As if pandemic, threats of nuclear war, and a lack of Tesla charging stations aren’t enough to worry about, there is always the possibility that an asteroid could hit the earth and wipe-out all of us. A team at NASA discovered a way to alter the path of an asteroid, should one come too close and they garnered the distinction of being finalists in this year’s Service to America Medals program, also known as the Sammies. For the details, the Federal Drive with Tom Temin talked with two members of NASA’s Planetary Missions Program Office: Program Manager Brian Key and Mission Manager Scott Bellamy.
Tom Temin All right. You launched a rocket that crashed into an asteroid. And I guess my first question is this rocket was able to change somewhat the trajectory of that asteroid. I want to understand what the math calculus was. I mean, generally, how did you figure this out? Because an asteroid is very big. A rocket is very small. You could launch something as big as the asteroid. That’s not possible. But if you shot a marble at it, it wouldn’t make any difference. What was the process to figure out how you could do this? Scott.
Scott Bellamy I think the easiest way to, you know, start that answer that question is realize that it’s not just Brian and I. There’s an entire team behind us. Here we sit and management position. But, you know, supporting this entire effort is a large group of scientists, engineers working at the Applied Physics Laboratory to help answer that.
Scott Bellamy So if you look at it like you’re playing billiards in space, you’re playing pool, galactic pool. So this is not dissimilar from how you described this scenario with the smaller spacecraft hitting the larger asteroid. But when you take the smaller spacecraft and you look at how fast is it flying, what is its mass relative to the object that its impacting, you determine how much kinetic energy has to be imparted from one body to the other to effect a change in its orbit. And so the scientists that have been working on the design of the mission came up with the parameters that needed to be adjusted in order to achieve the result of altering the orbit of the Dimorphos.
Tom Temin All right. And what happened when you launched it? It hit the asteroid.
Scott Bellamy Most definitely. That is actually the point of highest tension in this entire event is what happens when it hit the asteroid. It hit the asteroid. It’s, you know, a very high velocity. And the smaller asteroid Dimorphos is that we ended up with a lot of spacecraft confetti. We had a spacecraft that’s just a little over 1200 pounds in mass, you know, slightly larger than, you know, your typical refrigerator. And it hit at, you know, over 13,000, almost 13,500 miles per hour. So, you know, it was not just a glancing blow. It was a very precisely targeted impact with a certain spot on the surface of Dimorphos to achieve that perfect little amount of English on the spacecraft’s trajectory and bound to, you know, get that all to sink right into the core pocket the way they planned it.
Tom Temin The speed is a big factor in this, almost like a hypersonic missile. It’s the impact of the wait times, the speed that is the power. It doesn’t even have to have an explosive.
Scott Bellamy That’s the energy mass times velocity. You’re calculating the kinetic energy of the impact. And so with a known kinetic energy impacting an object that is traveling in its orbit at its certain velocity, you know, you take the velocity and you break it down into what you’re facing head on. And then you know, what the mass is roughly that’s coming at you and you sized the spacecraft large enough to hopefully surpass what’s needed to change it, because you can get hit by a Volkswagen out on the interstate. And if you’re driving a huge SUV, it’s still going to affect your trajectory down the road.
Tom Temin Yeah, it can flip you over if the angle is right, I guess.
Tom Temin And Brian, you’re the program manager. How did you convince NASA? And I guess ultimately Congress, I mean, it sounds like a little bit science fiction. You know, you’ve seen cartoons of rockets landing in the moon’s eyeball, this kind of thing. How did you convince them that this was a worthwhile experiment?
Brian Key It didn’t take much convincing. These ideas have been out there for quite a while. And the Science Mission Directorate at headquarters stood up a planetary defense office within the Planetary Science Office. And it was the planetary defense office that basically brought forward the idea. Once they selected the mission, we took over management of it. So it was Planetary Defense Office that actually brought it forward and said, Yeah, this is a good thing for us to try and do. And they went to APL and got a proposal of what it would take. Then they turned it over to us to implement it.
Tom Temin The rocket itself was it just a rocket in the weight of its self? Was there. Was there lead weights in the front or anything to get it to that proper mass that you calculated it required?
Scott Bellamy Well, first, let’s think about like this. It’s not the entire rocket. It’s just the spacecraft that the rocket is launching. So now everything on the spacecraft, the essential things to be able to fly it, you have to be able to have the items that control the trajectory of the spacecraft, point the solar arrays, solar arrays themselves, the optical instrument that has to be there to do the targeting. So the spacecraft in and of itself was literally what it needed to fit inside of the launch vehicle. The other fairing at the top, the enclosure and have enough mass to affect change. Now its weights are sometimes added to any spacecraft to get the balance where you want it to. But no, it wasn’t like a race car that’s carrying an extra 1500 pound of weight just to get to the mass where they want it. In this case, in most cases, it’s like, you know, if you have space left to play with, you prefer to put something usable in there for mission accomplished. But other than just dead weight.
Tom Temin And it’s been, you know, a couple of eons, I guess, since an asteroid has hit the earth, 60, 65 million years, maybe a long time. Does NASA generally watch asteroids? And what is anyone’s best guess of the chances of being hit any time soon by another asteroid big enough to do damage to humanity? I guess we get hit by little meteorites all the time.
Brian Key The last asteroid to hit was not 65 million years ago. We’ve had fairly good sized asteroids hit the earth more recent than that. Just not in the United States. I think the last one was over in Russia. We do have a sister mission that is in development right now that will put basically a camera up in orbit around the earth that will basically monitor the sky and collect data to determine where these asteroids are, what their trajectories are, whether they’re a danger to earth or not. That particular mission, I think, scheduled to launch in 2027. It’s called Neo Surveyor.
Tom Temin Sure. And a couple of final questions. The asteroid that you did, this proof of concept on that you could change. What was its mass? And so what is the greatest mass that you think that a launch could actually affect?
Scott Bellamy So the Didymos system is the target here for this test. Didymos is a binary asteroid. It has the larger primary and the smaller secondary moonlight that was targeted. This gave us an opportunity to actually be able to observe the change that we were hoping for. So the smaller asteroid is named Dimorphos. it has a mean diameter of 160 meters. And we don’t necessarily have a good mass estimate for either the primary or the secondary. I can pull something out to share with you, but it’s still just an estimate. The largest factor here was is that it’s in a stable orbit around its parent. It’s typically measured at a average plus or minus some seconds of 11.9 hours. And we know how big it is. So we can estimate the mass of it and use that information compared to the orbital dynamics between the two to understand how large the change might be. Now, usually, I mean, you were asking about how heavy one of these is. We usually talk about them in terms of how big they are in the mean diameter. Yeah, there’s some interesting data out there, you know, of asteroids that are roughly four meters and there could be 500 million of them out there that, you know, teasers in their orbits, those that are around 25 meters, you know, 5 million. But then you get up to the dinosaur killers, which are 10,000 meters roughly, and they think that they’re roughly only four of those hanging around out there in space. These are the ones that we have to worry about. They have orbits that cross Earth’s orbit periodically, or they can pose a potential earth crossing hazard. Now, there are a large number of asteroids out in the two belts, the one between Earth and Mars and the one further out past Pluto, there’s just, you know, LA 405 at 5o’clock rush hour that kind of looks like that.
Tom Temin But you were able to change the trajectory of something that was 160 meters across. Could you change the trajectory of something that’s 10,000 meters across?
Scott Bellamy My answer is yes. The answer depends on, what’s more important in this scenario is when you find it and how big it is and how soon it’s going to get here. So if you detect it early enough, you have time to put together the mission, get it built, get it launched to travel there. If you find it too late, yeah, you’re already behind playing catch up to generate the largest benefit from a mission like Dart. You want to find the asteroid when it’s as far away as possible? Sure. And be able to get to it as soon as possible. The further away the asteroid is, the smaller the change in its trajectory you have to make because a half degree change in its trajectory when it’s five years out will result in a really large missed distance once it finally gets to Earth.
Tom Temin Is there the danger that it could accidentally be knocked into a better chance of hitting the earth?
Scott Bellamy That’s a difficult question to answer, and I don’t even know if I want to try.