Reality check on SF action scenes

[chasrob]

I just realized that the pic is rather confusing! It's supposed to be a perspective from close behind the asteroid viewing toward the distant earth.
Perhaps this would be clearer-

EDIT: I wonder if I could find out if I got Kerbal?

 

[Janus]

I just realized that the pic is rather confusing! It's supposed to be a perspective from close behind the asteroid viewing toward the distant earth.
Perhaps this would be clearer-

EDIT: I wonder if I could find out if I got Kerbal?

From your diagram I'm going to assume that the Sun is to the left. In this case the asteroid will miss 1,000,000 km further out. The problem with just shoving the Asteroid in is that as the asteroid moves in towards the Sun, it will gain gravitational potential energy. This will result in a velocity gain of ~4.3 km/sec . This will have it arriving at the intercept with the Earth's orbit sooner (earlier than the Earth reaches that point). You would have to compensate the Shove direction and magnitude to compensate. More of a problem is the fact that if your trajectory was that far off from the start, that means that the asteroid was following a different orbital path. The proper trajectory was chosen because it got to Earth orbit distance at the same time as the Earth was there. If you alter the orbit, you also alter the timing. An orbit that misses by 1000,000 further out would also miss by a factor of time. (In other words, when it arrives at its closest approach to Earth orbit, the Earth won't be there.

If you need the 1,000,000 km miss for your plot, I'd suggest an orbital inclination error instead, The asteroid will arrive at Earth orbit distance at the same time as the Earth, but above its orbital plane by 1,000,000 km. This is a much easier problem to correct as you don't have the GPE or orbital timing issues.
In this case, A miss by 1,000,000 km that needs to be corrected when the asteroid is 2,000,000 km short of the Earth's position will take a delta v of ~18 km/sec in order to correct the inclination for a proper interception. Though honestly, I would think that 2,000,000 km, is awfully close for the asteroid to have gotten before the cohorts noticed the discrepancy( by this time the asteroid would be ~26 degrees from where it should be as seen from the Earth.)

 

[chasrob]

Why did I consider the miss? Delving deeper into my plot, I see that superguy has a major problem. Such precision in orbital maneuvers would not be possible as I see him. He can get the velocity down to +/- 1km/s but the vector angle? His cohorts on Earth number a half dozen trusted friends, the handiest of which has a minor in astronomy. She plots his courses and has an automated 16” Dobsonian with a camera attachment. Which I suppose could be used to track the planetoid (plus use Stellarium?) and alert him of trouble.

The point is superfella is a couple hundred million kms from home and ~15-20 minute wait on radio, has no obvious way to determine the body’s own directional vector; I can’t see how he can even visualize a new vector accurate to a tenth of a degree. So he’s going to screw the pooch there by 5 +/- deg I reckon. And the velocity too, as above.

If you need the 1,000,000 km miss for your plot, I'd suggest an orbital inclination error instead, The asteroid will arrive at Earth orbit distance at the same time as the Earth, but above its orbital plane by 1,000,000 km. This is a much easier problem to correct as you don't have the GPE or orbital timing issues.

Interesting. Wouldn’t the asteroid have its own inclination that would probably have to be taken into account too?

Though honestly, I would think that 2,000,000 km, is awfully close for the asteroid to have gotten before the cohorts noticed the discrepancy( by this time the asteroid would be ~26 degrees from where it should be as seen from the Earth.)

True, even though they’re using the rather crude amateur equipment I mentioned above.

If he launched the asteroid from the belt at ~53-54 deg and a velocity of 38 km/s could his miss be that 1 million km? Or even more of a whopper of a miss?

Maybe if its that or more, he could just do what Superman would do, just grab the chunk and fly, piloting the last 1 million klicks.

 

[Janus]

Why did I consider the miss? Delving deeper into my plot, I see that superguy has a major problem. Such precision in orbital maneuvers would not be possible as I see him. He can get the velocity down to +/- 1km/s but the vector angle? His cohorts on Earth number a half dozen trusted friends, the handiest of which has a minor in astronomy. She plots his courses and has an automated 16” Dobsonian with a camera attachment. Which I suppose could be used to track the planetoid (plus use Stellarium?) and alert him of trouble.

The point is superfella is a couple hundred million kms from home and ~15-20 minute wait on radio, has no obvious way to determine the body’s own directional vector; I can’t see how he can even visualize a new vector accurate to a tenth of a degree. So he’s going to screw the pooch there by 5 +/- deg I reckon. And the velocity too, as above.
Interesting. Wouldn’t the asteroid have its own inclination that would probably have to be taken into account too?
True, even though they’re using the rather crude amateur equipment I mentioned above.

If he launched the asteroid from the belt at ~53-54 deg and a velocity of 38 km/s could his miss be that 1 million km? Or even more of a whopper of a miss?

Maybe if its that or more, he could just do what Superman would do, just grab the chunk and fly, piloting the last 1 million klicks.

Some quick rough calculations show that 38 km/sec at 54 deg deflection results in a perihelion that is a better part of 1 AU further out from the Sun than Earth orbit is. Put another way, your asteroid wouldn't even get inside of Mars' orbit. Your superfella is going to either going to need to start with very precise calculations or being making constant corrections along the way. And the only way he is going to know what those corrections need to be is if someone is tracking the asteroid in the whole way.

Inclination correction is generally taken care of with what is known as a "broken plane" maneuver, in which you wait until you reach the point in your trajectory where it is crossing the orbital plane of the target body to make the correction. This is an easier method than trying to include the correction at the onset.

 

[chasrob]

Some quick rough calculations show that 38 km/sec at 54 deg deflection results in a perihelion that is a better part of 1 AU further out from the Sun than Earth orbit is. Put another way, your asteroid wouldn't even get inside of Mars' orbit. Your superfella is going to either going to need to start with very precise calculations or being making constant corrections along the way. And the only way he is going to know what those corrections need to be is if someone is tracking the asteroid in the whole way.

Inclination correction is generally taken care of with what is known as a "broken plane" maneuver, in which you wait until you reach the point in your trajectory where it is crossing the orbital plane of the target body to make the correction. This is an easier method than trying to include the correction at the onset.

I was afraid of that :), hoping that a small velocity error would minimize the mistake, until I finally realized a 1km/s error is actually a huge screw-up on McGuyver-man’s part.

If he instead made the same deflection but the body ended up with a 37.05 km/sec velocity, would the perihelion be closer to Earth (a few million klicks)?

 

[Janus]

I was afraid of that :), hoping that a small velocity error would minimize the mistake, until I finally realized a 1km/s error is actually a huge screw-up on McGuyver-man’s part.

If he instead made the same deflection but the body ended up with a 37.05 km/sec velocity, would the perihelion be closer to Earth (a few million klicks)?

Sorry I took so long to get back to you, but this took a bit finer calculation then my earlier one did. In order to determine by how much the asteroid would miss, you need to consider a number of factors, 1) the new perihelion distance, 2) how the perihelion position shifts with respect to the original target position and 3) how this effects the timing of the orbit. (remember we calculated for what it would take for the asteroid to arrive at a given point at the same time as the Earth was there.)
Also, the 37 km/sec value was a rounded number, so I had to go back and refine it first.
The end result is that the perigee will shift by ~1,000,000 km clock-wise (the orbit directions are CCW), it will be ~1.4 million km further out, and it will arrive there ~4 hrs later than originally planned. In other words, when it arrives at perigee, it will be ~1.5 million km "behind" the Earth (The Earth will have moved past the original rendezvous in that 4 hrs) . and 1.4 million km further from the Sun.
It will take most of 1 day for it to catch up to the Earth, so its nearest approach will be a bit over 1 day later than originally planned. It will move out from the Sun a bit more as it will be past perihelion, but this won't account for much and the asteroid will miss the Earth by just a bit over 1.4 million km. This seems to be right in range you wanted.

 

[chasrob]

Sorry I took so long to get back to you, but this took a bit finer calculation then my earlier one did. In order to determine by how much the asteroid would miss, you need to consider a number of factors, 1) the new perihelion distance, 2) how the perihelion position shifts with respect to the original target position and 3) how this effects the timing of the orbit. (remember we calculated for what it would take for the asteroid to arrive at a given point at the same time as the Earth was there.)
Also, the 37 km/sec value was a rounded number, so I had to go back and refine it first.
The end result is that the perigee will shift by ~1,000,000 km clock-wise (the orbit directions are CCW), it will be ~1.4 million km further out, and it will arrive there ~4 hrs later than originally planned. In other words, when it arrives at perigee, it will be ~1.5 million km "behind" the Earth (The Earth will have moved past the original rendezvous in that 4 hrs) . and 1.4 million km further from the Sun.
It will take most of 1 day for it to catch up to the Earth, so its nearest approach will be a bit over 1 day later than originally planned. It will move out from the Sun a bit more as it will be past perihelion, but this won't account for much and the asteroid will miss the Earth by just a bit over 1.4 million km. This seems to be right in range you wanted.

Yes, thanks to your fine calculations, the plot goes as I planned. Protag is transformed. Hears about the greater than $100 trillion value of these asteroids. Gets greedy and plots, along with his small team of cohorts, to get the body into Earth orbit. Superguy is told to launch according to your parameters, so he can just let the planetoid come to him in 3 months while he’s doing various feats of derring-do. Unfortunately, he fouls up, although unintentionally, and is eventually informed of that fact when said cohorts comparatively crude equipment reveals he’s screwed the pooch. They decide to sit tight and let it reach perigee, and since its only 1-2 Mkm distant, he can guide constantly and ride it into orbit within a few hours.

Now I only have to dig up some magic somewhere that allows him to apply pressure to the asteroid during maneuvers that equals hundreds of thousands of times that in the center of the Sun. Enough to fuse the iron for an extra kick?

 

[GTOM]

I speculated about 100MW fusion drives (for a 100ton ship).
Then i guess, a space destroyers cannons could expend 10 MJ x-ray beams in every second. ( at least for a while, focusing lenses are more vulnerable than the thrusters, i expect, that the focusing stuff of laser cannon can be damaged by a scale smaller cannon)
A fleet of 15 ships, destroyers, cruisers, battleship could expend around 400 MJ in every sec.
As far as i know, martian atmosphere swallows 10-20% of x-rays at most.

Is it a bit plausible, that a reinforced government building (on Mars, capital at equator, so they could built a space elevator near to it) could withstand such a laser siege for about a minute?
I read the WTC bomb was around 600kg, and it wasnt enough for collapse.

 

[chasrob]

Concerning the superhero story above; I am at a loss for how the super could perform a maneuver which requires him to slow/accelerate the body at a precise vector, considering the tools he could use. If he wants to do that discreetly, how would he, McGuyver-man, sitting on an asteroid a couple hundred million klicks from nowhere, determine its motion close enough for even a rough maneuver?Would a potato-shaped Ni-Fe asteroid, undisturbed for millennia, settle into an orbit with its long axis identical to its velocity vector? It couldn’t be that easy, could it? He could then position a protractor and...

 

[chasrob]

I have a protagonist who is super powered and doesn't need to breathe. Ergo, he needs no spacesuit when he ventures into outer space.

He is helping construct a moon base. In one instance Superguy absent-mindedly steps outside his habitat into the vacuum in his everyday clothes. His shirt is polyester-cotton and he's wearing denim jeans, and say, he's wearing cotton socks and leather shoes.

Would this outer wear stand up long in the rigors of space? Particularly the wild temperature ranges in shade and sunlight would be too much on the cloth; even spandex, eh?

 

[Janus]

Okay, while the daytime vs. nighttime surface temps on the Moon can vary from 123 to -153c, this comes from being exposed to the Sun for 14 days straight and then cooling for 14 days. You aren't going to get those kinds of temp changes just walking from sunlight to shade, as you are going to get some heat conduction from the Sunlit surface flowing to shadowed ones. Also, in a vacuum, anything not in direct contact with the surface will not get much heating or cooling. His shoes, making contact with the surface, would take the brunt of the abuse.
Even in the dead of Lunar night I don't see a problem for most of his clothing, as being close to his skin, his own body heat should be enough to protect it from the lack of heat (since your super himself can withstand the rigors of space, we can assume that he can also regulate his body temp under such conditions.)

 

[chasrob]

Does that mean on lunar midday he could be walking over moon dust heated to 123C? Hot enough to boil water?

 

[DaveC426913]

Does that mean on lunar midday he could be walking over moon dust heated to 123C? Hot enough to boil water?

What would happen if you took a pair of sneakers, a T and a pair of jeans and dumped them in a steam cooker?

Well, the rubber sneakers would melt, but I suspect the rest would simply come out very clean*.

* assuming there's steam that is. Does your super-guy also not perspire any water from his skin or breath?

 

[chasrob]

No, the character doesn't do either. He's non-biological--an entity.

Hmm. I don't recall if any of the moon walkers suffered from hot foot.

 

[Janus]

No, the character doesn't do either. He's non-biological--an entity.

Hmm. I don't recall if any of the moon walkers suffered from hot foot.

That's because the landings were always timed to take place near Lunar dawn at the landing sites.( Notice that there are always long shadows in all the Moon mission photos)

 

[chasrob]

That's because the landings were always timed to take place near Lunar dawn at the landing sites.( Notice that there are always long shadows in all the Moon mission photos)

Plus it appears they did have some heavy duty boots-

 

[GTOM]

I have wondered about the following, i would describe a laser duel between spaceships, that part of the exterior armor plates have been vaporized, but a magnetic field quickly rearranges the plates, so no spot remains undefended (except own laser cannons)
Could it work in near future?

 

[DaveC426913]

a magnetic field quickly rearranges the plates

Why magnetic? Why not mechanical?

 

[GTOM]

Why magnetic? Why not mechanical?

I just thought a magnetic field can properly rearrange armor shards without attaching mechanical arms to each plate.

 

[GTOM]

What would happen to people inside a room, if enemy throw in a dozen stun grenades (flashbangs)?

It should be a generator room, strong walls, enough to house a 100-200 MW generator, so i guess it should be at least 10m long, 5m wide, 4m tall.

 

[GTOM]

Can it be right, that transhuman heroine can fry RFID chips with EMP, open an electromagnetic door lock, but can't knock out permanently an electric torch?
(I guess transistors of control systems are more sensitive than electric lighting.
Later she would fight a cyborg bodyguard, at first her pulse would be rather ineffective, but after multiple bullet hits, Faraday cages damaged, and she can slow the cyborg down a bit with next pulse)

 

[DaveC426913]

I just thought a magnetic field can properly rearrange armor shards without attaching mechanical arms to each plate.

View attachment 120168

I didn't see this till now.

Magnetism doesn't quite works that way. The filings are aligned with the field, true, but they are held in position by the paper substrate.
Without gravity and friction, your armour playing would simply be attracted directly to the magnets.

 

[DaveC426913]

Can it be right, that transhuman heroine can fry RFID chips with EMP, open an electromagnetic door lock, but can't knock out permanently an electric torch?
(I guess transistors of control systems are more sensitive than electric lighting.
Later she would fight a cyborg bodyguard, at first her pulse would be rather ineffective, but after multiple bullet hits, Faraday cages damaged, and she can slow the cyborg down a bit with next pulse)

She could do whatever you want her to. In a fantasy setting, there's little point in drawing a line between this fantastic events and that fantastic event.

 

[GTOM]

I didn't see this till now.

Magnetism doesn't quite works that way. The filings are aligned with the field, true, but they are held in position by the paper substrate.
Without gravity and friction, your armour playing would simply be attracted directly to the magnets.

She could do whatever you want her to. In a fantasy setting, there's little point in drawing a line between this fantastic events and that fantastic event.

The shards can be held by a nonmagnetic layer above the magnet.

Besides FTL (mostly communication), no fantasy. She get nano upgrades, but she can't do anything that a sophisticated lab equipment can't do. Microwaves can definitally affect electromagnetic stuff.
The constraint of her abilites has to be not enough energy density to seriously harm humans, or disarm them from a distance.
I just wondered, whether its enough to say a portable electric lamp is much more robust than an electromagnetic lock, so a well directed microwave pulse can deal with the later, not the former.
(The lock supposed to protect a generator room, in case of power failure, some kind of damage it should open so they can access the generator. It could be opened remotely by system administrator, but maybe local radio key should also work in case of central operating system crashes or whatever. )
If that scenario isn't realistic enough, i can find other ways, i already modified escape plot several times.

 

[chasrob]

While surfing the net this morning, I came across this paper about the probability of human self-teleportation. After a (admittedly quick) skim, are they concluding that it is equal to a number with something like ten thousand trillion trillion zeros after the decimal point? Geez, that's disheartening to a lot of SF authors (; .

With regard to an SF novel I'm working on, the setting's cosmology (which I dreamed up, of course) consists of a bubble of numerous domains, one of which we live in. With physics conducive to matter and life. There are 4→7→3→3 of these domains in the cosmic bubble, a minuscule number compared to the total number of domains in the bubble, but a large number nonetheless (: . Am I right in concluding that there are googolplexes upon googolplexes of domains where self-teleportation is possible in my setting?

 

[stefan r]

While surfing the net this morning, I came across this paper about the probability of human self-teleportation. After a (admittedly quick) skim, are they concluding that it is equal to a number with something like ten thousand trillion trillion zeros after the decimal point? Geez, that's disheartening to a lot of SF authors (; .

What prevents the atoms from rearranging as iron? Would be much easier to teleport a mouth full of water and make a fusion device.

 

[chasrob]

I’m working on a story that has an amateur astronomer tracking an asteroid. Its H is about 12, and this body is on an (approximate) earth-intercept trajectory from the main asteroid belt. It will pass within a million or so miles on its current trajectory. She minored in astronomy and is quite knowledgeable about that subject.

I didn’t, so a few questions. She wants to get a snapshot of the body at different times before it arrives, and compute how close it will be when it arrives in the vicinity of earth.

Will a telescope setup like https://www.meade.com/telescopes/lx600-acf-10-f-8.html?___SID=U be adequate? Most importantly, can she then calculate a new trajectory for the asteroid (using that scope and a camera) that will bring it closer to the earth?

 

[chasrob]

In my story with a superman protagonist, he tries to impress by pushing his fist through a battleship’s armored deck hatch (similar to this).

We’re talking about 8-10 inch thick high tensile steel, although manufactured during WWII.

What would actually happen if he just casually pushed his fist through the hatch? Would the steel liquefy under so much pressure, as I guess? Or would it just distort and rend apart? With a loud racket, as far as noise is concerned?

If he rapidly punched through instead, you’d hear a god-awful loud racket, would you not?

 

[stefan r]

What would actually happen if he just casually pushed his fist through the hatch? Would the steel liquefy under so much pressure, as I guess? Or would it just distort and rend apart? With a loud racket, as far as noise is concerned?

If he rapidly punched through instead, you’d hear a god-awful loud racket, would you not?

It would be loud either way. Pushing through slowly you run into the problem of feet pushing through the floor.

As steel (or similar crystals) deform there are dislocations in each crystal grain. Most dislocations in a lattice disappear if you have two of them. The individual atoms are dislocated by half a step and a full step is just a normal crystal with no dislocation. At high velocity the perpendicular(or angled) dislocations get "tangled". So the same plate will shatter or spall under a high velocity impact and it will stretch, become thinner, and then rip when subjected to low velocity pressure.

We’re talking about 8-10 inch thick high tensile steel, although manufactured during WWII.

Usually high tensile strength is more likely to fracture. It is not very likely that they used high tensile strength steel for a hatch. After the 1890s navies were using Krupp armor. (or Harvey armor which is similar) The outside face will be high carbon steel. It will have higher tensile strength, an harder surface, and it is much easier to shatter (low fracture toughness). The inside face will be low carbon and soft. This is one solid piece of metal but a gradient in the carbon content. The soft steel is much less likely to spall. Sometimes armor bounces a shell away but little bits of shrapnel fly off the inside surface and kill anyone on the other side. Modern armies have anti-tank shells that maximize spall.

Punching from the inside out will be easier than punching from the outside in. It is still hard to punch through a steel plate regardless. The difference in direction will be the equivalent of ±10 to 20% in thickness. Punching out will just break the clamps.

 

[DaveC426913]

What would actually happen if he just casually pushed his fist through the hatch? Would the steel liquefy under so much pressure, as I guess? Or would it just distort and rend apart? With a loud racket, as far as noise is concerned?

It would buckle and crimp with groaning and clanking. Eventually, it would fold enough that it would just fall through the opening.

Assume his fist is simply a solid steel pole, with an arbitrarily massive weight on the top.
Think about what would happen if you stood a tank on its main gun on the hatch.

If he rapidly punched through instead, you’d hear a god-awful loud racket, would you not?

Imagine it being hit with a kinetic artillery shell (i.e. no explosive, just kinetic energy) just massive enough to bust it.
That's exactly what his arm is doing.

 

[stefan r]

It would buckle and crimp with groaning and clanking. Eventually, it would fold enough that it would just fall through the opening...
.

The hatch looks like a 45°angle, is hard to tell from a picture. Suppose it is 20 cm thick and the top width is 1 meter. The inner width of the hatch would be 60cm. In order to fold the hatch through the portal without breaking the portal you will need to compress the top by 40%. The "fold" would be more than 90°. The bottom inside of the hatch needs to stretch. It is hard to find a steel that can elongate 20% without failure. I believe that either the hatch will rupture with cracks growing from the inside or the corners of the portal will rip outward.

...

Assume his fist is simply a solid steel pole, with an arbitrarily massive weight on the top.
Think about what would happen if you stood a tank on its main gun on the hatch.
...
Imagine it being hit with a kinetic artillery shell (i.e. no explosive, just kinetic energy) just massive enough to bust it.
That's exactly what his arm is doing.

This cannot be the same. The recoil on a tank gun has more force than the shell it fires because gas also leaves the barrel. We do not normally see tank barrels punching a hole through the turret of tank that fires a shell. The turret also does not usually shear off the shoulder. The tank moves backwards and the suspension system transfers the momentum to the ground. If another tank fires a shell at the rear of a tank's turret the shell does usually go through. Sometimes shells can shear off turrets too. A piddly wave will displace an Iowa battleship much more than firing the 16 inch gun (video skip to 2:24).

There is no time for the displacement to spread around the mass of the tank when it gets hit by a shell. The damage is done in the impact area and a ring/cone around the impact location. A pole with weight on it is very different. You could push most ships under the water without rupturing a 20cm iron plate.

 

[DaveC426913]

This cannot be the same. The recoil on a tank gun has more force than the shell it fires because gas also leaves the barrel. We do not normally see tank barrels punching a hole through the turret of tank that fires a ...

Wait, wait.

Two unrelated scenarios that the OP provided.
1] A slow, inexorable push.
2] A punch.

The first scenario is comparable to simply balancing a sufficient mass on a contact surface the size of a fist. A tank, or any other massive object - balanced on a pole - will simply push its way through the hatch.

The second scenario is comparable to any method of conveying sufficient kinetic energy to the hatch. A ballistic mass sufficient to penetrate the hatch will be tantamount to a punch of equivalent kinetic energy.Actually, I'm not sure if that directly addresses your comments after all. Still, I see no flaw in my logic. Nor do I see where your logic counters mine.

A slow, inexorable push can be simulated by a sufficient weight on a fist-sized area.
A punch can be simulated by anything delivering sufficient kinetic energy.

 

[chasrob]

When y’all said pushing through, low velocity, would be loud, do you think it will be deafening in a small compartment like that on a ship? As in ear damage to any humans?

 

[DaveC426913]

When y’all said pushing through, low velocity, would be loud, do you think it will be deafening in a small compartment like that on a ship? As in ear damage to any humans?

It is plausible that a particularly large release of bending steel could cause a squeal that would make most people cringe and plug their ears.
I would guess it would not be so loud as to do damage, and it's only for a moment or two. So, no.

(I hope our hero is suitably embarrassed afterwards, for not knowing his own strength, and causing such a commotion just to show off. It sounds irresponsible.

Then again, I've been assuming the demonstration is for friendlies. If it's to impress baddies, then presumably he could make the noise arbitrarily loud if he chose to.

Either way, it doesn't really sound all that heroic. Heros tend to act - when they need to - not posture.)