Putting DAUs on a Diet for Small Launcher Applications

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August 03, 2018

Putting DAUs on a Diet for Small Launcher Applications

The world of space launchers has changed; the last 10 years have shown a shift from government dominated launches to commercial organizations as well as a move towards increasingly smaller launchers which provide a lower cost way of getting newer, smaller satellites into orbit. Cost is a big driving factor for all launchers, and one significant expense is the cost of the instrumentation system.

The obvious answer to lowering cost is to use commercial off the shelf (COTS) systems, but space is a harsh environment where standard COTS systems are unlikely to meet reliability requirements. Ruggedized systems, like those used in aerospace applications such as flight test instrumentation, can prove useful as a low cost alternative for some mission profiles, as they have been designed to be reliable in harsh environments. These systems are often called ‘Space COTS’.

 

For missions where radiation is a factor driving requirements, engineers can take one of two approaches to designing electronics that will be exposed to significant doses: they either make it radiation-hardened, meaning the inherent technology provides protection from radiation, or radiation-tolerant, which means there is acceptance of some degree of performance loss from exposure to radiation.

Radiation hardened systems are the most reliable, but they are also the most expensive. Radiation tolerant systems come with a lower price tag and consequently, lower reliability. However, there are many mission profiles where lowering the level of space qualification is acceptable and the cost savings are significant enough to justify an increased risk of failure; such cost savings can be on the order of 50%. The smart backplane technology used in the Acra KAM-500 is one example of a radiation tolerant system.

Keeping these systems small is vital for smaller launchers as their reduced size means everything onboard must also be smaller as mass and size are precious resources that should be assigned to payload as much as possible. Every kilo is valuable which means every gram spent on instrumentation, wiring, or supporting systems is no longer available for payload.

In principal, shrinking COTS electronics is simple enough, but standard approaches may not work as well for space launchers. Cost pressures mean COTS is a desirable approach, but this means small custom units that can fit close to sensors to reduce cable length are not possible. Additionally, small modular units are limited in compactness by their power supplies.

Another approach is to locate modules away from the chassis using a serial link to a chassis that provides the power. This yields the best of both worlds. This is exactly what Curtiss-Wright has done with our new Axon data acquisition system. It allows off-the-shelf data acquisition modules to be placed in ultra-miniature “Axonite” housings that can be separated from the chassis by up to 15 meters.

The Axon builds on the Acra KAM-500’s heritage in space applications and also uses hardware-based acquisition engines to minimize data loss, support deterministic operation, and ensure rapid recovery in the case of a power brownout. Axon uses a high-speed serial backplane (1 Gbps dedicated link per module) to ensure future high data rates are supported.

Axon is therefore ideal for space COTS, and future radiation tolerance is planned using the same smart backplane technology that has been successfully used in several radiation environments.

As the space launch market moves towards smaller launchers, everything onboard needs to be smaller, lighter, and lower cost. This presents a challenge to data acquisition system vendors, and Curtiss-Wright Defense Solutions has responded with the Axon as it’s perfect for small launcher applications. Indeed it has already been selected for such due to its ability to handle large amounts of data in such a small footprint. Read our “Miniaturizing Space COTS for Small Launcher Applications” white paper to learn more.

Space COTS Data Acquisition

Get the cost-saving benefits of space COTS without sacrificing reliability