Accident Review Board Hearing

[GarrisonChisholm]

Good morning. I had my first fatalities last night, and am trying to assess where the fault lies (someone has to be cashiered, right?), so I would like to ask if anyone care to offer an opinion upon the following tragedy (eventuality);

The mission was a sub-orbital hop for 4 Private Enterprise Individuals (tourists). The rocket was tested on a 6 km flight down the coast from KSC, and functioned nominally with full recovery. Upon the Sub-orbital attempt all 4 tourists were killed upon un-decelerated contact with ground following terminal staging and re-entry.

Boost stage was nominal, and the upper stage was delivered to roughly 75k altitude on a polar trajectory. Final stage was then pointed retrograde and all remaining fuel burned off prior to terminal staging, thrusting concluding at about 67k altitude, speed about 1050 m/sec. The 5 solo-capsules were then jettisoned. All 5 were toggled to and showed good chute pre-deployment, valid heat shields, and nominal orientation. Re-entry heating began rather lower in the atmosphere than expected, right about 20k, and persisted down to about 12k. About 14k MC began receiving reports of Primary & Back-up chute failures on the 4 tourist capsules, with the eventual & resulting impacts terminating flight operations.

I cannot conclude if the error was to trust in pre-deployment of the chutes, or if the low-altitude re-entry heating was anomalous and un-predictable.

Please offer any advice which may occur to our fledgling, now tainted program-

[Randazzo]

If you pre-deployed the chutes, they got torn off/burnt off during re-entry. Sometime below 10k, I'd imagine, though that's pretty high for my tastes.

You could have entered the atmosphere sideways from Minmus and not had too much entry heat for the mk1 capsule. (That might be a slight exaggeration.)

[SemiaCloud]

If you pre-deployed the chutes, they got torn off/burnt off during re-entry. Sometime below 10k, I'd imagine, though that's pretty high for my tastes.

You could have entered the atmosphere sideways from Minmus and not had too much entry heat for the mk1 capsule. (That might be a slight exaggeration.)

Thats probably why. I have had problems with that.

[Nich]

I have always wondered why the parachutes default to .04 pressure to release when they do not have the strength/too much drag to be deployed in the upper atmosphere as a drogue chute. I have not done much testing in the upper atmosphere with very slow re-entries but i suspect you have to go through the super sonic burning phase before you can deploy chutes and there is no way to avoid it.

I set all my chutes to .34 and have yet to loose one yet. I tend to set my PE to 35-38k for entry

Edited June 17, 2015 by Nich

[A_name]

I set the blame on the design team that put together a craft and flight plan that left room for this kind of eventuality. Leaving a free-falling, crewed pod unsupervised was a bad idea from the start, not to mention 4 of them. The design team was asking for trouble IMHO.

[Scotius]

I set the blame on the design team that put together a craft and flight plan that left room for this kind of eventuality. Leaving a free-falling, crewed pod unsupervised was a bad idea from the start, not to mention 4 of them. The design team was asking for trouble IMHO.

This. As long as you keep crew together you have at least a bit of control over their fates. Throwing them at game engine's mercy (with all its glitches) was asking for trouble.

[match]

I think the tourists started monkeying with the controls after separation and caused their own demise. Probably one of those doomsday cults.

No liability here.

[GarrisonChisholm]

Noted. Thank you for the brutal honesty A_name. I'll have them start packing their cardboard boxes now. ...though, of course, the same fellow that hired Them is going to be hiring their replacements...

[A_name]

Noted. Thank you for the brutal honesty A_name. I'll have them start packing their cardboard boxes now. ...though, of course, the same fellow that hired Them is going to be hiring their replacements...

Hahahaha

[Laie]

Theory 1) I heard of a bug when you staged off several pods in one event. Might be it.

Theory 2) To the best of my knowledge, tourists are inert. They won't pull their own ripcord, the vessel needs a pilot or probe core.

Theory 3) Randazzo might be up to something though I doubt it. Anyhoo, it doesn't hurt to move parachute pre-deployment to it's maximum value (equals ~4500m above sea level).

[Torquemadus]

If you want to pre-deploy the chutes, you need to set the minimum atmospheric pressure to a suitably high setting. Otherwise, the chutes will deploy before the craft has slowed down to a safe speed.

[Randazzo]

Theory 3) Randazzo might be up to something though I doubt it. Anyhoo, it doesn't hurt to move parachute pre-deployment to it's maximum value (equals ~4500m above sea level).

I laughed.

[mikegarrison]

I have always wondered why the parachutes default to .04 pressure to release when they do not have the strength/too much drag to be deployed in the upper atmosphere as a drogue chute. I have not done much testing in the upper atmosphere with very slow re-entries but i suspect you have to go through the super sonic burning phase before you can deploy chutes and there is no way to avoid it.

I set all my chutes to .34 and have yet to loose one yet. I tend to set my PE to 35-38k for entry

Pressures differ on other planets. Anyway, the chutes should really be triggered by dynamic pressure, not static pressure.

And 35-38K is pretty high on Kerbin. 20K is quite safe, in stock 1.02 KSP.

[SpacedCowboy]

Elon said "Your'e fired!"

[GarrisonChisholm]

I see when I get home I will be researching how to adjust the chute-deployment altitude- which, I did not know could be adjusted!

[Randazzo]

I see when I get home I will be researching how to adjust the chute-deployment altitude- which, I did not know could be adjusted!

Right click on the chute, it will show you the options. I think there might be some presets available, but I use RealChutes so I'm a terrible source.

Yet here I am answering...

[Laie]

I laughed.

Sorry... it's just that I think that suborbital makes for the easiest returns. Then again, how high is 0.04atm? I habitually tweak them to deploy late, because impatience, so I don't now.

[Randazzo]

Sorry... it's just that I think that suborbital makes for the easiest returns. Then again, how high is 0.04atm? I habitually tweak them to deploy late, because impatience, so I don't now.

Assuming you're referring to my Minmus remark, that was addressing the OP's thought that perhaps re-entry heating was somehow responsible for destruction of the pods. I was just pointing out that was unlikely.

I personally don't pre-deploy chutes until 1k and open them at 400m with a 5 second deploy.

[Finndibaenn]

A similar issue occurred to my team once too where I had accidentally stage the chutes in orbit, and they burned off during reentry.

My stace agency found that it's quite cool to keep all the capsules together (saves on decoupler, chutes, and heat shield mass too), 4 of them are not an issue. I thinkg i even did 5 once.The issue will be with them tipping over during reentry if the pilot is not able to keep it straight enough though

[mikegarrison]

Assuming you're referring to my Minmus remark, that was addressing the OP's thought that perhaps re-entry heating was somehow responsible for destruction of the pods. I was just pointing out that was unlikely.

I personally don't pre-deploy chutes until 1k and open them at 400m with a 5 second deploy.

400m is cutting it very, very fine.

[sam.johnson841]

Depend on your ship and the number of chutes, i can do 300m and i can do 1000m.

- Sam

[Zild]

I can't tell if people are joking or being serious in this thread...

The problem here has to be the 'chutes getting ripped off. It is obvious. At least - like so many of the perils in KSP - it is obvious after the first time you see it happen to you! (I am not ruling out the prospect of other problems too, but this definitely WILL be a problem.)

Adjusting the deployment pressure higher may help - I have not actually tried it, but I trust the person who said it first in this thread because everything else he said appeared true and correct. Adjusting the deployment altitude will NOT help!

It seems 'chutes actually get deployed in two parts - the pressure affects when they are initially released (after which they can be burned / torn off by airflow), the altitude affects when they bloom (spread out, becoming more effective at slowing you down). The first phase slows you down a little, the second phase slow you down a lot.

My actual advice would be to separate the craft AFTER re-entry, maybe around 10-15km. (Also, try going for final burn when re-entry friction starts fading away rather than so early, as this should bring your final speed much lower than burning before the re-entry friction - you can take a lot of re-entry friction punishment, so you might as well make use of the free aero-braking). If you can't or won't do that then definitely experiment with the deployment PRESSURE settings. Altitude can probably stay where it is for now (I have not yet had to adjust it).

I was actually running into similar problems trying to salvage my early lift stages with automatic 'chutes (saving the planet and money at the same time!) so I will have to play with the deployment pressure settings on those when I get home.

As for the person who said this was probably a bug... Damnit, there are plenty of genuine bugs out there to complain about, stop inventing new ones just because you don't know how physics works!

[GarrisonChisholm]

Well, as far as "bugs", I did notice an anomaly in the pre-entry capsule separation (at about 60km). Staging all 5 capsules at once did separate them, however the de-couplers did not themselves break off- they remained around the heat shield, with the shield visible immediately within. This may be a simple "bug" which *does* occur in such high-dynamic situations, but yet I do not believe played any part in the accident.

It seems most logical after hearing opinions here that the fault was the pre-deployment during the end of re-entry heating, and their subsequent burn-off. It was a rookie mistake on my part, not realizing that re-entry heating could occur so low in the atmosphere. However, while I did see the extra parameters (RMB) while right-clicking the chutes in the VAB, I could not see any means by which to edit them. Does this require a mod to change their deployment factors?

[lost_in_space]

I set the blame on the design team that put together a craft and flight plan that left room for this kind of eventuality. Leaving a free-falling, crewed pod unsupervised was a bad idea from the start, not to mention 4 of them. The design team was asking for trouble IMHO.

This.

Never trust gimmicky gadgets.

[wossname]

Human Resources personnel can be made culpable for practically anything. Just say that the new HR assistant secretary was jammed in the final stage decoupler, leaving the craft unstable.