SpaceX is readying a Falcon 9 rocket for its static fire test ahead of the Crew Dragon Demo-2 mission. The static fire is part of the ongoing series of final tests and reviews before SpaceX embarks on its first human spaceflight mission. The test is scheduled to take place today no earlier than 16:33 EDT (20:33 UTC).
The test is the final time NASA has to gather data on SpaceX’s load-and-go fueling process as Demo-2 will be the first time NASA allows a rocket to be fueled for flight with a crew onboard.
Demo-2’s launch is currently set for May 27th at 16:33:31 EDT (20:33:31 UTC). If a problem comes up that necessitates a scrub – such as poor weather or a vehicle issue – the next available date would be May 30th.
The flight will mark the first crewed orbital mission from the United States since July 2011, when the Space Shuttle was retired. The Falcon 9 and Crew Dragon will carry NASA astronauts Bob Behnken and Doug Hurley to the International Space Station (ISS) for one to four months depending on Dragon’s on-orbit performance.
But before that can happen, one of the last major milestones before flight is has to take place: the static fire.
The test consists of a complete rehearsal of most launch day activities. SpaceX has performed at least one static fire before every mission to date – all the way back to the Falcon 1.
A day prior to the test, teams rolled the completed Falcon 9 stack out of the Horizontal Integration Facility (HIF) to launch pad LC-39A and raised it vertical. This specific rocket contains first stage core B1058 on what will be its first flight.
NASA will require new boosters on all Crew Dragon flights, at least initially.
The static fire test follows the same countdown as an actual launch – including fueling 35 minutes before engine ignition on the test.
Propellant load of the first stage with RP-1 kerosene and densified Liquid Oxygen begins at this time, as does RP-kerosene loading of stage 2. Liquid Oxygen begins flowing into the second stage at T-16 minutes.
At T-3 seconds, the nine Merlin 1D engines on the first stage are ignited for a brief test-firing.
For most missions, SpaceX only performs a 3.5-second firing. However, for certain high-profile missions, or those with reused first stages, they sometimes opt for a longer 7-second test. It is unclear how long Demo-2’s firing will be.
After the test, SpaceX and NASA personnel will perform a deep dive into the data gathered to assess how the vehicle performed.
Closer to the launch date, a final in-depth analyses of all launch-related systems will take place. The Launch Readiness Review will then clear SpaceX and NASA to proceed to launch day with Demo-2.
On launch day, Hurley and Behnken will wake up and eat a traditional pre-launch breakfast at T-5 hours. From there, the two will suit up and ride to LC-39A in Tesla Model X SUVs. They will then ascend to the 265-foot level of the Fixed Service Structure (FSS). The two will walk across the Crew Access Arm and board Crew Dragon 2 hours 35 minutes prior to launch.
At T-42 minutes, the Crew Access Arm will be retracted away in preparation for fueling.
The exact timing of propellant loading into the Falcon 9 had been the subject of a major debate in the Commercial Crew Program for several years.
Two different fueling procedures were proposed. The first would involve completely fueling the rocket, then loading the astronauts into the capsule. The second – aptly named “load-and-go” – has the astronauts board Dragon prior to fueling.
SpaceX preferred the load-and-go method because of the Falcon 9’s use of chilled propellants. The rocket’s performance was increased substantially by cooling the liquid oxygen and RP-1 propellants to near their freezing points, thus increasing their density. Higher-density propellants allow for more vehicle performance while using the same-sized tanks. If SpaceX had to fuel the rocket prior to astronauts boarding, the propellants would heat up – impacting the vehicle’s performance.
The load-and-go procedure received heavy scrutiny following the on-pad conflagration of a Falcon 9 rocket in September 2016, ahead of what would have been the launch of Amos-6. The cause of the anomaly was narrowed to solid oxygen forming and igniting with the carbon fiber of the composite-overwrapped pressure vessels (COPVs), which store helium gas to pressurize the tanks.
To prevent future formation of solid oxygen, SpaceX modified their fueling procedures.
Certain officials – notably Gemini and Apollo astronaut Thomas Stafford – were concerned by the incident. However, following in-depth studies of vehicle systems and performance, the Aerospace Safety Advisory Panel (ASAP) approved the load-and-go procedure in May 2018.
Fueling under this process lasts until just a couple minutes before liftoff. Falcon 9’s tanks are then pressurized for flight at T-1 minutes.
The final “Go for launch” determination and call will be made at T-45 seconds by the SpaceX Launch Director.
At T-3 seconds, the first stage engines ignite. If the onboard computers detect no issues, liftoff occurs at T-0.
The first stage’s engines will cut off T+2 minutes 33 seconds into flight. It will then attempt a landing on SpaceX’s Autonomous Spaceport Drone Ship (ASDS) Of Course I Still Love You.
After Falcon 9’s second stage places Crew Dragon into a Low Earth Orbit, Hurley and Behnken will perform several tests on the vehicle – including taking manual control just before docking to the ISS. The transit to the station will take approximately 19 hours.
Once they arrive, the two astronauts will live and work onboard the Station for one to four months before returning to Earth.
The mission’s exact duration has not been decided, but will be capped at 119 days.
After Dragon splashes down in the Atlantic Ocean off the coast of Florida, SpaceX’s twin recovery ships GO Searcher and GO Navigator will recover the crew and capsule.
If all goes well, the first operational Crew Dragon mission, dubbed Crew-1, will liftoff from LC-39A about one month after Demo-2 lands.
(Lead image: SpaceX)
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