A rocket that was to resupply the International Space Station blew up Tuesday night a few seconds after lift-off from Wallops Island, Va. (NASA)

For months, students across the United States and Canada conducted scientific experiments. Some wanted to know how crystals would change without gravity. Others wondered whether plants would grow or how fast milk would spoil in space. Nearly 1,600 pounds of science and research was loaded onto a cargo spacecraft bound for the International Space Station.

And Tuesday evening, it was all destroyed.

Many students watched as an unmanned Antares rocket exploded above its launchpad in Wallops Island, Va. Some saw it on video from the classroom. Others, like students from Knoxville, were “close enough to feel the percussion of the blast.” Teachers described the scene as a “flash and then the explosion” with smoke that “blotted out the stars.” Some elementary school kids in British Columbia were said to be in shock — and “then they started laughing.”

“I think the adults took it harder in the room than the kids did,” Serena Connally, a sixth-grade science teacher in Texas, told the San Antonio Express-News.

The incident could raise concerns about whether NASA and its private contractors can ensure launches are safe only a month after the agency chose SpaceX and Boeing to send astronauts to the space station as early as 2017.

This year, students from grade school through college submitted hundreds of proposals to the nonprofit Student Spaceflight Experiments Program launched by the National Center for Earth and Space Science Education with the private space company NanoRacks. Eighteen experiments were chosen to go into space.

“The payload was supposed to be returning early in December and we were going to analyze the data and see if we could draw any conclusions,” Greg Adragna, a science teacher at Cristo Rey Jesuit College Preparatory School in Houston, told the Houston Chronicle. “This was about a year-and-a-half of work. This is not the way we wanted to have the evening end.”

NASA officials apologized late Tuesday to those who lost their experiments — and some students in Houston were already being asked to do more research.

Hobby Middle School in San Antonio had planned to raise $8,000 to send its group to Washington, D.C., next summer to make a presentation at the Smithsonian Institution. The group spent seven months experimenting to see how crystals could change their size and shape in space.

They were unbowed.

“It won’t always go your way,” Hobby Middle School student Madelyn Hickman, 11, told the Express-News.

“And if you fail one time, just try it again and see what happens,” 13-year-old Anthony Holmes added. “And rocket explosions look cool.”

A group of Knoxville, Tenn., kids had found an environmentally-friendly way to dispose of human waste in space. The project may have been lost, but that fact only reiterated an important lesson in science, L&N STEM Academy Principal Becky Ashe said.

“One of the mantras of the program all the way through it has been … this is real space fight, and you can’t ever take it for granted,” Ashe told the Knoxville News Sentinel. “There’s always risk.”

Students weren’t the only ones who lost valuable research. The spacecraft was also carrying an asteroid-hunting satellite designed by Planetary Resources, a start-up company in Redmond, Wash. As the Seattle Times reported, the company was as undeterred as the kids. The corporate tweet after the explosion said: “Live to fly another day. Onward!”