Ingeniously, by using part of the rocket itself as the impactor, scientists make room for a separate spacecraft—one that follows a few minutes behind, flies through the ejected material to analyze its contents, and hurriedly sends the data back to Earth before smashing into the Moon itself.
Scientists Launch Rocket into the Moon to Find Water
Published: July 16, 209
Anthony Colaprete: We said, “Okay, what if we crash something into the moon and we looked at the ejecta?”
I called up Pete, because he’s the guy you go to if you want to crash something into another body, planetary body, he knows impacts.
Peter Schultz: I thought, “Oh, yeah, bash something into the moon?” Well, this was something that was going to smash through to an area you couldn’t see in the cold traps.
Narrator: By crashing an object into the moon, they hope to observe lunar material ejected from the impact and determine if it contains ice.
Colaprete: So, we came up with the idea of, “Why don’t we use the spent upper stage of the rocket that was pushing us to the moon?”
Narrator: Ingeniously, by using part of the rocket itself as the impactor, they can then use the extra payload space for a separate spacecraft, carrying instruments that will follow a few minutes behind, recording the impact at close range and hurriedly sending its data back to Earth, before smashing into the moon itself.
Such a complex mission is hard to pull off with such little time, but the rewards, should they succeed, will be huge.
Schultz: I was really intrigued, and I knew that we could do this. But the idea of actually using a spent rocket? That was almost like crazy talk.
Narrator: Anthony and Peter calculate that they would need to create a debris cloud at least half a mile high to stand a chance of detecting any water. To test the feasibility, they turn to a trusty tool from the Apollo era.
Colaprete: This facility is the Ames Vertical Gun Range. It’s a large vertical gun, used for firing projectiles into targets to study cratering processes.
Schultz: We have a battery of high-speed cameras, going up to a million frames per second. We can look at it from different locations and just be able to simulate, get a sense of what we might see.
High voltage is good. We have ready lights.
Narrator: Firing projectiles at high speed into a simulated lunar surface, Peter and Anthony spend months trying to figure out what the impact plume might look like.
Schultz: Oh, stop, stop. Go. Go backwards. That’s the projectile coming down. Ha! Okay, pow.
The idea behind these experiments were to get a better handle on getting enough material into sunlight from that deep hole. If we didn’t get enough material, we were dead.
Narrator: LCROSS launches on June 18th, 2009. It takes four months to catch up with the moon and get into position for impact.
In the early evening of October 8th, 2009, the Centaur rocket stage impactor begins its approach.
Centaur Rocket Mission Control: All stations flight. Thirty seconds to end of science cal.
Narrator: With the spent rocket stage and following spacecraft now on unstoppable impact trajectories with the moon, all Peter and Anthony can do is watch and wait.
At 3:31 in the morning, Pacific Time, the Centaur hits.
Minutes later, the shepherding craft follows and starts collecting data, rushing to transmit it before its own demise.
Colaprete: So, we had a press conference. Of course, everyone’s like, “What? What’d you see? Did you see water? Did you see this?”
Schultz: “How much? How much?”
Colaprete: Yeah, “How much?” Yeah.
(File Footage) Indeed, yes, we found water. And we didn’t find just a little bit, we found a significant amount. In the 20 to 30-meter crater LCROSS made, we found maybe about a dozen of these two-gallon-buckets worth of water.
Back to the Moon
Executive Producers for Bigger Bang: Iain Riddick & Ben Bowie
Produced by: Christopher Riley
Digital Production: Rachel Swansburg
© WGBH Educational Foundation 2019