Kerbals stuck in orbit, fuel is present but electric charge has ran uit

[Ciphra]

Hello peeps,

 

when I look for solutions of Kerbals stuck in space I usually come across ones where fuel has ran out. Althought I've encountered that problem more than once too, this time the problem is a little more sofisticated. I have more than enough fuel to re-enter the atmosphere at whatever periapsis I see fit, the problem is the speed at which I re-enter. Because I ran outof electric charge (lesson of today; don't attempt a moon fly-by without solar panels or extra battery packs), so I won't be able to hold it in the correct angle to have the heatshield soak up the heat. I'm 99.9% sure it's going to explode upon re-entering. Anyone with a nifty solution to save my kerbals?

 

Thanks in advantage,

Ciphra

 

Edit:

Image of the shuttle I'm trying to bring down. From top to bottom the parts:

Mk 16 Parachute, Mk 1 Command Pot, Mk 1 Crew Cabin, Service Bay, SC-9001 Science Jr., Heat Shield.

On the side I have 4 radial mounted Mk 2 radial mount Parachutes and some steps down 1 side so my scientist could go up and down to reset Goo's and Material Bays to gain maximum science in 1 trip without weighing the whole thing down too much with 5-ish science units.

Slowly it's starting to dawn the steps are the reason I'm flipping over, I'm going to check whether that's the side it keeps tilting towards.

Edited January 4, 2016 by Ciphra
Info and Image

[sal_vager]

Hi Ciphra, welcome to the forums!

First I suggest you save your progress by holding the alt key and pressing F5 to make a save.

Command pods are aerodynamically stable with the bottom into the airflow, as long as you do not have too many other parts on top that might make the pod unstable.

So you should be fine even with no electric power, the pod will fall the correct side up (and down).

And a periapsis of 30km should be fine.

[Snark]

What sal_vager said.  As long as your ship is aerodynamically stable the right way 'round, it will naturally sort itself out.

What sort of engine do you have on your craft?  Many engines have an "alternator" and produce electric charge when running. So depending on your fuel supply, you may be able to use your engine to recharge your batteries.  It's incredibly wasteful, but if you have plenty of fuel and no electricity, it may be worth it in this case.  However, it's only possible if the engine has an alternator on it.  Examples of engines that have an alternator are the Swivel, the Poodle, and the Skipper (not an exhaustive list).  The Terrier, notably, does not.

If you find yourself in a situation where you have limited battery supply, and it's running out with no way to recharge it, and you don't actually need the electricity now but are going to in the future, you can turn off your battery so that it won't drain.  This means your ship will go dead electrically, the same as if it had run out of electricity, but it means that later on you can turn the battery back on when you need it.  However, this only helps if the battery still has charge in it when you turn it off.

If your engine has gimbal, then you can steer somewhat even without electricity.

 

[Geschosskopf]

Assuming you built the rocket so that you're only returning the capsule (and a few small external parts), you should be OK on reentry as Sal says.  However, you might have other problems.  Such as orienting the ship in the proper direction to do the needed burns.  If your reaction wheels don't work and you don't have RCS, you'll have to have a Kerbal get out and push :).  The problem with this, however, is that you can probably only do it once, and it had better be for the de-orbit burn.  This is because the ship will probably have some slight tumbling motion on it after the Kerbal gets done pushing, which the burn will make worse, resulting in a rapid spin that you can't stop.  Which means no docking of a rescue ship and GREAT difficulty with EVA-ing to a rescue ship (of course, warping will stop the spin but you didn't hear that from me).

So, if you have to make multiple burns to get home, I'd recommend just sitting still and stable (if you can) and await rescue.

Way back when career mode first started, I tried a Mun landing without solar panels and also ran out of electricity.  This happened when I was reorienting the ship to adjust my Kerbin Pe after escaping from Mun on the way home.  So when the power failed, the ship just kept on spinning and it was too fast to risk trying to get out and stop it.  And I didn't think to warp it into stillness.  And my Kerbin Pe was like 500km.  So what I did was watch the navball and every time the retrograde marker flashed across it (never through the center, the ship was spinning about 45^ to all the cardinal directions) , I did a short burn.  Which usually changed the rotation into something more extreme in a different direction.  Still, but doing this I managed to get my Pe down in the atmosphere and land safely.  Of course, in this days, there was no reentry heat.......

[Tatonf]

Sorry but using the engine's alternator isn't an option in your case, because you can't turn on your engine if you ran out of electric charge.
You basically can't do anything with your ship if you don't have electric charge. The only thing that can still move are your kerbals.

[sal_vager]

You can run the engine just fine, and if it has gimbal you can use a short low-thrust burn to make the craft turn, then wait until you're lined up in the direction you want before using full thrust to change your orbit.

Electric charge is required for reaction wheels.

[Snark]

25 minutes ago, Tatonf said:

Sorry but using the engine's alternator isn't an option in your case, because you can't turn on your engine if you ran out of electric charge.
You basically can't do anything with your ship if you don't have electric charge. The only thing that can still move are your kerbals.

Actually, as sal_vager points out, you can-- as long as the ship has crew.  Without electricity, you can't use reaction wheels and you can't transmit data, but just about everything else is fine.  (An unmanned ship, however, is totally dead without electricity).

33 minutes ago, Geschosskopf said:

If your reaction wheels don't work and you don't have RCS, you'll have to have a Kerbal get out and push :).  The problem with this, however, is that you can probably only do it once, and it had better be for the de-orbit burn.  This is because the ship will probably have some slight tumbling motion on it after the Kerbal gets done pushing, which the burn will make worse, resulting in a rapid spin that you can't stop.

Firing the engine shouldn't make the spin especially worse, as long as the ship is symmetric.  And, in fact, if the engine has gimbal, firing it will make things better because SAS will use the gimbal to correct rotation.

[cubinator]

Do you have a potato on board? You might be able to hotwire your pod batteries to a potato to get a little power. If that doesn't work, get the potato to grow in sunlight and set up a mechanism so that the oxygen outputted by the potato spins a turbine which makes energy for the battery. Or you could just blow on the turbine and eat the potato for more energy to blow the turbine longer.

[TsurugiSan]

Just recently found myself in this predicament when replaying the career mode on hard.  I found that Right-clicking on the engine and dropping the output down as low as you can without zero, you can put in about 10% throttle, get a roll started, then shut it off and wait.  Bring in throttle to stop roll. Re-adjust output for the entry burn, and you're fine... some what.   This mostly works with gimbled engines like the Terrier (no alternator) and the Swivel (alternator)  Level 1+ pilots can still align with the gimble engines and no battery using SAS directions. Just remember they need active engines to do those SAS commands if no battery... 

Now, if you're using the non-gimble Reliant (I think that's what its called... ) you'll have to drop engine output, fire it up to charge battery, then use small inputs to the gyros to get attitude change started. Just keep the SAS turned off, and pay close attention to your orbit changes. Transmitting data will KILL all progress, so just save the data, recover it on land, and be thankful for small science... 

There IS life after battery...  ... and yes, your parachutes will still deploy without battery.

[Ciphra]

Hey all, thanks for the responses.

As some of you may have indicated already, recharging with use of the engine is a no-go, as the only one attached still is the terrier engine. I saved the game yesterday, and just tried to re-enter, but after my engine blew out because of the over heat and discoupling the fueltanks, it took about 5 seconds to flip over and boom. Luckily I indeed made a quicksave (thanks sal_vager ^^ ), so I can retry a couple of times. It's my first play-through, so I'm allowing myself a bit of cheating here and there to keep my kerbals alive :')

I'm going to try to have it roll while in the proper angle like TsurugiSan suggested, maybe it will keep it still. I'll also try to include a picture of the capsule if I blow up again, so you can point out any difficulties in the design (if there are any complicating the re-entry).

Thanks for the tips and suggestions everybody

[Ciphra]

welp, making it roll was not happening, and once more my shuttle blew out because it tipped over. I had it with all the heating effects perfectly alligned with the retrograde marker on the nav-ball, but after a brief it just tipped over and boomed again. I'll include a picture (and description) in the main post, maybe there's a reason it tips over, one I can hopefully work around :')

[Snark]

1 hour ago, Ciphra said:

welp, making it roll was not happening, and once more my shuttle blew out because it tipped over. I had it with all the heating effects perfectly alligned with the retrograde marker on the nav-ball, but after a brief it just tipped over and boomed again. I'll include a picture (and description) in the main post, maybe there's a reason it tips over, one I can hopefully work around :')

If it's tipping over the wrong way when you don't have any reaction torque, then what that means is that your aero stability is such that it wants to be nose-first.  So there's probably nothing you can do about it.

If it has a docking port, you could send up a rescue ship to resupply it with electricity.  If it doesn't, you could send up a ship with the Klaw to do the same.  Or you could just abandon the ship, send up a rescuer to take the kerbals (and any science).

[Ciphra]

35 minutes ago, Snark said:

If it's tipping over the wrong way when you don't have any reaction torque, then what that means is that your aero stability is such that it wants to be nose-first.  So there's probably nothing you can do about it.

If it has a docking port, you could send up a rescue ship to resupply it with electricity.  If it doesn't, you could send up a ship with the Klaw to do the same.  Or you could just abandon the ship, send up a rescuer to take the kerbals (and any science).

Yes, it definitely wants to be nose first xd

Anyway, I'll have to sort out a rescue mission in that case. I'm not in possession of enough science to recharge the battery with the Klaw.

However, how do I measure (and correct) the aero stability before launch? Just to make sure I'm not going to make the same error over again.

[Snark]

2 hours ago, Ciphra said:

However, how do I measure (and correct) the aero stability before launch? Just to make sure I'm not going to make the same error over again.

Unfortunately, there's not really any totally-reliable way to do that.  It's more of an art than a science.

Here's the deal:  To be aerodynamically stable in a certain orientation, your center of mass needs to be in front of your center of drag.  It's easy to see the center of mass-- there's a toggle button in the VAB / SPH that will show you the CoM.  However, there is no way to see center of drag in the vehicle editor.

(Side node:  There's a "center of lift" indicator, but it's not the same thing and isn't useful for this purpose.  Its presence can be misleading, i.e. people who think "my CoM is in front of my CoL, why isn't it stable".)

So what can you do?

Well, basically, all you can do in the vehicle editor is to try to visually estimate where the center of drag will be.  A useful default is to just assume it's in the geometric center of your ship, then bias it away from low-drag parts (like nosecones) and towards high-drag parts (like fins).

If your CoM is right in the middle of your ship, then it's very hard to guess which way is stable, because if you've mis-estimated where the CoD is, it could be on either side of the CoM which will completely change the stable orientation of your ship.

The closer your CoM is to one end of the ship or the other, the more confident you can be, i.e. "I don't know exactly where my CoD is, but since my CoM is way out at this end, I'm pretty sure my CoD is on this side of it."

So basically all you can do is visually guesstimate.

If you do that, and then you turn out to be wrong (i.e. you think it should be stable, but it's flipping), and you're trying to debug why it's wrong, then you can toggle the debug aero display via F12 while you're flying through atmosphere.  This will draw a bunch of arrows on the various parts of your ship, showing aero forces (lift, drag), which may help you figure out "where's all the drag coming from."

One thing to bear in mind, when you're adding pieces (such as fins, control surfaces, etc.) to try to fix your aero stability:  the closer they are to the CoM, the less effective they are.  For example, putting fins at the bottom of a rocket won't help much if the CoM is also at the bottom of the rocket.  You want your fins or control surfaces to be as far behind the CoM as possible, for maximum effectiveness.  (It's also possible to put steerable control surfaces (like canards) as far in front of the CoM as possible, but that's less desirable because they're only effective when your AoA is less than the maximum deflection angle of the control surface; beyond that and they become a liability rather than an asset.)

Edited January 4, 2016 by Snark

[Kryxal]

I don't think there's going to be much you can do at this point about this coming in nose-first ... the science component is just too light, even with what appears to be a heat shield under it.  A design fix would be to put the science junior and service bay between crew cabin and capsule and make up the difference with rotation wheels.  In the meantime, just have your Kerbals go EVA and reach a stable orbit, then rescue them.

[Ciphra]

43 minutes ago, Snark said:

Unfortunately, there's not really any totally-reliable way to do that.  It's more of an art than a science.

Here's the deal:  To be aerodynamically stable in a certain orientation, your center of mass needs to be in front of your center of drag.  It's easy to see the center of mass-- there's a toggle button in the VAB / SPH that will show you the CoM.  However, there is no way to see center of drag in the vehicle editor.

(Side node:  There's a "center of lift" indicator, but it's not the same thing and isn't useful for this purpose.  Its presence can be misleading, i.e. people who think "my CoM is in front of my CoL, why isn't it stable".)

So what can you do?

Well, basically, all you can do in the vehicle editor is to try to visually estimate where the center of drag will be.  A useful default is to just assume it's in the geometric center of your ship, then bias it away from low-drag parts (like nosecones) and towards high-drag parts (like fins).

If your CoM is right in the middle of your ship, then it's very hard to guess which way is stable, because if you've mis-estimated where the CoD is, it could be on either side of the CoM which will completely change the stable orientation of your ship.

The closer your CoM is to one end of the ship or the other, the more confident you can be, i.e. "I don't know exactly where my CoD is, but since my CoM is way out at this end, I'm pretty sure my CoD is on this side of it."

So basically all you can do is visually guesstimate.

If you do that, and then you turn out to be wrong (i.e. you think it should be stable, but it's flipping), and you're trying to debug why it's wrong, then you can toggle the debug aero display via F12 while you're flying through atmosphere.  This will draw a bunch of arrows on the various parts of your ship, showing aero forces (lift, drag), which may help you figure out "where's all the drag coming from."

One thing to bear in mind, when you're adding pieces (such as fins, control surfaces, etc.) to try to fix your aero stability:  the closer they are to the CoM, the less effective they are.  For example, putting fins at the bottom of a rocket won't help much if the CoM is also at the bottom of the rocket.  You want your fins or control surfaces to be as far behind the CoM as possible, for maximum effectiveness.  (It's also possible to put steerable control surfaces (like canards) as far in front of the CoM as possible, but that's less desirable because they're only effective when your AoA is less than the maximum deflection angle of the control surface; beyond that and they become a liability rather than an asset.)

That's a whole lot of sciency guesttimation xd

Anyway gonna keep this in mind when building my next shuttle.

19 minutes ago, Kryxal said:

I don't think there's going to be much you can do at this point about this coming in nose-first ... the science component is just too light, even with what appears to be a heat shield under it.  A design fix would be to put the science junior and service bay between crew cabin and capsule and make up the difference with rotation wheels.  In the meantime, just have your Kerbals go EVA and reach a stable orbit, then rescue them.

Especially this tip ^ next time I'll put the sciencybits more on top and see if I can weigh down the bottom more. And the occasional CoM check before building stages around it, too

 

Thanks guys!