While the main campus of the Johns Hopkins University in Baltimore is open and inviting, there is another division of the school that discourages visitors.
The Hopkins Applied Physics Laboratory is tucked miles away in Laurel, with building access blocked by guards. Outsiders enter with an approved escort for the most part, handing over proof of identity first. Much of what goes on in there is secret — including some of the billions of dollars in work the lab does for the federal government.
The lab, and a facility at the University of Maryland in College Park where admitted National Security Agency leaker Edward Snowden once toiled, are two of 13 university-affiliated research centers doing contractual work for the Department of Defense in areas ranging from ship design to missile defense.
While the federal government and universities have collaborated since World War II, universities must balance academic integrity with the millions to be made in covert projects. Some universities have eschewed classified work because of the pitfalls; others have publicly bumbled the balancing act.
This week, a Hopkins dean ordered a university professor to take down a blog post criticizing the National Security Agency, which does business with the Applied Physics Laboratory. A lab employee had incorrectly claimed that the post linked to classified material. That led to an outcry from academics who questioned Hopkins' commitment to the free flow of ideas.
Proponents of classified research at universities say it helps the national good, brings in much-needed dollars and opens doors for students to get jobs in high-security fields after graduation.
But critics counter that teachers and students can't tell anyone about the work, so it won't bolster a curriculum vitae. And because the work can't be openly evaluated, it's tough to tell if it's in the public good.
"It's kind of a fundamental belief in American higher education that research is designed to be shared, it's designed to be disseminated," said Cary Nelson, an English professor at the University of Illinois' flagship campus and past president of the American Association of University Professors. "When you start crossing a line and decide, 'Well, I'll hide this and keep that secret,' the whole fabric begins to unravel.
"Academic freedom is so jealously guarded and vigorously pursued, the denial of it is a slippery slope," Nelson said.
Hopkins soon restored the post, and the dean apologized to the blogger, an outspoken assistant professor in the school's Information Security Institute named Matthew Green.
The episode shined a spotlight on classified efforts by universities, typically kept in the dark.
Other schools work for different federal agencies, such as NASA or the Department of Homeland Security. The University of Maryland, Baltimore County, for example, has a cybersecurity focus and a partnership with the National Security Agency.
Not all of their work is classified, nor is all of the work done under the partnerships with the Department of Defense.
Many schools that do classified work, as Hopkins and the University of Maryland do, say all classified research must be conducted off campus, even if it's only a short drive away.
"When classified research takes place, it occurs off-campus in order to make a clear distinction between research activity on-campus — where, in support of academic freedom, there is an open environment with no restrictions on the dissemination of the results of our research — and the sensitivity to needs of government and industry regarding certain topics that should not be in the open," Mike Lurie, a spokesman for the University System of Maryland, wrote in an email.
The system sets the classified-research policy for its member schools, including the University of Maryland.
Other schools expressly forbid the research altogether, including — at least for now — George Washington University, where a policy states that "classified research is not compatible with open communication of knowledge" and therefore, as a general rule, not accepted or performed.
But this spring, George Washington approved a 10-year plan that allows the university to "explore modifying" policies to "allow some faculty and staff members to engage in classified research." The plan also raises the possibility of building a specialized facility for the work on the university's Science and Technology campus in Virginia.
"There is a lot of funding in this area, and we're not competitive for that funding" said Leo Chalupa, vice president for research at George Washington.
"We're here, five blocks from the White House, and we're big in areas like cybersecurity and homeland security," Chalupa said. "I'm told by people in the field that, boy, if we had classified research, there's so much more possibility to get funding and expand these areas."