Draco (rocket engine family)
|Country of origin||United States|
|Application||Reaction control system|
|Propellant||NTO / MMH|
|Thrust (vac.)||400 N (90 lbf)|
The original Draco thruster is a small rocket engine for use on the Dragon spacecraft,. These engines were also used on early Falcon 9 upper stages to provide attitude control, but more recent versions now use nitrogen cold gas thrusters in place of Dracos.
SuperDraco is derived from Draco, and utilizes the same storable (non-cryogenic) propellant as the small Draco thrusters, but are over 100 times larger in terms of delivered thrust. The much larger SuperDraco engines will be used on later versions of the Dragon spacecraft to provide launch-escape capability on crew transport flights to low Earth orbit, as well as entry, descent and landing control of the proposed Red Dragon robotic probe to Mars.
Draco thrusters generate 400 newtons (90 pounds-force) of thrust using a storable propellant mixture of monomethyl hydrazine fuel and nitrogen tetroxide oxidizer. The Draco thrust is comparable to the Marquardt R-4D engine developed for the Apollo Service and Lunar Modules in 1960s and used for apogee/perigee maneuvers, orbit adjustment, and attitude control.
Eighteen Draco thrusters are used on the Dragon spacecraft for attitude control and maneuvering. This system is not dual-redundant in all axes; rotational and translational control by thruster requires at least 7 thrusters.
Four Draco thrusters were used on the Falcon 9 v1.0 second stage as a reaction control system. However, as of 2015 the current version of Falcon 9 no longer uses these, instead using nitrogen cold gas thrusters.
SuperDraco firing at full thrust
|Country of origin||United States|
|Application||LAS (Launch Abort System), powered landing|
|Propellant||NTO / MMH|
|Thrust (SL)||73 kN (16,400 lbf)|
|Isp (SL)||235s |
|Burn time||25 seconds |
|Propellant capacity||1,388 kg (3,060 lbs)|
|Crew Dragon, DragonFly test vehicle|
On February 1, 2012 SpaceX announced that it has completed the development of a new, more powerful version of a storable-propellant rocket engine, this one called SuperDraco. This high-thrust hypergolic engine—about 200 times larger than the Draco RCS thruster hypergolic engine—offers deep throttling ability and just like the Draco thruster, has multiple restart capability and uses the same shared hypergolic propellants. Its primary purpose is for SpaceX's LAS (launch abort system) on the Dragon spacecraft. According to the NASA press release, the engine has a transient from ignition to full thrust of 100 ms. During launch abort, eight SuperDracos are expected to fire for 5 seconds at full thrust. The development of the engine is partially funded by NASA's CCDev 2 program.
SuperDracos will be used on both the Crew Dragon and on the DragonFly (rocket), a prototype low-altitude reusable rocket that will be used for flight testing various aspects of the propulsive-landing technology. While the engine is capable of 73,000 newtons (16,400 lbf) of thrust, during use for DragonFly testing, the engines will be throttled to 68,170 newtons (15,325 lbf) to maintain vehicle stability. First firing of all 8 Super Draco engines took place on 6 May 2015 at 9am EST at the SpaceX Crew Dragon Pad Abort Test.
As of 2015[update], SuperDraco is the third most powerful engine developed by SpaceX, approximately 200 times more powerful than the Draco thruster engines, and only outmatched by the Raptor and Merlin. By comparison, it is more than twice as powerful as the Kestrel engine that was used in SpaceX's Falcon 1 launch vehicle second stage, and about 1/9 the thrust of a Merlin 1D engine.
In addition to the use of the SuperDraco thrusters for powered-landings on Earth, NASA's Ames Research Center is studying the feasibility of a Dragon-derived Mars lander for scientific investigation. Preliminary analysis indicates that the final deceleration will be within the retro-propulsion SuperDraco thruster capabilities.
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