and how to expand my cosmodrome (as we Poles like to say Baikonur Cosmorome, Cape Canaveral Cosmodrome) in such way can build something like a Saturn V + Apollo lander, or N-1 + Soyuz and LK Lander, but i prefer Apollo with LOR configuration.

I heard that in 1.0 we can do this with stock parts, i did something similar in previous updates, but my more successful MUNar projects, ware more similar to concealed NASA Constellation than real Apollo, i mean two rockets and rendezvous on Kerbin orbit KEOR But i wan do it in one rocket like a real Apollo/or Soyuz 7K-LOK as Korolyev planed to do in first place.

I probably will need to download MechJeb for smart SAS, and rendezvous helper, but i want did this with stock parts and real Jebediah instead MechJeb :-) or Va;, but probably Jeb will be Pissed off to the limit when he finds out that I chose the girl, instead of him

There remains the question of dock, regardless of the selected variant of mission

Doing this manually is very frustrating, recently I loaded the training scenario. The same close-in orbit went as smoothly worse with the manewem docking, I tried to use these new "piloting skills" BTW how to train Kerbals i mean how they get experience i need mostly pilot one, the scientist and engineers are very much useless, sorry Bob and Bill :-( During most critical phases (launch, re-entry (albeit the re-entry are not so dangerous as i thin it would be, kerbonauts are very much safe to safe IMHO

(maybe i'm psycho or sadist, maybe both )

But i think we need something like Gemini not Lander Can.