Uncontrollable rocket -- I don't know why

[Loren Pechtel]

(Note:  I've been away from the game for a while, maybe something has changed that's messing with me.)

I have a probe core--the OKTO2, tweakscaled up to fit.

I also stuck Jeb on board after the first flight got stuck.

I have power (although no way to generate it--this is a tourist hop, it's only staying up a fraction of an orbit.)  Note that the engines gymbal if I attempt to turn the rocket.

I have a reaction wheel.

Furthermore, I have two designs.  The first is the core of the rocket--chute, core, wheel, passengers, fuel, engine.  This flies fine and has successfully completed a mission other than coming down in the mountains.  The second design adds a ring of chute/passengers/fuel/engine, all exactly the same as the core--I'm simply scaling it up to carry more tourists.  Mechjeb takes this up but won't circularize.

The only thing unusual here is the lack of decouplers--I'm bringing the whole thing back and trying to drop it in ocean (no way it's not going to fall over on land) off KSC.

[RoninFrog]

How big of a rocket is it?  How many reaction wheels and what size?  You can see if you are out of electricity by clicking the little gas can icon in the upper left.

[bewing]

Reaction wheels use a heck of a lot of power. If you can't generate power, your reaction wheels have probably already used it all up. Unless you've got a nice big battery or 3.

[OhioBob]

A screenshot of your vehicle would help immensely.

[Linkageless]

Yes, a screenshot please.

From your description it sounds rather like you have a much heavier vessel to be moved around by the same reaction wheel.  Try adding a battery and reaction wheel to each additional stack on the vessel.   I would even add a few ox-stat panels to keep the batteries topped up, but I like to over-engineer.

Fuel remaining will add to the mass to be manoeuvred, although it doesn't sound like you have too much to spare.

The other option is to add mono or LFOx RCS thrusters, but the ksp magic reaction wheels are typically preferable for this application.

[Loren Pechtel]

I do have a much heavier vehicle with the same wheel but this is not a case of being out of power!  That was my first thought, but I looked, the battery is nearly fully charged.  I expect it to turn slowly but it's got 7 minutes to turn maybe 10 degrees for the circularization burn.  I do not believe I need panels--the battery will be used to orient for circularization, but then recharged by the circularization burn.  It will be used again to reorient, partially charged by the deorbit burn and then probably fully charged when I burn to get it down to opening velocity (aerobraking alone won't slow this beast anywhere near enough.)  Once the chutes come out there's no more need for SAS anyway.

[Loren Pechtel]

I decided to try something.  I took the wheel off and put the very same wheel back on the outer part (so now there are multiple wheels)--I never picked up a different part.  Now it steers properly.  The only thing I can think of is roundoff--maybe the wheel's rotation is being rounded to zero.

It does turn out I need more power for some reason, though--the battery drained while doing nothing in orbit.  I guess those tourists had too many lights on.

And now I'm really confused!!  It didn't come down exactly where I planned but I thought I was doing ok.  I put it in the ocean as intended at about 3.5 m/s.  I hit recover and walked away to deal with a problem.  I come back to find it blown to bits by a hard landing.  How do I have a hard landing after I've already landed??  I've seen rockets damaged by tipping over in the water but I've never seen one annihilated.

Edited April 28, 2020 by Loren Pechtel

[AHHans]

6 hours ago, Loren Pechtel said:

I've seen rockets damaged by tipping over in the water but I've never seen one annihilated.

If all parts with a command point - i.e. command capsules, probe cores etc. - get destroyed then the remaining parts are "just" debris. Did you check if there is debris at the crash site?

[Loren Pechtel]

9 hours ago, AHHans said:

If all parts with a command point - i.e. command capsules, probe cores etc. - get destroyed then the remaining parts are "just" debris. Did you check if there is debris at the crash site?

I couldn't check, the box that tells you about the crash blocked everything and couldn't be dragged.

However, I got the deorbit point dialed in right, put it in the ocean within sight of KSC at about .2 m/s (chutes plus the rocket) so it didn't bobble at all (the usual cause of water breakups I've seen is the rocket going too deep and being destroyed after the rebound), it looked perfect.  Then it slowly tipped over and every bit of the rocket that mattered was obliterated, I was left with a pile of engines and fuel tanks.

It seems completely insane but I think the only way this design will fly is if I put decouplers on it and blow off the boosters at touchdown.

[AHHans]

54 minutes ago, Loren Pechtel said:

I couldn't check, the box that tells you about the crash blocked everything and couldn't be dragged.

You can go to the tracking station in the KSC and activate the display of debris there, then you'll see where you have how many pieces of debris.

56 minutes ago, Loren Pechtel said:

Then it slowly tipped over and every bit of the rocket that mattered was obliterated, I was left with a pile of engines and fuel tanks.

Yes, that can happen! My standard recoverable booster is fine when it lands on ground, where it either stays upright or topples over with the parachutes still deployed. But when it lands on water it bobs around in the water, the parachutes get automatically cut, and sooner or later it topples over without the parachutes to slow the fall. The resulting "crash" onto the water usually leads to several parts being destroyed and leaves me with several pieces of debris.