Asteroid Intercept

[steve_bank]

Something useful from the space program, actually saving the Earth from a future killer asteroid.

NASA is about to crash a spacecraft into an asteroid

The test is set for Monday evening.

www.axios.com

Why it matters: The first-of-it-kind mission — called DART — marks the first true test of whether or not NASA will one day be able to push a potentially dangerous asteroid off a collision course with Earth if the need should ever arise.

 

[Tigers!]

Changing the momentum of an asteroid is no small feat.

 

[Loren Pechtel]

NASA can't even avoid running into things!

 

[bilby]

Changing the momentum of an asteroid is no small feat.

On the contrary, it can be achieved by applying any force to it, however minuscule.

There are no immovable objects, and ALL forces are irresistible.

 

[steve_bank]

A momemtus event.

 

[Jimmy Higgins]

I still say the winning option is using a trojan. That mass is already in space. The hard part would be getting out of it's generally Earth like orbit and at a velocity high enough to impart enough momentum to the asteroid. But as hard as that is, requiring AI, snagging an engine to the rock, being able to control it, etc..., it seems remarkably more possible than launching anything from Earth to disturb the track of an asteroid travelling 10,000+ kph.

Changing the momentum of an asteroid is no small feat.

On the contrary, it can be achieved by applying any force to it, however minuscule.

There are no immovable objects, and ALL forces are irresistible.

Thank you Captain Pedantic. Shouldn't you be at an airport telling the staff to tell people to get "in" the plane instead of "on" it?

 

[lpetrich]

I'd started an earlier thread on it: Planetary Defense Experiment | Page 4 | Internet Infidels Discussion Board

NASA’s DART Mission Hits Asteroid in First-Ever Planetary Defense Test | NASA

After 10 months flying in space, NASA’s Double Asteroid Redirection Test (DART) – the world’s first planetary defense technology demonstration – successfully impacted its asteroid target on Monday, the agency’s first attempt to move an asteroid in space.

Mission control at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, announced the successful impact at 7:14 p.m. EDT.

...
DART targeted the asteroid moonlet Dimorphos, a small body just 530 feet (160 meters) in diameter. It orbits a larger, 2,560-foot (780-meter) asteroid called Didymos. Neither asteroid poses a threat to Earth.

...
The spacecraft’s sole instrument, the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO), together with a sophisticated guidance, navigation and control system that works in tandem with Small-body Maneuvering Autonomous Real Time Navigation (SMART Nav) algorithms, enabled DART to identify and distinguish between the two asteroids, targeting the smaller body.

...
These systems guided the 1,260-pound (570-kilogram) box-shaped spacecraft through the final 56,000 miles (90,000 kilometers) of space into Dimorphos, intentionally crashing into it at roughly 14,000 miles (22,530 kilometers) per hour to slightly slow the asteroid’s orbital speed. DRACO’s final images, obtained by the spacecraft seconds before impact, revealed the surface of Dimorphos in close-up detail.

Fifteen days before impact, DART’s CubeSat companion Light Italian CubeSat for Imaging of Asteroids (LICIACube), provided by the Italian Space Agency, deployed from the spacecraft to capture images of DART’s impact and of the asteroid’s resulting cloud of ejected matter. In tandem with the images returned by DRACO, LICIACube’s images are intended to provide a view of the collision’s effects to help researchers better characterize the effectiveness of kinetic impact in deflecting an asteroid. Because LICIACube doesn’t carry a large antenna, images will be downlinked to Earth one by one in the coming weeks.

 

[lpetrich]

DART’s Final Images Prior to Impact | NASA

After 10 months flying in space, NASA’s Double Asteroid Redirection Test (DART) – the world’s first planetary defense technology demonstration – successfully impacted its asteroid target Dimorphos on Monday, Sept. 26, 2022, the agency’s first attempt to move an asteroid in space. During the spacecraft’s final moments before impact, its Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) imager took four images capturing its terminal approach as Dimorphos increasingly fills the field of view.

The camera's final picture was only a little bit radioed back before the spacecraft crashed on the asteroid.

Planetary Defense Coordination Office (PDCO) - about the DART spacecraft.

DART Asteroid Impact LIVE with Mission Team - YouTube
Mostly a lot of gabbing about the mission, but one could see the pictures from DART as it approached the asteroid system, starting with Didymos barely resolved.

NASA's DART Mission Post-Asteroid-Impact News Briefing - YouTube
Mentioned the NEXT-C ion engine that DART had. They used the engine for only a few hours, then shut it down for the rest of the mission, since it was using too much electricity, and they didn't want to risk the mission. But if DART missed Dimorphos, then DART would likely have used its ion engine to go into an orbit that will hit some other asteroid.

 

[lpetrich]

Ground Telescopes Capture Jaw-Dropping Views of DART Asteroid Impact

“It is hard to comment on the stunning experience we had last night,” wrote the Virtual Telescope project in a blog post. “We saw in real-time, with our very own eyes, the effects of DART slamming into its target asteroid Didymos, making it much brighter, with a huge cloud of debris.” To track the impact, the Italy-based Virtual Telescope Project collaborated with the Klein Karoo Observatory in Calitzdorp, South Africa. “The target asteroid is visible on the bottom right of each image and clearly develops a dusty cloud, which expands quite quickly in [an eastern] direction, where the asteroid was moving, to,” according to the post. The astronomers estimate that dust cloud was expanding at a rate of 1.8 miles per second (2.9 km/s).

Double Asteroid Redirection Test (DART) impacted on Didymos/Dimorphos... and it was a huge show! - The Virtual Telescope Project 2.0

The ejecta easily left Dimorphos because the asteroid was so small. I estimate its escape velocity as 0.09 m/s or 9 cm/s. That is MUCH less than the collision velocity of 6.6 km/s.  Double Asteroid Redirection Test

 

[bilby]

...
DART targeted the asteroid moonlet Dimorphos, a small body just 530 feet (160 meters) in diameter. It orbits a larger, 2,560-foot (780-meter) asteroid called Didymos. Neither asteroid poses a threat to Earth.

...

Neither asteroid posed a threat to Earth before the impact.

Now we're not necessarily so sure

 

[lpetrich]

No threat afterward. DART's impact on Dimorphos likely gave it a kick of 2 cm/s, and since Didymos is about 100 times more massive, that's an overall kick of 2*10^-4 m/s With an orbit velocity of around 30 km/s, that's 7*10^-9 of the orbit, or about 1 km offset. Not enough to make much of a difference.

 

[Worldtraveller]

I think he missed the joke, bilby.

 

[lpetrich]

 LICIACube - Light Italian CubeSat for Imaging of Asteroids - a 3*2 cubesat weighing 31 km and having its own solar panels.

ASI | Agenzia Spaziale Italiana

LICIACube on Twitter: "Ecco le prime immagini scattate da #LICIACube dell’impatto di #DARTmission su #Dimorphos. Adesso iniziano settimane e mesi di grande lavoro per gli scienziati e i tecnici coinvolti in questa prima missione di difesa planetaria, quindi restate collegati! (pix link)" / Twitter
Google Translate:

Here are the first images taken by #LICIACube of the impact of #DARTmission on #Dimorphos .
Now weeks and months of hard work begin for the scientists and technicians involved in this first planetary defense mission, so stay connected!

Has pictures taken by the cubesat of the impact.

 

[Loren Pechtel]

I still say the winning option is using a trojan. That mass is already in space. The hard part would be getting out of it's generally Earth like orbit and at a velocity high enough to impart enough momentum to the asteroid. But as hard as that is, requiring AI, snagging an engine to the rock, being able to control it, etc..., it seems remarkably more possible than launching anything from Earth to disturb the track of an asteroid travelling 10,000+ kph.

Changing the momentum of an asteroid is no small feat.

On the contrary, it can be achieved by applying any force to it, however minuscule.

There are no immovable objects, and ALL forces are irresistible.

Thank you Captain Pedantic. Shouldn't you be at an airport telling the staff to tell people to get "in" the plane instead of "on" it?

There are big problems with this. First, that means you have to go get a Trojan, that takes time and if the threat is real time is of critical importance. Second, you have to be gentle because there's no guarantee the object you're moving is solid, too big a shove and it comes apart.

Second, that's going to apply one massive shove to the target--how do you guarantee it doesn't come apart leaving a cloud of rubble heading for Earth?

 

[lpetrich]

Second, that's going to apply one massive shove to the target--how do you guarantee it doesn't come apart leaving a cloud of rubble heading for Earth?

If one hits an asteroid far enough in advance, then the fragments will disperse enough to make it highly improbable that any one of them will hit us.

To work that out, I considered how much energy a nuclear bomb will impart.  List of nuclear weapons has the deployment history of US nuclear bombs.

The US nuclear bombs in service are: B61 l=360cm d=34cm m=324kg, e=1.7PJ, B83 l=370cm d=46cm m=1,100kg e=5.0PJ, W76 m=95kg e=0.4PJ, W78, W80 l=80cm d=30cm m=130kg e=0.63PJ, W87 l=180cm d=56cm m=270kg e=2.0PJ, W88 l=150cm d=46cm m=360kg e=2.0PJ

Other notable nuclear bombs: Little Boy l=300cm d=71cm m=4,400kg e=0.063PJ, Fat Man l=330cm d=150cm m=4670kg e=0.088PJ, Tsar Bomba l=800cm d=210cm m=27,000kg e=240PJ

l = length, d = diameter, m = mass, e = energy, PJ = petajoule = 10¹⁵ joules

 Tsar Bomba and The Soviet Weapons Program - The Tsar Bomba

The most energy released per unit mass was by Tsar Bomba at 8.9 terajoule/kg, with the W87 not far behind at 7.4 TJ/kg. The two 1945 bombs are far behind.

 

[bilby]

Second, that's going to apply one massive shove to the target--how do you guarantee it doesn't come apart leaving a cloud of rubble heading for Earth?

If one hits an asteroid far enough in advance, then the fragments will disperse enough to make it highly improbable that any one of them will hit us.

To work that out, I considered how much energy a nuclear bomb will impart.  List of nuclear weapons has the deployment history of US nuclear bombs.

The US nuclear bombs in service are: B61 l=360cm d=34cm m=324kg, e=1.7PJ, B83 l=370cm d=46cm m=1,100kg e=5.0PJ, W76 m=95kg e=0.4PJ, W78, W80 l=80cm d=30cm m=130kg e=0.63PJ, W87 l=180cm d=56cm m=270kg e=2.0PJ, W88 l=150cm d=46cm m=360kg e=2.0PJ

Other notable nuclear bombs: Little Boy l=300cm d=71cm m=4,400kg e=0.063PJ, Fat Man l=330cm d=150cm m=4670kg e=0.088PJ, Tsar Bomba l=800cm d=210cm m=27,000kg e=240PJ

l = length, d = diameter, m = mass, e = energy, PJ = petajoule = 10¹⁵ joules

 Tsar Bomba and The Soviet Weapons Program - The Tsar Bomba

The most energy released per unit mass was by Tsar Bomba at 8.9 terajoule/kg, with the W87 not far behind at 7.4 TJ/kg. The two 1945 bombs are far behind.

Centimetres are all very well if we are living in the 1960s, but these days the civilised world uses SI, in which prefixes other than 10³ⁿ are deprecated.

At first glance I was astonished at how small and how dense those warheads were, because I automatically assumed the use of mm.

I suppose I should be impressed that any American has chosen to use metric units, even if they have elected to use one that's half a century out of date.

 

[lpetrich]

Let's see what booster rockets one can use to get these bombs on their way.  Comparison of orbital launch systems lists payload masses for a large number of rocket systems and destination orbits.

Most of the numbers are for low Earth orbit (LEO) and geosynchronous transfer orbit (GTO), and I estimate that (GTO payload) = 0.55 (LEO payload). For translunar injection (TLI), I find 0.4, for transmartian injection (TMI), I find 0.27, and for a heliocentric orbit (HCO), I find 0.35. I will use 1/3 as my HCO/LEO estimate.

So for a W87 bomb, one needs to get 810 kg into LEO, and that is feasible for most orbital-launch rockets. Tsar Bomba weighed 100 times more, putting it out of reach of all present-day rockets, though the Falcon Heavy almost makes it, and all but a few upcoming and retired rockets. Those ones are (upcoming) Long March 9, Space Launch System, Starship, Yenisei (retired) Saturn V, Energia, N1.

Now for some calculations of how much effect on 65803 Didymos (5.4*10¹¹ kg) and Dimorphos ("Didymoon") (5*10⁹ kg)

Let's say that all these bombs' energy goes into moving these asteroids. Little Boy: 0.063 PJ, W87 2 PJ, Tsar Bomba 240 PJ.

Dimo: LB 160 m/s, W87 890 m/s, TB 9800 m/s
Didy: LB 15 m/s, W87 86 m/s, TB 940 m/s

So a nuclear bomb's explosion should be more than enough to kick a small asteroid into a less troublesome orbit.

 

[Swammerdami]

Changing the momentum of an asteroid is no small feat.

On the contrary, it can be achieved by applying any force to it, however minuscule.

There are no immovable objects, and ALL forces are irresistible.

I think many of the Zoomer Generation will miss your cryptic reference. (Here is an alternate cite.)

But the key to asteroid deflection is the old adage A stitch in time saves nine. Don't wait until the rock is hurtling straight at Trump Tower but instead give it a gentle nudge an orbit or two earlier.

Just today, on Floating Fortune Road, it was explained that a gentle stroke is valued more than a more muscular stroke.

Let's say that all these bombs' energy goes into moving these asteroids. Little Boy: 0.063 PJ, W87 2 PJ, Tsar Bomba 240 PJ.
...
So a nuclear bomb's explosion should be more than enough to kick a small asteroid into a less troublesome orbit.

A team of scientists (from NASA?) studied this and concluded nuclear bombs were not a solution. The problem is that the bombs' energy does NOT go into moving the asteroid, but just reduces it to rubble, still pointed at the Earth.

 

[lpetrich]

Let's say that all these bombs' energy goes into moving these asteroids. Little Boy: 0.063 PJ, W87 2 PJ, Tsar Bomba 240 PJ.
...
So a nuclear bomb's explosion should be more than enough to kick a small asteroid into a less troublesome orbit.

A team of scientists (from NASA?) studied this and concluded nuclear bombs were not a solution. The problem is that the bombs' energy does NOT go into moving the asteroid, but just reduces it to rubble, still pointed at the Earth.

I don't find that to be that great of an objection, because even a small kick will be more than enough if done far enough in advance.

The main problem with a nuclear bomb, however, is possible inefficiency. Nuclear bombs produce very high temperatures - I've seen 10⁶ K for Little Boy and 10⁸ K for hydrogen bombs. If their energy goes into vaporizing themselves and nearby asteroid material, and not much more, then they won't produce a very big kick. Momentum p = m*v is related to kinetic energy T = (1/2)*m*v² by p = (2*T)/v -- so for best results, the bomb should accelerate as much material as possible, even if that material ends up moving relatively slowly.

So one should bury the bomb in the asteroid.

 

[Jarhyn]

Changing the momentum of an asteroid is no small feat.

On the contrary, it can be achieved by applying any force to it, however minuscule.

There are no immovable objects, and ALL forces are irresistible.

I think many of the Zoomer Generation will miss your cryptic reference. (Here is an alternate cite.)

But the key to asteroid deflection is the old adage A stitch in time saves nine. Don't wait until the rock is hurtling straight at Trump Tower but instead give it a gentle nudge an orbit or two earlier.

Just today, on Floating Fortune Road, it was explained that a gentle stroke is valued more than a more muscular stroke.

Let's say that all these bombs' energy goes into moving these asteroids. Little Boy: 0.063 PJ, W87 2 PJ, Tsar Bomba 240 PJ.
...
So a nuclear bomb's explosion should be more than enough to kick a small asteroid into a less troublesome orbit.

A team of scientists (from NASA?) studied this and concluded nuclear bombs were not a solution. The problem is that the bombs' energy does NOT go into moving the asteroid, but just reduces it to rubble, still pointed at the Earth.

Anyone who has ever played Kerbal Space Program will know that it isn't always about total Delta-V, usually it's about when you apply it.

As you say, if you change the path of something by .3 arc-seconds, and the earth itself paints a target .1 arc seconds wide from it's perspective, you just missed the earth by .2 arc seconds. It doesn't matter that you imparted a tiny amount of energy because it isn't about stopping it or destroying it, but deflecting it.

The further the earth is in total traveled distance to intersect determines the arc-width of the earth and at further distances that arc-width is smaller.

It's similar to the effect of course failures in an airplane. A course failure at the start and you could end up 1000 miles away, where an identical course failure halfway on only leads to 500 miles difference!

Asteroids should never be allowed to be a falling-(rock)-problem.