Modeling Threat Of Nuclear War

Massachusetts Institute of Technology

It's a question that occupies significant bandwidth in the world of nuclear arms security: Could hypersonic missiles, which fly at speeds of least five times the speed of sound, increase the likelihood of nuclear war?

Eli Sanchez, who recently completed his doctoral studies at MIT's Department of Nuclear Science and Engineering (NSE), explored these harrowing but necessary questions under the guidance of Scott Kemp, associate professor at NSE and director of the MIT Laboratory for Nuclear Security and Policy.

A well-rounded interest in science

Growing up in the small railroad town of Smithville, Texas, Sanchez fell in love with basic science in high school. He can't point to any one subject - calculus, anatomy, physiology - they were all endlessly fascinating. But physics was particularly appealing early on because you learned about abstract models and saw them play out in the real world, Sanchez says. "Even the smallest cellular functions playing out on a larger scale in your own body is cool," he adds, explaining his love of physiology.

Attending college at the University of Texas in Dallas was even more rewarding, as he could soak in the sciences and feed an insatiable appetite. Electricity and magnetism drew Sanchez in, as did quantum mechanics. "The reality underlying quantum is so counterintuitive to what we expect that the subject was fascinating. It was really cool to learn these very new and sort of foreign rules," Sanchez says.

Stoking his interest in science in his undergraduate years, Sanchez learned about nuclear engineering outside of the classroom, and was especially intrigued by its potential for mitigating climate change. A professor with a specialty in nuclear chemistry fueled this interest and it was through a class in radiation chemistry that Sanchez learned more about the field.

Graduating with a major in chemistry and a minor in physics, Sanchez married his love of science with another interest, computational modeling, when he pursued an internship at Oak Ridge National Laboratory. At Oak Ridge, Sanchez worked on irradiation studies on humans by using computational models of the human body.

Work on nuclear weapons security at NSE

After Oak Ridge, Sanchez was pretty convinced he wanted to work on computational research in the nuclear field in some way. He appreciates that computational models, when done well, can yield accurate forecasts of the future. One can use models to predict failures in nuclear reactors, for example, and prevent them from happening.

After test-driving a couple of research options at NSE, Sanchez worked in the field of nuclear weapons security.

Experts in the field have long believed that the weapons or types of delivery systems like missiles and aircraft will affect the likelihood that states will feel compelled to start a nuclear war. The canonical example is a multiple independently-targetable reentry vehicle (MIRV) system, which deploys multiple warheads on the same missile. If one missile can take out one warhead, it can destroy five or 10 warheads with just one MRV system. Such a weapons capability, Sanchez points out, is very destabilizing because there's a strong incentive to attack first.

Similarly, experts in nuclear arms control have been suggesting that hypersonic weapons are destabilizing, but most of the reasons have been speculative, Sanchez says. "We're putting these claims to technical scrutiny to see if they hold up."

One way to test these claims is by focusing on flight paths. Hypersonic missiles have been considered destabilizing because it's impossible to determine their trajectories. Hypersonic missiles can turn as they fly, so they have destination ambiguity. Unlike ballistic missiles, which have a fixed trajectory, it's not always apparent where hypersonic missiles are going. When the final target of a missile is unclear it is easy to assume the worst: "They could be mistaken for attacks against nuclear weapons or nuclear command-and-control structures or against national capitals," Sanchez says, "it could look much more serious than it is, so it could prompt the nation that's being attacked to respond in a way that will escalate the situation."

Sanchez's doctoral work included modeling the flights of hypersonic weapons to quantify the ambiguities that could lead to escalation. The key was to evaluate the area of ambiguity for missiles with given sets of properties. Part of the work also involved making recommendations that prevent hypersonic weapons from being used in destabilizing ways. A couple of these suggestions included arming hypersonic missiles with conventional (rather than nuclear) warheads and to create no-fly zones around world capitals.

Helping underserved students

Sanchez's work at NSE was not limited to his doctoral studies alone. Along with NSE postdoc Rachel Bielajew PhD '24, he started the Graduate Application Assistance Program (GAAP), which helps mitigate some of the disadvantages that underrepresented students are likely to encounter.

The son of a Latino father and middle-class parents who were themselves the first in their families to graduate from college, Sanchez considers himself fortunate. But he admits that unlike many of his peers, he found graduate school difficult to navigate. "That gave me an appreciation for the position that a lot of people coming from different backgrounds where there's less higher education in the family might face," Sanchez says.

GAAP's purpose is to lessen some of these barriers and to connect potential applicants to current NSE graduate students so they can ask questions whose answers might paint a clearer picture of the landscape. Sanchez stepped down after two years of co-chairing the initiative but he continues as mentor. Questions he fields range from finding a research/lab fit to funding opportunities.

As for opportunities Sanchez himself will follow: a postdoctoral fellowship in the Security Studies Program in the Department of Political Science at MIT.

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