The high-reliability markets (space, aerospace, military, etc.) are changing as commercial entities are successfully venturing into space and paving the way for the future.
Higher volume satellite constellations in low earth orbit are driving a requirement for increasingly cost-effective components. TT Electronics' New Space Electronics® team offers a solution that delivers reduced screening but fully traceable and proven space-grade heritage.
This article aims to explore what this means specifically for resistive component technology and component standards. It also explores the suitability against radiation effects in thin film resistor technology, which becomes an important factor when operating in space environments, i.e., NiCr networks vs TaN Film networks against total ionising dose radiation (TID).
New Space: Gaining Momentum Again With Newer Technologies
What is “New Space”?
The term “New Space” ironically isn’t that new. The name has been in existence and used since the early 1980s. It came about to describe companies starting to develop space systems capable of reaching outer space without assistance from government space agencies such as NASA. This activity and independent development gave rise to a significant shift in U.S. policy favouring private space activity. This resulted in the landmark Commercial Space Launch Act of 1984.
The idea is that NASA and other large government based space agencies are bureaucratic and slow. By empowering private space activity, technology moves faster; more competition is introduced, further improving the technology. Great examples of private space companies that have seen great successes within the last few years include SpaceX, Blue Origin and the Space Frontier Foundation.
Now we know the term “New Space” has been around for a while; why is it now gaining momentum again and being used more frequently.
Quite simply, it is because of the success of the aforementioned private space companies. As private companies have emerged and have been making significant breakthroughs for the private sector, it has highlighted a market gap.
The tables have turned, and now NASA themselves buy privatised space technologies and launches.
So what does this all mean?
It is an extraordinary time to witness seeing more rapid development and exploitation of newer technologies in space.
Subsequently, with the advent of newer technologies being adopted more readily under a New Space ideology, it raises questions about what component standards should be used.
Traditional Versus New Space Opportunities
Before more commercialised technologies such as mobile phones and laptops were developed, aerospace and space electronics consumed a large proportion of the semiconductor fabrication manufacturing. Therefore, at this time, aerospace and space electronics dominated the development of semiconductor manufacturing.
In the present, where so much of the semiconductor fabrication manufacturing is dominated by commercial and automotive electronics, the aerospace and space electronics market has little influence on the new semiconductor devices developed and qualification standards used. Therefore newer, more sophisticated devices offering advantages over older devices are mostly qualified for commercial and automotive use only.
Of course, technologies are improving all the time. The more times you repeat a process using the same processing techniques, you would expect the accuracy to improve over time from a series of incremental learnings and optimisations.
This consequently led to the aerospace and space electronics market turning to older commercial devices and up screening them to ensure reliability. This meant that aerospace and space electronics would constantly lag behind commercial technologies.
Traditional Space, i.e., government space agencies, i.e., NASA, accepted this as their number one priority to ensure safety and reliability. I.e., for manned missions or large (up to the size of a double-decker bus) geostationary satellites, reliability is paramount.
This has to be the case to ensure safety for humans on manned missions and to protect the significant value of larger satellites designed for mission cycles of 15 years+.
New Space Opportunities (Commercial space market & LEO orbits)
New Space electronics challenges the premise of sizeable long life geostationary satellites with smaller, shorter life LEO (Low-Earth Orbit) satellites and questions the Traditional Space component qualifications. With commercial spacecraft lowering the cost of access to space, and in particular, LEO orbits, there very well might be a paradigm shift to how we operate electronics in space.
LEO orbits are also below the Van Allen radiation belts and are not subject to high radiation doses, which exist in the more distant Geosynchronous Orbits (GEO). This means that electronics in Low-Earth Orbit (LEO) will not have to be radiation tolerant or radiation hard to the same degree as electronics in Geosynchronous Orbit (GEO). This has clear benefits leading to saving space and saving weight within the satellite structure.
New Space, being linked directly to private industries, has more cost focus. Although space technologies are enormously expensive to develop, private companies, however cash-rich, will have less money to develop technologies than government organisations such as NASA.
This subsequently leads private space development companies to operate in a more lean/efficient manner and keep hardware/component costs down. It has also seen companies such as SpaceX pioneer reusability strategies and technologies, which are extremely impressive.
With these combining and coupling effects which New Space presents, i.e., smaller, lighter, LEO orbit, reduced costs to launch, and shorter lifecycles, the commercial space market starts to open up to companies who could have never before entertained the idea of operating their own payload in space.
We are only at the very forefront of space development in terms of the possibilities to create more sophisticated space hardware and infrastructure both inside and outside of orbit around the Earth.
With a new and exciting market opening up, the question becomes...
What does the electronics look like to support it?
Fundamentally the electronics themselves won’t change. However, New Space's ideas support more commercially available COTS parts than heavily qualified traditional radiation-hard older devices.
It is not a choice of one or the other moving forward, but both will run in tandem where required.
It is apparent that if LEO satellite constellations take market share from GEO satellites, we may see a significant rise in more commercial electronics used in space.
Military & Aerospace Markets
Moving away from space for a moment and addressing military/aerospace technologies, it is apparent that military and aerospace manufacturers implement component strategies dependent on the project. This supports the idea for both heavily qualified traditional and more commercial components to be used together.
After all, if a project is human life critical, reliability must be of the highest priority. This provides evidence that high space level qualification can run in parallel with lower grade component technologies.
John Keller highlighted a primary example in an article he wrote and published in June 2019, “Electronics in space: traditional market faces-off against New Space.”
In this article, John Keller talks about Curtiss-Wright Defense Solutions, which have modified COTS for space applications. This also supports thoughts regarding how both heavily qualified traditional and more commercial components can be used together.
John explains Curtiss-Wright Defense Solutions have created an approach where space applications can be implemented economically and with the latest modern technology. This would seem impossible from a pure Traditional Space perspective but has been established because both Traditional Space and New Space complement each other.
John Keller explains that Curtiss-Wright Defense Solutions customers are worried about single-event upsets. However, he says that Curtiss-Wright implements a radiation hard backplane that goes on the back of stacks of data acquisition modules.
Therefore, the system has radiation hard components built into the backplane; however, the modules are COTS. If you encounter a single event upset, the current usually spikes; however, the radiation hard backplane continually monitors such spikes. This gives the ability for the radiation hard electronics to protect and look after the COTS modules.
The customer can program current limits in an upset event and then have the backplane reset the power to the upset module to clear the latch-up. Rather impressively, the COTS modules can survive as many as 120 latch-ups with no degradation.
New Space Component Grades
Due to the nature of New Space, the advised component standards are far from defined. Everything from entirely commercial electronics through to space qualified radiation hard parts has been used in space. The reality is that it depends solely on the primary purpose of the payload. I.e., if it is a CubeSat LEO project with no criticality or expectation of years of life, then using fully space-qualified radiation hard electronics would make no sense whatsoever.
This presents a new opportunity for both space system designers and space component manufacturers to define new standards that are robust and reliable for New Space LEO orbits without being overly expensive. This might mean coming up with a new standard altogether or adopting something like AEC-Q200 or an AEC-Q200+. It is only speculated currently about what would be an appropriate standard, and as mentioned in every case, it always relates to the mission's intention.
At TT Electronics, we are starting to see Aerospace and Space look to using AEC-Q200 components, so this may be a sign that things are beginning to change already. With the New Space market predicted to grow in the coming years, this may increase the demand for automotive grade components.
Of course, automotive grade electronics is already a growth market, with much more electronics being designed into cars these days than ever before. This is also set to continue with more advanced vehicle platforms, including fully electric and autonomous vehicles. These two factors also support AEC-Q200 becoming a standard that takes precedence.
So what will this mean for Traditional Space component manufacturers?
New Space is a disruptive technology and will create a shift as the reliability of more cost-effective component grades is explored. However, as more demanding and life-critical applications grow in space, reliability is always of paramount importance. It should be fit for purpose in line with the primary mission objective, whatever that may be.
These new and existing applications will drive the demand for fully space-qualified components, whilst commercial LEO satellite constellations will use cheaper component grades. For this reason, it is not a case of New Space versus Traditional Space.
What Does This Mean for Resistor Components and Why are Radiation Effects Important?
Potentially for resistor components, not only MIL qualified or equivalent parts can be considered for various Aerospace and Space projects. For example, other standards of a component such as automotive AEC-Q200 may be possible to design for some Aerospace and Space projects.
Radiation Effects in Film Resistors
Radiation effects within electronics are critical when operating in space and even more so in more distant orbits such as Geostationary orbits.
In some components such as semiconductors, different device structures, and new materials such as SiC (Silicon Carbide), the radiation effects are still being explored and understood.
This section explores radiation in relation to New Space and, in particular passive resistor components.
We explored the idea of Traditional Space qualified radiation hard components working alongside COTS parts. However, if New Space sets precedence to using more COTS or automotive grade components, then radiation data will not be available.
This makes one ask the question, how radiation-tolerant standard COTS parts are...
For resistors, the construction is mostly large feature bulk materials. Therefore, there is inherently less risk of permanent damage due to TID (Total Ionising Dose) exposure or SEE (Single Event Effect) radiation types.
The primary concern arises upon small feature, thin layer and large 2D area devices. As you can imagine, more complex devices such as transistors fall into this category. Thus, if we apply the above criteria for resistors, our concern becomes focused on mostly thin film resistor networks. Such networks are available in either NiCr or TaN film technologies, Nickel-Chromium (NiCr) or Tantalum Nitride (TaN) film.
We commissioned some radiation testing to understand the radiation effects in one of our TaN thin film resistor networks. This comprised resistance measurements taken before and after neutron radiation, 1013/cm2, fast neutrons, gamma radiation, and 100kRads from a Cobalt-60 source. Five networks were tested with varying resistance values of 50Ω, 25kΩ and 50kΩ.
Results: Resistance Variation Before/After the Defined Radiation Exposure
The results are presented below and assess the resistance variation before and after the defined radiation exposure. It is instantly recognisable that larger resistance variations are recorded for the 50Ω results. These resistance changes are believed to be caused by contact variations during the measurement.
Overall, these quantities of radiation have minimal effect on TaN resistor networks. When comparing more widespread test methods such as load life, dry heat and temperature cycling tests on the TaN WIN chip series, you can see that they are an order of magnitude lower. They are also the typical radiation levels which you would find in LEO orbit, i.e., 100kRads TID/year.
The graph below shows the annual dose from protons, electrons, and bremsstrahlung as an orbit altitude function.
Source: Daly, E. & Drolshagen, G. & Hilgers, A. & Evans, Hugh. (1996). Space Environment Analysis: Experience and Trends. 392. 15.
We can infer from this that COTS or AEC-Q200 grade TaN (Tantalum Nitride) thin film resistor networks could be used in LEO New Space applications with a reasonable degree of robustness.
However, TaN (Tantalum Nitride) thin film resistors aren’t as standard in these marketplaces as NiCr (Nickel Chromium) thin film resistors, which are well established, easier and cheaper to produce.
From research, we have discovered a test that made a direct comparison between NiCr (Nickel Chromium) and TaN (Tantalum Nitride), albeit at higher radiation doses than we have tested.
The total dose irradiated to both film types was 1016 fast neutrons cm-2 and over 108 Rads of gamma radiation. Regardless of manufacturing details, the Nichrome resistors all showed a fall in resistance, the median value being 0.035%.
However, after similar irradiation, the tantalum resistors, on the other hand, showed an increase of under 0.02%. The temperature coefficient of resistance (T.C.R.) of TaN resistors remained constant during irradiation, whereas NiCr resistors showed a considerable increase.
These differences in behaviour are consistent with the assumption that the TaN films are continuous or have closely spaced grains and NiCr films are agglomerated. The model proposed by Hill for conduction in agglomerated gold films offers an attractive explanation for the changes observed in NiCr resistors.
For more information, see the source of this testing: The effect of neutron irradiation on thin film resistors
New Space Component Technologies (Market Shift)
As markets continue to evolve with time and disruptive change, it is important for component manufacturers to keep up with the latest market demands. Quite clearly, there are and will be more changes to come in the space industry.
New space Electronics® - Tackling the challenges of new space flights with traceable, innovative solutions
What is TT Electronics doing to support this market shift?
First, we recognise from looking at several markets that AEC-Q200 is becoming somewhat of a converging standard. We always, where possible, will release new resistor products with AEC-Q200 qualification. TT Electronics recommends its AEC-Q200 resistor portfolio to be used in New Space applications along with our New Space MCAs and discrete portfolios, which were launched during 2018.
We are also working on certifying our range of TaN film chips resistors, WIN series, to AEC-Q200 qualification level. With radiation-tolerant TaN film combined with AEC-Q200 qualification and being re-engineered to be more cost- efficient, the WIN series is perfect for New Space applications.
New Space Unknowns to be Explored
Although the New Space approach has many advantages utilising the latest component technologies at a better cost, it does face some unknowns that need to be explored. For example, New Space's premise is to build satellite constellations instead of a single, massive and costly geostationary satellite.
If this becomes the case, it will mean that satellite design will become a lot more compact and hence power dense. With the satellite electronics being closer together and having increased power density, a new type of satellite design will be established. Therefore it is possible that new failure modes could emerge from having a new satellite design with more integrated and, thus, power-dense electronics.
Just as with the Traditional Space approach, failures need to be made to define the appropriate component and system test methods. This will ensure the required degree of reliability for the satellite.
Although New Space lifetimes may not be expected to be that of a 15 years+ geostationary satellite, they will still be expected to have a certain degree of reliability to serve their purpose whilst in space.
This is currently estimated to be around seven years but will ultimately depend on the mission objective.
Space Junk - Unwanted Debris
Another unknown is how much material we can launch into orbit around the Earth until we reach a limit. This is especially important to consider as the amount of unwanted debris starts to build in and around Earth's orbit.
How can we monitor and control this accurately and reliably?
We need to develop the technology and space infrastructure to ensure we have a sustainable future operating in Space.
We are only scratching the surface with possible space infrastructure both inside and outside of orbit around the Earth. It is clear that space is being more commercialised and growing as a potential future significant market that technology and humanity increasingly rely on.
It is vital that component manufacturing and standards maintain pace with disruptive change and evolving markets. We hope we gave you further focus on this and demonstrated what we are doing to ensure the future sustainability of space component technologies well into the future for decades to come.
As innovators in the New Space market, TT Electronics is committed to staying on top of the market trends that arise in the space industry.
If you’re looking for a partner that delivers reduced screening but fully traceable and proven space-grade heritage, get in touch with our New Space Electronics® team.