Mission Trouble - How to land near beacon ?

[Spaceweezle]

I don't understand why, but when I get near the site beacon on re-entry, facing Retrograde my ship spins like a drill even though I have a reaction wheel with RCS and SAS on with plenty of juice.

Eventually this makes the ship oscillate and I'm lucky if everything doesn't blow up. The ship is so out of control that I cannot take the reading. This is strange to me because it's the same ship I have taken to orbit and back without issues.

How many reaction wheels do I need to stop spinning like that ?

Also, how do you guys land accurately after ejecting your final stage ? When I do this my momentum changes and I can't correct the trajectory with no engine. I have tried re-entry with my last engine, but as above it causes great instability.

Every time I try this, my trajectory is pin-pointed right under the beacon, then upon re-entry my course changes wildly, it doesn't matter if I'm just in the pod or with my last stage still attached. This is driving me mad, please help!

[Kobymaru]

I don't understand why, but when I get near the site beacon on re-entry, facing Retrograde my ship spins like a drill even though I have a reaction wheel with RCS and SAS on with plenty of juice.

Eventually this makes the ship oscillate and I'm lucky if everything doesn't blow up. The ship is so out of control that I cannot take the reading. This is strange to me because it's the same ship I have taken to orbit and back without issues.

How many reaction wheels do I need to stop spinning like that ?

Please post a pic of your craft.

My crystal ball tells me that your craft is not aerodynamically stable. In which case answer to your question would be: an impractical amount. Better build your ship to be stable in Atmo.

Also, where are you even re-entering? What is a beacon? What are you trying to do?

Also, how do you guys land accurately after ejecting your final stage ? When I do this my momentum changes and I can't correct the trajectory with no engine. I have tried re-entry with my last engine, but as above it causes great instability.

Every time I try this, my trajectory is pin-pointed right under the beacon, then upon re-entry my course changes wildly, it doesn't matter if I'm just in the pod or with my last stage still attached. This is driving me mad, please help!

Precision landing under atmosphere is hard. I would suggest the Trajectories mod, but it has the problem that it cannot know how your craft will look like until you actually do stage it. I suggest putting small maneuvering engines (or RCS) on your final stage, and then correcting the reentry.

[Taki117]

The Spinning is likely caused by some aerodynamic abnormality, or a CoM that is not in the exact center of your rocket. A part that is only on one side of the craft for instance.

As far as this "Site Beacon" that's not a term I've heard before, and as such have no real idea what it is. I agree with Kobymaru in that a pic of the craft in question, preferribly in the VAB and also at various stages of reentry would be a great help.

[Spaceweezle]

Hey, thanks for the reply.

My ship in it's entirety flies straight as an arrow without any SAS/RCS, And I don't have any stability issues when flying the last stage, it's quite responsive. But as soon as I hit re-entry it becomes an uncontrollable beast.

Worse so, even after re-entry I cannot regain control of her, with or without SAS/RCS.

Here is a picture:

[KerikBalm]

My guess is that the beacon is related to a survey contract... I think you can click on those things and select activate navigation beacon.

Second... that craft is obviously not stable in a retrograde reentry with all those fins on the back.

When its travelling the other direction, you'll have a lot of drag in front of your CoM... very bad... I suspect if you were reentering facing prograde, everything would be fine

Also, the "spinning like a drill" is a problem with the SAS.

It doesn't realize that the airflow is coming from the other direction, and thus when it tries to correct the role, it makes things worse.

You'd have to fly it manually, and I wish reaction wheels could be disabled for roll but not everything else, because when going retrograde, the aerodynamic roll forces and the reaction wheel torque will fight each other.

The only way around this is to have something facing rearward that you can rightclick and select "control from here"... like an upsidedown probe core/landercan/pod.

Then the SAS will correctly interpret the direction of flight, and the control surface effects wont be reversed, and will be in agreement with the reaction wheel torque.

"Every time I try this, my trajectory is pin-pointed right under the beacon, then upon re-entry my course changes wildly, it doesn't matter if I'm just in the pod or with my last stage still attached. This is driving me mad, please help! "

Well the trajectory doesnt take drag into account, you always have to "estimate" how much you'll be slowed down, and place the trajectory ahead of your target point. Furthermore, the planet rotates underneath, and the trajectory is not displayed with the planets surface as the frame of reference, so that means the longer it is until you reach the surface, the more westward you will land of the point you intended... so you need to aim farther east.

Also, I like to put a pair of RCS thrusters on a pod after I decouple... the pod/can/cockpit's monoprop supply is typically good for dozens of m/s at least.

Edited October 9, 2015 by KerikBalm

[ForScience6686]

Your trajectory will change because you are experiencing drag which will slow you down. It will be hard to pin point a landing spot if you have no thrust available on your lander.

Are those radiators on the ship? I don't see why you would be needing those. I would guess you have a lot of drag on the science Jr, causing the instability. Does it try to fall facing prograde?

[Warzouz]

Survey contracts are a pain. They are tedious and very little rewarding. On Kerbin, use a plane to do them. At least flying is quite restful !

Survey can also but fine on low gravity bodies, but even though, after doing a last one on Bop, I swear to myself never do that again...

[Spaceweezle]

My guess is that the beacon is related to a survey contract... I think you can click on those things and select activate navigation beacon.

Second... that craft is obviously not stable in a retrograde reentry with all those fins on the back.

When its travelling the other direction, you'll have a lot of drag in front of your CoM... very bad... I suspect if you were reentering facing prograde, everything would be fine

Also, the "spinning like a drill" is a problem with the SAS.

It doesn't realize that the airflow is coming from the other direction, and thus when it tries to correct the role, it makes things worse.

You'd have to fly it manually, and I wish reaction wheels could be disabled for roll but not everything else, because when going retrograde, the aerodynamic roll forces and the reaction wheel torque will fight each other.

The only way around this is to have something facing rearward that you can rightclick and select "control from here"... like an upsidedown probe core/landercan/pod.

Then the SAS will correctly interpret the direction of flight, and the control surface effects wont be reversed, and will be in agreement with the reaction wheel torque.

"Every time I try this, my trajectory is pin-pointed right under the beacon, then upon re-entry my course changes wildly, it doesn't matter if I'm just in the pod or with my last stage still attached. This is driving me mad, please help! "

Well the trajectory doesnt take drag into account, you always have to "estimate" how much you'll be slowed down, and place the trajectory ahead of your target point. Furthermore, the planet rotates underneath, and the trajectory is not displayed with the planets surface as the frame of reference, so that means the longer it is until you reach the surface, the more westward you will land of the point you intended... so you need to aim farther east.

Also, I like to put a pair of RCS thrusters on a pod after I decouple... the pod/can/cockpit's monoprop supply is typically good for dozens of m/s at least.

Hey,

I know you can activate the nav on the beacon, I've been using it for the last 30-40 attempts. When I try Prograde re-entry all my stuff burns up. I have a heat shield on the bottom of the pod, but it's useless because once I disengage the last stage my course goes to hell. Perhaps I should remove everything bar the parachutes.

Thank you for the useful info on using SAS, that makes sense now I think about it.

Your trajectory will change because you are experiencing drag which will slow you down. It will be hard to pin point a landing spot if you have no thrust available on your lander.

Are those radiators on the ship? I don't see why you would be needing those. I would guess you have a lot of drag on the science Jr, causing the instability. Does it try to fall facing prograde?

Hey, I've had a real problem with heat so I added two rads symmetrically, even with them the heat bars almost max out on re-entry. I think you have a valid point about the science bay, I shall try removing it.

Survey contracts are a pain. They are tedious and very little rewarding. On Kerbin, use a plane to do them. At least flying is quite restful !

Survey can also but fine on low gravity bodies, but even though, after doing a last one on Bop, I swear to myself never do that again...

Haha, damn straight, this is a nightmare.

I used to play this ages ago, And was able to land on planets way beyond Mun and return. I even once rescued a Kerbal stuck in a 32 million meter orbit around the sun, but this survey mission is really testing my patience.

- - - Updated - - -

Yep, just tried Prograde re-entry.

Chute blew up, then half a second later the Pod blew up from overheating.

This is just with a Pod, chute and nothing else.

EDIT: Just tried again with 2 rads on the pod, still blows up from overheating. Prograde definitely not a possibility it would seem.

My course.

Edited October 9, 2015 by Spaceweezle

[Spaceweezle]

Ok, this is just silly now.

I had a perfect trajectory to the beacon- faced Prograde with no throttle, the atmosphere just pushes the ship miles off course. To avoid overheating I had to had 4 rads, 2 large +2 small, plus heatshield on the nose.

Before re-entry:

After re-entry:

[Randazzo]

I would reiterate the above suggestion to use a plane, with great emphasis.

Trying to do this with a rocket is going to be an exercise in frustration and nothing more.

[Spaceweezle]

Not once have I tried building or flying a plane type craft. I thought it would take even longer to do in a plane given my ineptitude with them.

Well, you've sold me on the plane now, it has to be less impossible than this BS.

The thing that irritates me the most about this mission, is the fact that they give it to you so early on. I would sooner be able to place a flag on the sun.

[ForScience6686]

The radiators are not for re entry, they will absorb the heat. Those are primarily for nukes at this point. But they are causing drag so remove them. You will have to come in retrograde or you will continue to burn up. Without thrust you will have to test and repeat the proper de orbit to hit the target exact, you would be better off with a different approach to this.

[Randazzo]

Not once have I tried building or flying a plane type craft. I thought it would take even longer to do in a plane given my ineptitude with them.

Well, you've sold me on the plane now, it has to be less impossible than this BS.

The thing that irritates me the most about this mission, is the fact that they give it to you so early on. I would sooner be able to place a flag on the sun.

I have a couple basic craft files available on dropbox, you can find them in this thread if you are a visual learner like me. You could probably also find some at the appropriate tech level on KerbalX. I imagine, as often is the case with planes, landing will be the hard part.

[Spaceweezle]

The radiators are not for re entry, they will absorb the heat. Those are primarily for nukes at this point. But they are causing drag so remove them. You will have to come in retrograde or you will continue to burn up. Without thrust you will have to test and repeat the proper de orbit to hit the target exact, you would be better off with a different approach to this.

My first 30 or so attempts were Retrograde re-entries. It didn't matter if I was in the pod or with the last stage still attached, the atmosphere just pushes me all over the place. I fail to see what difference the drag from 2 radiators would make compared to the pod itself. If the radiators are placed in perfect symmetry shouldn't there should be equal drag/resistance ?

Regardless, the atmospheric resistance on the pod alone has the same effect, I still land to buggery away.

I have a couple basic craft files available on dropbox, you can find them in this thread if you are a visual learner like me. You could probably also find some at the appropriate tech level on KerbalX. I imagine, as often is the case with planes, landing will be the hard part.

Thanks man, I might take a look if I get desperate, but I usually like to build in my own stubborn way, and see how my flawed logistics hold up in space, it's half the fun.

[ForScience6686]

Think of your craft like a dart. The fins on the back add drag which keeps the front facing forward. In your case, you're trying to throw the dart backwards.

[technion]

Survey contracts are a pain. They are tedious and very little rewarding. On Kerbin, use a plane to do them. At

This has been something I always felt should be balanced. Kerbin's surveys start showing up early, and reward accordingly.

But by the time you've unlocked enough science, and played enough that you want to try building a plane, you've already completed survey missions on Dres or something at a much higher reward level.

[Spaceweezle]

Think of your craft like a dart. The fins on the back add drag which keeps the front facing forward. In your case, you're trying to throw the dart backwards.

Yeah, I know what you are saying, but if you look above at my Prograde re-entry you can see just how "un-dartlike" it is lol.

I'm just going to start over. This time avoiding any survey missions on Kerbin.