Recently I have been involved in discussions about public risk resulting from commercial space flight. It is interesting to think back to the shuttle days and how those calculations were made.
If you ever were invited to a shuttle launch and got a car pass to park on the causeway – seven miles from the launch pad – you might not have noticed the fine print at the bottom of the windshield placard – noting that you were accepting the risk to you and your family from launch hazards. I’m betting you didn’t read that. By the rules of the Range Safety organization, you should not have been there. But the KSC center director had ‘accepted’ the responsibility for allowing you to be present when the risk calculations exceeded the standard that the Range set for the general public.
The limit for public risk was 30 chances in a million that one person could be seriously injured or killed from an event. Don’t ask how they came up with that number.
The LCC building at KSC was constructed a full 3 statute miles from the Apollo launch pads because somebody did a calculation about the maximum explosion hazard from a Saturn V. Three miles was far enough to be safe, or so they thought in the 1960s.
We still used that LCC building for the Space Shuttle launches and I was present in the firing room for several of them. Every time before the clock counted down to zero, I would remember the hazard calculation for that room.
Follow this logic: If, exactly at the moment of liftoff, the Orbiter blew up and took out not only itself and the astronauts but the External Tank as well so that the Solid Rocket Motors would be free flying, then if the hydraulic systems on the SRBs – now without any computer brain to command them – steered randomly but in just the right direction, and if the Flight Safety Officer took the maximum seven seconds to recognize the problem and send the destruct command, and then if the aft segment of the SRB – which did not have the linear shaped charge but was generally thought to peel apart when the rest of the booster destructed, rather stayed intact and burning – Then there was a non-zero probability that the flaming solid rocket aft segment could land on the LCC building with catastrophic results.
That is a lot of ‘ifs.’ And for several ‘ifs’ there was no way to calculate the probability, it is just assumed that they occur. Given that all of those things happened, the only variable was the exact direction that the errant flaming segment might travel. Assuming an equal probability for each degree of heading, the ‘calculated’ hazard for the LCC exceeded the maximum allowed by the range rules, even for essential personnel. But the firing room crew is essential to the launch so the KSC director again ‘accepted’ responsibility.
Those big louvers on the windows facing the launch pad were merely for shade, not for blast protection. If something big hit them, they would probably just add to the shrapnel.
But even more, the KSC director ‘accepted’ responsibility for the hazard to workers in the Orbiter Processing facilities and the VAB who were not essential to the ongoing launch but were critical for maintaining schedule to the next shuttle launch. And the KSC director also ‘accepted’ responsibility for the VIPs gathered on the balcony of the office building across the street from the LCC, and for the media at the Press site, and for other VIPs at the Banana Creek viewing stands.
That is a lot of ‘acceptance’ which let the Range organization off the hook, so to speak. Many of the guests and workers were not aware that they were in a hazard area. It wasn’t a secret, it was quietly announced or in the fine print; never dwelt on.
That is for hazard areas as the Range calculated them. Probably 1 chance in a ten thousand that you could be harmed. Would you have still wanted to go?
As we go forward with ‘commercial’ launches, the FAA is responsible and has adopted virtually unchanged the calculations performed by the USAF Eastern Range. But here is the catch; the KSC director is not allowed to ‘accept’ risk for commercial launches; its not in his/her area of responsibility.
Hopefully those smaller rockets will have a smaller hazard area than the shuttle. But maybe not for some of the proposed super heavy boosters.
It will be interesting to see how all this plays out. Public safety – what is your personal risk acceptance? What probability would make you stay home and watch on TV rather than come see it live? 1 in a million, one in a hundred thousand, one in ten thousand, what?
And I wonder about the relatively unsophisticated calculation about the hazard from the Saturn V back in the 1960s. I am guessing that most of the folks who came out to watch those launches would have accepted some risk, probably more than people would today.
They were willing to take more risks for a worthwhile cause in those days.