Overview
While technology has improved since NASA’s final Apollo mission almost 50 years ago, the underlying physics principles that dictated Apollo’s shape and general design remain the same. That is largely why Apollo and Orion bear a striking visual resemblance from the outside. Building off what was learned from the Apollo program, Orion’s major advancements will allow NASA to extend our reach past Earth to the Moon and beyond, expand the range of mission destinations, and accommodate larger crews for longer missions.
Orion and Apollo systems are similarly comprised of three major elements – a launch abort system, which protects the crew during launch and ascent; a crew module, which houses the crew and maintains a crew environment; and a service module, which provides main propulsive forces and supplies the crew module with power and life sustaining commodities.
Launch Abort System
Orion’s launch abort system (LAS) looks like the escape tower flown on top of Apollo’s Saturn V rocket, but upgrades make it possible for Orion to escape from its launcher under more extreme conditions. This is largely due to the attitude control motor on Orion’s LAS, which consists of eight variable-thrust nozzles that can be independently controlled and modulated. In the event of an abort, Apollo’s non-vectoring “pitch” motor would only send the capsule in one direction. Orion’s computer, however, can sense the vehicle’s orientation and send commands to the attitude control motor to adjust each nozzle’s position and thrust, keeping Orion properly positioned away from the rocket.
Crew Module
At the system level, there are significant differences between Orion and Apollo. The Orion elements are larger in scale, offering greater volume to accommodate larger crews and provide greater range. Where Apollo was designed to transport three crew for 14 days, Orion can transport up to four crew for 21 days, and is designed to be versatile and support a variety of destinations.
Orion has about 60 percent more habitable space than Apollo, allowing more room for the crew. Orion is also designed with many more crew comforts to support longer duration spaceflight, such as a food warmer for preparing meals and a functioning waste management system.
Crew exercise was very difficult inside Apollo, as the environmental control system was not designed to compensate for crew workouts. However, Orion provides full exercise capability, and is also designed to maximize available privacy and mitigate noise and odors, enabling longer, healthier, and more hygienic missions.
Modern features have also been incorporated into Orion, including composite materials, 3D printed parts, solar arrays, and an improved heat shield design. Orion also has over 1,200 sensors, and the crew module has a glass cockpit with screens and user-interfaces reflective of our digital age, rather than Apollo’s analog inputs and outputs.
Avionics
Where Apollo ushered in the era of computers and software, Orion capitalizes on decades of computing advancements. Orion’s guidance, navigation, and control (GN&C) system is comprised of flight computers, displays and controls, optic measurement, and advanced software. Compared to Apollo’s single flight computer, Orion has two simultaneously operating redundant flight computers that each include two redundant computer modules, giving it a total of four redundant systems. In addition, just one of Orion’s redundant computers is only 75 percent the weight of the sole computer aboard Apollo, has 128,000 times more memory and is 20,000 times faster. Orion’s computing redundancies not only improve safety, they also improve data collection and processing power.
Radiation
Relative to Apollo, Orion’s systems have also been upgraded to account for the effects of space radiation exposure, an environmental hazard that is better understood since the Apollo missions. To counter the radiation hazard, electronic components within the computers are radiation hardened. This is something Apollo did not account for as missions were flown during a period of minimum solar activity.
Power
The power system on Orion enables an entirely new class of missions when compared to Apollo. Orion provides a renewable power supply using solar cells to capture energy from the Sun, where Apollo generated power using a finite supply of hydrogen and oxygen loaded at the start of the mission to harness energy as they combined in a fuel cell. Free from the constraint of a resource-limited power supply, Orion pioneers more distant crewed exploration and sustains extended mission durations.
Parachutes
Orion’s parachutes may also look similar to those used during the Apollo-era, but through testing and analysis, technicians have developed Orion’s parachutes to be lighter, their performance better understood, and more capable than Apollo’s. Engineers have figured out how to manage the stresses on the system during deployment more efficiently, decrease the mass of the parachutes by using high tech fabric materials rather than metal cables for the risers that attach the parachute to the spacecraft, and improve how the parachute is packed into Orion so they deploy more reliably.
Crew Module Uprighting System
There are a number of differences between Orion and Apollo’s crew module uprighting system (CMUS), the airbags responsible for uprighting the crew module in the case of an inverted splashdown. Due to Orion’s larger diameter as compared to Apollo, five airbags are required to upright Orion, whereas the smaller Apollo only required three airbags. The Apollo airbags were inflated using a compressor and solenoid valves, while Orion’s CMUS uses pyro-valves and helium to inflate the airbags. As a result, the Orion CMUS inflation system is lighter than the Apollo system.
