For Questions That Don't Merit Their Own Thread

[DDE]

6 hours ago, SOXBLOX said:

Also, this. 

I do wonder if this is the longest AAM shot for the US specifically, or worldwide.

There's a 1994 claim of an R-37 hit at 304 km. Given theoretical, "paper" max range of 397 km, it should have had plenty of KE left for a maneuvering target.

The article you linked claims it's for the US specifically.

[SOXBLOX]

4 hours ago, DDE said:

The article you linked claims it's for the US specifically.

I don't see that. The AF never clarified.

Longest US shot previously was an AIM-54, which hit a target drone at 132 mi (212 km). So, it's further than that.

Edited April 15, 2021 by SOXBLOX

[kerbiloid]

Never heard about it before.

https://en.wikipedia.org/wiki/Kaidun_meteorite

Ah, Phobos. So far, so close.

Spoiler

We need an anti-Martian defence, before they repeat.

 

Edited April 15, 2021 by kerbiloid

[Gargamel]

On 4/12/2021 at 5:16 AM, Starhelperdude said:

how deep can a digged hole in the earth be without it collapsing? (like earth and stone falling from the sides into it)

That really depends on the material it's made in.    Some material, like sand, collapses instantly.   Rock may never collapse.  I've seen people trapped in collapsed holes less than a couple meters deep. 

[Selective Genius]

What would be the ISP of a pressure-fed kerolox rocket engine with regenerative cooling and active tank pressure management? What would be the maximum thrust we could obtain from such an engine before it gets impractical?

[cubinator]

Are nuclear thermal rockets...quiet? A chemical rocket has basically a bomb going off in the combustion chamber with all the associated noise and vibration, but a nuclear rocket just heats up a gas to get it going fast. It would basically be like a multiple-km/s wind. I also imagine that a spaceship moving under NTR propulsion would feel totally smooth, unlike shaky chemical propulsion. It would be like driving an electric car vs. a gas car. It seems to me like nuclear thermal propulsion would be very quiet even when running at full power, like maybe you could stand near it with standard shop earmuffs and not be hurt by the sound  (of course, you wouldn't actually want to do this because you'd be hurt by the, you know, nuclear).

[kerbiloid]

28 minutes ago, cubinator said:

It would basically be like a multiple-km/s wind.

Roaring.

[Spica]

It would sound basically the same as a normal chemical rocket of the same thrust and dimensions, since the loudest part of a rocket engine is the supersonic exhaust gas jet.

So it would be just as deafening.

[Terwin]

1 hour ago, cubinator said:

Are nuclear thermal rockets...quiet? A chemical rocket has basically a bomb going off in the combustion chamber with all the associated noise and vibration, 

Current rockets burn more like a candle, as rockets use combustion not detonation.  There is research into continuous detonation engines(which would have a higher isp), but that is not something that is useable just yet. ( https://en.wikipedia.org/wiki/Rotating_detonation_engine )

Even a roaring fire is only loud due to tiny detonations of vaporized fuel, something that does not happen in a happy rocket.

 

[tater]

 

[DDE]

6 hours ago, tater said:

 

Quote

In spite of its location, this atmospheric feature is not linked to volcanic activity but is rather a water ice cloud driven by the influence of the volcano’s leeward slope on the air flow – something that scientists call an orographic or lee cloud – and a regular phenomenon in this region.

 

[kerbiloid]

Looking at this photo. Interesting, can there be phoens on Mars.

[JoeSchmuckatelli]

Probably asked and answered before - but I can't find it.

 

Would carbon fiber be better as a rocket body / reentry vehicle than steel? **

 

 

 

**(Thinking in terms of Starship & Falcon, but this is more of a general question than something specific to SX)

[kerbiloid]

Carbon in theoretical upper limit is several times stronger than steel.

[StrandedonEarth]

1 hour ago, JoeSchmuckatelli said:

Probably asked and answered before - but I can't find it.

 

Would carbon fiber be better as a rocket body / reentry vehicle than steel? **

 

 

 

**(Thinking in terms of Starship & Falcon, but this is more of a general question than something specific to SX)

Price not an issue? Then probably, depending on the propellants, for a rocket body. But steel retains its strength over a much larger temperature range than CF, meaning a reentry vehicle would need more thermal protection.

But  as SpaceX noticed, CF cost ten times more; needs an autoclave to cure (as I understand it) and the scrap is garbage. Steel is easily recycled and much more machinable/weldable. 

[JoeSchmuckatelli]

2 minutes ago, StrandedonEarth said:

CF cost ten times more

Is there a trade-off in weight that could be captured in reduced propellant costs / greater lift capacity that might make it more economical?

 

As to the reentry - I've read that CF gets stronger as it gets hotter, but steel weaker... but that doesn't tell the story of shedding heat, etc.

[Terwin]

1 hour ago, JoeSchmuckatelli said:

Would carbon fiber be better as a rocket body / reentry vehicle than steel? **

**(Thinking in terms of Starship & Falcon, but this is more of a general question than something specific to SX)

It depends on what you want.

Carbon fiber is much more expensive to fabricate and is much less heat tolerant, but it is also much lighter.

Elon said that for the thermal robustness needed for their reentry regime, Steel is actually the lighter option compared to all of the protection that carbon fiber would need.

It is just a bonus that steel also happens to be much faster/easier to work with and is dirt cheap by comparison.  (you don't see actual water towers made out of carbon fiber after all)

In the shuttle they used aluminum protected by heat tiles, and at least one loss was caused by thermal leakage melting thorough the aluminum(and another vessel only survived because there was a steel support right behind the burned-through aluminum).

 

I would not be surprised if SS had small gaps between the tiles and could survive losing some tiles, so long as enough tiles remained to reject most of the heat.

Yu also have a lot more options for doping your steel to have different properties compared to carbon fiber.

[JoeSchmuckatelli]

Interesting to read that you would have to protect the CF.  

[kerbiloid]

That's what SiF is for.

[SunlitZelkova]

Do any Soviet/Russian spacecraft have/had navigation/running lights? There don't seem to be any from what I can find, only the docking light.

[kerbiloid]

Why use lights except on docking?
There is nobody else to see them.

[magnemoe]

On 4/23/2021 at 8:23 PM, Terwin said:

It depends on what you want.

Carbon fiber is much more expensive to fabricate and is much less heat tolerant, but it is also much lighter.

Elon said that for the thermal robustness needed for their reentry regime, Steel is actually the lighter option compared to all of the protection that carbon fiber would need.

It is just a bonus that steel also happens to be much faster/easier to work with and is dirt cheap by comparison.  (you don't see actual water towers made out of carbon fiber after all)

In the shuttle they used aluminum protected by heat tiles, and at least one loss was caused by thermal leakage melting thorough the aluminum(and another vessel only survived because there was a steel support right behind the burned-through aluminum).

 

I would not be surprised if SS had small gaps between the tiles and could survive losing some tiles, so long as enough tiles remained to reject most of the heat.

Yu also have a lot more options for doping your steel to have different properties compared to carbon fiber.

Another factor is that carbon fiber need baking.  This get more expensive as the rocket get larger. Electron uses carbon fiber who makes sense since surface area is large compared to volume compared to larger rockets. Aluminum is most common for rockets today. 

[SunlitZelkova]

4 hours ago, kerbiloid said:

Why use lights except on docking?
There is nobody else to see them.

*shrugs* helping to know orientation?

To be clear, I meant the green and red. The Gemini, Apollo CSM and LM, Crew Dragon, and maybe Starliner have them.

[ARS]

In movies, Time Bomb, no matter who made it or what it's original purpose, whether it's a jury-rigged bomb made by terrorist in a garage to blow up a city block or a nuclear bomb made by NASA to destroy asteroid by splitting it in two, there's bound to be a scene of 'Wire dillema' (aka the classic red or green wire to cut?), now I'm not going to ask about the wire color problem, as any self-conscious bomb maker would definitely made it harder to defuse. What I want to ask is, does this mechanism really exist in real-life bombs? A bomb mechanism where at the end of it, there's 2 wires that when one is cut, it just stops the timer and if the other is cut, the bomb explodes instantly?

[magnemoe]

31 minutes ago, ARS said:

In movies, Time Bomb, no matter who made it or what it's original purpose, whether it's a jury-rigged bomb made by terrorist in a garage to blow up a city block or a nuclear bomb made by NASA to destroy asteroid by splitting it in two, there's bound to be a scene of 'Wire dillema' (aka the classic red or green wire to cut?), now I'm not going to ask about the wire color problem, as any self-conscious bomb maker would definitely made it harder to defuse. What I want to ask is, does this mechanism really exist in real-life bombs? A bomb mechanism where at the end of it, there's 2 wires that when one is cut, it just stops the timer and if the other is cut, the bomb explodes instantly?

Don't think the red or green wire is common or realistic.
More common is it to have anti tamper devices. In an car bomb having the car alarm set off the bomb is one way to stop people from disarming it. 
Perhaps an second trigger to opening the back hatch. 
Mines can have an anti tamper on lifting them, then mine is armed an lever below the mine will set it off if lifted. 
Know some WW2 air dropped bombs had anti tamper systems to make them hard to defuse. 

But for military systems stuff like this is rare, its increases the risk of the thing going off in the first place and you assume you win the war and has to clean it up
And you can have an secondary trigger like an timer who set up an bomb if it fails to detonate on impact. 
For other stuff like the bomb to blow up the asteroid its no point having it hard to disarm as its nobody who can do it anyway as the bomb would be on an probe in space. 
However say it miss you probably have an timer so it blows up just after you assumed it would impacted or came at correct distance.