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3I/ATLAS: Probably NOT an alien interstellar probe

 
 
 
DBT said:
He must realize that he can end up looking like a fool? So why risk it? Because he thinks the pay-off would be huge if he is right?

What are the odds?
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Because it’s clickbait and somewhere downstream he is making money. Those people who tell you the world is going to end on such and such a date suffer no penalty for being proven wrong. They just move on to the next date. And keep their fan base.
 
Basically I think Loeb is like a religious leader or a cult leader, like Trump. He tells people what they want to hear, and can never be proven wrong.
 
Wow, I just figured it out.

ET in orbiting in invisible spaceships are on the net posting on the forum.

That explains a lot.
 
Elixir said:
Loren Pechtel said:
No, the point is there is no possible suspension as you can only transmit the force at the speed of sound.
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Yet you can continuously apply 16000 gs to a tardigrade for a full minute without killing it?
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No idea on the g-tolerance of a tardigrade, but what's the relevance? I'm talking about speed, not acceleration. Your 16,000g is unquestionably from a centrifuge, it's just going round and round, not smacking the atmosphere.
 
bilby said:
Loren Pechtel said:
bilby said:
The maximum velocity increase achievable relative to the Sun, by gravitational slingshot from a planet, is twice the planet's orbital velocity. So the best you can do in the Solar System with a single manoevre is about 96km/s (twice the orbital velocity of Mercury).

Each slingshot manoevre is effectively a perfectly elastic 'bounce', transferring momentum to your spacecraft from tne planet. As far as I can see, if you have infinite time for the task, you could keep doing such manoevres until you have stolen all of the momentum from everything in the Solar System, and all the planets have fallen into the Sun.

Your final velocity would be huge in such a scenario; although your accelerations would get very small as your probe's mass increased due to its speed. You should achieve a sizable fraction of c for any probe with a reasonable rest-mass.
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Two problems:

1) They're not in the right place to do this.
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The setup in the question assumes that we can wait until they are, however long that takes.
Loren Pechtel said:
2) While in theory you could get 96km/sec out of Mercury look at the periapsis. It's way, way below the surface.
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Sure, but we are looking for an upper bound to the achievable velocity relative to the Sun. Some assumptions are justified, such as treating planets as point masses. It's not like I am asking you to consider a spherical planet in a vacuum...
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Moo!

Tables exist for the maximum velocity that can be obtained from the various planets.
 
Loren Pechtel said:
No idea on the g-tolerance of a tardigrade, but what's the relevance? I'm talking about speed, not acceleration.
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Speed isn’t an issue. You don’t mind going 500+ mph in a plane because the rate of your acceleration is gradual. If you were simply placed in the way of the plane while it was going 500+ mph, you’d get “smacked” by your instant acceleration from zero to 500. In fact you’d be pizza. Not from the speed, from the acceleration.

Same deal with imbedding a terrestrial object in a fast moving interstellar object - it ain’t the speed that will get you, it’s the acceleration, aka getting “smacked”. Surviving the impact means reducing the G forces of acceleration.

It’s NOT about the speed (until you get to relativistic speeds). Kinda like how falling from great heights won’t kill you, the rapid deceleration upon impact will.
 
Elixir said:
Loren Pechtel said:
No idea on the g-tolerance of a tardigrade, but what's the relevance? I'm talking about speed, not acceleration.
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Speed isn’t an issue. You don’t mind going 500+ mph in a plane because the rate of your acceleration is gradual. If you were simply placed in the way of the plane while it was going 500+ mph, you’d get “smacked” by your instant acceleration from zero to 500. In fact you’d be pizza. Not from the speed, from the acceleration.

Same deal with imbedding a terrestrial object in a fast moving interstellar object - it ain’t the speed that will get you, it’s the acceleration, aka getting “smacked”. Surviving the impact means reducing the G forces of acceleration.

It’s NOT about the speed (until you get to relativistic speeds). Kinda like how falling from great heights won’t kill you, the rapid deceleration upon impact will.
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I'm not talking about acceleration, I'm talking about slamming through the atmosphere very fast.
 
What atmosphere? The interstellar object ain’t in the atmosphere and if it had one of its own the sun would probably blow it away. The ability of a tardigrade to withstand such acceleration relates to its survival chances if placed in a shock absorbing capsule in the path of 31/Atlas. Are you saying it has a thick atmosphere?
 
Elixir said:
What atmosphere? The interstellar object ain’t in the atmosphere and if it had one of its own the sun would probably blow it away. The ability of a tardigrade to withstand such acceleration relates to its survival chances if placed in a shock absorbing capsule in the path of 31/Atlas. Are you saying it has a thick atmosphere?
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We were talking about launching from a planet.
 
If the capsule can be maneuvered to be in front of the object and it is low mass then having an engine to decelerate would be the thing to do.

Getting a probe or capsule directly in line with path of the object would be hard to do ballistically. There would have to maneuver engines.

Arrive in style and comfort.

moon probes have course corrections to stay on their planned trajectory
. These adjustments are made using small thrusters to make minor changes, while larger burns are used for more significant maneuvers, such as entering lunar orbit. The corrections are often pre-planned and calculated on Earth, then uploaded to the spacecraft, but some limited autonomy can also be used.
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Mars probes have in-course corrections, which are necessary to ensure they reach their destination due to the long, multi-month journey. These adjustments, performed by firing thrusters, are vital for fine-tuning the probe's trajectory after launch and can be performed multiple times before arrival to correct for external factors or the initial, less precise aim point
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Loren Pechtel said:
Elixir said:
What atmosphere? The interstellar object ain’t in the atmosphere and if it had one of its own the sun would probably blow it away. The ability of a tardigrade to withstand such acceleration relates to its survival chances if placed in a shock absorbing capsule in the path of 31/Atlas. Are you saying it has a thick atmosphere?
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We were talking about launching from a planet.
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Earth, in particular. All you need is escape velocity at the right trajectory to be intercepted. impacted and absorbed by the fast-traveling interloper. And I was only concerned with payload survival. YOU could probably do the math to figure out how long and how far the impact must last under acceleration of less than 16,000 Gs in order to reach the 218,000mph speed of 31/Atlas relative to earth … that will give you a size of compressible material and its required characteristics for a given payload to survive the acceleration of impact and go on an interstellar ride polluting the rest of the universe with the same crap that once infected this rock.
 
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Loren Pechtel said:
Elixir said:
What atmosphere? The interstellar object ain’t in the atmosphere and if it had one of its own the sun would probably blow it away. The ability of a tardigrade to withstand such acceleration relates to its survival chances if placed in a shock absorbing capsule in the path of 31/Atlas. Are you saying it has a thick atmosphere?
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We were talking about launching from a planet.
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That's a different conversation, and is happening in another thread.
 
steve_bank said:
Arrive in style and comfort.

moon probes have course corrections to stay on their planned trajectory
. These adjustments are made using small thrusters to make minor changes, while larger burns are used for more significant maneuvers, such as entering lunar orbit. The corrections are often pre-planned and calculated on Earth, then uploaded to the spacecraft, but some limited autonomy can also be used.
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Limited autonomy??

Apollo 13 made a mid-course correction on the way back from the Moon entirely manually, with the calculations done in Houston, and radioed to the astronauts before the manoevre; The burn was executed with two astronauts manually controlling the attitude of the (severely unbalanced) spacecraft, while the third used a stopwatch to time the burn and shut off at the appropriate time.

Attitude control was done by eye, using the Earth as a visual reference. Initial setup also used the Sun as a pitch reference.

https://www.nasa.gov/history/afj/ap13fj/19day5-themanualcoursecorrection.html
 
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