NASA Releases Failure Report On Outback Crash

cybrpnk2 writes "In a Friday news release, NASA Goddard Space Flight Center has issued Part 1 and Part 2 of an excellent and very interesting failure review on the April 28 failed balloon launch of the Nuclear Compton Telescope at Alice Springs, Australia. Bottom line: make sure you don't need a gorilla to pull the payload release handle at balloon launch; if the release mechanism does fail then make sure your safety cables are sized for lift loads and a swinging payload, not just static hanging payload weight; and oh yeah — keep people and vehicles out of the downwind flight path. One spectator was nearly crushed while running from his SUV that was hit and flipped (Figure 29, Vol I). At least nobody ordered video evidence destroyed."

Comments

On the 50th Anniversary of the Nedelin Disaster

[eldavojohn]

and oh yeah — keep people and vehicles out of the downwind flight path

Thankfully no one was seriously injured or killed. It's been fifty years today since the infamous Nedelin Disaster happened at the Baikonur cosmodrome. It shocks me that as recently as 15 years ago these sort of catastrophes happened.

At least nobody ordered video evidence destroyed.

Given the above incidents and their cover-ups, I'd agree. We must study these mistakes, own up to them and learn from them.

Re:Link?

[CptnSbaitso]

Here's a local news report with several angles and interviews from three people who were nearly killed: http://www.youtube.com/watch?v=ieyD1FfQOIg

It's surprising that they expected this to work

[Animats]

After reading through the whole report, the most surprising thing is the design of the launch mechanism. The basic setup was that the launch was done from a moving crane truck. The truck was equipped with special outrigger wheels, so it could handle some side load without rolling over, and a platform for the "launch director", who was supposed to release the payload by yanking on a strap attached to a cable, pulley, and pin. The launch setup is that the balloon is inflated, allowed to rise, and then the crane truck. which is carrying the payload, tries to get under the balloon, chasing the balloon if necessary. When the payload is in position, the launch director yanks the strap and releases the payload.

This is obviously a setup which is highly dependent on what the wind does during the launch process. Some of the time, the wind is not going to cooperate, and an abort will be required. That's to be expected. But this time, they didn't abort until it was far too late.

During the process of chasing the balloon, the stresses on the restraint system were about 3x higher than at rest. It would have taken a 300 pound pull to release the pin; this was tested after the event. The guy who was supposed to pull the strap, while standing on a moving platform atop the crane truck, wasn't even wearing gloves. There was no backup system for releasing the payload. The payload eventually released when the crane truck reached the airport perimeter fence and had to stop. The wind forces from the balloon were then great enough to tear off a mounting plate on the truck, releasing the payload, which plowed through the fence and wiped out an SUV.

They didn't have an explosive bolt system to release the payload. The launch system used remote controlled pyrotechnics for releasing the balloon's restraining ring, and for the balloon-release abort system, so they already had all the systems and procedures in place for using pyrotechnics. But the main launch function was a guy pulling a strap.

There's clear video of the incident. This is useful to watch. When the payload tears loose from the crane, the crane truck is facing 90 degrees from the wind direction and stuck at the fence line. The crane boom is under high sideways stress. The abort system should have been triggered when the truck got into that situation, but it wasn't. (An abort prior to release loses the balloon and saves the expensive payload.) But the person with the abort button (the "campaign manager") and the guy trying to pull the release strap (the "launch director") were in different places and not coordinated, so when things went wrong, the abort didn't happen until after the payload had come loose and wiped out the perimeter fence and an SUV.

Re:It's surprising that they expected this to work

[Animats]

A video that shows a second or two before the payload broke loose yields more information. It looks like the crane truck was starting a left turn, pulling against the balloon, when the pull from the balloon broke the attachment to the truck. The previous video made it look like the balloon was pulling the crane boom sideways, and the boom snapped back after release. But no. The truck was doing a left turn (they had to do something, they'd reached the perimeter fence) while the balloon pulled it to the right. That's where the big stress came from.

If the plate on the crane holding the cable to the balloon (safety factor 1.3, far too small, as later computed by NASA) hadn't failed, the launch team would have been able to hold the balloon and save the payload. They'd had failed launches before, and knew the truck was heavy enough to hold the balloon. So one can see why they held off on an abort. They might have been able to back the truck out and try the launch again. But their crane rigging wasn't built for sizable side loads.

In retrospect, they should have aborted sooner. The payload is the valuable part; it's normally recovered by parachute. An abort would have saved the payload and lost the balloon. The balloon is a consumable. But, as NASA's critique points out, they didn't have formal abort criteria, and tried an ad-hoc fix to get out of the mess they were in. If the bolts on the crane's attachment plate had been stronger, it would have worked.