On December 21 at 10:07 UTC, a SpaceX Falcon 9 launched the CRS-24 resupply mission towards the International Space Station (ISS) from LC-39A at the Kennedy Space Center in Florida. The final SpaceX launch of 2021 used capsule C209, which marked its second flight.

Like most of the CRS missions SpaceX flew in 2021, the first stage for this mission was a brand new booster, Booster 1069. The last maiden flight of a booster was B1067, which first flew on CRS 22 six months ago, in June 2021.

Booster 1069 landed about nine minutes after launch on the droneship Just Read the Instructions, making this the one-hundredth successful landing of a Falcon 9 booster six years to the day of the first one.

As usual, CRS-24 brings with it lots of science and station equipment. There are too many to talk about in the time that we have, so here are a few of our favorites.

One experiment being brought up by CRS-24 is laundry detergent. I know – laundry is boring. It’s a hard, thankless task that never ends. But at least here on Earth, we can do our laundry. Currently, astronauts on the ISS do not wash their clothes. They can’t – the process would use a lot of precious water that the existing filtration system simply can’t get clean enough for humans to drink. Instead, crew members wear the same item of clothing several times and then throw it out with the rest of the space station’s trash by burning it up in the atmosphere. For future missions beyond Earth orbit, astronauts may not be capable of getting fresh new clothes on a regular basis, so they will need the ability to do laundry.

Proctor & Gamble’s cleverly named PGTIDE experiment has two objectives: to determine the efficacy of the active ingredient, amine oxide, on stain removal in microgravity and to see if any part of the detergent’s enzymes or surfactants become inactive or break down and become less effective with extended time in microgravity.

To test how effective amine oxide is in space, the astronauts will first stain and then clean cotton swatches using Tide Pens and Tide To Go Wipes. They will also clean swatches that were stained on the ground.

The second part of the experiment is much simpler. Detergent samples will be brought up to the station and stored for six months. The astronauts will take pictures of the samples at various points to track changes, like cloudiness or color. Both parts of the experiment will be returned to the ground at the same time.

The BioPrint FirstAid experiment will demonstrate the use of “bio-ink” bandages made from an astronaut’s own skin cells, which ensures that the body won’t reject it while accelerating the healing process. It also has the benefit of avoiding potential allergic reactions to materials in a conventional bandage, such as latex or adhesive.

BioPrint FirstAid will allow an astronaut to treat themselves quickly without relying on ground-based medical support. The completely mechanical device can make a personalized patch in only ten minutes. Since the purpose of this initial demonstration is to see how the “[t]he distribution pattern of the printed samples on Earth compare[s] to the printed sampled in space”, the first demonstration of the technology won’t contain human cells or be used directly on an astronaut’s body. Instead, the astronaut will strap foil to their arm or leg and then use the bioprinter to apply a simulated patch to the foil.

My favorite experiment is the ESA-sponsored “concrete hardening” experiment. It will investigate how cement mixed with different aggregates, from sand to simulated lunar regolith, affects how the resulting concrete hardens in microgravity. 

Concrete is the most common building material and the second most used substance in the world after water. The right concrete for a particular application is a balance between its three major ingredients: aggregates, cement, and water. Aggregate in this context is simply material such as crushed rock, sand, or even old concrete that provides the structure for cement to bind together, creating a matrix for everything to bond to.

The optimal ratio depends on cost and the required amount of strength. If there’s not enough water, not all of the aggregate will bind to the cement, reducing its strength. Too much water and the concrete’s strength is reduced because of pores in the material that let water permeate it. Too much cement and it has lower strength and is more expensive because cement requires a lot of energy to produce. Too much aggregate and the concrete is hard to pour and brittle when cured. Of course, it’s a lot more complicated than that: there are different kinds of aggregate for different uses, but this is a show about rockets, not civil engineering.

Determining how concrete hardens in space will be essential to building large permanent structures on other solar system bodies. Using readily available local materials instead of bringing materials with the mission will allow much more science to get done.

Once the concrete is cured in space, it will be brought back to Earth for analysis, focusing on its pore microstructure and mechanical strength.

CRS-24 also contains the CubeSats of NASA’s ELaNa 38, a few CubeSats from JAXA, and two payloads which will be mounted to the outside of the Kibo module.

To read more about the experiments on CRS-24, you can check out the link in the show notes and Patreon supporters can check out the bonus content for this show, too.

In total, CRS-24 brought up 2,989 kilograms of cargo including packing material: 2,081 in the capsule and 908 in the trunk.

More Information

Experiments Riding 24th SpaceX Cargo Mission to Space Station Study Bioprinting, Crystallization, Laundry (NASA)

P&G Telescience Investigation of Detergent Experiments (NASA)

Bioprint FirstAid Handheld Bioprinter (NASA)

Material Science on Solidification of Concrete (NASA)

“Cement and concrete as an engineering material: An historic appraisal and case study analysis,” Colin R.Gagg, 28 February 2014, Engineering Failure Analysis

ELaNa 38 CubeSats: Small Satellites Making a Big Impact (NASA)

Launch video