By George Mancuso

On September 16, 2014, NASA awarded Boeing and SpaceX contracts to provide crewed launch services to the International Space Station (ISS). For the same contract requirement, Boeing could receive up to $ 4.2 B, while SpaceX could receive up to $ 2.6 B.

As Boeing and SpaceX are approaching initial test flights in 2019 it is worthwhile to summarize similarities and design differences. It is interesting to note how two highly competent teams arrived at somewhat different solutions for the same mission. Both spacecraft are capsules (frustum) of approximately the same size and accommodate a crew of up to 7, and both have heatshield and parachute recovery systems. The two spacecraft utilize pusher escape systems as opposed to the traditional tractor type design. The NASA Docking System (NDS) is also used on both spacecraft. From here the designs diverge.

Dragon 2 will ride to orbit on a Falcon 9 (Block 5) whereas the CST-100 will utilize an Atlas V. The Falcon 9 LOX / RP-1 Merlin engines are optimized for atmospheric and vacuum performance (first and second stages). Two LOX / RP-1 RD-180 engines are used in the Atlas 5 first stage and two RL-10 engines LH2 / LOX for the second stage. NASA has also approved SpaceX for a load-and-go fuel procedure with astronauts on-board enabling densified LOX to be fueled.

Starliner consists of a Crew and Service Module somewhat like the Apollo Command and Service module. Starliner is battery powered and can free fly for approximately 60 hours or remain docked to the ISS with keep alive power for extended periods. The Dragon 2 configuration includes a pressurized crew section and payload trunk. The trunk has a volume and 14 cubic meters and includes solar arrays that can support one (1) week of free flight. Dragon 2 may be docked to the ISS for long durations.

Light weight Intravehicular Activity (IVA) spacesuits were developed by Boeing and SpaceX. The suits provide life support in the event of a cabin depressurization via a closed loop vehicle air supply. Both suits are designed for comfort and appearance. Boeing’s suit includes a soft helmet whereas SpaceX incorporates a light weight stylized hard helmet. Gloves are designed for use with a touch screen with either suit.

The Starliner incorporates airbags to enable a land landing. The Starliner Service Module may be reused up to 10 times. Dragon 2 lands in water. Portions of the Dragon 2 are reusable.

It will be interesting to see how the designs will influence the utilization of the two different spacecraft.

 

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