Tag: DART mission

Space News Special: NASA’s Double Asteroid Redirection Test (DART) is a successful first demonstration of a Planetary Defense Shield.

One of Hollywood’s favourite science fiction plots is that of a massive asteroid or comet headed straight for our planet, a threat to our civilization if not to all life on Earth. The recent movie ‘Don’t Look Up’ (See my Post of 5 January 2022) is just one of many such productions. Of course one reason that the plot is popular is that the threat is actually very real; 66 million years ago the dinosaurs were driven to extinction by a space rock some 10 kilometers in diameter colliding with the Earth.

A somewhat more serious take on the end of the world by asteroid was the 1998 film ‘Armageddon’. (Credit: Rotten Tomatoes)

While 66 million years may seem like a long time scientists are now coming to realize that collisions with smaller asteroids are fairly common, and can still be quite destructive. Archaeologists now have evidence that it may have been an asteroid strike that gave birth to the legend of Sodom and Gomorrah (see my post of 6 October 2021) while the demise of the mound builder culture here in North America has also be linked to an asteroid. So the possibility of a large space rock coming down in the middle of a densely populated area and causing a tremendous amount of destruction is very real.

In 1908 a meteor crashed in the Tunguska region of Siberia. Fortunately few people were hurt because the region was so remote but few such unpopulated areas exist anymore so the next such event could cause enormous destruction. (The Conversation)

Before the space age there was really very little that humanity, or indeed any of Earth’s species, could do to protect themselves from an asteroid strike. The dinosaurs certainly had no idea an asteroid was taking aim at them and they surely all died having no idea what it was that was killing them.

They surely had no idea! (Credit: Space.com)

We can do something to protect ourselves however, we have the technology. Our successes in space have given us the ability to not only see a potentially dangerous asteroid before it strikes, hopefully years before it strikes, but we can even send a spacecraft to that asteroid in a effort to prevent that strike from ever happening.

There are literally thousands of Near Earth Objects, space rocks whose orbit around the Sun comes close to our Planet’s. Fortunately space is awfully big so we don’t get hit very often! (Credit: Astronomy Magazine)

So the question becomes, what is the best way to stop an asteroid that’s headed straight at our planet. Well Hollywood producers certainly knows how they’d do it, nuke the bloody thing. Trouble is that blowing up an asteroid doesn’t completely solve the problem, it could even make the things worse. After all when you blow up something there are still a lot of pieces of it left. So blowing up an asteroid headed for Earth just means you now have a lot of smaller asteroids headed for Earth.

We may like to blow things up but that’s probably not the best way to avoid getting hit by an asteroid. (Credit: YouTube)

NASA’s plan for dealing with a potentially dangerous asteroid is far more gentle. For one thing the space agency has organized and funded dozens of astronomers to search for any ‘Earth Crossing Asteroids’ that could become a danger in the years to come. They have found several thousand but so far fortunately none of them will strike our planet within the next fifty or so years. What NASA hopes is that, when a dangerous asteroid is finally found we will have years if not decades of warning. That will be enough time to deal with any dangerous asteroid more efficiently, more effectively and even more cheaply.

NASA’s DART Mission to test a possible technique for protecting Earth from dangerous asteroids. The idea is to crash a small spacecraft into an asteroid to see how much we can alter its trajectory. (Credit: Applied Physics Labouratory, Johns Hopkins University)

The idea is to simply nudge the asteroid, not much, just a little. Given enough time, let’s say exactly one year, a change of just one meter per second in the velocity of an asteroid that is headed straight for Earth is all that is needed to cause that asteroid to miss our planet by more than 30,000 kilometers, a fair safety margin. That’s all, just one meter per second to save the Earth, if done early enough.

We all know the old story. Slow but steady wins the Race. (Credit: VirilityUnemployed)

But can an asteroid be nudged? Are they solid enough bodies to be gently pushed, or are they just piles of rubble that might break up from even a nudge? Will slamming a projectile into the asteroid work or will we have to spread our push out in order to keep the asteroid in one piece?

Those are some of the questions that NASA’s Double Asteroid Redirection Test (DART) was designed to find out. Launched on the 23 of November in 2021 the Dart spacecraft was targeted at a system of two asteroids, the larger asteroid is named Didymos and is about 780 meters in diameter. Didymos is orbited by a smaller asteroid named Dimorphos, which is roughly 160 meters in diameter.

The DART Spacecraft isn’t going to study Dimorphos but crash into it. Therefore it only carries the instruments it needs to steer it at its target. (Credit: DART)

The plan was for the DART spacecraft to slam into the smaller asteroid Dimorphos at approximately 6 kilometers per second (kps) after which astronomers will measure the change in Dimorphos’ orbit around Didymos. You see the reason for choosing the smaller in a two asteroid system as a target is that it has always been easier for astronomers to measure the time an astronomical event takes compared to the distance to an astronomical object.

Human beings learned how to measure time by watching the rhythm of the objects in the sky and even today it is easier to measure time in astronomy than distances. (Credit: www.astronomy.ohio-state.edu)

Think about it, how would you, all by yourself measure the distance to the Moon? But, with only a little effort you could measure the time it takes to go from full Moon to full Moon, at least approximately. Ancient astronomers actually knew pretty accurately the time it took the various planets to orbit the Sun before they knew that the planets really orbited the Sun not the Earth.

Measuring the distance to the Moon requires two different observers plotting the Moon’s position against the stars at the same time from a great distance apart. (Credit: Medium)

Before DART reached Dimorphos astronomers had measured the orbital period of that asteroid around Didymos at 11 hours and 55 minutes. It is expected that the collision with DART will reduce that orbital period to about 11 hours and 45 minutes but again astronomers can take their time and get a very precise measurement of that change. Then, using the well-known laws of orbital dynamics, they’ll be able to calculate exactly how much they’ve succeeded in changing the velocity of Dimorphos.

Kepler’s three laws of Planetary motion are still the basis for any study of astronomy. (Credit: Teachers Pay Teachers)

The DART spacecraft got only one chance at hitting Dimorphos however, if it missed the probe and the asteroid would fly past each other at 6 kps never to meet again. So as you can imagine the atmosphere at the Applied Physics Labouratory of Johns Hopkins University was pretty tense as DART drew ever closer to its target. All the apprehension was unnecessary however for the spacecraft’s autonomous control computer behaved flawlessly. At 07:14 PM on the night of the 26th of September DART smashed into Dimorphos less than 17 meters from the asteroid’s center, a bull’s eye at 10 million kilometers.

Just seconds before the crash DART sent back this picture of Dimorphos. Like many asteroids Dimorphos appears to be nothing more than a pile of rubble. (Credit: CNN)

And DART was taking pictures the whole way in, sending back dramatic images of Dimorphos as the asteroid appeared to grow larger and larger. Not only that but the day before the collision DART had released an smaller Italian cube satellite whose job it was to take pictures of the collision from a few kilometers away. Finally there were several telescopes back here on Earth that also got in the act, taking images of the collision from 10 million kilometers distance.

DART crashing into Dimorphos (top center) as seen by the Italian LICIA cubesat. The larger asteroid Didymos is lower left. (Credit: New Scientist)

So all of the hardware worked, DART smashed right into Dimorphos exactly as planned and NASA got plenty of pictures. In the weeks to come astronomers here on Earth will determine exactly how much the asteroid’s trajectory has changed. Then we’ll know whether or not humanity has at least the beginnings, a breadboard model of a technology that could save us from going extinct the way the dinosaurs did.

Space News for December 2019.

There a lot going on in space right now. There’s both good news and bad. Let’s deal with the bad news first.

By now I’m certain that you’ve heard about the problems that occurred during the Orbital Test Flight (OTF) of Boeing’s Starliner space capsule. Planned as an unmanned flight to the International Space Station (ISS) the OFT was to be the last scheduled test of Starliner before manned missions could begin hopefully starting early next year.

The launch of Boeing’s Starliner capsule on its OFT appeared to be perfect! (Credit: Forbes)

The launch of Starliner took place as scheduled at 6:36AM on December 20th with the Atlas V booster rocket making what looked like a perfect takeoff. The trouble started about 15 minutes later as the capsule was ordered to make a 40 second burn designed to circularize the spacecraft’s orbit. That orbital insertion burn suffered an ‘anomaly’ however, burning for far too long and using up the majority of Starliner’s maneuvering fuel.

Because of that anomaly Starliner was left without enough maneuvering fuel to successfully make its planned rendezvous with the ISS. Since the mission could not complete its most important objective it was quickly decided to terminate the planned eight-day mission after only two days. Starliner’s re-entry and landing took place without incident on the 22nd of December.

The Starliner’s reentry and landing went off without a hitch! (Credit: News 13)

Faced with Starliner’s problems both NASA and Boeing stressed that had any astronauts been on board they would never have been in any danger. Indeed, it is likely that a human pilot would have recognized that there was a problem with the engine burn and quickly corrected it before the capsule had used up so much fuel.

NASA chief administrator Jim Bridenstine puts on a confident face but Starliner has problems. How long will it take to fix them? (Credit: Phys.org)

Still there definitely was a problem and speculation as to the cause is already spreading across the Internet. At the moment it appears that what happened was that the computer onboard Starliner grabbed the wrong ‘Start Time Clock’ signal from the rocket’s first stage clock. (Since the liftoff of the first stage is the official start of the mission its clock is the master clock for the entire launch system and payload.) By grabbing the wrong time Starliner thought it was in a different segment of the mission and performed an orbit insertion burn rather than the required orbit circularization burn.

How long of a delay this problem is going to cause for the Starliner program is unknown at present. The solution could be just a software fix but hey, the solution to the problems of Boeing’s 737 max 8 aircraft was only supposed to be a software fix and that program is still a mess after more than a year. The big question is probably whether or not NASA will require another OFT in order to verify that the fix, whatever it is, really works. In that event the first manned launch of Starliner would almost certainly be pushed back into late next year.

Meanwhile Boeing’s rival Space X is also preparing for the final test of its Dragon capsule early next month, in this case the test an in-flight abort test. So the space race between Boeing and Space X as to which will be the first to successfully launch a manned mission could go down to the wire. Right now it’s anybody’s guess who will win.

NASA also has a capsule of their own, the Orion capsule which is designed to carry astronauts beyond Low Earth Orbit (LOE), back to the Moon and perhaps one day even to Mars. For its Lunar missions Orion will be launched atop NASA’s massive Space Launch System (SLS). Both programs are several years behind schedule however and in fact the problems with the completion of the SLS is causing another blackeye in Boeing’s reputation.

The Orion capsule launched atop the SLS in this artist’s impression. Maybe one day we’ll see it for real. (Credit: NASA)

The current hope is that an unmanned flight test of both the SLS and Orion, officially referred to as Exploration Mission -1 or XM-1, will take place in late 2020 with a goal of taking the capsule into and back from Lunar orbit. XM-1 will be the first mission in NASA’s ambitious Artemis program for returning humans to the Moon by 2024, a program that I have previously criticized as being already behind schedule, overly ambitious and underfunded.

Now NASA has announced plans to include two human dummies in the Orion capsule for that initial test flight. The dummies will be used to measure the effectiveness of NASA’s new anti-radiation vest known as StemRad. The space agency has long been concerned about the exposure to radiation that astronauts will be subjected to on missions beyond Earth’s protective magnetic field and into deep space. StemRad is one of the solutions the space agency is currently developing.

Model wearing the StemRad anti-radiation vest. (Credit: Space.com)

Employing polyethylene blocks to shield against solar radiation StemRad is designed to fit over the vital organs of its wearer giving the maximum of protection while imposing the minimum restrictions on the wearer’s movements. Also, because studies have shown that woman are more susceptible to harm from radiation than men are the dummies to be sent to the Moon will be female.

The plan for the XM-1 mission is for both dummies to be outfitted with radiation sensors but only one will wear StemRad. A direct comparison of the radiation exposure between the two dummies will then be a measurement of the effectiveness of the vest. At the moment StemRad is ready to go, it remains to be seen if Orion and the SLS will be.

Finally a somewhat smaller story caught my eye, a story about a space mission that could have huge consequences some day in the future. In my posts of 14 October 2017 and 11 May 2019 I talked about NASA’s plans for a mission to attempt to perturb the orbit of the smaller of the two asteroids in the system known as Didymos. This perturbation is intended as the first practical test of a planetary defense system. Officially the mission is known as the Double Asteroid Redirection Test or DART and the plan is to literally have a space probe slam into the smaller asteroid called Didymoon.

Radar scan from Earth based radio telescope of Didymos and Didymoon. (Credit: Wikipedia)

Scheduled to be launched aboard a Space X Falcon 9 rocket in July of 2021 the DART probe is expected to reach Didymos in October of 2022. Once DART has impacted into Didymoon Earth based telescopes will then monitor the changes in the smaller asteroid’s orbit caused by the crash.

NASA plans to impact a spacecraft into Didymoon to see what effect it will have on the asteroid’s orbit around its bigger companion. (Credit: NASA)

Of course a second space mission to measure those changes from close up would provide even more accurate measurements and now it appears there will be such a mission. The European Space Agency (ESA) has officially approved a new mission called Hera that will study the Didymos system starting in either 2025 or 2026.

The ESA’s HERA mission will provide precise follow up measurements of the Didymos system. (Credit: ESA.int)

In addition to measuring the effect of the Dart collision Hera will also land a small cubesat on each asteroid. Together the DART and Hera missions will give scientists their first actual measured data of an asteroid deflection. Such information will help in the development of a defensive program to protect our plant from an asteroid collision like the one that caused the extinction of the dinosaurs.

So as you can see it was a busy month in space. Some progress, some problems, I suppose that’s why they call it rocket science.