SpaceX CRS-6

The SpaceX CRS-6 Dragon spacecraft as seen from the ISS on 17 April 2015
Names	SpX-6
Mission type	ISS resupply
Operator	SpaceX
COSPAR ID	2015-021A
SATCAT no.	40588
Mission duration	36 days, 20 hours, 31 minutes
Spacecraft properties
Spacecraft	Dragon 1 C108
Spacecraft type	Dragon 1
Manufacturer	SpaceX
Launch mass	6,000 kg (13,000 lb)
Dimensions	Height: 8.1 m (27 ft) Diameter: 4 m (13 ft)
Start of mission
Launch date	14 April 2015, 20:10:41 UTC
Rocket	Falcon 9 v1.1 (B1015)
Launch site	Cape Canaveral, SLC-40
Contractor	SpaceX
End of mission
Disposal	Recovered
Landing date	21 May 2015, 16:42 UTC
Landing site	Pacific Ocean
Orbital parameters
Reference system	Geocentric orbit[1]
Regime	Low Earth orbit
Inclination	51.65°
Berthing at ISS
Berthing port	Harmony nadir
RMS capture	17 April 2015, 10:55 UTC
Berthing date	17 April 2015, 13:29 UTC
Unberthing date	21 May 2015, 09:29 UTC
RMS release	21 May 2015, 11:04 UTC
Time berthed	33 days, 20 hours
Cargo
Mass	2,015 kg (4,442 lb) [2]
Pressurised	2,015 kg (4,442 lb)
NASA SpX-6 mission patch Commercial Resupply Services ← SpaceX CRS-5 SpaceX CRS-7 → Cargo Dragon ← SpaceX CRS-5 SpaceX CRS-7 →

SpaceX CRS-6, also known as SpX-6, was a Commercial Resupply Service mission to the International Space Station, contracted to NASA. It was the eighth flight for SpaceX's uncrewed Dragon cargo spacecraft and the sixth SpaceX operational mission contracted to NASA under a Commercial Resupply Services contract. It was docked to the International Space Station from 17 April to 21 May 2015.

In July 2014, the launch was scheduled by NASA for February 2015, with berthing to the station occurring two days later. However, as a result of delays in the launch of the previous SpaceX CRS-5 mission, SpaceX CRS-6 launched on 14 April 2015. In late March, 2015, the launch was scheduled for 13 April 2015,^[3] but was later postponed to 14 April 2015 due to weather conditions.^[4]

A Federal Communications Commission (FCC) application submitted for temporary communication frequency authority noted the launch planning date as no earlier than 8 April 2015. The application also confirmed communication uplinks for use with the first stage of this mission as it attempted to conduct a first-ever propulsive landing on the Autonomous spaceport drone ship after staging.^[5]

NASA has contracted for the CRS-6 mission from SpaceX and therefore determines the primary payload, date/time of launch, and orbital parameters for the Dragon space capsule. The Dragon spacecraft was filled with 2,015 kg (4,442 lb) of supplies and payloads, including critical materials to directly support about 40 of the more than 250 science and research investigations that will occur during Expedition 43 and Expedition 44.^[2]

Among other items on board:

• Planetary Resources will transport an Arkyd 3 — known as Arkyd 3 Reflight — to the ISS aboard Dragon on CRS-6.^[6] Planetary plans to deploy the smallsat from the ISS via a Nanoracks-provided service, in an attempt to validate and mature the technology of its Arkyd series of spacecraft. This is the second Arkyd 3 satellite; in October 2014, the first Arkyd 3 satellite was destroyed on launch in the explosion of the Orbital Sciences Corporation Antares launch vehicle carrying it aboard the third Cygnus cargo resupply flight to the ISS.^[7][8]

• Planet Labs will transport 14 Flock-1e Earth observation CubeSat satellites for later deployment from the space station via an agreement with Nanoracks, operator of the Center for the Advancement of Science in Space (CASIS).^[9]

SpaceX has the primary control over manifesting, scheduling and loading secondary payloads. However, there are certain restrictions included in their contract with NASA that preclude specified hazards on the secondary payloads, and also require contract-specified probabilities of success and safety margins for any SpaceX reboosts of the secondary satellites once the Falcon 9 second stage has achieved its initial low Earth orbit (LEO).

SpaceX CRS-6 included science payloads for studying new ways to possibly counteract the microgravity-induced cell damage seen during spaceflight, the effects of microgravity on the most common cells in bones, gather new insight that could lead to treatments for osteoporosis and muscle wasting conditions, continue studies into astronaut vision changes and test a new material that could one day be used as a synthetic muscle for robotics explorers of the future. Also making the trip was a new espresso machine for space station crews.^[2]

A part of this payload includes science experiments from high schools, such as a project from Ambassador High School in Torrance, California.^[10]

Dragon returned 1,370 kg (3,020 lb) of cargo to Earth.^[2]

After the separation of the second stage, SpaceX conducted a flight test and attempted to return the nearly-empty first stage of the Falcon 9 through the atmosphere and land it on a 90 m × 50 m (300 ft × 160 ft) floating platform called the autonomous spaceport drone ship. The unmanned launch vehicle technically landed on the floating platform, however it came down with too much lateral velocity, tipped over, and was destroyed.^[11] Elon Musk later explained that the bipropellant valve was stuck, and therefore the control system could not react rapidly enough for a successful landing.^[12]

This was SpaceX's second attempt to land the booster on a floating platform after an earlier test landing attempt in January 2015 had to be abandoned due to weather conditions. The booster was fitted with a variety of technologies to facilitate the flight test, including grid fins and landing legs to facilitate the post-mission test. If successful, this would have been the first time in history that a launch vehicle booster was returned to a vertical landing.^[9][13]

On 15 April 2015, SpaceX released a video of the terminal phase of the descent, the landing, the tip over, and a small deflagration as the stage broke up on the deck of the ASDS.^[14]

The Dragon capsule used for this mission was successfully flown a second time in December 2017 with SpaceX CRS-13. The capsule made its third and final flight as part of the SpaceX CRS-18 mission on 25 July 2019.

• List of Falcon 9 launches

• NASA
• SpaceX/NASA CRS-6 press kit April 2015