The New Space Frontier: Why VLEO is an Emerging Trend
About new perspectives of new Very Low Earth Orbits: cheap high-resolution images, minimal signal loss for telecom, and even efficient space debris management.
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Very Low Earth Orbits (VLEO) are orbits at ~180-300 km altitudes. VLEO opens new perspectives: cheap high-resolution images, minimal atmospheric signal loss, and even efficient space debris management. Analysts forecast multiple growth in demand for these orbits in the coming years. However, operating in these orbits requires innovative solutions, such as low-thrust engines and new materials. Let's explore why VLEO It's so trendy and interesting now!
What is VLEO?
Regular spacecraft and satellites fly at altitudes higher than 300-350 km. For example, the ISS flies at an altitude of 450 km. Very-low orbits are defined as those below 300 km. Some companies are planning to launch satellites to lower altitudes, such as 250, 200, and even 180 km, which are classified as VLEO.
The main difficulty in such orbits is atmospheric drag. Although the official boundary of space is the Karman line at 100 km, atmospheric influence remains significant even at altitudes of up to 1000 km. Therefore, for example, the ISS has to make orbit maintenance maneuvers 1-2 times a month, at an altitude of 450 km. Of course, the ISS is a massive structure, but still, these figures are indicative. At altitudes of 150-300 km, the spacecraft is significantly affected by the atmosphere, causing it to de-orbit (will go down and burn up in the atmosphere) within 2-4 weeks. Because of the significant influence of the atmosphere, the key aspect of the satellite's life in this orbit will be to maintain orbit by propulsion.
Why is VLEO So Important?
Reducing the orbital altitude allows several preferences for some satellite missions:
For Earth Observation, the closer to the Earth, the better quality photos with simpler optics we can get.
For communications and telecommunications lower orbits allow the signal to travel less through the atmosphere, which reduces signal loss (because the distance from the ground station receiver to the satellite is reduced many times over. This includes the signal traveling through fewer layers of the atmosphere). This means that you can get the same signal strength with smaller antennas, which also enables making smaller payloads on the satellites and compact devices on Earth.
Reduced radiation background due to the proximity to the Earth's magnetic field, also part of the radiation will be taken away by the denser atmosphere than in LEO orbits. This allows the use of less resilient components. It is the radiation resistance that significantly increases the cost of spacecraft.
One needs less fuel to reach the orbit so it will be cheaper to launch satellites to this orbit, but on the other hand, requires propellant to maintain orbit. However, this orbit is now atypical for launches, so at the first stages of its operation launches to it may cost even more, but gradually the situation will level out.
One doesn’t have problems with space debris since even in the case of loss of a satellite it will fall on earth within 1 month (or even less).
Compare two images with the same optics shot from VLEO and LEO. Deimos-2 image over Qatar. Credit: Deimos Why Now?
Interest in VLEO has been increasing significantly in recent years. For example, Google Scholar cataloged documents mention that VLEO grew from 10 in 2010 to 160 in 2021 surpassing LEO.
The number of mentions of VLEO in Google Scholar. Credit: Springer Recently, the European Commission has funded the DISCOVERER program activity, led by the University of Manchester. It's a research program, resulting in the 1st Symposium on Very Low Earth Orbit Missions and Technologies and 8 direct peer-reviewed publications (it’s interesting to read). There are a lot of tasks to be researched in this project: aerodynamics of such orbits, air drag research, improvement of low-thrust engine technologies, control specifics, and others.
But why has this Niche begun to be explored now?
First of all, it is connected with the development of satellite manufacturing technologies. Nowadays, low-thrust engines are being actively developed. Another recent trend in astronautics is multi-satellite constellations. Because classical chemical jet propulsion is inefficient in space, low-thrust engines are often used for orbital maintenance and maneuvers. You can read about them in our article series here (jet propulsion overview) and here (overview of Low-Thrust engines). As the number of satellites in space (including within constellations) increases, the need for low-thrust engines increases. As a consequence, more and more companies are working in this direction, more such engines are developed and they are becoming more technologically advanced and efficient. This opens up opportunities for VLEO, as traditional chemical propulsion systems prove inefficient at such altitudes.
Air-breathing engines, which use atmospheric molecules as propellant, significantly extend the service life of spacecraft at low altitudes without requiring additional fuel delivery. These engines collect atmospheric molecules through specially designed air intakes optimized for the rarefied upper atmosphere. The collected molecules are ionized inside the engine (e.g., using a plasma source). The ionized molecules are accelerated by electric or magnetic fields, providing jet thrust. This approach is not effective at LEO because the atmospheric density is significantly lower, so the propellant is brought in from Earth. On VLEO, air-breathing engines are similar to an airplane engine, which takes a working body from the atmosphere and ejects it to generate thrust.
Working principle Air-Breathing Electric Propulsion Other, non-air breathing low-thrust engines - ion, plasma, Hall effect, and others - are also being considered for use in these orbits.
Among other things, the growth of interest in VLEO was influenced by the development of Cubesat technology, which has become fashionable over the last 10 years. Modern satellites are now smaller and lighter thanks to compact, energy-efficient components. These light engines are more influenced by the atmospheric drag, so it is important to use small engines to counteract this drag.
Moreover, an additional incentive to develop satellites on VLEO is space debris limitations. In VLEO, satellites will deorbit rather quickly with their engines off. No additional costs are needed to remove debris from these orbits, unlike LEO, where it is often necessary to spend fuel for debris re-entry into the atmosphere.
What are the Main Challenges of VLEO?
Of course, first and foremost, efficient low-thrust engines are needed to level out atmospheric drag, as discussed above.
Although we have been flying into space since 1957, we still know our atmosphere rather poorly. Understanding current atmospheric parameters, particularly its density, is critical for predicting satellite trajectories. At VLEO altitudes, where the atmosphere is substantial - the task becomes even more important. If you miss the moment of malfunction, the satellite will quickly descend into an orbit from which it will take a lot of energy to get back to the nominal orbit.
For example, not so long ago there was a case of loss of 40 Starlinks, which did not have time to maintain orbit, because the atmosphere became more dense during the solar storm. As a result, they fell from orbit and burned up in the atmosphere. The atmosphere is actually changing very dynamically and change of its density depends on many factors. We wrote more about it in this article.
Therefore, it will be necessary to accurately measure the parameters of the satellite motion and predict the atmosphere. This is an interesting scientific task.
Due to the same influence of the atmosphere, the control of the vehicle's orientation (rotation around its axis) also changes. Usually, this is done either by reaction wheels or low-thrust engines. The atmosphere brings in its specificity and more effective controls are needed to resist the aerodynamic flow, oscillations are possible, etc. This task needs to be solved. Interestingly, satellites may then have wings and other interesting designs for better control due to the dense atmosphere. Also, it will be critical to have the most aerodynamically efficient shape of the satellite. So perhaps future satellites on VLEO will look like rockets or jet airplanes.
Another interesting problem is atomic oxygen in the atmosphere. Atomic oxygen is present in noticeable amounts in the upper atmosphere at VLEO altitudes. The high chemical activity of oxygen causes corrosion and degradation of satellite materials. Therefore, it will be necessary to use special protective coatings.
It will also be necessary to investigate the thermal balance of the satellite. Due to the significant influence of the atmosphere in VLEO orbits, heating of the satellite due to friction with the atmosphere may occur.
Powering the vehicle will also be an interesting challenge. On the one hand, low-thrust engines require high power supply costs. On the other hand, large solar panels are ineffective at such orbits, because due to the influence of the atmosphere, they will slow down the spacecraft like a parachute, which will cause a descent from orbit. Therefore, there will be limitations on the size and shape of the solar cells, so calculating the energy balance will be a key challenge for such satellites.
Challenge: Access, Coverage, and Revisit. Due to decreasing flight altitude, Earth coverage and access from ground stations are decreasing. This reduction in communication windows with ground stations will affect the total amount of data uplink/downlink the communication channel, which may cause additional difficulties.
However, it should be noted that all these are technical difficulties that the engineers are already working on. As the saying goes - designing a rocket starts with the engines - the same saying applies to VLEO satellites. Having efficient low-thrust engines, it will be very easy to solve other problems.
VLEO Companies and Startups
Several companies and organizations are actively researching and developing technologies to operate at VLEO, focusing on building satellites, propulsion systems, and solutions to overcome the unique complexities of this orbital zone:
Thales Alenia Space delivers cost-effective solutions for telecommunications, navigation, Earth observation, environmental management, exploration, science, and orbital infrastructures. ESA funds 2.3 million euros for a demonstrator satellite for VLEO. The company secured the funds in partnership with QinetiQ, a British aerospace company planning to provide altitude and orbit control systems, among other capabilities for the platform.
Redwire announces a second VLEO satellite platform called Phantom. Phantom is being developed for the European Space Agency’s Skimsat mission, on which Redwire is partnered with Thales Alenia Space, and is now being offered for European and international customers.
Redwire announced a contract to serve as prime mission integrator for a DARPA satellite with a novel propulsion system for very low Earth orbit (VLEO). SabreSat, Redwire’s VLEO satellite for government intelligence, surveillance, and reconnaissance missions, will house “air-breathing” electric propulsion systems being developed through DARPA’s Otter program. DARPA’s Otter program funds the development and demonstration of “air-breathing” electric propulsion technologies to enable extended satellite operations at altitudes between 90 and 250 kilometers.
Albedo raises $35 million for commercial Very Low Earth Orbit constellation.
Colorado-based Electric Propulsion Laboratory Inc. announced a DARPA Otter contract with a maximum value of $6.7 million. Under the contract, EPL plans to further development of its Air Breathing Electric (ABEL) engines. Similarly, California-based Phase Four announced a $14.9 million DARPA Otter contract in April 2024 for an “air-breathing” electric propulsion system for extended satellite operations at altitudes ranging from 90 to 450 kilometers.
AFWERX has awarded $1.25 million to LeoLabs for a contract to demonstrate a new radar system aimed at tracking objects in VLEO.
Michigan-based Orbion Space Technology builds Aurora, a new type of propulsion system that employs what are known as Hall-effect thrusters, which accelerate propellant using an electric field. The company began shipping the system to customers in 2023. For less than 0.5 kg of added mass, a spacecraft can deliver up to two Newtons of thrust. Orbion claims the efficiency of Aurora thrusters on VLEO.
Viridian develops on air-breathing electric propulsion (raised about $2.5 million in pre-seed), Kreios Space, the Very Low Earth Orbit satellite company, closes a Pre-Seed round of €2.3M.
An early-stage US startup DeepSat offers satellite imagery of a selected area every 15 minutes using a constellation of satellites on VLEO.
We spoke to Hayk Martirosyan (Co-Founder & CTO at DeepSat) and got his opinion on the prospects for VLEO:
“As technology evolves, VLEO is poised to become a key enabler for the next generation of satellite services. Advances in materials science, propulsion systems, and satellite miniaturization will likely overcome many of the current challenges, making VLEO a competitive option for both commercial and scientific missions.
VLEO is an exciting frontier for satellite technology, offering unique advantages in image resolution, communication speed, and cost efficiency. As companies and governments look for new ways to leverage space technology, VLEO will likely play a crucial role in shaping the future of global connectivity and observation”.
As we can see, there are few companies, but they offer quite a wide range of solutions, from radar to complete satellite imagery.
VLEO offers exciting new opportunities for science, communications, Earth observation, and other missions. Despite many technical challenges - from atmospheric drag to the effects of atomic oxygen - modern technologies such as low-thrust engines, compact satellite systems, and new materials make it possible to overcome these difficulties.
Interest in VLEO is already stimulating research and investment, and the development of new solutions promises to make this area of space available for widespread use.
It's interesting how space technology is evolving. 20 years ago it was hard to imagine satellites in such orbits! We at Space Ambition believe that investing in deep technology can lead to the creation of entire new niches, as it has happened with low-thrust propulsion and VLEO. And perhaps soon satellites will fly at altitudes of 100 kilometers using new engines.
What do you think about using VLEO? Write in the comments or email us via hello@spaceambition.org!
