Friday, March 15, 2019

What are the differences and similarities between SpaceX's Crew Dragon and NASA's Orion?

What are the differences and similarities between SpaceX's Crew Dragon and NASA's Orion?

Crew Dragon
Mock-up of Orion
I was recently scrolling through twitter when I saw a post where this user was asking for a comparison of SpaceX's Crew Dragon vs. NASA's Orion spacecraft so i decided to write a post on this. I did a little research, and here's what I came up with. In short, although both spacecrafts have crew capable components, but their goals differ quite largely. Orion's goal is to facilitate human exploration of the moon, asteroids, and Mars, while the Crew Dragon plans to just operate as a vehicle for ISS operations. This is a very general statement, so let's get down to some specifics. 
The Orion spacecraft, developed and manufactured by NASA and the ESA, can carry up to 4 astronauts to LEO and beyond. As I said, its goal is to help reach the end mission of a human presence on Mars. Of course, it has a long way to get there, and it will be used for other missions before that such as the lunar Gateway and others like the EM-1. NASA has scheduled EM-12, a mission to orbit Mars, sometime in 2030. There is no source for what Orion would do after this mission mainly because it is too far in the future to plan anything. This is the main difference from the Crew Dragon, besides the fact that the CD is commercially made. The only plan for CD right now is missions to the ISS, with the first crewed mission, the first to launch from US soil since the space shuttle program, launching sometime this summer. Orion is the future of interplanetary travel, while CD is just acting as a transfer vehicle to the ISS. For this reason, I don't think they are comparable just yet, but for the sake of this post I'm going to talk about construction and capabilities as both. Now I know I just said that I think they aren't comparable, but I think they could be in the future. With a few upgrades, CD could do the same job that Orion will do.

Orion MPCV, or multi-purpose crew vehicle, is made up of 3 main modules. They are the Crew Module(CM), ATV-based European service module(ESM), and the Launch Abort System(LAS). The CM is the reusable transportation module that houses the crew during trips, provides storage for food and research instruments, and serves as the docking port for crew transfers. It is a frustum shape, very similar to the one used by the Apollo command modules. The CM is 16 ft 6 in in diameter and 10 ft 10 in. in length, with a mass of 19,000 lbs. It is manufactured by the Lockheed Martin Corporation. The CM uses many advanced technology, such as the Glass Cockpit control systems, an autodock feature, improved waste management and far more advanced computer systems. Also, the construction used as generic parts as possible to make the CM easier to upgrade with new technologies when they come. 
Let's move on to the ATV-based European service module, ESM. The ESM's job is to provide electricity, water, oxygen and nitrogen as well as keeping Orion at the right temperature and on course. The module is a 4 m long unpressurized cylinder which includes the main engine and tanks for gas and propellant. The main engine is the Orbital Maneuvering System Engine which will be incorporated in the ESM that will be introduced on EM-1. 
The last main module of the Orion is the Launch Abort System, or LAS. The function of the LAS is to act as an escape system in the event of an emergency. The LAS will separate from the CM using a solid rocket-powered launch abort motor. There are 2 other propulsion systems in the LAS: the attitude control motor and the jettison motor. The ACM is a thrust system which is used to position and orient the capsule. The jettison motor is part of the system that separates the LAS from the CM. Let's see how these modules compare to the Crew Dragon. 
Draco Thrusters
CD, as well as Orion, is made to be reusable for more than one mission. It is comprised of 2 main elements, the capsule and the trunk. The capsule is designed to carry crew and pressurized cargo, while the trunk is an unpressurized service module. The capsule has 3 main sections: the pressurized module, the service section and the nose cone. Near the external base of the capsule are the Draco thrusters which allow for orbital maneuvering. The trunk provides the mating interface for the Falcon 9. Once it is in orbit, the trunk expands its solar array to power the craft. This takes up half of the trunk, while the other half holds a radiator which rejects heat. The Crew Dragon is also equipped with an Environmental Control and Life Support System(ECLSS) which provides a comfortable on-board experience for the astronauts. The abort system of the CD is equipped with 8 SuperDraco engines and a series of parachutes. The CD is less intricate than Orion because of the difference in job they will perform, but they have their similarities. 
To wrap it up, Orion and Crew Dragon are 2 promising spacecraft that can both transport people and goods to their respective destinations. They vary in mostly in their production and their job, but with some changes, these craft could become similar and eventually could serve the same purpose.

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