Thread of the Month: Be Kind to your Kerbonauts - Reentry Technique

[SlowThought]

30k for peri was right on... Hit atmosphere at 3200 m/s and only peaked out at 2g. Then Bill tripped getting out of the capsule and died. They may be tough, but they're brittle!

[Nano606]

Using deadly re-entry mod has gotten me into the habit of always returning with a 30-35km periasis, as that lessens the temperatures that the ship endures. I dont usually bother with the G readout but arriving back like this would definitely reduce the G forces on the poor little Kerbals.

[Xavven]

I use this as my guide: http://en.wikipedia.org/wiki/G_force#Human_tolerance_of_g-force

Sitting upright and sustaining g's along the vertical axis (spine), an untrained human can withstand 4 or 5 g's. Trained and equipped with flight suits, 9 g's can be sustained.

But astronauts get the benefit of sitting in a "laying on your back" position so that the g forces are sustained along the z-axis, or "eyeballs in". This gives an untrained human tolerance of 10 g's for a minute or 20 g's for 10 seconds. I'm sure a trained astronaut could sustain more. Apollo 16 reentry from the Moon peaked at 7 g's.

Assuming Kerbals have similar tolerance, I'm okay with a re-entry that peaks at 20 g for less than 10 seconds. Most of my interplanetary re-entries are direct with a periapsis of 20km, and are well within these g limits.

A 30km periapsis is more gentle, but unfortunately I did have a Jool return end with a skip out of the atmosphere and out of Kerbin's SOI. The resulting recovery mission was annoying, so now all my returns are at 20km periapsis.

[[email protected]]

Using deadly re-entry mod has gotten me into the habit of always returning with a 30-35km periasis, as that lessens the temperatures that the ship endures. I dont usually bother with the G readout but arriving back like this would definitely reduce the G forces on the poor little Kerbals.

Of course, and with deadly reentry it is possible to kill the kerbals with g force even if your ship survives the actual reentry, I managed to do this on an ill-planned return from Dres. I hit the atmosphere at around 8.2 KM/s. Killed the Kerbals but the ship survived and floated safely to the surface.

[Cmdr. Arn1e]

returning from Moho yesterday was fun; 12k+ m/s with a negative periapsis - i'm REALLY surprised Jeb survived!! The G's were off the charts...

I usually try for about 30-40 km, but it can be hard to do right on a long interplanetary mission... and being out of fuel when you encounter Kerbin can mean failure of at least the RP aspect of a mission... guessing it would be even worse if I were to use Deadly Re-entry

[Hans Dorn]

At 12km/s it gets a bit difficult to maintain tolerable G levels. There's just not enough atmosphere to brake at 5G...

[[email protected]]

returning from Moho yesterday was fun; 12k+ m/s with a negative periapsis - i'm REALLY surprised Jeb survived!! The G's were off the charts...

I usually try for about 30-40 km, but it can be hard to do right on a long interplanetary mission... and being out of fuel when you encounter Kerbin can mean failure of at least the RP aspect of a mission... guessing it would be even worse if I were to use Deadly Re-entry

With Deadly Reentry Jeb would have died only a few seconds into hitting the atmosphere from the g forces alone. Once you exceeed something like 7 KM/s with DRE you can't do a pure aerobrake on Kerbin without either burning up, dieing from G-force, or flying back out of the atmosphere at escape velocity.

[toric5]

whenever i return to kerbin from the min or minnumus, if i know that my craft can land on parches alone, i just spend the rest of my fuel accelerating straight down. ufortuantly, the meters tops out at 15 gs within seconds of entering he atmosphere. i can only assume how many gees my kernels really experience. (although at those speeds, the entire reentry sequence is about 15 seconds long)

[cantab]

If you hit F3 the flight log will tell you the peak g-forces.

[hazarada]

eh.. humans can survive up to 25g's for a few seconds, plus kerbals are green and u know what that means.

[rkman]

Don't do the gently skimming the atmosphere repeatedly thing. ...the maximum g force encountered on each reentry will decrease up to a point, and then you'll start to see it increase again once you get to the point where you lose horizontal velocity too fast and too high and end up dropping more like a brick.

Dropping like a brick from LKO (tested: 1400m/s @70km), you'll have a hard time pulling more than 5G's. Perfectly survivable. You can skim the atmosphere as often as you want.

[andysim212]

I heard women are less affected by G force because they are generaly (but by no means always) smaller. I bet thats why Kerbals can be subjected to immense G with no effects.

[Red Iron Crown]

Kerbals are clearly better evolved for spaceflight than humans, given their smaller mass, extreme G-force tolerance, zero life support requirements, and tolerance of multi-year missions in a cramped command pod (or seat!).

[tutrakan4e]

I tend to use all my fuel to make my arc a perfect line and I use the excess fuel to increase my speed towards Kerbin. Why? I like myrockets painted in flames.

[Decho]

I don't subject mine to anything more than 3Gs, preferably 2 or less. Generally haven't had a problem doing this.

[KvickFlygarn87]

I liek flattening kerbals.

'Nuff said.

[InterCity]

As i started developing spaceplanes, I have implemented some crew saving techniques: I call them all OMGGETMEOUTOFHERE.

This is OMGGETMEOUTOFHERE Mk.1b Contains 4 chutes and a decoupler, thus getting your crew down on the ground safely as long as you are on a suborbital trajectory of a planet with atmosphere. Version Mk.2 contains also some sepatrons, to get it far away. It isn't, however, RoHS compliant so i am not using it very often.

Version Mk.3 uses some radial engines and a fuel tank, for safe deorbit and in extreme cases even landing.

It's not exactly a reentry technique, but it's for sure a safety measure, so i posted it there.

[Frank_G]

I still havent lost a single kerbal during career, but i love to massively expose them to maximum carnage in sandbox simulations... Learning from errors is the best way, so i make everyone i could imagine... I love games where failing is fun.

I have recently installed deadly reentry and use the latest version of ferram aerospace where terminal velocitybecomes a factor. This will be a challenge...

Edited May 2, 2014 by Frank_G

[wasmic]

As i started developing spaceplanes, I have implemented some crew saving techniques: I call them all OMGGETMEOUTOFHERE.

http://i.imgur.com/cJKfwpj.png

This is OMGGETMEOUTOFHERE Mk.1b Contains 4 chutes and a decoupler, thus getting your crew down on the ground safely as long as you are on a suborbital trajectory of a planet with atmosphere. Version Mk.2 contains also some sepatrons, to get it far away. It isn't, however, RoHS compliant so i am not using it very often.

Version Mk.3 uses some radial engines and a fuel tank, for safe deorbit and in extreme cases even landing.

It's not exactly a reentry technique, but it's for sure a safety measure, so i posted it there.

2 questions:

What's RoHS?

Did you use cfg edits to make that decoupler?

[InterCity]

2 questions:

What's RoHS?

Did you use cfg edits to make that decoupler?

RoHS is an international agreement about pollution, don't know exactly what it is about.

I used the standard 2m decoupler available from stock, combined with some B9 adapters. Just simple stuff.

[MarvinKitFox]

According to my studies, kerbals are much more able than humans to withstand excessive G-forces.

I've had Jeb re-enter vertically at 53km/s

My rough calc puts his g-forces at 13500g

He landed just fine.

Yes, I think Kerbals are made of something sterner than mere flesh.

P.S.

Jeb was seated in a command chair. Without parachute, just 2 seperatrons to soften the last half a second of his death dive.

Edited May 2, 2014 by MarvinKitFox

[Starwhip]

I find a 20km periapsis from a Mun return gives about 4-5 g's, so I don't know what the big fuss is...

[doggie015]

Unless you are coming in at interplanetary velocity straight down then I fail to see how you can hit 15 G's at Kerbin. I've aerobraked at a 30km perapsis from a Duna return flight (If Kerbin had no atmosphere I would have been flung back into solar orbit) and I didn't even manage to hit 6 G's

[draeath]

For the curious: RoHS

I like to shoot for a periapsis of 25km on the return (I play with Ferram Aerospace and Deadly Reentry - whatever the new and maintained one is called). G's can be a bit high when the chutes pop, but I have never lost a kerbal to that and my heatshields have yet to fail me. I'd do it differently if I wasn't doing a free-falling capsule descent, of course - but I just really really enjoy those ballistic returns!

Does anyone happen to know what they shot for on the Apollo missions? I recall them being concerned with the angle being too shallow or too steep (and I know now that the "too shallow" skip-into-space wasn't escape, but another orbit or three and hence resource exhaustion) but I don't know what the periapsis would have looked like coming back from the moon.

[tstehler1]

I keep it out of the red. A Pe of 25k or so will usually do the trick, and since I always run an unmanned test of all my rockets before any manned (kerballed?) flight is attempted, it's usually not too much of a deadly problem. Ever since my new save, I've only lost one kerbal, and it was my brave test pilot of a new spaceplane.