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Draft:Crew Dragon Launch Abort System

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Crew Dragon Launch Abort System
Crew Dragon prototype DragonFly performing a pad abort demonstration.
ManufacturerSpaceX
Country of originUnited States
Launch history
StatusOperational
Crew Dragon Launch Abort System
Powered by8 * SuperDraco
Maximum thrust71 kN
Burn time25 seconds
PropellantNTO/MMH

The Crew Dragon Launch Abort System is a propulsive device designed to accelerate the SpaceX Crew Dragon Spacecraft away from a failing rocket. It is equipped with 8 SuperDraco engines capable of generating 71 kN of thrust.[1][2]

The abort system has several modes, or procedures for performing an abort in different phases of flight, including a pad abort, an in-flight abort, and the ability to use the abort system to fly into a lower than expected orbit should a failure occur late in flight.

Recovery zones are placed along the 51.64 degree inclination[3] of the ISS (International Space Station), and can be targeted with higher levels of precision than spacecraft such as Orion[4] and Shenzhou due to the throttling abilities of the SuperDraco engines. The recovery areas for a 2a abort are along the East Coast of the United States and the Canadian Maritime provinces, with a 2b abort landing the Crew Dragon capsule near Novia Scotia and the 2c and 2d abort modes resulting in a landing in Western Ireland.[5] 1a and 1b aborts result in landings near the American East Coast.

Design

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A diagram showing the configuration of Crew Dragon Endeavor during the Demo-2 mission.

Traditionally, spacecraft like Apollo and Soyuz have utilized solid-fueled "puller" launch escape systems, with the main spacecraft beneath a protective fairing attached to the escape system. Once in space, the escape system and the fairing are jettisoned, with the spacecraft's mode of abort switched to using its orbital maneuvering thrusters or upper stages.[6][7] Crew Dragon, however, has its abort system permanently attached to the sides of the spacecraft.[1]

Part of the reasoning behind this design is that it was originally planned to land dragon propulsively using the launch abort system.[8] (These plans were dropped after skepticism from NASA and the cancellation of SpaceX's Red Dragon capsule.)[9] Additionally, the ability to keep the abort system attached to the rocket throughout the entire ascent rather than jettisoning the launch escape system after stage separation allows for an abort capability in all stages of flight, increasing crew safety.[10]

Crew Dragon's "trunk", or cargo bay, also plays an important role in the abort sequence. Rather than leaving the trunk with the rocket like Apollo or Soyuz, Dragon keeps the trunk attached during an abort for aerodynamic stability.[11]

History

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Pad Explosion

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On 20 April 2019, Crew Dragon C204 was destroyed in an incident while testing its SuperDraco engines. A video leaked shortly the incident after shows the capsule exploding on a launch mount.[12][13] NASA and SpaceX confirmed the explosion and stated that there were no injuries.[14]

A diagram demonstrating a check valve.

Following an investigation, SpaceX stated that the explosion was the result of a faulty valve. During a nominal ignition sequence, valves keeping helium inside COPVs (Composite Overwrapped Pressure Vessels) are opened, causing the helium to flow through one-way "check" valves into the propellant tanks, pushing the fuel into the combustion chamber.[15]

See also: Pressure-fed engine

In this incident, however, the one-way oxidizer valve had allowed nitrogen tetroxide (NTO) to leak back through the helium tube.[16] When the helium valve was opened, the "blobs" of NTO inside the helium line were accelerated at high speeds, slamming into and nearly instantaneously destroying the one-way oxidizer valve. The internal titanium components of the destroyed valve were then exposed to the NTO, resulting in combustion and the loss of the vehicle.[17][18]

In-Flight Abort Test

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A video of the in-flight abort test.
Main article: Crew Dragon In-Flight Abort Test

On 19 January 2020, SpaceX conducted a test of Crew Dragon's launch abort system.[19] After a successful liftoff, the launch abort sequence was initiated 1 minute and 26 seconds into flight. Crew Dragon C205 successfully separated with the Falcon 9 rocket, with the rocket breaking up seconds later under the intense aerodynamic forces of max-q.[20] After separating the trunk, Crew Dragon reached an apogee of 42 kilometers before splashing down in the Atlantic Ocean.[21][22]

Abort Modes

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The Crew Dragon has multiple abort modes for different phases of flight, each with its own landing zones and procedures. As the flight progresses, SpaceX mission control calls out switches between abort modes.

Time Phase Recovery Zone[23][5]
T - 37 minutes Pad Abort Launch abort armed; Recovery zone in Florida Coast
T + 00 minutes, 00 seconds Stage 1a Recovery zones from Florida Coast to North Carolina
T + 01 minutes, 15 seconds Stage 1b Recovery zones along Virginia Coast
T + 02 minutes, 32 seconds Stage 2a Stage separation; Recovery zones along North American east coast
T + 08 minutes, 05 seconds Stage 2b Retrograde burn to land near Novia Scotia
T + 08 minutes, 28 seconds Stage 2c Prograde burn to land west of Ireland
T + 08 minutes, 38 seconds Stage 2d Retrograde burn to land west of Ireland
T + 08 minutes, 44 seconds Stage 2e Uses SuperDracos and Dracos to abort to orbit

See also

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References

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  1. ^ a b "SpaceX Dragon Overview". spacex.com. Retrieved 24 September 2024.
  2. ^ Berger, Eric (2016-04-30). "From zero to 100mph in 1.2 seconds, the SuperDraco thruster delivers". Ars Technica. Retrieved 2024-09-25.
  3. ^ "International Space Station - NASA". Retrieved 2024-09-25.
  4. ^ Jones, Daniel L. "Orion Launch Abort System (LAS) | Propulsion on Pad Abort 1 (PA-1)" (PDF). ntrs.nasa.gov. Retrieved 2024-09-25.
  5. ^ a b Gebhardt, Chris (2020-05-21). "Examining Crew Dragon's launch abort modes and splashdown locations". NASASpaceFlight.com. Retrieved 2024-09-25.
  6. ^ Gilbert, Michael G. "THE MAX LAUNCH ABORT SYSTEM – CONCEPT, FLIGHT TEST, AND EVOLUTION" (PDF). Retrieved 2024-09-25.
  7. ^ Hanneke Weitering (2019-04-24). "The Emergency Launch Abort Systems of SpaceX and Boeing Explained". Space.com. Retrieved 2024-09-25.
  8. ^ Karcz; Davis; Aftosmis; Allen; Bakhtian; Dyakanov; Glass; Gonzales; Heldmann; Lemke; Marinova; McKay; Stoker; Wooster; Zarchi. "RED DRAGON: LOW-COST ACCESS TO THE SURFACE OF MARS USING COMMERCIAL CAPABILITIES" (PDF). ntrs.nasa.gov. Retrieved 2024-09-25.
  9. ^ Foust, Jeff (2017-07-19). "SpaceX drops plans for powered Dragon landings". SpaceNews. Retrieved 2024-09-25.
  10. ^ Harwood, William (2020-05-27). "SpaceX Crew Dragon abort system a major boost for crew safety - CBS News". www.cbsnews.com. Retrieved 2024-09-25.
  11. ^ "The SpaceX Crew Dragon - NASA". Retrieved 2024-09-25.
  12. ^ Berger, Eric (2019-04-22). "Here's what we know, and what we don't, about the Crew Dragon accident". Ars Technica. Retrieved 2024-09-26.
  13. ^ Samantha Mathewson (2019-05-01). "NASA Workers Warned About Sharing Images After SpaceX Explosion Video Leak: Report". Space.com. Retrieved 2024-09-26.
  14. ^ "NASA urges patience as SpaceX investigates the Crew Dragon explosion". CNET. Retrieved 2024-09-26.
  15. ^ Cannon, James L. "Liquid Propulsion: Propellant Feed System Design" (PDF). ntrs.nasa.gov. Retrieved 2024-09-26.
  16. ^ Harwood, William (2019-07-15). "SpaceX: Explosion that destroyed Crew Dragon spacecraft in April was caused by leaking valve - CBS News". www.cbsnews.com. Retrieved 2024-09-26.
  17. ^ "UPDATE: IN-FLIGHT ABORT STATIC FIRE TEST ANOMALY INVESTIGATION | SpaceX". 2019-07-15. Archived from the original on 2019-07-15. Retrieved 2024-09-26.
  18. ^ Jeff Foust (2019-07-16). "SpaceX Says Faulty Valve Led to Crew Dragon Test Accident". Space.com. Retrieved 2024-09-26.
  19. ^ Amy Thompson (2020-01-19). "SpaceX aces Crew Dragon launch abort test, destroys rocket on purpose". Space.com. Retrieved 2024-09-26.
  20. ^ Staff, ScienceAlert (2020-01-19). "With a Spectacular Explosion, SpaceX's Crew Dragon Just Passed a Crucial Safety Test". ScienceAlert. Retrieved 2024-09-26.
  21. ^ Tariq Malik (2020-01-19). "How SpaceX's Crew Dragon launch abort test today works in 10 not-so-easy steps". Space.com. Retrieved 2024-09-26.
  22. ^ Atkinson, Ian (2020-01-17). "SpaceX conducts successful Crew Dragon In-Flight Abort Test". NASASpaceFlight.com. Retrieved 2024-09-26.
  23. ^ DeSisto, Austin (2020-05-24). "Crew Dragon Launch Day Timeline: From Suit Up to Docking with the ISS". Everyday Astronaut. Retrieved 2024-09-25.
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