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Victor Corp. recently announced that its radiation fault-tolerant DC-DC converter power modules will be used in the O3b mPOWER satellites manufactured by Boeing. The O3b mPOWER ecosystem is a constellation of Medium Earth Orbit (MEO) satellites that SES will use to deliver global connectivity services to customers around the world.

Refocusing on the LEO and MEO satellites

There are basically three main types of satellites: GEO, MEO and LEO. Geostationary satellites in Earth orbit (GEO) require fully radiation-hardened components and are therefore very expensive. Each satellite can cost up to $500 million and must last 15-20 years to be worth it. The main advantage of GEO orbits is that at an altitude of 35,000 kilometers it is possible to cover a very wide geographical area with as few as three satellites.

Medium Earth Orbit (MEO), located between 5,000 km and 12,000 km in altitude, requires a constellation of 10 to 20 satellites to achieve global coverage. Since this orbit is inside the Earth-protecting Van Allen belt, electronics vendors have the latitude to use radiation-tolerant COTS solutions.

Low Earth Orbit (LEO) typically includes a constellation of hundreds or even thousands of satellites for stable global coverage, making it the growth segment of this market in the future. With LEO, there is even more leeway to use radiation tolerant products, while the mission requirements are somewhere in the 3-5 year range.

More satellites for New Space

“Low Earth orbit missions are generally part of what we call New Space or Space 2.0. This market is lower cost than deeper space orbits and is primarily focused on increasing internet bandwidth while reducing latency,” said Rob Russell, Vice President of Satellite Business Development at Vicor.

Low transmission latency and high throughput are critical requirements for applications such as 5G, live TV, military communications, and financial trading. As many of us have experienced, satellite television transmissions are subject to a delay (latency) of a few seconds compared to terrestrial or cable transmissions. While this delay can be inconvenient during sporting events, for example, the consequences can be far worse when it affects military communications on a battlefield.

Latency issues are also very important in financial trading since even a millisecond delay can make the difference between a profitable trade and a trade with losses. In high-frequency trading, a large number of financial transactions are made with a profit that can be as low as pennies for each trade, and thus reducing latency is a big issue. The same considerations apply to the deployment of 5G technology, where massive bandwidth utilization and extremely low latency are mandatory for telecommunications, IoT and other next-generation services, such as autonomous vehicles.

Besides high bandwidth and low latency, another advantage of LEO applications is coverage, as multiple overlapping ranges can achieve full terrestrial coverage.

“Bringing broadband to where they can’t get it is a huge benefit. One of the primary goals of O3b, which is worth another three billion, is to bring high-speed internet to the many people around the world for whom it is not available today,” Russell said.

In order to achieve full coverage in LEO applications, hundreds or even thousands of satellites are required compared to only three for GEO. This means high volume commercial parts are required to reduce the overall cost. Instead of using fully radiation-hardened devices, which are expensive and always two, three or even several generations behind, modern ASICs, FPGAs and custom chips are needed. These devices need modern high-density, high-current, low-cost, high-efficiency power solutions, while maintaining some degree of radiation tolerance.

“Once a satellite is in orbit, the only energy you have comes from solar panels. Due to the limited power available, you need high efficiency in all elements of your power chain. Vicor’s high-efficiency, high-density, high-intensity solutions fit perfectly into this new spatial model,” said Russell.

Vicor Rad Tolerant Power Solutions

Today, the largest satellites use a 100V power bus, which the current Vicor solution handles. As shown in the figure to the right, the 100V that comes out of the batteries (charged by solar panels) is split to provide the two rails (0.8V at 150A max and 3.3V at 50A max) needed to power the ASICs.

The BCM isolated bus converter has a conversion ratio of three to one (or K-factor) because it takes 100 V as input and reduces it to a more suitable and efficient voltage to be regulated. The 28V secondary bus drives the VTM current multipliers, which are also ratiometric devices (1/32 and 1/8, respectively) and further reduce the output voltage to the required values.

“Our basic solution is ideal for LEO and MEO satellites using 100V buses. Our modular approach provides tremendous design flexibility allowing designers to change the bus voltage or change the rail voltage relatively easily,” said Russell.

Innovative designs, careful component selection, and extensive component and system testing ensure full tolerance to Ionizing Dose (TID) radiation and unique effect mitigation suitable for LEO and MEO missions.

Single-event effects are electronic events caused by a single highly energetic particle. For this type of test, devices under test (DUTs) are bombarded with high-energy particles to simulate what they will find in space. Rather, the total effects of ionizing doses refer to the damage caused to electronic devices by long-term exposure to radiation. It is a kind of cumulative effect, and corresponds to the radiation provided by the sun. In this case, radiation exposure over time proves that the DUTs are robust enough to withstand the maximum radiation level required for this type of mission.

Regarding the potential expansion of the product line, Russell says that along with the 100V bus voltage, the 28V bus is one of the most popular solutions, while the 50V and 70V buses will be required for specific applications. Different K-factors for VTMs will likely be provided, and solutions optimized for lower power will likely be needed as well. Some of the currently available technologies, especially BCMs, could be modified to support bi-directional power flow, improve the efficiency of the battery charging/recharging process, and reduce the amount of space taken up.

According to Vicor, the product line is well suited to serving New Space. Reliability, high current and high density are important power requirements that play a key role in New Space’s power supply.