Credit: United Launch Alliance (ULA)


The Department of the Air Force Rapid Capabilities Office, in partnership with the U.S. Space Force, is scheduled to launch the sixth mission of the X-37B Orbital Test Vehicle (OTV-6) on May 16 from Cape Canaveral Air Force Station, Florida.

Encapsulated X-37B Orbital Test Vehicle for U.S. Space Force-7 mission.
Credit: Boeing

“This sixth mission is a big step for the X-37B program,” said Randy Walden, Director and Program Executive Officer for the Department of the Air Force Rapid Capabilities Office. “This will be the first X-37B mission to use a service module to host experiments. The incorporation of a service module on this mission enables us to continue to expand the capabilities of the spacecraft and host more experiments than any of the previous missions.”

Naval Research Laboratory (NRL) has pioneered “sandwich” modules that are far more efficient for space solar power.
Credit: NRL/Jamie Hartman

On the beam

One experiment that was announced by the Air Force is from the U.S. Naval Research Laboratory (NRL), an investigation into transforming solar power into radio frequency microwave energy “which could then be transmitted to the ground,” explains the release from the Secretary of Air Force Public Affairs.

In a subsequent statement from the Air Force, Air Force Secretary Barbara Barrett was attributed to have said — but not a direct quote — that the NRL experiment “will attempt to transform solar power into radio frequency microwave energy and then transmit the energy to Earth.”

NRL’s Paul Jaffe, the Innovation Power Beaming and Space Solar Portfolio Lead, explains: “The experiment is not beaming microwave energy anywhere,” he told Inside Outer Space in an exclusive interview.

“The focus of the experiment on X-37B is not establishing an actual power-beaming link. It is more on the performance of the sunlight to microwave conversion.”

NRL’s Paul Jaffe holds a module designed for space solar power in front of a customized vacuum chamber used to test the device.
Credit: NRL/Jamie Hartman


The experiment itself is called the Photovoltaic Radio-frequency Antenna Module, PRAM for short.

PRAM is a component of what would be a modular space solar satellite, Jaffe adds. PRAM is an outgrowth of a decade of work at NRL that includes developing “sandwich” modules where one side receives solar energy with a photovoltaic panel, electronics in the middle convert that direct current to a radiofrequency (RF), and the other side has an antenna to beam power away.

However, the PRAM, while it does generate RF energy, that energy does not go to an antenna due to a potential for interference with other X-37B-carried payloads. To be measured is how the PRAM is performing from an efficiency standpoint and also a thermal performance standpoint, Jaffe said.

More experiments

Secretary of the Air Force Barrett explains in the press statement: “Demonstrating the department’s innovation, this X-37B mission will host more experiments than any prior missions. This launch also demonstrates the department’s collaboration that pushes the boundaries for reusable space systems.”

X-37B readied for 6th mission of the space plane program.
Credit: Boeing

This will be the first X-37B mission to use a service module to host experiments. The service module is an attachment to the aft of the vehicle that allows additional experimental payload capability to be carried to orbit.

Along with toting NRL’s PRAM into Earth orbit, this flight of the X-37B will deploy the FalconSat-8, a small satellite developed by the U.S. Air Force Academy and sponsored by the Air Force Research Laboratory to conduct several experiments on orbit.

The FalconSat-8 is an educational platform that will carry five experimental payloads for the  United States Air Force Academy (USAFA) to operate.

In addition, two NASA experiments will be included to study the results of radiation and other space effects on a materials sample plate and seeds used to grow food.

X-37B handout.
Credit: Boeing

Milestone-setting space plane

Here’s a roster of the milestone-setting X-37B missions as told to Inside Outer Space by Major Will Russell, U.S. Space Force spokesperson at the Pentagon.

OTV-1 launched on April 22, 2010 and landed on December 3, 2010, spending over 224 days on orbit.

OTV-2 launched on March 5, 2011 and landed on June 16, 2012, spending over 468 days on orbit.

OTV-3 launched on December 11, 2012 and landed on October 17, 2014, spending over 674 days on-orbit.

OTV-4 launched on May 20, 2015 and landed on May 7, 2015, spending nearly 718 days on-orbit.

OTV-5 launched on September 7, 2017 and landed on October 27, 2019, spending nearly 780 days on-orbit.

X-37B hangar at Kennedy Space Center.
Credit: Michael Martin/SAF


The first four missions launched from Cape Canaveral Air Force Station, Florida thanks to an Atlas V booster.

The fifth mission launched from Kennedy Space Center on a SpaceX Falcon 9 launcher.

OTV-6, also called USSF-7 for the U.S. Space Force, will be launched atop an Atlas-V 501 booster.

OTV-1, OTV-2, and OTV-3 missions landed at Vandenberg Air Force Base, California, while the OTV-4 and OTV-5 missions landed at Kennedy Space Center, Florida.

Total time on orbit for all five previous missions is 2,865 days – or 7 years and 10 months, Russell adds.

Leave a Reply