Comparison of the Apollo and Orion EDL systems
In 1969 the US set the first two human beings on the moon. Days later on July 24th Armstrong, Aldrin and Collins entered the earth's atmosphere and landed safely in the north pacific ocean at 16:50 UTC. Soon a new set of moon missions will lift off under the Artemis project. Even though these missions' objectives are quite different, their entry descent and landing profile are quite comparable.
Apollo 11 entered the atmosphere with more than 11 km/s at an angle of -6.52 degrees. To compare this to the Apollo 4 re-entry demonstration mission which entered at 11.13 km/s at an angle of -6.93 degrees.
How does this compare to the upcoming Artemis missions and the Orion capsule? For Artemis 1 (comparable to what had to be Apollo 6) the entry velocity is 10.95 km/s. The demonstration mission EFT-1 flown in 2014 (comparable to Apollo 4) entered the atmosphere at 8.9 km/s. To put all these numbers in perspective, Dragon 2 is expected to enter the atmosphere at 7.5 km/s.
Size comparions of Apollo, Orion, and Dragon
Thermal protection
The heat shields of both Apollo and Orion are AVCOAT. AVCOAT is a fibreglass honeycomb impregnated with an epoxy phenol-formaldehyde resin with added ablatives. The significant difference is that for Apollo, the honeycomb was bonded to the structure of the capsule and then filled with the epoxy. For Orion, the blocks are made beforehand and then bonded to the capsule.
A clear advantage for Apollo was that there were no complex 3D shapes that had to be determined by a computer. One could attach the honeycomb to the structure and then fill them in. This process was, however, a very time-intensive one. For Orion, advanced computers were available, and thus the other method was chosen.
Parachute system
The increase in the mass of the capsule means the parachutes are also quite different. Where Apollo had 25.6 meters (84 ft) diameter parachutes, Orion will use 35.4 meters (116 ft) diameter parachutes. Both capsules are quite comparable in terms of the parachute system: two drogue parachutes and three main parachutes. Each main parachute has its own pilot chute. Furthermore, parachutes are included to remove the back thermal protection system. The significant difference is that Apollo used a single parachute on the back cover, where Orion uses three. This change brings the total parachutes onboard Orion to eleven, where Apollo had nine parachutes.
