Two quick questions...

[Streetwind]

...before I go sleep!

1.) What's the minimum thrust in kN for one ton worth of rocket to achieve liftoff on Kerbin? Plain mass, not payload. Is it 9.82, because gravity? Or is it something else? (Sorry my physics is bad )

2.) Are there any differences between probe cores that I am missing? There's so many of them, and they all seem to have largely the same stats. I am looking at weight, at reaction wheel torque, and at power consumption (both probe itself and reaction wheels). Is there something else to them that gives a good reason for this large a variety?

Edited January 9, 2014 by Streetwind

[Deathsoul097]

1) Basically, anything over 10kN will lift one ton (Albeit very slowly)

2) Some of the probe cores lend themselves toward different designs, such as the OKTO being good for mountable stuff, along with the HECS, and the OKTO2 having more powerful reaction wheels. Also some are just there for compatability with the larger sizes.

[TheDarkStar]

1. I'm not sure, but <disregard, it was pointed out that it was 10 kN per ton>. However, having a better acceleration is better if you are launching to be more efficient.

2. First, they are different shapes for different rockets. Second, the reaction wheel strength is also dependent on the mass of the part that has it, so the heavier cores have stronger reaction wheels.

[Sirine]

1.) What's the minimum thrust in kN for one ton worth of rocket to achieve liftoff on Kerbin? Plain mass, not payload. Is it 9.82, because gravity? Or is it something else? (Sorry my physics is bad )

A) You are asking about... TWR. (Thrust to Weight Ratio). There are formula that you don't want to go into. Simple solution, get a mods call Engineer Redux. TWR > 1 = lift.

2.) Are there any differences between probe cores that I am missing? There's so many of them, and they all seem to have largely the same stats. I am looking at weight, at reaction wheel torque, and at power consumption (both probe itself and reaction wheels). Is there something else to them that gives a good reason for this large a variety?

No. Aside for aesthetic (Good looking Satellite)

[capi3101]

10 kN is it; technically it would be 9.81 kN, but that rounds up to 10 nicely (technically 10 kN would give you a TWR of 1.02 in the case of a one tonne rocket). Good luck building a rocket that light, though.

9.81 (not 9.82) for KSP. For purposes of the rocket equation that figure is a convenient conversion factor, and it's always the same regardless of the reference celestial body.

The question about probe cores has largely been answered.

Edited January 9, 2014 by capi3101

[Soda Popinski]

General consensus is build to have a thrust to weight ratio of about 2 (1.8-2.2 is usually good). So for every ton, you need have 19.6 kN of thrust.

[Streetwind]

A) You are asking about... TWR. (Thrust to Weight Ratio). There are formula that you don't want to go into. Simple solution, get a mods call Engineer Redux. TWR > 1 = lift.

Nah. Mostly I was wondering if an ion thruster could lift itself under ideal conditions. But with 2 kN per ton of thruster, not ever happening

Second, the reaction wheel strength is also dependent on the mass of the part that has it, so the heavier cores have stronger reaction wheels.

Oooh, so a 0.5 torque reaction wheel in a 1-ton part will exert a stronger turning force than the same 0.5 torque reaction wheel in a 0.2 ton part? That's kind of a little silly, considering how light all the inline reaction wheel / SAS parts are...

9.81 (not 9.82) for KSP.

Another thread said 9.82, specifically.

Right, another question:

3.) Do large extended solar panels have a g-force tolerance limit? I.e. will I tear them off if I fire up the engine without retracting them first?

[Kasuha]

Nah. Mostly I was wondering if an ion thruster could lift itself under ideal conditions. But with 2 kN per ton of thruster, not ever happening

You can do so if you choose method of lifting that does not require inefficient orbital maneuvers.

On Kerbin you can get a spaceplane to orbit with just ion engines.

On Minmus, you can get a ship weighing more than what an Ion engine can lift if it is on wheels and you get it to orbital speed by horizontal thrust.

Oooh, so a 0.5 torque reaction wheel in a 1-ton part will exert a stronger turning force than the same 0.5 torque reaction wheel in a 0.2 ton part? That's kind of a little silly, considering how light all the inline reaction wheel / SAS parts are...

I believe the weight of the probe core plays exactly the opposite role - the heavier probe core, the more energy you need to turn it.

If you put a small probe core on the launchpad, you can turn it on the side and roll it around using its own torque and battery. AFAIK you cannot do the same with the large one because it doesn't have enough torque to turn on its side.

2.) Are there any differences between probe cores that I am missing? There's so many of them, and they all seem to have largely the same stats. I am looking at weight, at reaction wheel torque, and at power consumption (both probe itself and reaction wheels). Is there something else to them that gives a good reason for this large a variety?

Important difference is strength of connection to other parts. In VAB that strength is indicated by diameter of the green ball marking the connection point. You can notice that certain parts - although with large diameter - have particularly weak connections. Large Monopropellant container is a good example.

3.) Do large extended solar panels have a g-force tolerance limit? I.e. will I tear them off if I fire up the engine without retracting them first?

As far as I know, no. But I may be wrong. However you will certainly tear them off if you enter the atmosphere with them deployed.

Edited January 9, 2014 by Kasuha

[Monkeh]

3) Only in an atmosphere.

[Streetwind]

Thanks for the answers!

[ripvanlemon]

As to 3) I have had the Gigantor panels detach on me in space. I was in map mode at the time, so I can't be sure what happened, but I was in circular 100+km orbit around Kerbin. It was on the probe pictured below (different launch, though). The previous stage had an LV-T30 and I went to full throttle with the panels out. Switched back to normal view, and they ripped right off. That was in .22, but I can test again tonight.