Gee Force Challenge

[Ebu]

Peewee: Yes, landing on the Mun is the rule you have to follow. You can do almost everything. Rules say you need to land on the Kerbin/Kerbol/anything - how many times you want, but the final position is on the Mun, where (at least) one member of your crew must land and survive.

r4m0n, Thinine: Wow, we have new leaders ;D

[Peewee]

Can\'t land on Kerbol. I tried (several versions ago).

http://imgur.com/a/4bG7Y

[Ebu]

Peewee: It seems we need a new technology to achieve this important milestone 8). I\'m not against the new ideas and new challenges! If you have a concept for new challenge, feel free to post your vision .

[Evilchicken]

I\'ve made a small modification to the rocket by putting the ASAS on the first stage, remove some fins and very small other changes struts and stuff. But nothing else has change even the flight path is the same as last time. This is for the Bill challange.

[Nooblet68]

142g?

Seriously, these are getting very high...

[Ebu]

Evilchicken: Yay! These values are suprising. Very nice

[Bluejayek]

There seems to be some problems with the recording system for the g-force.

I made an attempt where I was going 5700+ (downwards) and accelerating at 38km in the atmosphere when I cut engines. Clearly, I must have been pulling some serious g\'s to avoid splatting, and yet it recorded my max gforce as 4.2.

With a similar ship (incidentally, accidentally dropping the first stage before launch) I managed a respectable 80gs for the bill challenge.

[Ebu]

Bluejayek: Yes it seems that kerbal computing centre is not without measurement errors S:|. I hope this will be repaired soon...

Anyway, I see a big future for your team and there is a great potential . Keep it up .

[Thinine]

I\'ve been noticing low forces as well. My 110 G entry was going just over 5k m/s but I haven\'t been able to reach that again, despite getting over 7500 m/s on entry. I\'m thinking it has something to do with the framerate. That is, the lower the framerate (looking toward the planet), the higher the g-force because the engine does fewer samples per second and can get higher rates.

Also, in my quest for higher entry speeds I\'ve done several gravity assisted flybys. What does it mean when the system map doesn\'t show a trajectory for the capsule? I\'m assuming it means I\'ve reached system escape velocity. I was over 13000 m/s at any rate.

[Bluejayek]

Further on the measurement errors...

I did another flight and took screenshots about every half second during the major deceleration. I then took the values off of these screenshots for altitude, velocity, and time. From these values, I calculated accelerations and compared it to the maximum g force quoted in the flight logs, assuming 1g = 9.8m/s/s as quoted on earth.

Note that I had to aproximate the time as kerbal only shows to the nearest second. To do this, I simply took the number of screenshots showing a given time and devided by that number. Eg, if I had two screenshots at 18s, the first is 18.0, and the second 18.5.

Some of the deceleration screenshots

The spreadsheet

Graphs

These show an average acceleration over the period 16s-18s of

-120+/-15g\'s

and a maximum acceleration at 16.3s of

-157+/-75.54g\'s.

The flight log below shows a max g of 58 g\'s which is clearly low.

Therefore... Either kerbal is not using a value of 9.8m/s/s as a measure of gforce (Possible, but unlikely as that is the surface gravity of kerbin...) or there are errors in the calculations.

Hence, I submit this result of 105g\'s as the lower bound on my calculated average maximum acceleration. Add it or not as you please, I was just bored and decided to figure this out.

[Bluejayek]

I\'ve been noticing low forces as well. My 110 G entry was going just over 5k m/s but I haven\'t been able to reach that again, despite getting over 7500 m/s on entry. I\'m thinking it has something to do with the framerate. That is, the lower the framerate (looking toward the planet), the higher the g-force because the engine does fewer samples per second and can get higher rates.

Also, in my quest for higher entry speeds I\'ve done several gravity assisted flybys. What does it mean when the system map doesn\'t show a trajectory for the capsule? I\'m assuming it means I\'ve reached system escape velocity. I was over 13000 m/s at any rate.

My experience seems to be that the g force reading caps out. If you are going 6000+ when you hit atmosphere, you decelerate too fast and the system just doesn\'t read it at all.

[r4m0n]

The so called 'Most Gee Force Endured' seems to to only record the value if you can keep approximately the same G reading for a period of time. This was probably coded in to ignore spikes in G, but else than averaging the last few values or something more sensible, it is simply ignoring values that change too fast, making the G meter useless.

Trying to find the angle that measures the most G in my 400G deceleration ship going straight down is frustrating, so I\'ll just wait until it\'s fixed.

PS: You can measure what the actual G\'s would be with the Reentry module of MechJeb. Just fire it up and check the predicted max G after you stop burning.

[Ebu]

Bluejayek: I really appreciate your analysis of the problem . Could you make a 'Bug topic' for KSP development and copy there your results? I think that\'s the way we can speed up the process of debugging. Maybe they don\'t know about this problem! We value your work . Thanks!

And 105 G is added .