SpaceX Falcon 9 V1.1 - CRS-7 - Launching June 28, 2015
Screenshot from NASA TV of the launch of CRS-7
Mission Rundown: SpaceX V1.1 - CRS-7 accident
Written: February 2, 2021
Don’t burp while flying
SpaceX CRS-7, also known as SpX-7, was a private American Commercial Resupply Service mission to the International Space Station, contracted to NASA, which launched and failed on June 28, 2015.
It disintegrated 139 seconds into the flight after launch from Cape Canaveral, just before the first stage was preparing to separate from the second stage.
It was the ninth flight for SpaceX's uncrewed Dragon cargo spacecraft and the seventh SpaceX operational mission contracted to NASA under a Commercial Resupply Services contract. The vehicle launched on a Falcon 9 v1.1 launch vehicle. It was the nineteenth overall flight for the Falcon 9 rocket and the fourteenth rocket flight for the substantially upgraded Falcon 9 v1.1. A NASA press conference was held after the accident. Watch.
The Launch/Mission Failure
Performance was nominal until 139 seconds into launch when a cloud of white vapor appeared, followed by a rapid loss of pressure in the liquid oxygen tank of the Falcon 9's second stage. The booster continued on its trajectory until the vehicle completely broke up 7 seconds later.
The Dragon CRS-7 capsule was ejected from the exploding launch vehicle and continued transmitting data until it impacted the ocean. SpaceX officials stated that it could have been recovered if the parachutes had deployed, but the software in the capsule did not include any provisions for parachute deployment in this situation. Dragon capsules does now include abort software programming especially in the future manned flights.
It’s assumed that the capsule crumpled and broke up on impact. Subsequent investigation traced the accident to the failure of a strut that secured a high-pressure helium bottle submerged inside the second stage's liquid-oxygen tank. With the helium pressurization system in the COPV integrity breached, excess helium quickly flooded the liquid-oxygen tank, causing it to over pressurize and burst.
The 5 foot tall COPV - Carbon Overwrapped Pressure Vessel was actually buoyant in the LOX - Liquid Oxygen so it shot up to the LOX surface hitting the top bulkhead and breaking it with catastrophic consequences for the launch vehicle. Given the fact that SpaceX had a number of related problems with test failures of COPV made by external suppliers, they should have been alerted to the fact that COPV was an achilles heel on Falcon 9.
The report from SpaceX pointed out that the stainless-steel eye bolt was rated for a load of 10000 pounds, but failed at 2000 pounds. Submerged in liquid Oxygen. Experiencing 3,2 G of force during flight. A frozen tread failed. The bolt snapped.
An independent investigation by NASA concluded that the most probable cause of the strut failure was a design error: instead of using a stainless-steel eye bolt made of aerospace-grade material, SpaceX chose an industrial-grade material without adequate screening and testing and overlooked the recommended safety margin.
The lost Dragon Payload
As of July 2013, the first International Docking Adapter, IDA-1, was scheduled to be delivered to the International Space Station on CRS-7. This 526 kg adapter would have been attached to one of the existing Pressurized Mating Adapters (specifically, PMA-2 or PMA-3) and convert the existing APAS-95 docking interface to the new NASA Docking System (NDS).
The new adapter is intended to facilitate future docking of new U.S. human-transport spacecraft. Previous United States cargo missions since the retirement of the Space Shuttle have been berthed, rather than docked, while docking is considered the safer and preferred method for spacecraft carrying humans.
The mission would have transported more than 4,000 pounds (1,800 kg) of supplies and experiments to the International Space Station including the Meteor Composition Determination investigation which would have observed meteors entering the Earth's atmosphere by taking high resolution photos and videos.
The Center for the Advancement of Science in Space had arranged for it to carry more than 30 student research projects to the station including experiments dealing with pollination in microgravity as well as an experiment to evaluate a sunlight blocking form of plastic.
In total, 2,477 kilograms (6,461 lb) of cargo was aboard the Dragon, including provisions, care packages and food for the crew, hardware for the station’s healthcare, life support, electrical and computer systems, 529 kilograms (1,166 lb) of scientific hardware for NASA, ESA and JAXA and hardware aka. parts of spacesuits for performing EVAs.
Dragon was also expected to return 675 kilograms (1,488 lb) of cargo to Earth.
