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==Production== |
==Production== |
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The hybrid rocket motor and its oxidizer valve system were produced in SNC’s manufacturing facility in [[Poway, California]] in conjunction with Scaled Composites. In 2013, the Poway facility was reported to be "currently producing motors for both SpaceShipTwo and SNC’s own [[Dream Chaser]] orbital crew vehicle".<ref name=pa20130429sn/> |
The HTPB hybrid rocket motor and its oxidizer valve system were produced in SNC’s manufacturing facility in [[Poway, California]] in conjunction with Scaled Composites. In 2013, the Poway facility was reported to be "currently producing motors for both SpaceShipTwo and SNC’s own [[Dream Chaser]] orbital crew vehicle".<ref name=pa20130429sn/> |
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SNC closed the Poway facility in late 2014.{{cn|date=October 2014}} |
SNC closed the Poway facility in late 2014.{{cn|date=October 2014}} |
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The polyamide hybrid rocket motor is a modified version of the polybutadiene version, with different oxidizer valve arrangement. Most of the engine remains the same, but for changing the fuel cartridge from rubber to plastic fuel.<ref name=PressConference-20141031@5pmEDT/> |
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==See also== |
==See also== |
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RocketMotorTwo is the first generation hybrid rocket engine that was under development for the Scaled Composites SpaceShipTwo suborbital spaceplanebySierra Nevada Corporation (SNC),[1] and was first ignited in flight during a SpaceShipTwo test launch in April 2013.[2][3] This engine design was subsequently flown in only two additional flight tests.[4]
SNC was a subcontractor to Scaled Composites through May 2014 when the program ended after Virgin Galactic elected to replace SNC's version of RocketMotorTwo powered by HTBD rubber fuel, with its own internally-developed hybrid motor for SpaceShipTwo.[4] The new RocketMotorTwo engine is a variant of the SNC basic design, powered by polyamide plastic fuel.[5]
RocketMotorTwo is a hybrid rocket engine utilizing solid hydroxyl-terminated polybutadiene (HTPB) fuel and liquid nitrous oxide oxidizer – sometimes referred to as an N2O/HTPB motor[6][7] – providing 60,000 pounds-force (270 kN) of thrust. The design makes use of lessons learned during the development of the SpaceShipOne hybrid rocket motor.[8]
As of March 2013[update], Sierra Nevada had performed over 300 hybrid rocket test firings. The company also developed the rocket engine for the first private spacecraft to reach space, SpaceShipOne, which won the Ansari X-Prize in 2004. Sierra Nevada is also developing a similar hybrid engine, the Dream Chaser rocket engine.[9]
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Scaled Composites performed a series of subscale rocket hot-firings between June 2005 and April 2009, before choosing a full-scale rocket motor design.[10] By December 2012, 21 full-scale hot-fire ground tests had been carried out on RocketMotorTwo.[10][11][12] On 20 June 2012, the first hot-fire test under the control of SpaceShipTwo's proprietary Rocket Motor Controller (RMC) was successfully conducted.[10]
On 26 July 2007, during the early rocket testing phase, an explosion occurred during a propellant flow test at the Mojave Air and Space Port. The test included filling the oxidizer tank with 4,500 kg (10,000 pounds) of nitrous oxide, followed by a 15-second cold flow injector test. Although the tests did not ignite the gas, three employees were killed and three injured, two critically and one seriously, by flying shrapnel.[13]
In July 2012, Virgin Galactic, the owner of VSS Enterprise – the first SpaceShipTwo spaceplane built – announced that RocketMotorTwo was fully qualified for powered flight, and that the ground test program was substantially complete.[14] SpaceShipTwo conducted its first gliding test flight with the engine fully installed in December 2012.[15] Additional ground rocket tests continued into March 2013 as the company prepared for powered test flights.[16]
VSS Enterprise conducted its first powered flight on 29 April 2013,[2] marking the first flight test of RocketMotorTwo. The test was a 16-second burn as planned, and was ignited at an altitude of 47,000 feet (14,000 m), shortly after Enterprise was released from its WhiteKnightTwo carrier aircraft and the pilots cross-checked data and verified stable control. The RM2 control system opened the main oxidizer valve and fired the igniters inside the fuel case. The burn was completed at an altitude of 55,000 feet (17,000 m), by which point Enterprise was supersonic, achieving Mach 1.2 (1,300 km/h; 790 mph). SNC stated after the test that "The rocket motor ignition went as planned, with the expected burn duration, [and] good engine performance."[3]
In May 2014, Virgin Galactic announced a change to the hybrid engine to be used in SpaceShipTwo, and took the development effort in-house, terminating the contract with Sierra Nevada and all development on the first-generation rocket engine.[4]
Rather than use rubber-based HTPB in the solid portion of the hybrid rocket motor—which had experienced serious engine stability issues on firings longer than approximately 20 seconds—the Virgin Galactic-developed SS2 hybrid rocket engine would now use thermoplastic polyamide (i.e., nylon) as the solid fuel component of the propellant. The plastic fuel was projected to have better performance (by several unspecified measures) and was expected to allow SpaceShipTwo to make flights to a higher altitude.[17][18][19]
As of May 2014[update], the new engine formulation had already completed full-duration burns of over 60 seconds in ground tests on an engine test stand.[18] However, four additional ground tests of the polyamide-fueled engine are anticipated before the SpaceShipTwo flight test could resume with the new-fuel rocket motor.[19]
On 31 October 2014, the new polyamide engine fuel formulation was used in flight for the first time in the PF04 powered test flight of SpaceShipTwo. At 10:12am PDT, VSS Enterprise suffered an engine malfunction, and subsequently broke up in mid-flight. The inflight mishap resulted in the death of one test pilot and severe injuries to the other test pilot, and a total loss of the vehicle.[20][21][22]
The HTPB hybrid rocket motor and its oxidizer valve system were produced in SNC’s manufacturing facility in Poway, California in conjunction with Scaled Composites. In 2013, the Poway facility was reported to be "currently producing motors for both SpaceShipTwo and SNC’s own Dream Chaser orbital crew vehicle".[3] SNC closed the Poway facility in late 2014.[citation needed]
The polyamide hybrid rocket motor is a modified version of the polybutadiene version, with different oxidizer valve arrangement. Most of the engine remains the same, but for changing the fuel cartridge from rubber to plastic fuel.[20]
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