Asteroid Intercept

[steve_bank]

It is an expensive demonstration of Newtonian mechanics.

If the velocity of the probe goes to zero then all the kinetic energy goes to the asteroid. The quetion is how much energy actually goes to deflection.

That will be measured over time which is the point of the experiment.

A good mass to hit the asteroid might be a flatt stff metal plate. Distribute the force over a large area and reduce fragmentation.

 

[Loren Pechtel]

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.

If you can ensure the energy is evenly distributed that would be feasible. That's pretty hard to accomplish unless you can put the bomb near the center of the target, though.

 

[Loren Pechtel]

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.

Orion works. Limited flight testing has been performed with both chemical and nuclear explosives. Whether you can get something into orbit or not is questionable (it comes down to how much heat the pusher absorbs, thus whether it can do a long enough burn to reach orbital velocity without overheating is problematic) but you don't want high thrust when moving rocks.

 

[Loren Pechtel]

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.

Vaporizing asteroid material is quite useful--Newton's Third Law. And you have some control of how fast it comes off--the energy flux is a function of the bomb energy and standoff distance. I've seen numbers of 10% for this assuming ordinary h-bombs--and suggestions that a Casaba howitzer approach (effectively, shaped charges) might reach 80% but the data is still classified. While a buried bomb obviously is more efficient you pay a huge efficiency penalty in landing and burying the bomb--that requires rendezvous rather than merely flyby. Unless it's a NEO that you can catch in a flyby on a previous orbit that means a huge amount of fuel.

 

[bilby]

Don't wait until the rock is hurtling straight at Trump Tower but instead give it a gentle nudge an orbit or two earlier.

To ensure that it hits Trump Tower dead centre?

 

[Jimmy Higgins]

It is an expensive demonstration of Newtonian mechanics.

If the velocity of the probe goes to zero then all the kinetic energy goes to the asteroid. The quetion is how much energy actually goes to deflection.

That will be measured over time which is the point of the experiment.

A good mass to hit the asteroid might be a flatt stff metal plate. Distribute the force over a large area and reduce fragmentation.

This wasn't about momentum, this was about a computer resolving a smaller object, near a bigger one, and targeting the smaller object. That worked perfectly.

 

[Loren Pechtel]

It is an expensive demonstration of Newtonian mechanics.

If the velocity of the probe goes to zero then all the kinetic energy goes to the asteroid. The quetion is how much energy actually goes to deflection.

That will be measured over time which is the point of the experiment.

A good mass to hit the asteroid might be a flatt stff metal plate. Distribute the force over a large area and reduce fragmentation.

This wasn't about momentum, this was about a computer resolving a smaller object, near a bigger one, and targeting the smaller object. That worked perfectly.

And seeing if any gotchas show up--they know how much energy it hits with, because it's a moon they can very accurately measure how much velocity was imparted. You don't want to find out your models are wrong when the threat is real.

 

[steve_bank]

If you wanted to pulverize a large asteroid it might take multiple atomic bombs drilled into ateroid expaloding simualteneously.

Conventional explosives might work. That would probably require humans on the asteroid.

There is an idea to keep a probe at a combatant distance form the asteroid. Use gravitational attraction.

'Gravity tractor' could deflect asteroids

The gravitational pull of a spacecraft placed near an Earth-threatening asteroid could pull the asteroid off course, a new NASA study finds

www.newscientist.com

A “gravity tractor” could deflect an Earth-threatening asteroid if it was deployed when the asteroid was more than one orbit away from the potential impact, according to a new study. If the space rock was found heading straight for Earth, a combination of techniques – including a gravity tractor – might save the day.

The study, carried out by NASA’s Jet Propulsion Laboratory in Pasadena, California, shows that the weak gravitational pull of a nearby spacecraft could deflect a hypothetical asteroid 140 metres across, big enough to cause regional devastation if it hit Earth.

“Prior to this study, the gravity tractor deflection technique had been proven in only a conceptual way,” says Clark Chapman of the Southwest Research Institute in Boulder, Colorado, who was not involved in the study.

“Although there were few, if any, substantive criticisms of these concepts, some of us had the feeling that the ideas were viewed as quaint but not-ready-for-prime-time,” he says. “The JPL study gives it the solid engineering underpinnings that we never really doubted, but now are there for anyone to see.”

Exactly how much of a push is needed to deflect an asteroid depends on how long before a potential impact the intervention begins, and what kind of orbit the object is going to follow in the interval, says Rusty Schweickart, a former Apollo astronaut and chairman of the B612 Foundation, which funded the study.

M solution.

A flat plate that unfolds in transit. Engines on the plate with thrust vectoring. Give it a long push.

 

[steve_bank]

NASA's Asteroid-Capture Mission May Test New Method to Defend Earth

NASA's bold plan to park an asteroid near the moon may also test out a new way to protect Earth from dangerous space rocks.

www.space.com

NASA's bold plan to park an asteroid near the moon may also test out a new way to protect Earth from dangerous space rocks.


Last year, the agency announced that it intends to tow a near-Earth asteroid into a stable lunar orbit, where it could be visited repeatedly by astronauts for research and exploration purposes. NASA officials are still ironing out the details of the mission, which may bag up an entire small space rock or snag a boulder off the surface of a large asteroid.

If NASA decides to go with the boulder option, the asteroid-capture mission will also include a planetary-defense demonstration, providing the first in-space test of a so-called "enhanced gravity tractor," officials said. [Images: NASA's Asteroid-Capture Mission]

 

[Jarhyn]

Don't wait until the rock is hurtling straight at Trump Tower but instead give it a gentle nudge an orbit or two earlier.

To ensure that it hits Trump Tower dead centre?

I mean... Find a rock big enough to do the damage, small enough not to damage anything else, and a rocket far enough out to aim it and stick the landing...

 

[lpetrich]

DART’s Small Satellite Companion Tests Camera Prior to Impact | NASA - LICIACube's test pictures of the Earth and the Pleiades.

HUBBLE on Twitter: "1/ #BFFinSpace ..." / Twitter

1/ #BFFinSpace Hubble (L) and Webb (R) have captured detailed views of the #DART impact, marking the first time that the two observatories have viewed the same target simultaneously. Read more: https://esahubble.org/news/heic2212/

2/ On 27 September at 01:14 CEST, #DART intentionally crashed into #Dimorphos, an asteroid moonlet. It was the world’s first test of the kinetic impact technique using a spacecraft to deflect an asteroid, a test for defending Earth against asteroid or comet hazards.

3/ This gif shows Hubble's view of the collision: ejecta, material thrown out from the impact, appears as rays stretching out from the body of the asteroid. The bolder, fanned-out spike of ejecta to the left of the asteroid is where DART impacted.

4/ And here is @ESA_Webb 's complementary view of the impact, a tight, compact core, with plumes of material appearing as wisps streaming away from the centre of where the impact took place.

5/ Both Hubble and Webb will continue to monitor Dimorphos in the coming months. Hubble will monitor Dimorphos ten more times over the next three weeks.

6. ESA's #HeraMission, due to launch in October 2024, will also perform a detailed post-impact survey of the target asteroid Dimorphos.

@NASA @esa @csa_asc @stsci

Some of these tweets have inline video from Hubble's and Webb's observations.

 

[lpetrich]

Webb and Hubble Capture Detailed Views of DART Impact | ESA/Hubble
With pictures from the Hubble and Webb space telescopes.

Webb took one observation of the impact location before the collision took place, then several observations over the next few hours. Images from Webb’s Near-Infrared Camera (NIRCam) show a tight, compact core, with plumes of material appearing as wisps streaming away from the centre of where the impact took place.

Observing the impact with Webb presented the flight operations, planning, and science teams with very unique challenges. Because of the asteroid’s speed of travel across the sky, the teams worked in the weeks leading up to the impact to enable and test a method of tracking asteroids moving over 3 times faster than the original speed limit set for Webb.

ESA - Hera

In the world’s first test of asteroid deflection, Hera will perform a detailed post-impact survey of the target asteroid, Dimorphos – the orbiting Moonlet in a binary asteroid system known as Didymos. Once NASA’s DART mission has impacted the moonlet, Hera will turn the grand-scale experiment into a well-understood and repeatable planetary defence technique. Demonstrating new technologies from autonomous navigation around an asteroid to low gravity proximity operations, Hera will be humankind’s first probe to rendezvous with a binary asteroid system and Europe’s flagship Planetary Defender.

Hera Launch: October 2024
Target: Dimorphos
Impact date: September 2022
Hera rendezvous: December 2026

 

[lpetrich]

There was a previous asteroid impactor,  Deep Impact (spacecraft) - back in 2005, that spacecraft released an impactor that struck comet Tempel 1. The rest of the spacecraft then flew by that comet and observed that impact.

Even earlier was Missions - Ranger 1-9 over 1961 - 1965. The first six missions failed in various ways, and the last three were successful, with the spacecraft sending back pictures of the Moon as they headed toward crashing onto that celestial body. Deliberate crashing, I must add, to get closeups of the Moon's surface.

 

[Elixir]

Rather than burying bombs, wouldn't it be more propitious to "dart" the asteroid with a rocket motor? Anchor it to the asteroid surface and fire it up... if the asteroid is rotating, have it fire repeatedly at the same point in its rotation. Bombs do seem really inefficient with their non-directionality and more, their brevity. I'd intuit that a sustained push would be far more effective. If there's water on the moon, that would be the place to launch from.

 

[Loren Pechtel]

If you wanted to pulverize a large asteroid it might take multiple atomic bombs drilled into ateroid expaloding simualteneously.

Conventional explosives might work. That would probably require humans on the asteroid.

There is an idea to keep a probe at a combatant distance form the asteroid. Use gravitational attraction.

'Gravity tractor' could deflect asteroids

The gravitational pull of a spacecraft placed near an Earth-threatening asteroid could pull the asteroid off course, a new NASA study finds

www.newscientist.com

Why is this even in consideration?

The only thing a gravity tractor does is allow you to pull the target without landing on it--it doesn't matter if it's a pile of dust, it will still move. However, it requires more thrust than it would take if the engine simply landed on the asteroid and does nothing to provide such thrust. It also has the problem that the thrust has to be applied off-axis because on-axis means your rocket hits the target and wastes much of your thrust--in an extreme case it could actually push the asteroid the other way.

 

[Loren Pechtel]

Rather than burying bombs, wouldn't it be more propitious to "dart" the asteroid with a rocket motor? Anchor it to the asteroid surface and fire it up... if the asteroid is rotating, have it fire repeatedly at the same point in its rotation. Bombs do seem really inefficient with their non-directionality and more, their brevity. I'd intuit that a sustained push would be far more effective. If there's water on the moon, that would be the place to launch from.

Casaba howitzer might not be all that inefficient. However, the energy density really matters.

Hydrolox is 15.8 Mj/kg but nobody has ever used beyond the burn leaving Earth's orbit because it's such a pain to store. Of things that could be reasonably handled in deep space the best is methalox at 11.1 MJ/kg. The most efficient fusion bombs are 2.51+7 MJ/kg.

 

[bilby]

Casaba howitzer might not be all that inefficient.

You want to shoot Hungarian sausages at an asteroid??

 

[Loren Pechtel]

Casaba howitzer might not be all that inefficient.

You want to shoot Hungarian sausages at an asteroid??

That's Csaba, not Casaba.

 

[Bomb#20]

It is an expensive demonstration of Newtonian mechanics.

If the velocity of the probe goes to zero then all the kinetic energy goes to the asteroid. The quetion is how much energy actually goes to deflection.

That will be measured over time which is the point of the experiment.

A good mass to hit the asteroid might be a flatt stff metal plate. Distribute the force over a large area and reduce fragmentation.

This wasn't about momentum, this was about a computer resolving a smaller object, near a bigger one, and targeting the smaller object. That worked perfectly.

Actually, it was also very much about momentum. The amount of deflection of the asteroid isn't just due to the momentum transferred from the spacecraft, but also due to the equal and opposite reaction to the force that blasted debris from the impact crater into space. NASA will be studying the new orbit to calculate how much material was thrown out of the crater and how fast it escaped. The recoil is a significant factor in how effective this deflection method is, and it had to be determined by experiment, not just calculated from Newtonian mechanics.

 

[Cheerful Charlie]

https://whyevolutionistrue.com/wp-content/uploads/2022/09/309545533_5485547358178463_1785300537982417708_n.jpg