The maiden voyage of Lockheed Martin’s first Atlas V rocket lifted off from Space Launch Complex 41 at Cape Canaveral on August 12, 2002, freed from its earthly bonds by flight control software created with DDC-I’s Tartan Ada Development System (TADS).
Incorporating numerous systems developed for the flight-proven Atlas III, development of the Atlas V — the most powerful Atlas launch vehicle ever built — began in 1998, to meet the growing needs of the U.S. Air Force Evolved Expendable Launch Vehicle (EELV) program and International Launch Services (ILS) commercial and government satellite customers worldwide.
"Every Atlas variant during the past ten years has had a flawless first flight," says ILS President Mark Albrecht. "With a modular design and increased capability, the Atlas team provides a vehicle that meets a wide range of customer needs. To the development team, I say thank you."
According to Michael Bethancourt, Flight Software Development Lab Manager and Team Leader for the Atlas Flight Software Operating System (OS) group, the flight software package begins with the preflight checkout before performing guidance, navigation, steering, flight sequencing, autopilot, engine control and fluid & pressure management operations during actual flight. The Atlas V also features unique, in-house developed ROM, BIT and Operating System software.
"We have a highly experienced team, and what we did, moving from Atlas II to Atlas III, was to restructure and layer the OS in a more object-oriented fashion. This affected much of the Atlas III software" he explains. "When we started on Atlas V, what we did was bring forward our sophisticated and proven control algorithms and implement them into a software structure that was fully object-oriented. We employ a number of powerful Ada 95 features, not all of them, but we essentially have Ada95 here."
He adds that Ada is the appropriate language for much of what they do. The modern features that are critical to building reliable and robust flight software, including strong typing, dynamic binding, polymorphism, and a secure environment merge to produce far fewer interface errors, and an effortless enforcement of proven development standards. "Ada is definitely the right language for mission critical, safety critical, real-time embedded systems" he adds.
Describing the stability and performance of the AdaTest95 processor and the file-coupled TADS system as "turnkey," he adds that the multi-window interactive symbolic debugger within the 1750A simulator and target chipset is a major advance over previous development subsuites.
"We have a homegrown debugger built into our flight box downstairs for Atlas II & III. We did full module testing on our test set downstairs, using capabilities written years ago on a DEC VAX. We still do full module testing for II & III on the VAX and we go down and do our branch testing on that flight-equivalent test set."
The branch testing combined with the Computer Software Component and system testing — where the software is "flown" against a simulation of the vehicle — provides the team with solid confidence in the reliability and robustness of their software.
"With the Atlas V, instead of having to do all of our branch testing on the single test set, now we can run against any one of a number of single-board computers with the debugger in place. We can sit up here at our desks and test on computers that are actually located in our Software Integration Laboratory that is nearly one mile away. We get much more accomplished, and the whole process is just more productive."
With 34 years in software, including a stint teaching OS internals, and 26 years of hands-on experience in the real-time embedded systems world, Bethancourt is well-equipped to comment on the state of programming tools and the value of solid support from the vendors.
Though as a Lockheed Martin employee he can not endorse products or vendors, Bethancourt’s feelings about DDC-I and the TADS programming tools are crystal clear: "DDC-I has demonstrated that they understand the importance of responsiveness. During the Atlas V development phase, the representatives visited often and quickly deduced the critical nature of the software we’re building and flying. As a result of their early interest and continuing concern, we don’t have to worry about the development suite, and are able to direct our full attention to achieving 100% Mission Success" he says.
Lockheed Martin Space Systems depends on TADS to develop modern, object-oriented real-time flight control software for the new Atlas V launch vehicle