More miniature satellites are launched each year, increasing the demand for smaller rockets.
Contemporary life would hardly be possible without satellites. Much of what people do on Earth today depends heavily on what’s happening far above their heads, from monitoring wildfires, deforestation and sea surface temperatures to enabling connections to new technologies mobiles like 5G in areas that are difficult to access.
A recent wave of cheaper miniature satellites being sent into low orbits of 500 to 1,000 kilometers above Earth by Elon Musk’s SpaceX and UK-based OneWeb indicates a growing trend.
Less is more
With some tracking the entire landmass of the world and providing unprecedented detail, these satellites can be the size of a shoebox or even smaller. More than 2,500 of them are expected to be launched each year on average over the next decade.
To reach space economically, small satellites often need to carpool with large rockets. The development of smaller rockets could allow faster and more personalized access to space, opening the market to a wider range of specialized suppliers.
“Small satellites can travel on large launch vehicles, but there are issues such as time to orbit because you need to reserve space well in advance and go exactly where the satellites need to go,” said Xavier Llairó, commercial director and co-founder. from Pangea Aerospace in Barcelona, Spain. “Companies launching these need access to the bespoke space.”
The Pangea-led RRTB project has been researching cost-effective ways to put small rockets that can carry up to 500 kilograms of cargo into space. The hope is to have an engine ready for flight by 2025.
The key is to find ways to reuse these microlaunchers while minimizing the impact they have on re-entry into the Earth’s atmosphere and allowing them to land safely. This would also be more environmentally friendly than using launchers only once.
“Through reuse you can reduce the investment, use less means of production and have a higher release frequency”, said Llairó.
At the moment, Europe does not have a proven method for doing this, according to RRTB, which ends this month after three years.
First section
RRTB has focused on the reuse of the first section – or stage – of the rocket, located at its base. This section provides most of the thrust just after launch, before it separates and falls back to Earth, often in the ocean. With a lighter payload, the other stages of the rocket continue to carry their payload into orbit.
But the first stage can be damaged during its high-speed descent by the Earth’s atmosphere and also by seawater. The difficulty and expense of recovering and returning the rocket to the launch site may be more trouble than it’s worth.
“When they fall into the sea, it takes a long, long time to reuse them”, said Llairó.
The answer is to find a way for the first stage to re-enter Earth’s atmosphere safely and land on a docking station near the launch site or on a floating barge, according to Llairó.
At the same time, the design of the rocket must allow it to carry a large enough payload to make the operation economically viable.
To find ways to reduce damage to micro-launchers during re-entry into the Earth’s atmosphere and landing, the RRTB team tested a scale model of a small rocket in a wind tunnel.
The ideal goal for smaller launchers, according to Llairó, is to prevent the engines from being ignited by re-entry. This would allow launchers to carry a larger initial payload by reducing the weight of fuel they need to carry.
New nozzle
The team struggled when the rocket had a traditional bell-shaped nozzle around its engine, but found more promise with a cone shape. This “aerospike” nozzle helps to spread the heat in a way that decreases the shock that the vehicle takes.
“It makes the penetration of the atmosphere smoother,” said Llairó. “This is not only true for small launch vehicles, but also for larger vehicles. It was an unexpected finding because we weren’t looking for this initially.”
While aerospikes also burn less fuel than conventional engines, Llairó said those benefits have so far been offset by engineering complexity and costs, including cooling difficulties. However, techniques such as 3D printing, which is being taken advantage of by Pangea, are making them more viable.
“Aerospike technology will change the way we access space and how we return to Earth,” Llairó said. “It’s a major enabler for rocket reuse.”
Meanwhile, he said, the engine the team plans to use will rely on biologically-derived methane as a propellant.
Research is also underway to make individual rocket parts more reusable, for example using aluminum-based material for the fuel tanks.
“You need to land most rockets safely and reuse as many of their components as possible to make things economically viable,” Llairó said.
Ready for launch
While RRTB has focused on reusing rockets, aerospace company Orbex in the UK is preparing to debut its own lightweight, eco-friendly microlauncher.
Under the PRIME project, Orbex unveiled a prototype of its 19-meter-long rocket in May last year, which will be Europe’s first full-orbital microlauncher for small satellites.
The rocket is also designed to be reusable by recovering parts that don’t burn up in the atmosphere. While the company has yet to reveal how it will do this, an Orbex spokesperson said the method would be “completely new”.
The company expects the Prime rocket to make its first launch this year, pending certain prerequisites, including the granting of a launch license.
“We have already sold several launch slots to commercial satellite providers, but we have yet to announce the date of our maiden launch,” said Orbex CEO Chris Larmour. He was also the coordinator of PRIME, which lasted three years until June 2022.
greener rocket
The rocket will use clean biopropane fuel formed as a by-product in the creation of biodiesel, which is made from sources such as used vegetable oils and used cooking oil.
This will be combined with liquid oxygen, a “cryogenic propellant”, a gas cooled below freezing and condensed into a highly combustible liquid.
Through these measures, the rocket could reduce carbon emissions by up to 96% compared to similarly sized fossil-fueled launch vehicles.
“The Orbex Prime will be the most environmentally friendly space rocket in the world, powered by a renewable biofuel,” Larmour said.
The fuel tanks are made of carbon fiber, which combines high strength with low weight.
Orbex estimates that Prime weighs about 30 percent less than traditional launchers, allowing for the kind of increased efficiency and performance crucial for small satellites. In addition, the rocket is designed to leave zero waste on Earth and in orbit.
At its Sutherland spaceport on the north coast of Scotland, the company hopes to launch up to 12 rockets a year. The port is also expected to be carbon neutral in its construction and operation.
Its relative proximity to Glasgow will help capitalize on the area’s growing space industry, with the city producing more satellites than anywhere else in Europe. Orbex believes this will provide the right setup to help players in the region get on the air.
“The satellite industry and its requirement for launchers that can put satellites into specific orbits has grown in recent years and continues to grow exponentially,” Larmour said. “This creates a huge demand for dedicated and sustainable launches.”
