SpaceX Falcon 9 Block 5 - CRS-21 - Launched December 6, 2020
Screenshot from SpaceX Webcast of the roll out of CRS-21 - Note the 3 foot PAF neck ring
Mission Rundown: SpaceX Falcon 9 Block 5 - CRS-21
Written: August 2, 2021
Where are We going with this?
The Commercial Resupply Services-21 (CRS-21) mission lifted off from Launch Complex 39A (LC-39A) at the Kennedy Space Center on 6 December 2020 at 11:17:08 EST local time - 16:17:08 UTC to start an approximately 30 day mission to the ISS to resupply the seven member Expedition 64 crew. CRS-21 consists of the Cargo Dragon C208.
CRS-21 launched on SpaceX’s Falcon 9 Block 5 rocket, and marked the first SpaceX launch under the CRS 2 contract. The Falcon 9 lifted off from Launch Complex 39A, at the Kennedy Space Center in Florida. Booster B1058-4 landed on “Of Course I Still Love You'' 623 km downrange North Northeast from LC-39A some 8-9 minutes after launch.
After Dragon was deployed, it performed a number of phasing burns to adjust its orbit and catch up to the ISS. Just over 26 hours after launch, at 18:40 UTC, Dragon docked with the ISS. Docking marked the first time that two Dragons were at the ISS at once, as C207 was docked at the station with the USCV-1 crew. Once C208 docked, and after the completion of hatch opening, the astronauts aboard the ISS started unloading cargo.
In the following weeks the teams aboard the ISS conducted the time-sensitive research experiments, and deployed the payloads. After this, they began packing Dragon for its flight home. Along with some of the experiments that went up with Dragon, Dragon will be bringing home 2,360 kg of payload, including a treadmill avionics unit; a Carbon Dioxide Removal Assembly Air Selector Valve; Thermal Amine Bulk Water Save Valve; Minus Eighty Laboratory Freezer; and a Rodent Research Habitat and Transporter.
After being docked to the ISS for 37 days, Dragon undocked from the ISS on January 12, 2021 at 14:05 UTC. Undocking was pushed back a day due to the weather in the recovery zones; the primary landing location was changed to Tampa due to unfavorable weather in the Cape Canaveral, Daytona Beach, and Jacksonville landing zones. Dragon then performed a number of phasing burns to lower its orbit, then jettisoned its trunk and performed a deorbit burn.
B1058 first flew on its maiden flight on the SpaceX Demonstration Mission 2, which launched Bob Behnken and Doug Hurley to orbit on May 30, 2020. CRS-21 is its fourth flight; so its designation changes to B1058-4.
SpaceX conducted a static fire test at 14:44 EST December 3 with Falcon 9 booster B1058-4 at KSC LC-39A in preparation for the launch of the CRS-21 mission.
The Cargo Dragon Payload
Aboard CRS-21 is 2,914 kilograms of pressurized and unpressurized cargo, broken down into ISS crew supplies of 364 kg, scientific experiments 953 kg, spacewalk equipment 120 kg, vehicle hardware 317 kg, computer gear 46 kg and Russian hardware 24 kg.
Included in that are five scientific experiments sponsored by NASA and their international partner agencies being flown to the Station in order to be carried out under the unique microgravity environment the orbital laboratory provides.
NASA’s BRazing of Aluminum alloys IN Space (BRAINS), a physical science experiment, is one of those individual investigations being carried uphill by Cargo Dragon. The purpose of BRAINS is to study the effect of microgravity on “capillary flow, interface reactions, and bubble formation” during the solidification of brazing metals.
Brazing is a process that involves superheating certain metals in order to melt them and then solidifying them in a manner which allows them to be joined without the use of any other adhesive. How this could occur in microgravity is consequential to future space exploration as it is believed that brazing could be a process used to build future space habitats and other space hardware.
ESA’s BioRock experiment that studied the interactions between microbes and rocks in microgravity, possibly affecting the future of biomining on Earth and in space.
Also included within the scientific payload are NASA’s Cardinal Heart, HemoCue and Space Tango-Human Brain Organoids experiments.
Bishop is a commercially funded airlock module for the ISS, built by NanoRacks, Thales Alenia Space, and Boeing. The airlock is relatively small with a mass of 1,059 kg (2,300 lbs) and a pressurized volume of 4 cubic meters, and will be used to deploy cube sats and smallsats.
Following Dragon’s arrival, Bishop will be remotely removed from the truck by the Space Station Remote Manipulator System (SSRMS; also known as Canadarm 2) and moved to the Tranquility (Node 3) module near the middle of the Station, where it will be located for the foreseeable future, allowing for the Canadarm 2 to be used to deploy payloads.
Although mainly intended for use in deploying small satellites, NanoRacks also advertises some of Bishop’s other uses, including being able to support spacewalks, being capable of easily getting new tools other other equipment outside the Station for use by astronauts already outside, or as a platform for scientific experiments and external payloads that would be exposed to the vacuum of space.
Regarding spacewalks, the ISS crew can put 2-3 astronauts in fully equipped spacesuits in the Bishop airlock module with tools and spare parts. Depressurize it and undock it with the Canadarm, so the astronauts have free access to the exterior of the Station. After the spacewalk they can go back inside Bishop, redock with ISS and after pressurization be back inside in a jiffy. It must be a timesaving measure compared to going through a normal airlock one at the time.
CRS-21 contact and soft capture with ISS at 13:40 EST - 18:40 UTC some 268 statute miles (431.3 km) over the Southern Indian Ocean.
Time to leave this place
Cargo Dragon CRS-21 completed its 36-day stay at the ISS today after undocking at 09:05 EST. It will splashdown in the Gulf of Mexico late Wednesday.
After completion of CRS-21 Cargo Dragon Deorbit Burn splashdown should be occurring 40 minutes later. Dragon C208 is expected to splash down west of Tampa off the Florida coast about 8:27 p.m Eastern.
Splashdown LZ offshore near Tampa in the Gulf of Mexico - Note three other possible LZ
The helikopter N554AC retrieving time-sensitive cargo from the CRS-21 Cargo Dragon arrived at approximately 23:30 EST to Kennedy Space Center for processing. This cargo was brought directly from the deck of GO Navigator which was stationed at the Tampa splashdown zone.
The CRS-21 Cargo Dragon will be sailed to the Port Canaveral submarine station to be drained for hazardous fuel residues. - Wrong - Just easier to keep people out and unloading it to a transport bound for SpaceX hangar for inspections and drainage.
The upgraded cargo Dragon capsule used for this mission contains double the powered locker availability of previous capsules, allowing for a significant increase in the research that can be carried back to Earth. That means freezers and cryo freezers to you and me.
The SpaceX Cargo Dragon will be loaded with 5,200 pounds of scientific experiments and other cargo before departure from the ISS. This listed below is just some of it.
Cardinal Heart - Microgravity causes changes in the workload and shape of the human heart, and it is still unknown whether these changes could become permanent if a person lived more than a year in space. Cardinal Heart studies how changes in gravity affect cardiovascular cells at the cellular and tissue level using 3D-engineered heart tissues, a type of tissue chip.
Space Organogenesis - This investigation from JAXA (Japan Aerospace Exploration Agency) demonstrates the growth of 3D organ buds from human stem cells to analyze changes in gene expression. Cell cultures on Earth need supportive materials or forces to achieve 3D growth, but in microgravity, cell cultures can expand into three dimensions without those devices.
The sextant used in the Sextant Navigation experiment are returning to Earth. Sextants have a small telescope-like optical sight to take precise angle measurements between pairs of stars from land or sea, enabling navigation without computer assistance. Sailors have navigated via sextants for centuries, and NASA’s Gemini missions conducted the first sextant sightings from a spacecraft.
Rodent Research-23 - This experiment studies the function of arteries, veins, and lymphatic structures in the eye and changes in the retina of mice before and after spaceflight. The aim is to clarify whether these changes impair visual function. At least 40 percent of astronauts experience vision impairment known as Spaceflight-Associated Neuro-ocular Syndrome (SANS) on long-duration space flights, which could adversely affect mission success.
Thermal Amine Scrubber - This technology demonstration tested a method to remove carbon dioxide (CO2) from air aboard the International Space Station, using actively heated and cooled amine beds. Controlling CO2 levels on the station reduces the likelihood of crew members experiencing symptoms of CO2 buildup, which include fatigue, headache, breathing difficulties, strained eyes, and itchy skin.
Bacterial Adhesion and Corrosion - Bacteria and other microorganisms have been shown to grow as biofilm communities in microgravity. This experiment identifies the bacterial genes used during biofilm growth, examines whether these biofilms can corrode stainless steel, and evaluates the effectiveness of a silver-based disinfectant.
The Cargo Dragon 2
CRS-21 marks the first launch of SpaceX’s upgraded Cargo Dragon 2 spacecraft. Well if You don’t count Demo-1, Demo-2 and Crew-1. Ah - And the Dragonfly pad launch too.
Dragon capsule C208 during processing at SpaceX HQ in Hawthorne prior to CRS-21
Cargo Dragon 2 is essentially a Crew Dragon, without an abort system, so it has all of the upgrades from Crew Dragon. Most importantly, Dragon 2 is designed to be reused up to 5 times, with a turnaround time of under 6 months, which is significantly lower than Dragon 1; Dragon 1’s fastest turnaround time was 418 days, with most turnaround times being significantly longer.
Dragon 1 was unable to dock with the International Space Station. Meaning that Dragon 1 would hold a position away from the ISS. In this position the Canadarm would capture the spacecraft, and attaching it to the ISS. This is called berthing.
Dragon 2 autonomously attaches itself and docks to the ISS. CRS-21 will mark the fourth fully autonomous docking SpaceX has completed: DM-1, DM-2, Crew-1 and now CRS-21.
Cargo Dragon 2’s trunk is also different from both Dragon 1’s and Crew Dragon’s. Dragon 2 has its solar panels integrated into its trunk, while Dragon 1 had a deployable solar array from its trunk. However, Crew Dragon is equipped with 4 fins, which are used for aerodynamic control during ascent. Cargo Dragon 2’s trunk only has 2 solar cell fins.
Externally, Cargo Dragon 2 differs from its crewed counterpart, lacking windows and the SuperDragon abort system. The differences between Crew Dragon and Cargo Dragon are derived from the fact that Crew Dragon is required to have launch escape capability.
Crew Dragon is fitted with eight SpaceX-developed SuperDraco engines, located in four, two engine clusters around the outside of the capsule, which are there to pull the capsule and its crew to safety away from a Falcon 9 in the event of a catastrophic failure during fueling or launch.
Since Cargo Dragon does not carry crew, the spacecraft does not have to carry those systems; therefore the SuperDracos have been removed from the Cargo Dragon capsule giving a mass reduction that allows for additional cargo to be carried to ISS.
Cargo Dragon 2 also lacks all of the life support and onboard control systems present on Crew Dragon that are needed for humans. Instead, it carries minimal support systems to ensure conditions are kept acceptable for hatch opening on the Station and ISS Crew ingress to the vehicle.
Cargo Dragon 2 is also significantly more massive, with a dry mass of ~12,000 kg. With this mass increase Dragon 2 is able to carry ~50% more science to the ISS than Dragon 1. Because of this, missions past CRS-22 will stay docked to the ISS for 3 months, rather than the 1 month that they stay docked to now.
Dragon 2’s nose cone is also significantly different as it opens instead of being jettisoned on ascent.
At a press conference after Crew-1, Gwynne Shotwell said SpaceX is expecting to have a fleet of 8 dragons: 5 Crew Dragons and 3 Cargo Dragons. This will allow SpaceX to conduct up to 25 crewed missions and 15 resupply missions.
Unlike prior cargo resupply missions, the new Cargo Dragon 2 carried too much mass to permit a Return To Launch Site (RTLS) landing of the Falcon 9 first stage. Instead, the first stage — like Crew Dragon, from which Cargo Dragon is now derived — made use of a drone ship “Of Course I Still Love You'' in the Atlantic for landing and recovery.
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