Spaceflight Insider

Aeroskirt added to Atlas V configuration for CST-100 Starliner

CST-100 Starliner in orbit

An artist’s rendering of a CST-100 Starliner in orbit. Image Credit: Boeing

CAPE CANAVERAL, Fla. — United Launch Alliance (ULA) and Boeing unveiled an add-on aeroskirt to the Atlas V rocket that will launch Boeing’s CST-100 Starliner capsule for NASA. It was developed after engineers encountered difficulties with aerodynamic stability and loads resulting from the difference in width between the capsule and the rocket.

The Starliner capsule is wider than the Atlas V launch vehicle on which it would sit atop. During the ascent phase, this would cause an aerodynamic dead zone just behind the spacecraft, generating drag and dangerous differences in pressure.

Atlas V CST-100 Starliner

Right below the CST-100 Starliner Service Module is an aeroskirt designed to smooth out the airflow along the integrated capsule/Atlas V stack. Image Credit: ULA

The aeroskirt would attach aft of the spacecraft, extending the Starliner Service Module’s cylindrical surface to smooth out the air flow over the integrated capsule/rocket and bring load margins back to acceptable flight levels.

“Through incredible coordination and continued innovative thinking, the collective team of NASA, Boeing and United Launch Alliance completed three wind tunnel tests in six months to investigate the aerodynamic stability of various configurations and to anchor our analytical predictions,” Gary Wentz, ULA vice president of Human and Commercial Services, said in a news release. “Based on that information, we updated the configuration for the Atlas V Starliner integrated vehicle stack.”

Wentz said this configuration is unique because it combines the Atlas V launch vehicle without a payload fairing with the Starliner capsule, resulting in different aerodynamic interactions.

According to ULA, the aeroskirt is a metallic orthogrid structure designed to be jettisoned once the atmospheric pressure during ascent gets low enough for aerodynamic forces to no longer be an issue.

Additionally, if an emergency were to occur during launch, the aeroskirt has “venting provisions to control over-pressurization if the Starliner’s abort engines are fired.”

Following completion of the Production Readiness Review, fabrication of the aeroskirt is scheduled to begin this month at ULA’s factory in Decatur, Alabama.

“Our testing indicates the solution we chose will sufficiently smooth the air flow around the vehicle during ascent, ensuring crew safety and mission success,” said John Mulholland, vice president and program manager of Boeing’s Commercial Crew Program.

The Preliminary design review for the aeroskirt was completed earlier this month (October).

This news comes after Spaceflight Insider’s previous report that the company has delayed its first operational flight of its CST-100 Starliner by an additional six months.

As such, the current plan is for an unpiloted Starliner to launch atop an Atlas V in June 2018 with a piloted test in August. Boeing expects operational missions to begin a few months later.

John Mulholland, Boeing’s vice president and program manager for commercial programs in space exploration, told Aviation Week the delays have resulted from several different challenges, all of which have been resolved or in the process of being resolved.



Eric Shear is a recent graduate from York University, honors bachelor in space science. Before that, Shear studied mechanical engineering at Tacoma Community College. During this time, Shear helped develop the HYDROS water-electrolysis propulsion system at Tethers Unlimited and led a microgravity experiment on the Weightless Wonder parabolic aircraft. Shear has worked for an extended period of time to both enable and promote space flight awareness. Shear agreed to contribute to SpaceFlight Insider’s efforts so that he could provide extra insight into interplanetary missions, both past and present.

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