DARPA plans to dispatch satellites to 'spaceship graveyard'

The potentially disastrous barrier to satellite mobility is the atmosphere of the Earth.
Baba Tamim
Representational image: Space junk around Earth's orbital levels.
Representational image: Space junk around Earth's orbital levels.

Petrovich9/iStock 

The U.S. state's Defense Advanced Research Projects Agency (DARPA) intends to send satellites "where people send their spacecraft to die."

The research and development division of the Pentagon is investigating satellite advantages at a distance that most space companies try to avoid, according to a Bloomberg report published on Wednesday.

The very low Earth orbit (VLEO) radius is home to a cemetery of defunct spacecraft that satellite operators sent into space to burn up upon re-entry. "You're essentially hanging out in the area where people send their spacecraft to die," according to Caleb Henry, a senior analyst at space analytics firm Quilty Analytics.

Due to its propensity to destroy technology, Henry claimed that VLEO is a "self-cleaning orbit." Thus, it is also known as the "disposal orbit." To navigate the debris, operators "have to keep an eye out for derelict spacecraft that others have abandoned or are actively in the process of disposing" of.

There is a 250 km-deep development gap because space companies cannot launch the same spacecraft in VLEO as they can in other orbits. The purpose of the DARPA is to stimulate innovation in the commercial sector.

Anything below 280 miles (450 kilometers) is considered to be a very low Earth orbit by DARPA. Henry estimates that the lowest limit is about 124 miles (200 kilometers); however, there is no precise starting point for it.

Why take the risk?

Government and private satellites clog up space, especially in low Earth orbit (LEO) levels. Compared to satellites in VLEO, DARPA claims that there are fewer dangers of radiation damage and accidents with space junk in those orbit levels.

VLEO's proximity to Earth offers advantages worth examining, as per the paperwork for a future contract from DARPA, including improved image performance and more precise geographic positioning systems, Bloomberg cited.

DARPA seeks spacecraft that can function there if sensors and cameras work more effectively at altitudes lower than LEO- low Earth orbit.

The agency's November 7's classified event for potential Daedalus program (a program to expand the sustained use of the VLEO region for future spacecraft) vendors will probably reveal more about what the organization anticipates from its three-phase research and development (R&D) contract.

Daedalus is anticipated to last for at least 51 months and will consist of many awards made under accelerated "other transaction" authority (OTA).

OTA procurement enables organizations to fund R&D initiatives and purchase specific products and services more swiftly in accordance with conventional federal acquisition guidelines.

DARPA has made no comments except what's included in the solicitation.

Orbital limitations

There are unique challenges associated with operating in VLEO, such as heightened drag and the impact of atmospheric oxygen.

Another potentially disastrous barrier to satellite mobility is the atmosphere of the Earth. A specific amount of propulsion, which translates to fuel, is needed to overcome aerodynamic drag to prevent spacecraft from slowing down and de-orbiting.

"Whatever fuel they need, they'll need to carry a lot of it," said Bonnie Triezenberg, senior engineer at RAND, an American nonprofit global policy think tank.

But only if space companies can figure out how to achieve propulsion in such a thin atmosphere will the expenses of storing and continuously burning fuel become an issue, according to Triezenberg.

The sensors and equipment on current satellites are not intended to function when the thrusters are active.

Existing satellites and other spacecraft are made of materials that can be harmed by highly reactive atmospheric oxygen, necessitating new materials and techniques for system protection for prospective VLEO operators.

Any object entering a VLEO orbit must be optimized for the extremities of space "but also for the extremes of Earth's upper atmosphere," said Henry.

Benefits for science in VLEO?

Gaining a better understanding of the nature of propulsion, discovering how to travel in an orbit that was formerly thought to be impractical, and using that knowledge to spur future innovation, are exciting benefits for the science of resolving the issues with lower orbit, according to Triezenberg.

Government and commercial satellite operators may find it intriguing to capture sharp images using smaller and less expensive cameras than those necessary for LEO or geostationary orbit.

Because of VLEO's close view of Earth, their operators must decide whether to focus on a small portion of the globe or deploy more than one satellite to cover a large area.

"If you imagine that the satellite is a flashlight and the Earth is a wall, the closer you hold the flashlight to the wall, the less of that surface you're going to see," said Henry.

"You have the potential to get really high-quality images, but you're also looking through a soda straw."

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