SpaceShipTwo: Risk reduction of a sort

by | Aug 29, 2008 | Seradata News | 2 comments

The aerospace industry loves phrases like risk reduction. What they really mean is R&D to try to make sure the damn thing works. But R&D has cost connotations while risk reduction, well, it is like motherhood and applie pie. Reducing risk, how can that be bad? And so Spacedev is to help with SpaceShipTwo’s (SS2) propulsion system development, probably to reduce the risk of Scaled employees being involved in another oxidiser flow test explosion incident

Paul Allen’s Mojave Aerospace Ventures’ owns all the SpaceShipOne (SS1) intellectual property and it has a deal with Sir Richard Branson’s Virgin group to license that for SS2

I was expecting Scaled to keep that knowledge in-house and not to work with others. I have had indications that despite the apparent limited propulsion system work prior to the 26 July 2007 explosion Scaled had fired motors and the SS2 development company’s founder Burt Rutan went some way in confirming that in this interview with Flight

So the Spacedev contract was not something I expected, especially as there is a lot of bad blood between Scaled and the contractor’s founder Jim Benson. If Benson had still been at Spacedev I genuinely wonder if this contract would have gone ahead

Scaled’s senior management hated the fact that many media organisations reported that Spacedev had developed the SS1 motor. Scaled was/is quite sure that those journalists were not making assumptions but were reporting accurately what individuals at Spacedev at that time were telling them

My guess is that it has taken the take-over of Scaled by Northrop Grumman and the three deaths of Scaled employees last July to ensure that Spacedev’s engineers can now look forward to the dirty and dangerous jobs Northrop can’t stomach

I understand that Northrop’s lawyer who was assigned with Scaled in 2007, before the explosion and completed take over, insisted that all the propulsion work be shut down after the incident and she got her way. For at least six months nothing happened

Talking to Rutan at the WhiteKnightTwo (WK2) unveiling at Mojave air and space port he said that they would talk about propulsion after the “accident report”. And on 1 August a very short one and a half page “report” about Scaled’s own investigation was posted to its website

I wasn’t aware of this internal Scaled investigation and didn’t have time to follow up on his passing comment at the WK2 unveil but then a few days later Scaled posted the report anyway

What is very surprising about the 1 August Scaled report is its claim that “the body of knowledge about nitrous oxide (N2O) used as a rocket oxidiser did not indicate to us even the possibility of such an event.”

The tendency for the decomposition of N2O and its potential for combustion and explosions is well known to people who work in rocketry. The US government’s own website about occupational safety has a nitrous oxide webpage and it says of N2O, “Nitrous oxide can form an explosive mixture with air…contact of nitrous oxide with aluminum, boron, hydrazine, lithium hydride, phenyllithium, phosphine, sodium, tungsten carbide, hydrogen, hydrogen sulfide, organic peroxides, ammonia, or carbon monoxide may cause violent reactions to occur…toxic gases (such as carbon monoxide and oxides of nitrogen) may be released in a fire involving nitrous oxide.”

Wider reading about N2O will show that while it takes relatively high (much higher than ambient) temperatures and pressures to ignite nitrous oxide (SS1’s rocket used a pyrotechnic to get the motor fired up) contamination and other factors can substantially reduce the point at which this gas combusts

The 1 August report also says “the [California occupational safety and health] agency (Cal-OSHA) did not determine a cause for the accident.” While literally true, Cal-OSHA has not come to a conclusion so far in its investigation of the explosion it is indicated in what the organisation has produced about the accident that the problem began with the oxidiser tank

And Scaled’s own plans, stated in its 1 August report, also indicate that that is where the problem lies. It talks of “eliminating incompatible materials”, “replacing the composite liner” in the tank, “diluting” the N2O in the tank with an inert gas such as nitrogen and “revising cleaning procedures” to minimise contamination risk

For an explosion whose cause is a mystery those are quite specific actions

But for Scaled’s employees I would imagine that what the tank liner is made of and what cleaning procedures are used will be less immediate issues as Spacedev is probably going to be undertaking riskier work

I am not discounting the presence of Scaled employees at such tests but it seems logical to me that if you want to avoid future incidents, keep flow tests at arm’s length

This reality about the safety of chemicals such as N2O that are allegedly ‘harmless’ brings me round to engineer and author Homer Hickam’s comments made to Newsweek magazine in January and the sort of publicity it provides Virgin Galactic that quite frankly, they couldn’t pay for

Asked by Newsweek “how safe is this thing?” referring to the WK2/SS2 launch system, Hickam replies, “It should be very safe. There really isn’t much in the way of unproven technology about it with the exception of the composite materials used for its construction. No one knows how these materials will hold up over many flights, but computer models look good.”

You might think, that sounds good Newsweek says he’s a “NASA expert” and “former NASA engineer”. Sorry but there is nothing special about “NASA engineers,” whether they are employed directly by the agency or through subcontractors. There is no special qualification that gets you that job, no NASA specific undergraduate or postgrad degree for working there

Contacting Hickam I asked what he did at NASA that led Newsweek to call him an expert. Hickam wasn’t too specific about what he did at NASA, he emailed me this: “For NASA, I worked as a spacecraft designer and astronaut training manager. I was on the team that trained underwater the first Hubble Space Telescope repair crew. I also trained many astronauts how to scuba dive. I lived in Japan for a couple of years, training the first Japanese astronauts. I later became the first International Space Station astronaut payload training manager  I was also on the shuttle solid rocket booster redesign team after the Challenger accident.”

Well the Space Shuttle solid rocket booster (SRB) redesign team sounds good but that motor, beyond the fundamentals of solid fuel combustion, is not a hybrid system

My follow-up question to Hickam was not about the SRB but rather why he told Newsweek that “no one knows how these [composites] materials will hold up over many flights, but computer models look good.”

His answer? He pointed to this article from a design engineering title and a web page on Scaled’s own website. Nice to know that a company’s propaganda can be so comforting and that a magazine about computer aided design software packages can stand as such a cast iron source of composites data – I say these things in jest of course

I don’t want to sound as though I am making personal comments. No doubt Hickam liked the publicity for his books and had no say over the “NASA expert” description. And he did qualify his statement with the word “should”

The problem with this interview lies in how it will be read by the public for whom much of today’s technology is increasingly like magic

Assuming that a “former NASA engineer” can pontificate about a hybrid solid rocket motor system and the rocket-glider it propels is the same as asking a gynaecologist for their professional opinion about another doctor’s work in frontal lobe brain surgery. Yes they are both “doctors” but that doesn’t mean they are automatically experts in each other’s fields

Sadly, for the vast, vast majority of the population there is an assumption that one engineer, like one doctor, is equally qualified to judge another. Cue movies where the likes of McGyver can disassemble a nuclear warhead with seconds to go before detonation just because he knows techie stuff and The X Files’ Dana Scully can find the vaccine to an extraterrestrial disease just because she too is a doctor

So for Virgin I suspect this Hickam article is the sort of publicity they wish they could buy

My job is to investigate advances in all technologies relating to aerospace vehicles. Composites, their inspection and repair and issues surrounding delamination (that may one day come to be seen as deadly as fatigue for metal) is still a developing area

No all-composite vehicle has or will fly through the extreme temperature, speed and pressure ranges that SS2 will with such frequency; twice a day if you believe Rutan

So let me, as an engineer who has never worked for NASA, give my “expert opinion”

“You find out 80% about a vehicle on its first flight” and I am qouting Burt Rutan from the WK2 roll out. The outcome of the SS2 flight test programme is the only yardstick bywhich anyone should judge this development work’s ‘risk reduction’ and the expected safety level of the launch system. Even NASA will tell you that

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