Bench Talk

“Yes, of course duct tape works in a near-vacuum. Duct tape works anywhere. Duct tape is magic and should be worshiped.”  ―Andy Weir, The Martian

Design engineering for space means ultra-precision parts with high performance parameters—and zero margin for error. To leave our atmosphere, things must have strong structural elements that hold together, while being as lightweight and efficient as possible, not to mention robust and dependable. Most space equipment is also mission-critical, so the slightest design flaw can not only ruin an expensive endeavor, but also potentially put lives at risk. No pressure or anything!

Here’s the good news, though: Engineers in the Space industry are continually working on new materials and methods of structural design, as well as better ways to put things together. Here, we’ll explore a few of them. First, remember that space is a harsh, deadly environment. It’s an airless vacuum where temperatures fluctuate rapidly from below freezing to many hundreds of degrees. Not to mention the massive amounts of radiation that can fry electronic systems and human DNA to a crisp. There are also frequent meteor showers and space junk that pose collision possibilities, all of which make a challenging day at the office for a space engineer.

If You Can’t Handle the Heat…

Engineers have to build in both cooling systems and insulators to keep temperatures even on spacecraft.

The European Space Agency’s (ESA's) comet-chaser—Rosetta—for example, had to be designed to first fly into the heat of the inner Solar System before heading away into the freezing outer Solar System. Engineers who worked on Rosetta designed a system called “louvres” to fit over the spacecraft's radiator panels. In the inner Solar System, these louvres swung open, allowing the radiators to expel excess heat into space. Later, in the outer Solar System, the louvres shut, helping to retain heat inside.

Engineers can also use a more passive approach, painting one side of their craft white and the other black, or in the case of a satellite, have it spin around like a sort of BBQ roll, so it stays evenly heated.

Radioactive, Radioactive…

Building integrated circuits that resist the effects of space radiation is known as “space hardening.” This usually involves redesigning the chips so they are somewhat shielded from the harmful radiation. Hardened chips are often manufactured on insulating substrates instead of the usual semiconductor; silicon on insulator (SOI) and sapphire (SOS) are examples. Shielding the package against radioactivity to reduce exposure of the bare device is also useful. Choosing larger and more expensive SRAM over capacitor-based DRAM and a choice of substrate with wide band gap also helps give things a higher tolerance to deep-level defects.

Another approach is to detect the errors produced by space radiation and correct them using software like error correcting memory, which uses additional parity bits to check for and possibly correct corrupted data.

“I tested the brackets by hitting them with rocks. This kind of sophistication is what we interplanetary scientists are known for.” ―Andy Weir, The Martian

To protect satellites and astronauts (and soon, space tourists), engineers have to give the ships some sort of armor. NASA uses something called “Whipple shielding”: The Whipple shield is a thin, aluminum “sacrificial” wall mounted at a distance from a rear wall. The first sheet, called a bumper, breaks up the projectile into a cloud of material containing both projectile and bumper debris. This debris cloud expands out over a wider area and has less impact. Bulletproof Kevlar is also now used in Whipple shielding.

Another protective feature—and the biggest thing that sets a space craft apart from, say, a drone—is the sheer amount of redundancy a space craft has built in, by design. That’s because if you have a problem on a space craft, and you don't have back-up systems, you're out of luck. The notion of fault tolerance is essential. That means a lot of extra backup systems just in case.

But you can’t just cram tons of extra equipment onto a craft without considering overall weight, which is everything when it comes to heavier-than-air machines. Designers constantly struggle to improve lift-to-weight ratios, and to this end, composite materials have emerged as the materials of choice for building space craft. Since 1987, the use of composites in aerospace has doubled every five years, and new composites regularly appear. Today there are three main types in use: Carbon fiber, glass and aramid reinforced epoxy.

Keeping Costs Down

Space design is expensive. The only way to continue pushing forward with it is to find ways to economize. Various private companies are already trying, including recycling rockets. New space companies are taking the best of existing aerospace practice, merging it with state-of-the-art materials and manufacturing techniques, and are producing disruptive products much in the way the advent of microprocessors destroyed the mainframe business of years gone by.

For example, Artificial Intelligence (AI) in space design is one such cost-effective advance. Extremely fast supercomputers are being put to work solving a plethora of design problems, based on formulas that were previously inserted manually into spreadsheets. Thus, instead of a room full of engineers working for months on a spreadsheet, AI can now solve similar problems in mere seconds and often come up with the same (or better) designs as well. Of course, AIs aren’t 100 percent there yet, nor are they capable of designing entire spacecraft themselves. Most experts agree there’s always going to be a role for people, so if you’re looking for a career in space engineering, it’s still a (hard but entirely viable) option.