Thoughts on Theses: Chloe Revery
Issue   |   Wed, 09/16/2015 - 01:30

Chloe Revery is a history and computer science double major who is writing a history thesis on the software developed for the NASA space shuttle program. Her thesis adviser is Anson D. Morse Professor of History John Servos.

Q: What is your thesis about?
A: My thesis is a history thesis about the development of the software in the space shuttle missions. The software system that was used in the space shuttle was extremely complex. It was far more complex than any software that was used in previous NASA missions, which usually only used software for navigation and guidance purposes. With the space shuttle, the mission requirements forced NASA to integrate basically every component of the shuttle with software, which had never been done before. So it was a huge task. The size and complexity of the software requirements for the shuttle ended up forcing NASA engineers and subcontractors to innovate, and those innovations eventually ended up trickling down to the private sector.
It’s a really interesting story, and it hasn’t really been told for a few reasons. First of all, historians tend to be more interested in hardware than in software, because software is a newer field and it’s also more esoteric. You can have a pretty good understanding of hardware if you are an electrical or mechanical engineer, but to understand software, you really have to be a programmer or someone who has programmed in the past. And it’s a relatively new discipline. So there are not many historians who have expertise in software and history, as opposed to a high number who have engineering and historical expertise. It’s a really good opportunity because a lot of the space shuttle engineers are still alive, so there’s some chance in this thesis to do some original research, which is very exciting and unusual for an undergraduate history thesis. In particular, I’m hoping to focus on a woman named Margaret Hamilton, who recently got into the news because a photo of her standing next to a stack of papers with the Apollo source code printed out went viral. Hamilton was the lead engineer on the Apollo project, and a lot of the Apollo software was reused on the space shuttle. Margaret Hamilton, after working on the Apollo project, spun off her own firm in Cambridge, called “Intermetrics.” Intermetrics was commissioned by NASA to write the programming language in which the software for the space shuttle would later be written. That language is called HAL/S, and I am going to commit a good portion of my thesis to the language of HAL/S and its development.

Q: What is the significance of the HAL/S language and its impact today?
A: HAL/S was an important programming language mainly because it was the first high-level programming language. Back in the day of the space shuttle, there was a war going on in the industry of computer science over whether to use high-level programming languages (those that are more human-readable) or low-level languages (which are essentially just one step above zeros and ones.) Some incredibly smart programmers decided to make programs called “compilers” that took the more human-readable version of the code and then translated it into those zeros and ones for the computer to use. But some of the more hardcore programmers wanted to use the low-level language. This was a huge debate within NASA and within the private sector, simultaneously. And NASA decided, in a crucial decision, to go with a high-level language for the space shuttle. But there was no suitable high-level language, because nobody in the private sector had to accomplish what the space shuttle mission had to in terms of their software requirements. So NASA had to create their own language. The biggest innovation I have found so far in the HAL/S Language — which, by the way, some people think is named after the HAL computer in “2001: A Space Odyssey” — is that it incorporated a concept called “priority scheduling.” In traditional software systems, computing power is allocated to tasks in slices of time. So, one program gets processor time for ten seconds, and whether or not the process is completed, the processor moves on to the next task. But with the priority scheduling system, which HAL/S supported, all tasks are assigned a priority and processing power is allocated based on the priority of the task. In this sense, HAL/S actually looks a lot like the programming language Fortran, which a computer science major at Amherst would be familiar with.

Q: What was it that attracted you to this particular topic?
A: My dad is an aviation photographer, so he’s a photographer who specializes in taking photographs of anything that flies. That’s including military aircraft, rockets and even space shuttles. So I’ve always grown up around planes and things that fly. And space is cool!

Q: Where are you in the research process right now?
A: Over the summer, thanks to the generosity of the Department of History, I had the chance to do some research in Mountain View. I visited the Computer History Museum and also [the] NASA Ames [Research Center,] which is right next door, so I was able to meet with some of the historians there and take a quick gander at the archives. Right now I’m still in the research stage. I’m reading as much as I possibly can — as Professor Servos says, I’m “reading around the topic.” I’ve pretty much honed in on what I want to do, but the writing won’t start until probably around Thanksgiving, and in my opinion, that’s how it should be.

Q: Can you talk a little about being a double major in history and computer science?
A: I don’t think I’m different from any other Amherst student in that most of the students here are pretty well rounded. I know there’s a trend in higher education towards accepting students who are really good at one thing and maybe not so good at other things. But most of the students I’ve met at Amherst are good at the humanities and good at the sciences. I think that any student at Amherst could do computer science, and any student at Amherst could do history, and be successful at it. I don’t see any contradiction there. All the computer science majors I know have amazing writing skills. All the history majors I know, even though they profess differently, would be really good at writing programs.

Q: What is it like to work on a single project across two disciplines?
A: I think that when you’re working on a project with an interdisciplinary aspect, it’s important to find a mentor who has experience working across disciplines. My thesis adviser is a historian of science. His expertise has been invaluable as I figure out how to approach a technical topic from a historical angle.