An Essay
This week saw the crash and burn of two commercial space ships; one manned, the other unmanned. Regardless of how commonplace spaceflight seems to have become it is still dangerous business. As Elon Musk quipped when a SpaceX test vehicle self-destructed (as intended) when something went haywire over the McGregor Texas test site, “Rockets are tricky“.
The difference between the auto-destruct of the SpaceX RTLS (Return to Launch Site) test bed and this week’s crashes is more than one of degree. The spectacular crash of the Orbital Sciences Antares resupply ship was not an experimental test bed but rather a commercial launch to the International Space Station (ISS) with a $200 million plus price tag. The Scaled Composites Spaceship Two was a manned test flight with no apparent provision to safeguard the crew (and future passengers) in the event of a catastrophic failure.
Contrast this to SpaceX. On the first resupply mission to the ISS (October 7, 2013) the Falcon 9 suffered a premature shutdown of one of its Merlin main engines, yet successfully completed its mission.
Approximately one minute and 19 seconds into last night’s launch, the Falcon 9 rocket detected an anomaly on one first stage engine. Initial data suggests that one of the rocket’s nine Merlin engines, Engine 1, lost pressure suddenly and an engine shutdown command was issued immediately. We know the engine did not explode, because we continued to receive data from it. Our review indicates that the fairing that protects the engine from aerodynamic loads ruptured due to the engine pressure release, and that none of Falcon 9’s other eight engines were impacted by this event.
As designed, the flight computer then recomputed a new ascent profile in real time to ensure Dragon’s entry into orbit for subsequent rendezvous and berthing with the ISS. This was achieved, and there was no effect on Dragon or the cargo resupply mission.
Falcon 9 did exactly what it was designed to do. Like the Saturn V, which experienced engine loss on two flights, Falcon 9 is designed to handle an engine out situation and still complete its mission.
Source: PARABOLIC ARC and SpaceX
Redundancy and quality control are the reasons SpaceX stands out from the competion. American-made with superior attention to detail and designed for redundancy. SpaceX recently completed manufacture of its 100th Merlin 1D main engine.
The Orbital Sciences Antares launch vehicle has two main engines, both of them literally made in the 1960’s for the failed Russian Moon rocket. These 60s vintage rocket engines had been problematic for Orbital Sciences from the beginning with fuels leaks and an explosion on the test stand at NASA’s Stennis Space Center. With only two main engines, the failure of a single engine doomed the recent launch. This is exemplary of NEITHER redundancy or quality control.
“We got a great deal on some rocket engines at a Russian garage sale. They should fine. If we use the minimum of two required to get the necessary thrust we can save even more money. What could go wrong?” [Not an actual quote]
“I mean they start with engines that were literally made in the ’60s and, like, packed away in Siberia somewhere,” Elon Musk said in an interview with Wired magazine. [An actual quote]
On the manned spaceflight front SpaceX continues to excel. Launch abort safety is built into the Dragon V2 manned capsule … not added on with an old-school escape tower as used by the Soyuz, Orion capsule, or the Boeing CST-100.
Crew capability was the very reason SpaceX was founded, so we will do whatever it takes to make this happen. – Elon Musk
Spaceship Two appears to have none of the redundancy or abort safety mechanisms of Dragon V2, CST-100, Orion, or Soyuz, yet Virgin Galactic expects to fly civilian thrill seekers to the edge of space. One might just as easily (and more safely) build a 6-8 person parachute-equipped pressurized gondola and lift it to the edge of space via helium balloon ala Felix Baumgartner and Google VP Alan Eustace … except that the gondola would land intact without the passengers needing space suits and parachutes (but it might be good for them to wear those space suits and parachutes… for you know … redundancy).
One thing is for certain, the Scaled Composites and Orbital Sciences tragedies will have them each back at least year on their timeline, while SpaceX continues to move forward.
Contrafactual 