Comparing SpaceX’s Dragon and Boeing’s Starliner ::

Boeing’s CST-100 Starliner docked with the International Space Station (ISS) Friday night at 8:28 pm EDT about 22 hours after lifting off from Cape Canaveral. Starliner joins two other American vehicles (Crew Dragon and a Cygnus-17 cargo craft) and three Russian vehicles (a pair of Progress cargo craft and a Soyuz crew capsule).

ISS visiting vehicles as of May 20, 2022

This second Orbital Flight Test (OFT-2) comes after the first attempt on December 19 which failed to dock after a series of software problems left the spacecraft in too low of an orbit forcing the Boeing to re-fly the test mission to certify it. to carry astronauts to the ISS.

OFT-2 was to launch last summer but prelaunch checks found problems with valves in the propulsion system which required an additional eight months to find and correct.

Commercial Crew Program

With the shuttle program ending, NASA knew it needed a way to the ISS from US soil. Like the many redundant technical systems aboard these vehicles, it wanted two different spacecraft capable of ferrying astronauts.

Sierra Nevada Corporation, Blue Origin, SpaceX, and Boeing to begin developing vehicles. Ultimately SpaceX and Boeing won contracts for six flights each.

Both also had significant technical challenges to overcome before getting the okay to launch humans.

Issue found during test flights

This week’s OFT-2 comes after the first attempt in December 19 where Starliner failed to dock after a series of software problems left the spacecraft in too low of an orbit forcing the Boeing to re-fly the test mission to certify it to carry astronauts to the ISS. Prelaunch checks last summer found issues with valves in the propulsion system which required eight months to find and correct.

Starliner experienced issues with two of the twelve thrusters used to maneuver in space. These problems were not unlike those SpaceX experienced in 2013 with their similarly new Dragon capsule during the CRS-2 mission when three of the four thrusters failed forcing docking with the ISS to be delayed by 24 hours.


Both companies saw thruster problems on the ground as well.

In 2018 malfunctioning valves caused fuel leaks and a fire which damaged part of the test capsule during a launch abort test. A year later a SpaceX Crew Dragon capsule was destroyed in an explosion following a hot-fire test of thrusters used in the event of an abort on the launch pad.

Each company also struggled to develop the required parachute systems according to a 2019 report from NASA’s Inspector General’s office, created as concerns grew about NASA’s reliance on Russia as delays from SpaceX and Boeing stretched to four years.

When SpaceX changed its initial plan from propulsively landing on dry land to focus to splashdown in the Gulf of Mexico, the four lightweight parachutes needed to be redesigned. This required another 15 ground tests which uncovered more problems.

Boeing also experienced problems when one of the three parachutes failed to open during a Starliner pad abort test in 2019. The problem was traced back to a simple pin that was overlooked by the close-out crew.

Comparing Dragon and Starliner

  • Starting point: Starliner is a completely new spacecraft, Crew Dragon was originally created by modifying the company’s Cargo Dragon for human certification. Crew Dragon-2 a
  • Capacity: Starliner is designed to seat seven but will be configured for five astronauts including one paying passenger. Crew Dragon was to have similar capabilities but seating changes required to prevent injuring the crew during splashdown, reduced that to four.
  • Reuse: Starliner is designed for up to 10 flights according to Boeing, Crew Dragon up to 5 flights according to Jessica Jensen SpaceX’s director of Dragon mission management. Both vehicles are partially reusable with heat shields and unpressurized service module or trunk sections
  • Turn around time: each Starliner will require 6 months between flights, SpaceX has not publicly said how long refurbishment of Crew Dragon requires but it is probably similar.
  • Launch vehicle: Starliner will launch on Atlas V and its successor Vulcan rockets but Boeing says it was designed to be “launch vehicle agnostic”. Crew Dragon was designed for the Falcon 9 rocket.
  • Flight Duration: both are designed to spend up to 210 days docked at the ISS.
  • Cost: NASA awarded Boeing a 4.3 billion contract and SpaceX $ 3.49 billion (including an extension earlier this year)
  • Landing: Starliner can land on land or, in an emergency, water. Crew Dragon lands only on water.

Boeing Starliner landing

While both capsules were originally conceived as landing on land with ocean splashdown as an emergency backup option.

SpaceX originally envisioned landing legs extending through the heat shield in a propulsive landing but as work moved forward updating the Dragon capsule to human rating, that proved to be and complex modification. While each water landings is more expensive and salt water adds some complexity to refurbishing the capsule for reuse, this decision avoided a lot of costs in designing and certifying this new capability.

Boeing stuck with plans for their new spacecraft to land on dry land and successfully touched down in the New Mexico desert following the December 2019 flight which failed to reach the ISS. Additional landing locations in Utah, Arizona, and California are also available.

The final crucial test of the OFT-2 mission is the led undocking and landing in White Sands, New Mexico on Wednesday, May 25.

What is aboard Starliner

In addition to test equipment including a test-dummy dubbed mannequin dubbed Rosie the Rocketeer and a plush Jebediah Kerman from the popular Kerbal Space Program gameOFT-2 carried more than 800 pounds of cargo including food and and supplies for the ISS crew.

Boeing also included some commemorative items including mission patches, pins, challenge coins, American flags and items from 14 historically Black colleges and universities (HCBUs). These items will be presented to organizations that contributed to the commercial crew program and returned to the HCBUs including NC A&T.

HCBU flags aboard OFT-2

This mission also carried the same mix of seeds astronaut Stu Roose carried aboard Apollo-14. “Moon trees” grown from those seeds can be seen today Cradle of Forestry in North Carolina’s Pisgah National Forest and another in the Asheville, Botanical Gardens. A descendent of one of the moon trees was planted several years ago near the walking path as it crosses the island.

Whats Next

The first crewed Starliner flight is scheduled for later this year with another five flights contracted through 2026. Boeing plans to service the contract alternating between a pair of spacecraft. A third was retired following its use in a pad abort test.

SpaceX will continue to service its contract with four capsules. Rueters reported in March that manufacturing of new capsules was halted as the company’s focus shifts to its Starship vehicle. SpaceX President Gwynne Shotwell told Reuters “We are finishing our final (capsule), but we are still manufacturing components, because we’ll be refurbishing,”


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