Radiation Testing for BotBlox Hardware for Space (LEO, MEO and GEO)

Ethernet has become hugely popular for countless industries due to it’s scalability and ubiquity; Space is no exception. Next generation satellites have to lower launch costs which means reducing weight,and size while retaining performance in challenging environments. While nearly all BotBlox hardware is tested to MIL-STD-810H standards for environmental resilience - encompassing high and low temperature, temperature shock, vibration, mechanical shock, and altitude - space environments add an extra layer of complexity: radiation.

Understanding Radiation Effects

In space, electronics are subject to different types of radiation from solar flares, cosmic rays, and trapped particles in Earth’s magnetosphere. Radiation can affect hardware in a variety of ways, sometimes causing immediate failures or progressive degradation over time. Testing for radiation tolerance can be somewhat of a “black art” because of the many pathways radiation can take to disrupt or damage electronic components. Common test types include:

1. Total Ionizing Dose (TID)

• Assesses the cumulative effect of ionizing radiation (e.g., gamma rays) on electronic components.

2. Single Event Upset (SEU)

• Evaluates recoverable malfunctions caused by a single high-energy particle interacting with internal logic or memory.

3. Single Event Latchup (SEL)

• Measures irreversible “latchup” events which are permanent failures triggered by a single energetic particle that effectively shorts internal transistor structures.

4. Displacement Damage (DD)

• Gauges performance degradation caused by protons or heavier ions physically displacing atoms in the semiconductor lattice.

These tests (and others) build a comprehensive understanding of how hardware behaves under various radiation-induced stressors.

BotBlox and TID Testing

At BotBlox, our first step toward space qualification is Total Ionizing Dose (TID) testing. TID is often the baseline for assessing whether a component can handle a certain threshold of radiation over its operational lifetime.

• Radiation Source
  We used a Cobalt-60 source to subject our devices to gamma rays. This is a common method for simulating the total ionizing radiation environment.

• Dose Levels
  We tested up to 20 krad[Si][Si][Si] (kilo-rads of silicon). This included incremental exposures at 1, 5, 7, 10, 12, and 20 krad[Si]. Generally, anything above 10 krad[Si] demonstrates a good baseline for non-radiation-hardened hardware.

• Products Tested
  Two products were subjected to TID testing:

1. SwitchBlox Rugged – A bare board design.

2. Puck Mini – A more enclosed product providing some inherent shielding.

• Relevance to Orbit
  The amount of radiation a device encounters depends on orbit altitude, inclination, and the amount of shielding. The graph below compares TID levels for different orbital regimes under various shielding thicknesses. Puck Mini’s enclosed design may benefit from additional radiation protection compared to the open-air SwitchBlox Rugged.
  

Total Ionizing dose levels for various orbit levels, according to aluminium shielding thickness. 10KRad[Si] corresponds to 10⁴ on the graph above. SwitchBlox Rugged was tested without any shielding, whereas Puck mini inherently has around 1mm of Aluminium shielding between the radiation source and the main semiconductors. The pink line shows the maximum level we tested to. Thus if SwitchBlox Rugged passes at 20KRad[Si], this implies it is suitable for usage in Low Earth Orbit (LEO) with around 0.3mm of shielding. Whereas for Geostationary orbit (GRO), it would need more like 9mm of Aluminium shielding. 

 

Placement of SwitchBlox Rugged and Puck Mini next to the four Cobalt-60 Sources

Test Procedure

1. Pre-Irradiation Baseline
   Both devices were tested at 0 Krad[Si] to establish their baseline performance

2. Incremental Irradiation
   The samples were exposed to progressively higher doses of radiation while powered off, at intervals of 1, 5, 7, 10, 12, and 20 krad[Si][Si][Si].

3. Post-Irradiation Testing
   After each exposure, the devices were powered on and subjected to a full RFC2544 benchmark test.

What is RFC2544?

RFC2544 is a standardized methodology for benchmarking the performance of network devices such as switches and routers. It typically measures parameters like throughput, latency, frame loss, and back-to-back frames to provide a comprehensive performance profile. By comparing RFC2544 test results before and after irradiation, we can detect any performance degradation attributable to radiation. 

Test Results

Below are the summarized findings at 0 krad[Si] and 20 krad[Si]. The key takeaway is that no discernible performance difference was observed in throughput, latency, or packet handling across all tested doses. This outcome is highly encouraging - both SwitchBlox Rugged and Puck Mini functioned as normal even at cumulative doses well above 10 krad[Si][Si][Si].

SwitchBlox Rugged (BB-SWR-G-1)

Throughput Test

SwitchBlox Rugged TID = 0KRad[Si] (No Radiation), Throughput Test

  

SwitchBlox Rugged TID = 20KRad[Si], Throughput Test

Latency Test

SwitchBlox Rugged TID = 0KRad[Si] (No Radiation), Latency Test

 

 

SwitchBlox Rugged TID = 20KRad[Si], Latency Test

Puck Mini (BB-PUK-B-1)

Throughput Test

 

Puck Mini TID = 0KRad[Si] (No Radiation), Throughput Test

 

Puck Mini TID = 20KRad[Si], Throughput Test

 
Latency Test 

Puck Mini TID = 0KRad[Si] (No Radiation), Latency Test

 

Puck Mini TID = 20KRad[Si], Latency Test

Analysis and Limitations

This successful TID test demonstrates a promising level of resilience for our Ethernet hardware in space-like radiation environments. However, it is important to recognize that TID alone does not guarantee full radiation tolerance. Single Event Effects (SEE) including Single Event Upset (SEU) and Single Event Latchup (SEL), can still jeopardize system stability or lead to permanent failures, especially in the harsh radiation environment of higher orbits or long-duration missions.

Future Steps

To achieve a more complete radiation qualification, we plan to:

1. Conduct SEE and SEU Tests
   Understand how single high-energy particles might induce bit flips or latchups in our designs.

2. Explore Displacement Damage
   Assess how our hardware withstands proton or heavy ion impacts over time, which can degrade performance or lead to latent failures.

3. Long-Duration Testing
   Prolonged life testing at multiple dose rates and real-space conditions to further validate survivability in orbit.

Conclusion

Ethernet holds immense potential for space-based applications, owing to its flexibility, ubiquity, and robust network performance. Our initial TID testing on BotBlox products suggests these devices can tolerate moderate cumulative radiation doses without measurable performance degradation. While this marks an encouraging milestone, further radiation testing, particularly SEE and SEU, remains crucial before our hardware can be fully qualified for space missions.

By continuing to invest in a comprehensive suite of radiation tests, BotBlox aims to deliver rugged Ethernet solutions capable of thriving in the unforgiving environment of space.

If you'd like access to the full test results, please get in touch with us at info@botblox.org.

References

• MIL-STD-810H: Environmental Engineering Considerations and Laboratory Tests

• RFC2544: Benchmarking Methodology for Network Interconnect Devices
  

• Studying the Total Ionizing Dose and Displacement Damage Dose effects for various orbital trajectories