5 Engineering Lessons from Pluto
The flyby of Pluto in July of 2015 is being hailed as an event equivalent to the Apollo 11 moon landing. With all of its recent success and media hype about what it has taught us about Pluto, the New Horizons mission also offers key design tips for engineers. Here are five lessons drawn from design steps taken without which the mission would have been a no-go.
Lesson #1 – Be persistent The mission to Pluto almost didn’t happen this century. Starting in the early 1990’s a plethora of missions to Pluto were proposed, including Pluto350, Pluto Fast Flyby, and Pluto Kuiper Express. However, the costs, timelines, and mission parameters of these proposals weren’t acceptable. In the year 2000 any planned attempt at a flyby of Pluto had been canceled.
But scientists such as New Horizons principal investigator, Alan Stern, refused to give up. They joined forces with other investigators and proposed a last-ditch effort to develop a spacecraft that could fly by Pluto before it receded into the furthest depths of our Solar System. The persistence paid off, giving humans of the 21st century the opportunity to glimpse a dwarf planet that has already provided surprises and insights about how this far-away world came to be and evolves.
Lesson #2 – Reuse can drastically reduce project costs A number of the original Pluto proposals had staggering price tags of $2 – 3 billion dollars. The New Horizons mission had a final price tag of $720 million dollars. How did New Horizons cut the costs compared to its proposed predecessors? Mission planners and designers leveraged existing technologies and used spare parts rather than starting from scratch. For example, the radioisotope thermoelectric generator (RTG) that powered the spacecraft wasn't built for New Horizons. It was an unused spare for the Cassini mission to Saturn. Another example of reuse was the ALICE instrument - an ultraviolet imaging spectroscope – that was derived from another ALICE instrument currently onboard the ESA’s Rosetta mission to a comet.
Lesson #3 – Reuse can dramatically shorten deployment time One of the great benefits from reuse is that it can greatly reduce development time by leveraging assets and technologies that already exist rather than starting a design from scratch. By the time New Horizons was funded, NASA had little more than three years to complete design, implementation, testing, and integration of the spacecraft before losing their launch window. A spacecraft of New Horizons' capabilities could not have been completed in that timeframe had its technologies been developed from scratch.
Lesson #4 – Plan for glitches On Saturday July 4 at 1:54 EDT, just ten days before the historic closest approach, the New Horizons spacecraft experienced a computer glitch. It turned out that the glitch the spacecraft suffered was due to a race condition within the software as it prepared its command sequence for its closest approach to Pluto. Instead of self-imploding and wasting ten years of waiting and almost a billion dollars, the spacecraft entered safe mode, fired up a back-up computer, and phoned home for help.
An unpredictable system glitch that could have blown the mission was instead averted. Mission planners had expected there to be unforeseen issues. But rather than hope for the best they had built reliability and robustness into the hardware and software systems. Incredibly, they were able to resolve the issue within a manner of a few hours and restored the spacecraft's operational integrity despite being 3 billion miles away!
Lesson #5 – Low power design isn’t just for IoT One of the interesting aspects of the New Horizons mission (and there are quite a few of them) is that the entire spacecraft has a little under 200 Watts of power with which to perform its operations. The entire spacecraft, including instruments, radio, flight computers, attitude control, propulsion, etc., all run on not much more than the energy necessary to power a couple of light bulbs. Power requirements were undoubtedly an important constraint for engineers as they developed and while they commanded their historic spacecraft.
The New Horizons spacecraft made human history by starting manned exploration of the outer reaches of the solar system. Despite New Horizons scale and complexity, there are lessons that every engineer should consider, even for embedded systems that are not so out of this world.
Jacob Beningo is a Certified Software Development Professional (CSDP) whose expertise is in embedded software. He works with companies to decrease costs and time to market while maintaining a quality and robust product. Feel free to contact him at firstname.lastname@example.org, at his website www.beningo.com, and sign-up for his monthly Embedded Bytes Newsletter here.
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