For Questions That Don't Merit Their Own Thread

[Terwin]

21 hours ago, Spacescifi said:

In broad daylight I meant.

At night is too easy.

IT is often not difficult to spot the path of a laser due to dust passing through it, but it is very difficult to get a non-coherent beam brighter than the 98 000 lux(lumens/m^2) of direct sunlight.

According to this page, there is a LED flashlight that clocks in at 100,000 lumens, so in theory it should be able to produce crepuscular rays even in broad daylight(but the difference may be too faint to see).

Edited July 5, 2019 by Terwin

[kerbiloid]

A portable crepuscular ray impulse generator.

Spoiler

They want to see crepuscular rays.

 

Edited July 5, 2019 by kerbiloid

[tater]

http://www.planetary.org/explore/projects/lightsail-solar-sailing/lightsail-mission-control.html

 

[Nightside]

2 hours ago, tater said:

http://www.planetary.org/explore/projects/lightsail-solar-sailing/lightsail-mission-control.html

 

That’s an awesome website. It will be fun to watch the mission develop.

[ARS]

Is it possible for aircraft optimized for extremely high speed (such as SR-71) to destroy enemy aircraft by using sonic boom shock wave it generates while passing near them at maximum speed?

[Spacescifi]

20 minutes ago, ARS said:

Is it possible for aircraft optimized for extremely high speed (such as SR-71) to destroy enemy aircraft by using sonic boom shock wave it generates while passing near them at maximum speed?

 

Strange question... what? For a story or something? Hope not for reals.

Because in real life this could end up being suicide for both planes.

The answer is... like most things in science, it depends.

So yeah. You could do some damage, leading to a crash... or a two for one, with the attacker included.

 

[Gargamel]

2 hours ago, ARS said:

Is it possible for aircraft optimized for extremely high speed (such as SR-71) to destroy enemy aircraft by using sonic boom shock wave it generates while passing near them at maximum speed?

Don't know about destroy, but it would probably cause some issues at the least for them.

The issue is getting close to them.   Given the SR71 has a turn radius of about 80 miles, getting your target to hold still long enough to line up properly might be the real problem.   Not only that, but just like in KSP, it could only go at speed at altitudes higher than your average fighter would be at. 

 

[ARS]

6 hours ago, Spacescifi said:

Strange question... what? For a story or something? Hope not for reals.

No, I just read the history of supersonic aviation where US tested the prototype of supersonic aircraft and the effect of sonic booms towards local population. It's said that the frequent flight test caused a lot of disturbance to daily lives of locals and at times breaking the windows. Then I'm thinking, if sonic booms could break windows, could it destroy aircraft if it's close enough to the shockwave source?

[magnemoe]

On 7/5/2019 at 2:13 AM, micha said:

Ah yes, all the modern "safety features" which actually bury useful functionality.  Aim for the lowest common denominator and evolution will take care of the rest.

This, note that an railway crossing is an extreme example but an relative managed to get out of the exit of an turnabout then his car stopped. 
 

[magnemoe]

18 hours ago, Gargamel said:

Don't know about destroy, but it would probably cause some issues at the least for them.

The issue is getting close to them.   Given the SR71 has a turn radius of about 80 miles, getting your target to hold still long enough to line up properly might be the real problem.   Not only that, but just like in KSP, it could only go at speed at altitudes higher than your average fighter would be at. 

 

It don't take that much of an overpressure to destroy windows as long as it comes as an fast shock wave. You can punch in simple window glass after all and kicking is trivial. 
Planes on the other hand are pretty sturdy. to survive turbulence and hard landings. 
Know they have used b1 bomber going low and supersonic to rattle and hopefully panic enemies, not dangerous outside of hearing but would remove camouflage nets well. 

Turbulence is the real killer, its restriction on how fast planes can use an runway after the previous plane and you don't want an small plane taking off just after an huge one because of turbulence.
 At high attitude you should be able to recover but at takeoff it could be very dangerous. 
Back in WW2 they used this to take out V1 bombs, fly very close to it, flip closest wing up, the air would force the V1 wing hard up to and it tended to go into an spin and the primitive autopilot was not able to recover. 
 

[kerbiloid]

A shockwave overpressure.
Windows full destruction = 2..3 kPa, armored glass = 3..5 kPa.
A parked cargo plane or a helicopter: light damage = 5..8 kPa, full destruction = 15 kPa.
Jets are somewhat stronger.

Edited July 7, 2019 by kerbiloid

[DDE]

On ‎7‎/‎6‎/‎2019 at 1:40 PM, ARS said:

No, I just read the history of supersonic aviation where US tested the prototype of supersonic aircraft and the effect of sonic booms towards local population. It's said that the frequent flight test caused a lot of disturbance to daily lives of locals and at times breaking the windows. Then I'm thinking, if sonic booms could break windows, could it destroy aircraft if it's close enough to the shockwave source?

The Mythbusters were unable to shatter any glass, even with a jet fighter.

https://www.youtube.com/watch?v=GvtAElaDVz8

Edit: oh, wait... apparently under some circumstances it works.

Edited July 7, 2019 by DDE

[ARS]

Why, if two objects moving so close against each other (almost colliding, bordering on grazing) is called "near miss"? Should it be "near hit"? And if those two objects does collided, should it be called "near miss" instead of "collision"?

[tater]

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20180006734.pdf

[tater]

Cool, lightsail 2 will open up soon:

 

 

[tater]

 

[DDE]

20 hours ago, tater said:

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20180006734.pdf

Not twisted ribbons?

[tater]

 

[tater]

 

[kerbiloid]

Please, is there some picture of the Orion, or CST-100, or Dragon capsule-to-the-SM attachment place?

I mean, ye olde ship capsules of 1960s like Apollo, Soyuz, VA of TKS were attached with barbaric simplicity: just several metal bars/rods stick out from the capsule bottom, pierce the heatshield in several points (afaik, 3 for Apollo, 4x2 for TKS VA, many for Soyuz) and are attached to a ring (Soyuz) or radial stiffeners (Apollo) like in this Vintage Space video.
 

Spoiler

 

On deorbiting the bars/rods get cut, and their stumps totally burn off, leaving just spots on the smooth heatshield surface.

Do the modern capsules detach in same radical way? Or they use something more glamourous, like latches or so? After all, unlike those ones, these were designed as reusable.

***

The root of the question was:
the capsule bottom is a segment of sphere;
the service module is a hollow cylinder with flat ring-like face on top;
so, a sphere is attached to a flat ring.

As I can see, in real world  there is always a gap between the capsule and the SM, covered with insulation or so.

In KSP we can just make the SM's upper edge conform to the heatshield sphere, so there will be no gap between them.
But in this case the upper edge of SM starts looking sharp and unrealistic.

So, does anybody know how does this place look in modern ships?

[tater]

 

[magnemoe]

On 7/25/2019 at 2:59 PM, kerbiloid said:

Please, is there some picture of the Orion, or CST-100, or Dragon capsule-to-the-SM attachment place?

I mean, ye olde ship capsules of 1960s like Apollo, Soyuz, VA of TKS were attached with barbaric simplicity: just several metal bars/rods stick out from the capsule bottom, pierce the heatshield in several points (afaik, 3 for Apollo, 4x2 for TKS VA, many for Soyuz) and are attached to a ring (Soyuz) or radial stiffeners (Apollo) like in this Vintage Space video.
 

  Reveal hidden contents

 

On deorbiting the bars/rods get cut, and their stumps totally burn off, leaving just spots on the smooth heatshield surface.

Do the modern capsules detach in same radical way? Or they use something more glamourous, like latches or so? After all, unlike those ones, these were designed as reusable.

***

The root of the question was:
the capsule bottom is a segment of sphere;
the service module is a hollow cylinder with flat ring-like face on top;
so, a sphere is attached to a flat ring.

As I can see, in real world  there is always a gap between the capsule and the SM, covered with insulation or so.

In KSP we can just make the SM's upper edge conform to the heatshield sphere, so there will be no gap between them.
But in this case the upper edge of SM starts looking sharp and unrealistic.

So, does anybody know how does this place look in modern ships?

In KSP its an default fairing between the heat shield and the service module / last stage.
This was also shown in her video, assume dragons and orion uses the same setup as the heat shied is curved. 
Explosive bolts makes sense here, you do not want to reenter with an service module. 90% sure orion uses them. Not sure about dragon as spaceX don't like them as they can not be tested or reused. but reuse is not much of an option here as decopler has to be on the trunk, if inside the capsule it leaves an hole in the heat shield and the mechanic is toasted anywyay 

[tater]

On 7/25/2019 at 6:59 AM, kerbiloid said:

So, does anybody know how does this place look in modern ships?

That's Dragon.

[kerbiloid]

Thank you!

Looks like still piercing the heatshield in dedicated places.

These brown things with blue handles(?) look like plugs, screwed into the openings by rotating with the handle.

Probably they have some expendable things which they put in the channels before (every) flight and replace after.

Also looks like the channels are tilted, not vertical. So the fairing is probably wider than the circle of openings, and struts are not vertical.

 

Also it's nice how the tiles are asymetrically placed, not central, probably at the angle of attack of the capsule normal aerobraking,

It's strange then that the openings are placed asymmetrically relative to the tile pattern.

Edited July 26, 2019 by kerbiloid

[mikegarrison]

I've read George Dyson's book, but it was quite a while ago. One thing I don't recall is the following:

If you have a 10,000 tonne nuclear pulse spaceship, how do you steer it? What kind of RCS would it take to turn such a ship around in order to decelerate?