CubeSats Require Special ESD Handling Protocols for Launch Integrity — Part I

Figure 1: Tu-Pod in Space (Courtesy Amin Djamshidpour, Co-Founder Teton Aerospace)

CubeSats are relatively inexpensive when compared to traditional vehicle-size satellites. Since their inception, CubeSat spacecraft have shown functional success rates ranging from 40% to 75% for launch and deployment phases.

According to the International Journal of Aerospace Engineering, CubeSat deployment success rates now exceed 75%. In 2017, mission failures stood at 50%. Closing the gap from 25% to 0% may be achieved by implementation of electrostatic discharge (ESD) control measures.

One must ask whether NASA-STD-8739.6B, Section 7, protocols for ESD compliance in low relative humidity (RH) and extreme conditions are sufficiently in place to ensure best value for the taxpayer.

Since 2022, the manufacture of vertical transport field effect transistors (VTFETs) has exponentially increased transistor count for devices, now commercially available. Apple’s M1 Ultra contains 114 billion transistors compared to Intel’s 4004 microprocessor introduced in 1971 (see Table 1) at 2,300 transistors.

GOES-R Satellite weighs 6,299 lbs., compared to a CubeSat 1.0 at 3 lbs., as shown in Figures 2 and 3.

Due to microprocessor densification via VTFET-manufactured ESD-sensitive devices (ESDS), a swarm of 5 to 8 CubeSats in less than 10 years could replace a 2 to-3-ton satellite. Traditional ESD protective mechanisms for ESDS will require strengthening of ESD procedures in the EPA to safely handle Class 0Z (<±50 volts) components.

Without doubt, speed kills with microprocessor densification. Relying solely on internal ESDS protection mechanisms without an ESD Control program. Moreover, the author has reviewed CubeSat design specifications that incorporate ESD-sensitive devices, and often these requirements have overlooked ESD procedures to safeguard Class 0Z devices.

JPL has taken cleanliness and ESD control for their interplanetary CubeSats to a different level by redesigning a dedicated 1,250 square foot room — comparable to a modern high bay inspired by Moore’s Law — from an existing program. Many governmental, university, and commercial SmallSat manufacturers appear to have overlooked ESD procedures during CubeSat construction by using desktop or non-flight hardware surfaces without implementing static control safeguards.

CubeSat builds placed on charge-generating Plexiglas or Lexan platforms can facilitate field-induced model (FIM) discharges. Incorporation of an ANSI/ESD STM4.1 approved work surface (Figure 4) is required to protect today’s flight hardware Class 0Z devices at <±50 volts (see Table 2).

Adherence to static control protocols in compliance with NASA-STD-8739.6B, Section 7, is mandatory when building CubeSats. NASA-STD-8739.6B, Section 7, and MILSTD- 2073, appliey during test, inspection, transport, and handling of electronic parts, assemblies, and equipment susceptible to ESD damage greater than or equal to 100 volts HBM, 200 volts CDM, and 35 volts on isolated conductors.

NASA-STD-8739.6B, Section 7, along with the prime contracting community, takes precedence over other Industry Standards for ESD integrity in low RH and extreme environmental conditions.

An unfounded belief is that some commercial off-the-shelf (COTS) components are not Class 0Z. Classification for ESD-sensitive EEE parts has been equally applied to COTS and government off-the-shelf (GOTS).

COTS are ready-made and cheaper to use, whereas GOTS are intended for internal use by the US Government. To comply with NASA-STD-8739.6B, Section 7, one must have technical justification to downgrade practices or obtain a waiver.

Product qualification of ESD materials must conform to NASA-STD-8739.6B, Section 7, using traceable technical data, in-house or third-party testing with instrumentation specified by ANSI/ESD Standards or Standard Test Methods.

For in-house qualification, the on-site qualifier must conduct testing of ESD materials at 0% RH in support of NASA’s ongoing academia-funded CubeSat programs for low earth orbit (LEO) and deep space exploration.

For aerospace and defense, it is not uncommon to build and assemble products in Class A (<±35 V) ESD protected areas. This is illustrated in Figures 4 and 6.

An ANSI/ESD STM4.1 workstation is certified annually with periodic verification as outlined in the agency’s ESD Procedures.

Certification labels are affixed to the work surface, ionizers, flooring mat, static control chair, soldering iron, wrist strap monitor, and proximity voltage sensing antennas. Quantitative data must be recorded rather than using simple pass/fail statements.

As illustrated (Figure 7), the operator, engineer, or scientist gowns up and tests the ANSI/ESD S1.1 grounded wrist strap. The wrist strap is connected to ground; the cleanroom ANSI/ESD STM15.1 approved nitrile gloves are donned after turning on the ionizer.

In this case, an ESD Type 1 moisture barrier bag is then opened, housing a Tu-POD circuit card. Upon completion, the static ESD sensitive device (circuit card) is placed into a Type I bag (Figure 9).

When CubeSat manufacturers handle Class 0Z items (<±50 volts HBM), additional mitigation techniques should be adopted:

1. Maintain RH between than 40% and 60%, and monitor RH in the EPA
2. Use groundable ESD garments (overalls) with elastic wrist cuffs
3. Use steady-state DC ionization with offset voltage <±35 V
4. Use both dual-cord audio jack wrist strap and ESD safe shoe or sole grounding straps
5. Operators seated in ESD chairs must wear wrist straps
6. Qualify all ESD protective packaging before use on ESD work surfaces
7. Remove all non-process insulators from the work area

Special Recognition to Amin Djamshidpour, Co-Founder, Teton Aerospace, amin@tetonsys.com.

REFERENCES

1. NASA-STD-8739.6B, Section 7, For the Development of an Electrostatic Discharge Control Program for Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices), ESD Association Standard, 31 July 2014.
2. ANSI/ESDA/JEDEC JS-001, For Electrostatic Discharge Sensitivity Testing Human Body Model (HBM) Component Level, ESD Association Standard.
3. ANSI/ESDA/JEDEC JS-0002, For Electrostatic Discharge Sensitivity Testing Charged Device Model (CDM) Device Level, ESD Association Standard
4. NASA STD 8739.6; 6.1 TEMPERATURE AND RELATIVE HUMIDITY (RH)
5. MDA LESSONS LEARNED ADVISORY, MDA-LL-2016-0018 February 2016, Keith Peterson, Ph.D.
6. Illustration A; Tu-Pod in Space Courtesy Amin Djamshidpour, Co-Founder Teton Aerospace