Down-to-Earth Engineering in Space

09/07/2004


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Chet Vaughan, Boeing’s acting chief engineer for the International Space Station, says basic control and automation principles help the U.S. space program cope with challenges from galloping technical evolution to integration and standardization issues.

Chet Vaughan, acting chief engineer for the International Space Station (ISS) at Boeing Co., has been working on the ISS since 1996. He worked for the National Aeronautics and Space Administration (NASA) for 40 years on every major human space program project, including Mercury, Gemini, Apollo, Skylab, and others. Vaughan says he’s encouraged by recent changes in U.S. space exploration policy, and is excited by recent proposals to return humans to the Moon, and perhaps journey from there to Mars.

While not a typical control and automation environment, Vaughan says space exploration has included many classic sense-decide-actuate problems and solutions from its earliest days, and these have increased as space systems and vehicles have grown more sophisticated. “A lot of space-related automation initially had to do with maintaining space vehicle attitude control, so the crew wouldn’t have to worry about it,” says Vaughan. “Online sensors were automated, and functioned in closed loops to maintain many systems, such as small rocket engines,” says Vaughan. “Now, we have control moment gyros (CMGs), from L3 Co., which have three-axis orientation, function in control loops, and provide torque by changing momentum. This is important because many types of torque in space travel are cyclic, which means they reoccur every orbit, and so they have to speed up and slow down a fair amount.

“On the other hand, drag forces aren’t cyclic, but they too use sensor data to dial in correct orientations, which are then directed by thrusters. These systems were automated from the beginning, but started with very small, 64 KB computers, and even smaller ones on Gemini.”

In your experience, what do you consider to be the top three advances made in control and automation over the past 50 years? Which of these do you think is the most important and why?

I think the top three advances in control and automation in the past 50 years would have to include the ongoing improvements in computer technologies and their ability to perform increasingly huge numbers of calculations more rapidly. I think this is the most important advance that’s been achieved.

This overall advance paved the way for the second main advance—sensors have become sophisticated enough to provide more and more of the data needed to complete these advanced calculations and make the results useful.

The third most important advance is that network have gained enough speed and capacity to move data from sensing areas to computing functions.

For example, ISS uses 40-45 386 KB computers that are a lot more capable than in the past, and can be divided into two main types. The first computer group helps automate processes that keep the station alive, such as managing thermal controls, internal water-cooling systems, and external ammonia-based cooling systems. This equipment includes pumps, bypass valves, heat exchangers, dedicated software, external detection zones, fault isolation and recovery capabilities systems, and a redundant system for notifying crew and ground staff.

The basic principles haven’t changed because in space you must still get rid of all the heat that you can’t recycle and use. However, the implementation has changed because we now have a lot more electronics and a lot more heat.

The second group of PCs on the ISS controls the station’s experiments and housekeeping systems. These also are connected to more sensors, all of which have grown more capable and more complex. For example, astronauts on today’s longer duration flights breathe a 14.5-psi mix of nitrogen and oxygen. Air quality is monitored by a mass constituent analyzer, or mass spectrometer, which generates a lot more data. Most of this information is still analog, but the amount of digital data is increasing.

In the old days, we weren’t able to sample as often. Throughput was so small, and the response wasn’t fast. This was a problem on the ISS, and in space in general, because if something goes bad, it’s going to go bad very quickly. Now, we’re able to capture data at a millisecond pace, and report it to the crew and ground control.

What do you think will be among the next significant advances in the control, automation, and instrumentation arena in the next five to 10 years, and then crystal ball gazing 50 years into the future?

In the next five to 10 years, we’ll see accelerated improvements in the technologies that we have now. Components and systems will continue to become smaller, require less and less power, and produce less heat.

We’ll also see a lot of advances in new areas, which I think will replace former improvements in traditional areas. For example, we won’t see advances in liquid propulsion, which involves converting chemical energy to usable thrust, because we’re already running at 98-99% of all that we can theoretically get. Consequently, future gains in propulsion will likely come in the form of nuclear, electrical, and ion-based thrusters. Ion propulsion involves heating small amounts of gas to very high temperatures. This type of propulsion starts slow, but can achieve a lot of velocity.

In the robotics area, the ISS’ Canadian-made actuator arm already is able to handle large masses, and it’s highly mobile because both ends is the same and can perform that sane tasks. In the next few years, it will add more capabilities for putting modules where we want them to go, and this includes both pressurized and non-pressurized components. For example, one of the next improvements will likely be installation of a dexterous, multi-purpose robot running on the end of each arm, which will give them even more dexterity.

Several years further out, we’ll have automation, control, and other capabilities that will allow us to go and remove orbital replacement units on the ISS without performing extra-vehicular activity (EAV), or going outside, which will save a lot of time, labor, and risk.

What will be the biggest challenges facing engineering in the next decade with regard to plant infrastructure, technology, and the business of manufacturing in general?

The biggest challenge for engineering and engineers, at whatever level, has been and will continue to be securing and maintaining consistent funding. Countless useful programs have been killed by all the starts and stops in funding that they’ve had to go through.

In addition, engineers need to explore how they can work together on integration issues earlier in their projects. For ISS and other projects, this means making more pieces, modules, and vehicles more compatible with each other, as well as standardizing communications, especially at the component level.

We need to have architectures, both physical and software-based, in which we can embed new technology as we go along. For example, this will be important when we convert the ISS’s 386 KB computers to newer ones. We’re also seeing more multilateral cooperation among the countries working to build the ISS.

The ISS is addressing many of these questions and other challenges, and as it works through these problems, I think it can serve as a test bed for many other organizations and engineering projects. Lessons we learn often can be applied, not just in space, but also on the ground.

Looking back over your career, have there been any expected surprises for you in terms of new technology, business development, or industry direction?

One of the main surprises is that I just can’t keep up with all the new PC-based capabilities. All types of communications, from data to personal, have truly become a two-way street. The challenge here is that you still have to be clear about what you’re asking or saying, whether you have a PC communicating with a device, or if you’re managing and prioritizing communications between devices.

For instance, ISS data and communications move over a three-tier network that is mostly a hardwired blend of copper and fiber. The station also uses Ethernet for payload data, but not for its core systems. The core network is required to have fault detection, isolation, auto recovery, and multiple network synchronization.

Consequently, required changes are actuated mostly automatically, and either hard of soft notifications are generated about what happened. These can include cautionary audio tones to check the PCs, with data piped down to Earth via S- or KV-bands, or notifications to take components offline and troubleshoot them.

One of the main improvements over the years has been our implementation of parallel processing to prevent data bottlenecks. We’ve also learned to prioritize data better.

To advance their careers within manufacturing, what should engineers focus on in the next 10 years?

The number one priority is that engineers, from the young and recently graduated to the older and highly experienced, must continue to educate themselves, understand, and conscientiously apply basic engineering principles to design and manufacturing steps to help produce capable tools and electronic solutions. There’s always a tendency and temptation to think that you can skip steps, and this has to be avoided.

In the case of ISS, since the space shuttle Columbia went down, it’s been difficult to keep the station occupied and supplied. ISS has been in orbit for five and a half years, including three and a half years with people in it, and we’ve had a lot of Russian assistance. Overall, we’ve found that Russia brought a lot to the table. They don’t do things more cheaply, but they did have a lot less expensive labor.

The outsourcing issue is another overall challenge for engineers, of course, but, when you think about it, this type of economic pressure has been a problem since the beginning. As far as Western jobs going to other countries, such as India, this is a fluctuation that will inevitably even out.

Prior to upgrading controls, automation, and instrumentation, some organizations examine processes and culture as well. Can you provide an example, based on your experiences, in which paying attention to culture and processes helped the organization’s automation implementation?

One recent change in our culture has been a result of the fact that it’s presently harder to reach the ISS. Despite this, we’re trying to provide more survival capabilities, as well as offer the same level of redundancy, and prevent potential problems.

This has meant that our engineers have had to become more capable, develop better tools, and try to better understand how to get our jobs done. Hopefully, this may eventually help us better educate some of the students who’ll become future engineers.

For now, I think we’ve managed well, even though we haven’t had as much redundancy. Everyone has done a super job of keeping ISS manned and up and running.

Please provide a specific example of how you’ve been an advocate for change in manufacturing? Are there any additional changes you intend to bring about, and how?

Since the early to mid-1990s, we’ve started using a series of CAD programs to complete digital pre-assembly (DPA) of equipment that we can no longer put together on the ground because of gravity-related constraints. We’re also using more laser measurement systems in manufacturing and checking out what are often school bus-sized components, including the segment-to-segment trusses used to build the station.

In-orbit assembly is another reason why it’s becoming so important for us to adopt common items and elements, such as berthing mechanisms and even pressurized elements, which have the same manufacturer for both the parts and their connectors.

For instance, the 16 electric drive bolts, used to connect many of the larger components, are installed with a load cell that checks them for the proper tension.

This level of standardization also aids construction because a lot of the assembly is automated and monitored by the crew, but also because they still need to be able to do it manually if necessary.