

Apollo, Ansari and the Hobbling Effects of Giant Leaps - bmease
http://www.parabolicarc.com/2014/10/30/apollo-ansari-hobbling-effects-giant-leaps/

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nkurz
From the astonishingly prescient article, which was written shortly _before_
today's disaster:

    
    
      The Achille’s Heel
      ...
      But, there was a deeper, more fundamental problem that
      Rutan wasn’t even aware of, one that has bedeviled the 
      program to this day.
      ...
      Rutan steered away from liquid engines; he viewed them 
      as being overly complicated and possessing too many failure
      modes. Instead, he developed a novel hybrid motor that used
      nitrous oxide (laughing gas) to burn a large chunk of
      rubber fuel. SpaceShipOne was the first time a hybrid 
      engine had been used in human spaceflight.
      ...
      Rutan came out of SpaceShipOne’s short flight test program 
      believing the hybrid engine was simple and safe, and that
      it could be easily scaled up for the much larger 
      SpaceShipTwo. He was wrong on both counts.
    
      The first belief was shattered on a hot summer afternoon of
      July 26, 2007. Scaled engineers were conducting a cold flow
      of nitrous oxide that did not involve igniting any fuel.
      Three seconds into the 15-second test the nitrous tank
      burst, resulting in a massive explosion that destroyed the
      test stand and killed three engineers. Three others were
      injured.
      
      Explosions are not unusual in engine development. However,
      it is rare that anyone dies in them. Safety procedures call
      for the evacuation of personnel to a safe area before any
      tests begin. That was not done in this case; the dead and
      injured were part of a group of 11 people standing near the
      test stand.
    
      Following the accident, Rutan and Scaled Composites claimed
      ignorance. “The body of knowledge about nitrous oxide (N2O)
      used as a rocket motor oxidizer did not indicate to us even
      the possibility of such an event,” Scaled said in a press 
      release. The media and Scaled supporters have largely 
      parroted this explanation.
    
      A team of experts experienced in working with nitrous oxide
      reviewed the accident and disputed the claim. “This would
      seem to indicate either a lack of due-diligence in 
      researching the hazards surrounding N2O (negligence) or a
      wilful disregard of the truth,” they concluded.
    
      Whatever Scaled’s culpability, there is no dispute the
      accident delayed the program significantly. Work on 
      SpaceShipTwo was put on hold while engineers investigated
      the cause of the explosion. Hybrid engine tests would be 
      delayed for nearly two years.
    
      Once engine tests began again in April 2009, engineers 
      would discover that Rutan’s other assumption was wrong. The
      hybrid engine just didn’t scale very well. The larger the
      engine became, the more vibrations and oscillations it
      produced. As engineers struggled to find a solution, Scaled
      Composites and Virgin Galactic quietly began work on
      alternative motor designs.
    
      The failure of the hybrid to scale led to another problem. 
      SpaceShipTwo had already been designed and built. The
      dimensions of the ship, the size of the passenger and crew
      cabin, the center of gravity…all those were already set.
      So, engineers now had to fit an engine within those
      parameters that could still get the vehicle into space.
    
      This is the reverse of how rocket planes are typically
      designed. Engineers figure out the engine first and then
      build the ship around what it can do. Rutan – a novice in
      rocket propulsion who had hit a home run with SpaceShipOne
      – got the process backward, resulting in years of delays. 
      This failure would cause numerous headaches.
    
      The rubber hybrid engine did get a workout in three flight
      tests, but the vibrations and oscillations it produced were
      so severe the motor couldn’t be fired for more than 20
      seconds. The engine was sufficient to get SpaceShipTwo
      through the sound barrier, but it couldn’t get the vehicle
      anywhere near space.
    
      It was not until May 2014 – after spending nearly a decade
      on the program, and a reported $150 million on engine 
      development – Virgin Galactic announced it would be 
      switching to a different type of hybrid engine, one powered
      by nitrous oxide and plastic. They are hoping for much
      better performance in flight.
    
      By then, Rutan was gone, long since retired to a spread in
      Idaho. It was for others to make the new engine work and
      fix the mistake he had made.
      ... 
      Flush with success and not knowing what he didn’t know, 
      Rutan bet the future on a poor propulsion system that he 
      never took the time to fully test, much less understand. 
      His failure to grasp the nature of technology he selected 
      cost three men their lives.

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mikeyouse
Wow, he wrote that _yesterday_. Seems especially prescient given that he's on
the ground in Mojave today.

