For Questions That Don't Merit Their Own Thread

[ARS]

How does space telescope clean the mirror and maintained? Is there any maintenance schedule for it? Since Space Shuttle is already retired and it's unlikely Soyuz is equipped for such task

Edited May 28, 2020 by ARS

[kerbiloid]

Afaik, it doesn't, as any spysat.

There is no suspended dust in vacuum to settle on it;
its optical system is hidden inside a hood protecting it from sunlight and from the dust from aside;
it's turned to the target rather than just prograde, so the hood doesn't act like a dust scoop.

[K^2]

6 hours ago, ARS said:

unlikely Soyuz is equipped for such task

Soyuz spacecraft are suitable for fine maneuvering and spacewalks. So maintenance of something like Hubble by Soyuz crew is theoretically possible. The tricky part is getting the spacecraft to correct orbit. Hubble is inclined 28°, and Baikonur is 45°N. So a Soyuz launched from there would have to make a 17° inclination change. That's a whopping 1km/s of delta-V if you do it in orbit. The current variant of Soyuz spacecraft, the Soyuz MS, typically rides to ISS on top of the Soyuz-FG rocket. The later is capable of lifting 7,800 to LEO with Baikonur inclination. Soyuz MS is designed for launch mass of 7,000-7200kg. That's just too fine of a margin to try and start making inclination changes with. However, there's also Soyuz-2, which is designed to operate at least with Progress ships, and so might be possible to adapt to a Soyuz MS launch. Soyuz-2 can get up to 8,200kg to LEO, and that's a significant improvement. So what you do is you strap Soyuz MS to a Soyuz-2 rocket. You start a normal launch until second stage. Instead of burning to orbit, second stage inserts you into a rather unpleasant ballistic trajectory that gives you a good, clean opportunity for an inclination change at the apex. Because part of the acceleration is reserved to this stage, the inclination change actually costs a lot less than 1km/s. The downside is that failure to reignite second stage here will result in an extremely unpleasant re-entry with higher than normal G forces. But should be survivable and this is the emergency in-flight mission abort option, so that's fine? Maybe? Anyways, this gets you to Hubble's orbit, where you can do a spacewalk, using orbital module as an airlock, perform maintenance, and do a fairly routine return from orbit. Caveat on that last bit is that you couldn't land in Kazakh steppes. The most suitable landing spot for a Soyuz landing from Hubble's orbit is probably going to be in Australia with backups in Africa and maybe Texas? All of these are already on the list of potential emergency landing sites, but primary landing site would have to give agreement for a non-emergency landing. Australians certainly don't welcome spacecraft crashing on them without permission. *cough*SkyLab*cough*

Naturally, nobody's going to do this. Not worth the risk and probably not the expense, either. But if there was more of a do-or-die sort of reason to pull something like this than fixing a telescope, I think it could be done.

[DDE]

1 hour ago, K^2 said:

However, there's also Soyuz-2, which is designed to operate at least with Progress ships, and so might be possible to adapt to a Soyuz MS launch.

You're talking about a Soyuz-2.1b.

1 hour ago, K^2 said:

So what you do is you strap Soyuz MS to a Soyuz-2 rocket.

Otherwise known as the standard stack for Soyuz-2.1a. They're racking up launches for the same tech on the 2.1b, and I think they still have several unmanned qualification Soyuz flights on the manifest.

1 hour ago, K^2 said:

The downside is that failure to reignite second stage here

The second stage - unless you're using Western terminology - is ignited using the PZU, which is two flares on a birch stick shoved up each of the 32 nozzles. Not sure the third stage does much better.

Could be the job for the vaguely researched Fregat-Soyuz stack.

Edited May 28, 2020 by DDE

[K^2]

2 hours ago, DDE said:

The second stage - unless you're using Western terminology - is ignited using the PZU, which is two flares on a birch stick shoved up each of the 32 nozzles. Not sure the third stage does much better.

Western terminology. I'm talking about Блок И. There's no way it will be traveling fast enough before stage separation to coast to equator, so without ability to relight the engine, no way to do inclination change.

2 hours ago, DDE said:

Could be the job for the vaguely researched Fregat-Soyuz stack.

Might work. TWR on RD-0124 is a bit on the low side for this, but I guess if people are discussing it, it's sufficient to make it work. I'm also guessing the main use would be for TLI, which should give you something like 2km/s reserve after parking in LEO. That's plenty to do the inclination change in question.

[wumpus]

14 hours ago, kerbiloid said:

Afaik, it doesn't, as any spysat.

There is no suspended dust in vacuum to settle on it;
its optical system is hidden inside a hood protecting it from sunlight and from the dust from aside;
it's turned to the target rather than just prograde, so the hood doesn't act like a dust scoop.

I'd expect that they are especially careful as any dust wouldn't just stick to the lens, it would probably cause at least local breakage/damage/pitting.  Dust at orbital velocity changes things a bit.

[kerbiloid]

3 minutes ago, wumpus said:

I'd expect that they are especially careful as any dust wouldn't just stick to the lens, it would probably cause at least local breakage/damage/pitting.  Dust at orbital velocity changes things a bit.

If tle lens and the dust are on close orbits, their relative speed is unlikely high.

[ARS]

Does a non-hydrodynamical shape (no-sharp edges, but isn't streamlined) create a noise strong enough to be picked by submarine when it's just stand still underwater? Imagine a non-hydrodynamic stuff like undersea research station. It has curves and no sharp edges, but is not streamlined against water currents (It's just an assortment of metal tubes and tanks for habitat's structure) and it's just anchored on the seabed using cables like naval mines. Assuming there's nothing onboard that makes noise, if there's ocean current around it, will submarines picked the noise?

[K^2]

Cables and any other thin structures can generate cavitation noise at pretty low current speeds. So if there are anchoring cables, my guess would be yes on audible, but I have no idea if it's something that would be distinguishable from any other background sounds. Otherwise, I think the bigger problem is how the sounds are scattered. An artificial hull has very different properties from seabed, so even if the structure produces zero noise of its own, the background noise coming from its direction is going to be different, and I believe, modern passive sonars are designed to look for things like that specifically because it lets you find subs that are trying to play dead. As for how reliable that would be, what kind of ocean conditions it depends on, and what sort of range this might have, I got no clue. Realistically, I expect cutting edge on this to be heavily classified.

[TheSaint]

1 hour ago, ARS said:

Does a non-hydrodynamical shape (no-sharp edges, but isn't streamlined) create a noise strong enough to be picked by submarine when it's just stand still underwater? Imagine a non-hydrodynamic stuff like undersea research station. It has curves and no sharp edges, but is not streamlined against water currents (It's just an assortment of metal tubes and tanks for habitat's structure) and it's just anchored on the seabed using cables like naval mines. Assuming there's nothing onboard that makes noise, if there's ocean current around it, will submarines picked the noise?

Assuming nothing has radically changed in sonar in the last 30 years, my guess would be no. We used to pick up pelagics (fish) on the sonar pretty easily, but they're moving and there's a lot of them. Cetaceans too. But, again, they make a lot of very distinctive noise. Something anchored to the bottom of the ocean with water moving past it probably isn't going to make a noise that is any more distinctive than water moving past everything else on the bottom of the ocean, unless there is something about it that will make it unusual (like one of the cables is loose and the current is tapping it against the hull or something). This is why all of the shipwreck searchers use active sonar. 

[K^2]

1 hour ago, TheSaint said:

Assuming nothing has radically changed in sonar in the last 30 years

Computers changed, in particular in the past decade, deep learning algorithms. Things they can pull from what seems like pure noise are pretty nuts. Like, mapping building interiors from Wi-Fi noise. Of course, I only have a bit of a view on the civilian side of things, and most of that is research, so as far as what they're actually installing on modern subs *big shrug*.

[TheSaint]

3 hours ago, K^2 said:

Computers changed, in particular in the past decade, deep learning algorithms. Things they can pull from what seems like pure noise are pretty nuts. Like, mapping building interiors from Wi-Fi noise. Of course, I only have a bit of a view on the civilian side of things, and most of that is research, so as far as what they're actually installing on modern subs *big shrug*.

True, but the Navy is notoriously loathe to put bleeding edge technology on their fighting ships. They are far more concerned with whether or not it will keep working, continuously, flawlessly, under every possible circumstance, than they are with whether or not it is cutting edge technology. So while it may be possible to create a system that has those sorts of capabilities, it would remain to be seen whether or not it is actually deployed on a combat unit.

[kerbiloid]

5 hours ago, TheSaint said:

We used to pick up pelagics (fish) on the sonar pretty easily, but they're moving and there's a lot of them. Cetaceans too. But, again, they make a lot of very distinctive noise.

It was expectable.

Spoiler

They used to sing.

***

If the water currents around a non-streamlined object at the linear speed of submarine propeller blades, and the flow pulsates with frequency of such propeller, I believe this object will be audible and detectable.

[ARS]

During Space Shuttle Columbia disaster, one of the topic that's brought up post-disaster involves discussing the possibility to bring the crew back had the damage to the port wing is confirmed beforehand. Aside from launching 2nd shuttle to rescue them, one of the method involves altering reentry trajectory to minimize the exposure of the damaged port wing towards the atmosphere. I am curious as how it's done, considering there's a gaping hole on port wing's thermal shield (which is intended to be exposed towards the atmosphere). Is there a way to orient the shuttle during reentry to prevent the obvious hot spot on the wing to contact atmosphere? Does it mean exposing the non-shielded portion of the shuttle towards the atmosphere? If the shuttle is oriented in such a way, will the center of mass of the shuttle force it to return to "normal" (and dangerous) reentry profile? A shallow reentry angle could minimize the heat exposure, but it also makes the heat shield being exposed towards heat far longer (and there's a possibility to overshoot), while steep reentry angle expose the shuttle towards shorter heat duration but obviously a no-no since that heat is at a much much higher temperature that'll ensure it'll disintegrate

[StrandedonEarth]

15 hours ago, ARS said:

During Space Shuttle Columbia disaster, one of the topic that's brought up post-disaster involves discussing the possibility to bring the crew back had the damage to the port wing is confirmed beforehand. Aside from launching 2nd shuttle to rescue them, one of the method involves altering reentry trajectory to minimize the exposure of the damaged port wing towards the atmosphere. I am curious as how it's done, considering there's a gaping hole on port wing's thermal shield (which is intended to be exposed towards the atmosphere). Is there a way to orient the shuttle during reentry to prevent the obvious hot spot on the wing to contact atmosphere? Does it mean exposing the non-shielded portion of the shuttle towards the atmosphere? If the shuttle is oriented in such a way, will the center of mass of the shuttle force it to return to "normal" (and dangerous) reentry profile? A shallow reentry angle could minimize the heat exposure, but it also makes the heat shield being exposed towards heat far longer (and there's a possibility to overshoot), while steep reentry angle expose the shuttle towards shorter heat duration but obviously a no-no since that heat is at a much much higher temperature that'll ensure it'll disintegrate

Tough one. I know during reentry the Shuttle would do a series of S-turns to bleed off speed. Perhaps, after calculations to adjust the deorbit point to end up in range of a runway, they could have done a long, sweeping turn to port to protect that wing. 

There was also discussion about the possibility of packing the hole in the wing with water bags that would freeze to ice before reentry, temporarily plugging the hole. But I don’t think they could have reached the hole with the RMS (Canadarm), If it was even installed for that mission. Similarly, I don’t know if they even had EVA suits aboard, since IIRC rescue mission discussions involved having to first bring EVA suits to Columbia. 

Actually, I don’t think any scenarios involving getting the bird through reentry were meant to actually land; the idea was to get low enough to allow bailing out. Since the handling characteristics would have likely changed unpredictably due to the damage

[Aghanim]

If the astronauts have diarrhea when the rocket is in countdown because they eat too many spicy food on the night before launch, will they cancel the launch?

[StrandedonEarth]

42 minutes ago, Aghanim said:

If the astronauts have diarrhea when the rocket is in countdown because they eat too many spicy food on the night before launch, will they cancel the launch?

Their diet is carefully planned before a launch, both to prevent that sort of issue and to limit solid waste in general 

[DDE]

On 5/29/2020 at 12:53 AM, ARS said:

Does a non-hydrodynamical shape (no-sharp edges, but isn't streamlined) create a noise strong enough to be picked by submarine when it's just stand still underwater? Imagine a non-hydrodynamic stuff like undersea research station. It has curves and no sharp edges, but is not streamlined against water currents (It's just an assortment of metal tubes and tanks for habitat's structure) and it's just anchored on the seabed using cables like naval mines. Assuming there's nothing onboard that makes noise, if there's ocean current around it, will submarines picked the noise?

A problem seems that they're normally looking for very specific noises.

 

[ARS]

Post-WW2 warships has shifted the defense doctrine from heavy armor to point defenses with the advent of antiship missiles. The focus of warship defense is now focused on interception and evasion (CIWS, CAP, EW, decoys) rather than endurance (heavy armor, torpedo bulkhead, citadel armor). Now I wonder, if the modern-era warship do get hit by modern antiship missile, in terms of endurance compared to WW2-era heavy armor battleships, which one will outlast the other? (assuming both are hit by the same number of missiles and no missile are intercepted)

[magnemoe]

58 minutes ago, ARS said:

Post-WW2 warships has shifted the defense doctrine from heavy armor to point defenses with the advent of antiship missiles. The focus of warship defense is now focused on interception and evasion (CIWS, CAP, EW, decoys) rather than endurance (heavy armor, torpedo bulkhead, citadel armor). Now I wonder, if the modern-era warship do get hit by modern antiship missile, in terms of endurance compared to WW2-era heavy armor battleships, which one will outlast the other? (assuming both are hit by the same number of missiles and no missile are intercepted)

Now this depend on one thing, if the missile penetrate the armor the ww2 warship would far worse. Armor is actually worse  than nothing if penetrated as the blast has to go inside the ship. 

On the other hand lots of an battleship is not armored The superstructure has little to no armor outside of secondary turrets and some critical systems. Same with the front of rear of the ship. 
An missile hit here would be better than having no armor as the critical parts are armored. and would not be damaged here. 

Missile size is also critical, something like an Exocet missile would not penetrate armor on an battleship, the huge carrier killers the Russians have would. 

[kerbiloid]

https://en.wikipedia.org/wiki/HMS_Sheffield_(D80)

Quote

 The Exocet that struck "Sheffield" impacted on the starboard side at deck level 2, travelling through the junior ratings' scullery and breaching the Forward Auxiliary Machinery Room/Forward Engine Room bulkhead 2.4 metres (7 ft 10 in) above the waterline, creating a hole in the hull roughly 1.2 by 3 metres (3.9 by 9.8 ft). It appears that the warhead did not explode. Accounts suggest that the initial impact of the missile disabled the ship's electrical distribution systems and breached the pressurised sea water fire main, severely hampering any firefighting response and eventually dooming the ship to be consumed by the fire. The loss of Sheffield was a deep shock to the British public and government.

 

[SOXBLOX]

Most modern AShM types would bounce off a WWII battleship's hull. However, if it hit the superstructure, it would probably mission-kill the ship, if not outright trash it. On the other hand, a modern warship, such as an Arleigh Burke, has (apparently) very little armor, but possesses a state-of-the-art radar and combat control system, coupled to electronic countermeasures and the Phalanx CIWS. Naturally, these are rather fragile. If they aren't doing their job of decoying or intercepting inbound missiles, then they will be shredded.

Overall, though, one just has to look at the Falklands War to see the effect of AShM's on a modern target. Since the Sheffield and Antelope were smaller warships built for ASW, and they were basically one-hit-killed, I'd say a Burke or Ticonderoga would take two or three hits before total destruction. An Iowa -class, or even a midsized Alaska-class, would probably last four or more hits.

Of course, we could talk about the "modern" Russian Kirov and its brother the Frunze...

[DDE]

5 hours ago, ARS said:

Post-WW2 warships has shifted the defense doctrine from heavy armor to point defenses with the advent of antiship missiles. The focus of warship defense is now focused on interception and evasion (CIWS, CAP, EW, decoys) rather than endurance (heavy armor, torpedo bulkhead, citadel armor). Now I wonder, if the modern-era warship do get hit by modern antiship missile, in terms of endurance compared to WW2-era heavy armor battleships, which one will outlast the other? (assuming both are hit by the same number of missiles and no missile are intercepted)

Whoo, do I have a treatise to write now.
Basically, there's a huge difference between what is considered a missile.

This is a Harpoon, an increasing rarity on US ships in favour of a Rolling Airframe Missile launcher. It's subsonic and torpedo-sized, with a delay-fused semi-armour-piercing warhead.

This is a Basalt of the older Slava cruisers, Mach 3 with a proximity-fused directional warhead rated for 400 mm armour penetration.

On the other side, we have modern ships. The Zumwalt has a pseudo-armoured belt because of the Mk 57's blast protection, the Kirovs have a 100 mm citadel, and I've heard of 8 inches of aluminum on US carriers.
But this is largely beside the point. Even in WWII penetrating armour was of questionable value.
Consider the Bismarck. She was scuttled with her main belt intact - and everything above the belt blown away or on fire.

So, barring the optimistic claim that

2 hours ago, SOXBLOX said:

Most modern AShM types would bounce off a WWII battleship's hull.

WWII ships don't come off as that resilient. The equivalent of a mid-sized bomb coupled with burning jet fuel is going to cause quite a bit of damage above-deck, especially on a late-WWII "all-or-nothing" warship. At best, the WWII ship of a comparable tonnage will benefit from fewer elaborate systems that can catch fire - they had nowhere near the electrical generators and radar arrays, and could just hide the small engine rooms and magazines all the way below the waterline. Even a WWII ship was armoured mostly to avert a one-hit-kill, not to shrug off every projectile.

[SOXBLOX]

True, but I'd remind you of just what it took to sink the Yamamato. Also, what surface-surface engagements there were in WWII (mostly in the Aleutian campaigns) involved cruisers taking multiple direct hits from the main batteries of equivalent opponents.

Overall, WWII ships would be more resilient.

On the other hand, no modern warship will just be sitting and not defending itself with every trick in the book. With the exception of the USS Starke and such gross mismanagement, no ship in a threat zone will be vulnerable to a surprise attack, especially American ships (and others) with the Aegis ICS.

[kerbiloid]

Old ship = sword + shield
Modern ship = two swords or a halberd or a sabre + pistols + no shield

knights → dragoons

Edited June 3, 2020 by kerbiloid