An artist conception of the Bloostar rocket

Launching cubesats from stratospheric balloons

A Barcelona-based start-up is developing micro-rockets to launch small satellites from stratospheric balloons.

Responding to growing demand from the burgeoning nanosatellite industry, the Bloostar technology, proposed by Spanish rocket engineer and entrepreneur Jose Mariano Lopez Urdiales, would provide small-satellite operators with a greater control and choice of orbit than the currently available launchers.

“Nanosatellites today need to fly as secondary payloads, and hitchhike their way into orbit,” said Lopez Urdiales, who leads an engineering team at zero2infinity, a company he founded several years ago.

“Many new successful companies have business plans based on nanosatellites, like Skybox Imaging, but the dedicated launcher that they would need doesn’t exist yet.”

Frequently, cubesats are thrown to space from the International Space Station, having been brought up from Earth in cargo vehicles operated by the world’s space agencies like Esa and Nasa.

This procedure, however, is not only risky, as it involves the astronauts venturing out of the station to send the satellites for their missions, it also increases the cost of the satellites and precludes the use of some cutting-edge technologies.

“Building a nano-satellite can cost you as little as $10,” Lopez Urdiales explained. “But if you have to make it compatible with human space flight requirements, that would cost you maybe hundreds of dollars. You would have to invest in testing; you won’t be able to use any toxic propellants or high-energy systems such as some advanced batteries because these could put the astronauts’ lives at risk.”

Moreover, the cubesats launched by astronauts from the ISS are by default only able to follow the ISS orbit, which is not very convenient for many applications.

“If you are operating an imaging satellite, for example, you would like to have it in polar or Sun-synchronous orbits to get better images and complete coverage of the Earth’s surface,” said Lopez Urdiales.

“It doesn’t really make much sense to be launching from the ISS unless you’re getting a free ride. That’s why we are focusing on developing the Bloostar rocket, which would not only be extremely cost-effective but also allow the satellite operators to choose where exactly they want to send their spacecraft.”

The micro-rockets rely on stratospheric balloons, developed by zero2infinity with the ultimate aim to bring paying customers to the edge of space, to lift them to an altitude of more than 30km.

The balloon removes the need for the rocket to claw its way through the densest parts of the atmosphere closer to the Earth’s surface, all at minimal cost. In the stratosphere, which is where the balloon stops, the air density is so low the rocket doesn’t even need to have the traditional aerodynamic rocket shape.

“At this altitude, the rocket doesn’t have to be pointy as we don’t need to worry that much about its ability to go up,” Lopez Urdialez explained. “Instead, we can focus on how to make it return to Earth as safely as possible. Our propellant tanks, for instance, look like doughnuts because that allows the shock wave during the atmospheric re-entry to be evenly distributed over the surface to prevent excessive heating.”

Eventually, the engineer said, the Bloostar rockets should be reusable, further reducing the cost of every single nano-satellite launch.

The company says that thanks to the use of the balloon as the first stage, the hydrocarbon oxygen cryogenic rocket requires much less propellant than any commercially available alternative and is thus one of the greenest available options.

According to Lopez Urdiales, zero2infinity has received €200m in letters of interest from companies eager to purchase a ride on Bloostar for their satellites.

It was this enormous interest that persuaded the company to focus more resources into developing the nano-satellite launcher than the manned stratospheric balloon.

In September this year, zero2infinity successfully test-fired a scaled version of the Bloostar engine, and one year ago it flew an inflatable upper-stage tank on a balloon to the altitude of 27km to test the design and resilience of materials.

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