by S. Prasad Ganti
Artemis, the twin sister of Apollo, rises after five decades. The recent Artemis mission is NASA’s attempt to send astronauts back to the moon after a lapse of five decades. The initial mission carried a dummy crew in its capsule Orion which rode on top of a launch system called SLS (Space Launch System). This mission validated all the parameters before actual humans are launched towards the moon in a couple of years time. The launch and the journey to the moon and the return for a splashdown into the Pacific ocean all worked out well.
The SLS is very close to the Saturn V rocket which was used for earlier manned missions to the moon in the 1970s. The picture below, courtesy NASA, shows the two rockets side by side along with the famed Statue of Liberty in New York City. In comparison, the astronaut stands as a dot to the right of the Statue of Liberty.
The first stage of SLS is the lower half marked in orange. It houses the liquid hydrogen and liquid oxygen tanks which fuel the 4 RS-25 engines at the bottom. These are the same engines which powered the space shuttle of yesteryears. To each side is a solid rocket booster which provides additional thrust. Very similar to the space shuttle design.
The topmost spire-like structure is the launch abort system. If for some reason, the rocket needs to be aborted after the launch, the spire along with the astronaut carrying capsule are separated out and taken to a safe landing. The bell shaped tiny structure below the spire is the crew capsule. Named Orion, it carries human beings to the moon. For Artemis 1, it carried dummy human beings.
Just below the crew capsule is the cylindrical service module which carries the solar arrays and the communication equipment. This unit has been built by Airbus and is Europe’s contribution to the mission. The crew capsule and the service module fly together as one unit to the moon and come back to the Earth. The service module is jettisoned just before Orion enters the Earth’s atmosphere. Pretty much like the Apollo mission.
Wedged between the first stage and the service module top stages is the Interim Cryogenic Propulsion Stage (ICPS). It is likely to be replaced by other designs in future Artemis missions. That is why the word “interim”. After launch, the first stage falls off after pushing the rocket enough towards space. The ICPS pushes for some more time and then falls off. What is left is the crew capsule and service module which travel together for most of the life of the mission.
I recently visited the new exhibit called “The Gateway” at Kennedy Space Center. I took a picture of the mockup of the Orion crew module as shown below.
Artemis mission involved a new re-entry procedure called the skip entry, which meant that Orion dipped into the upper part of Earth’s atmosphere and bounced back into the atmosphere and then entered again for a splashdown. It is like skipping a rock across the water in a river or lake wherein it bounces and then on the final bounce, sinks into the water. The skip entry will allow astronauts to experience lower g-forces. Splitting up the acceleration events lowers the heat rate and the thermal stresses it creates on the crew module. It also allows for more precise splashdown within a narrow zone in the Ocean.
We have a limited inventory of the components available for future Aretmis missions, given the older technology the launch vehicle is based on. SpaceX’s Starship is on the horizon which will be flight tested early 2023. It is a two stage rocket and both of them are designed to come back safely to Earth and land. It is intended to be a fully reusable rocket and will reduce the launch costs. It will be powered by the newer Raptor engines compared to SLSs’ older RS-25 engines.
The crew module will be SpaceX’s own Crew Dragon shown in the picture below which I took at the Gateway exhibit. The module on the left where two people are standing is the Crew Dragon. In the center of the picture is Boeing’s Starliner which is another option for a crew module. To the right of the picture is the inflatable deep space habitat which might be used in future deep space missions.
With the rise of Artemis, the next few years look promising in going back to the moon and making this a regular exercise as the technology matures further and the costs come down.