For Questions That Don't Merit Their Own Thread

[JoeSchmuckatelli]

7 minutes ago, ARS said:

mechanical characteristic

What mechanical characteristic?

[SOXBLOX]

19 minutes ago, ARS said:

What's the design consideration specific for aircraft operating at extreme altitude? Because one one hand, we have the slow-moving aircraft with near-glider like characteristic such as U-2, but on the other hand, we have a literal speed demon with overkill engines like SR-71 or MiG 25/31

As light as possible and lots of wing. The highest horizontal flight was achieved by NASA's Helios something-or-other, which has long, straight wings and very low weight. The SR-71 and friends are able to get that high, I think, because they're moving so fast that they can use the thinner air more effectively.

Edited November 26, 2021 by SOXBLOX

[K^2]

1 hour ago, ARS said:

What's the design consideration specific for aircraft operating at extreme altitude? Because one one hand, we have the slow-moving aircraft with near-glider like characteristic such as U-2, but on the other hand, we have a literal speed demon with overkill engines like SR-71 or MiG 25/31

You are dealing with low pressure, so it's much harder to generate lift. You then either have to greatly increase the wingspan - the U-2 route, or greatly increase speed - the SR-71 route. Traditional swept-wings are critical for flight in the transonic region. We're talking Mach 0.9-1.1 or so. Airliners dip into that region, so they have to incorporate the swept wing design. Having very long swept wings is impractical, however. So U-2 is limited to lower speeds, around Mach 0.7 in cruise, where straight wings work perfectly fine. In contrast, if your answer to the low density is more speed, then your biggest factor is heating. To reduce heating, aircraft are made long and slender, with sharp points on leading edges and anything else that might have to stick out. There are also considerations for where along the aircraft the sonic shocks form. A shock forming along the surface of the wing can lead to separation and loss of lift and control. I suspect this is a big part of the reason for where exactly the engines are placed on SR-71, but it's getting into nitty-gritty of supersonic physics where I'm not proficient.

1 hour ago, ARS said:

Also, does this statement correct?: "A material with high melting point is stronger in terms of mechanical characteristic than material with low melting point"

Not entirely. For one, you have to be more specific about what you mean by strength. If we're talking purely tensile, there's a strong correlation between melting point and tensile strength, but it's hardly 1:1. More crucially, however, materials with high tensile strength can get brittle. So if you're making something like armor, you actually get "stronger" armor by either going for alloys that actually lower tensile strength (and the melting point) or by going with a composite material, where you're going to have two or more different melting points for different components. So it really depends on application.

[kerbiloid]

2 hours ago, ARS said:

What's the design consideration specific for aircraft operating at extreme altitude?

1. First rule of the high-altitude flights: "Never fly at high altitudes".

2. If you still have to fly at high altitudes, either make your wing as long as possible (to frantically grab as much remains of air as you can),
or fly fast, be flat, and cut off your wings because the air drag will anyway break them off.
I.e. do like U-2 and SR-71 respectively.

2 hours ago, ARS said:

Also, does this statement correct?: "A material with high melting point is stronger in terms of mechanical characteristic than material with low melting point"

Two intersecting clouds of values.

The strength of different steels may vary by order of magnitude 200-..2000+ MPa.

Also the strength depends very much on the crystal structure defects, and their concentration depends on various methods of the sample processing.

So, ideally, in whole - yes, but practically depends on technology.

[ARS]

7 hours ago, K^2 said:

You are dealing with low pressure, so it's much harder to generate lift. You then either have to greatly increase the wingspan - the U-2 route, or greatly increase speed - the SR-71 route. Traditional swept-wings are critical for flight in the transonic region. We're talking Mach 0.9-1.1 or so. Airliners dip into that region, so they...

With such a low-pressure environment, if we're looking for hypersonic realm of speed (from engineering standpoint, strictly about speed, not about it's application on hypersonic ordnance), which altitude is preferrable? Low or high? Since at low altitude, the higher air density makes hypersonic engine (ramjet, scramjet) easier to use since there's plenty of air to feed it, but the aerodynamic heating would be deadly, while at high altitude, the heating might not be as severe as in low altitude, but the thin air might impede the engine's performance

[kerbiloid]

Airliners fly at 10..12 km.

[K^2]

45 minutes ago, ARS said:

With such a low-pressure environment, if we're looking for hypersonic realm of speed, which altitude is preferrable?

For hypersonic, you want to go high. At these speeds, nearly all of your engine thrust is fighting ram drag. If you go lower, yes, you get more air to feed your engines, but you need more thrust by the same proportion - and more fuel to go along with the air you're getting. By going high, you need smaller, lighter engines, and you consume less fuel on top of not picking up as much heat. There is no reason to go low, and the further into hypersonic you go, the higher you want to be. Of course, at some point, you might as well skip the atmosphere entirely and go suborbital, but there is a sweet spot at about Mach 5 and 30km of altitude that, at least on paper, looks like it would be fairly economical. There are some design projects for airliners that are meant to operate at these altitudes and speeds, but it's hard to say if they'll actually be commercially viable. On paper, Mach 2 at 20km is also a fantastic sweet spot, with fuel consumption per distance traveled actually quite comparable to modern airliners, but supersonic flight came and went, and it's hard to say if it will be back without some major paradigm shift. So I have hopes but little confidence for hypersonic passenger flight.

[DDE]

10 hours ago, ARS said:

What's the design consideration specific for aircraft operating at extreme altitude? Because one one hand, we have the slow-moving aircraft with near-glider like characteristic such as U-2, but on the other hand, we have a literal speed demon with overkill engines like SR-71 or MiG 25/31

It's a matter of developing specifications/concepts, the design comes later. U-2 was built to fly above Soviet radar, a flawed model. Once this was realized (painfully), the CIA did their best to make it stealthy (Project RAINBOW), which failed, and began to study options for a replacement. Project GUSTO involved a lot of bizarre submissions, including lighter-than-air craft, but another running theme was an aircraft that simply moved so fast that operators would lose it on radar. There were three or so such submissions, Convair kept proposing a low-RCS parasite aircraft for its B-58, and Lockheed's SUNTAN was a hydrogen-powered aircraft, so the Archangel by Lockheed's U-2 team (then in its A-1 iteration) was selected.

MiG-25 was ordered to counter the Mach 2 B-58 and the even faster XB-70. When the target wasn't as insanely fast, namely spy baloons from Project MOBY DICK, Project GENETRIX et al and well after the MiG-25, the Soviets commissioned the Miasischev M-17 Stratosphera with a 23 mm gun turret.

Yes, some lineage from Gary Powers's Dragonlady may have been involved.

Edited November 26, 2021 by DDE

[JoeSchmuckatelli]

Commercial supersonic by 2035?

Putting supersonic flights back in the air - CBS News

 

[kerbiloid]

Quote

NASA pursuing supersonic commercial flight

Of course, it ain't of my business, but wasn't the whole idea that NASA is a budget governmental department created for spacing, while commercial airlines are private companies, and that's the corner stone of the free enterprise society?

[DDE]

13 minutes ago, kerbiloid said:

Of course, it ain't of my business, but wasn't the whole idea that NASA is a budget governmental department created for spacing, while commercial airlines are private companies, and that's the corner stone of the free enterprise society?

It's hardly new. Guess who did all the work on developing wingfoil profiles - there was a one-letter difference.

30 minutes ago, JoeSchmuckatelli said:

Commercial supersonic by 2035?

Putting supersonic flights back in the air - CBS News

 

Commercial supersonic in 15 years!

[JoeSchmuckatelli]

1 hour ago, kerbiloid said:

Of course, it ain't of my business, but wasn't the whole idea that NASA is a budget governmental department created for spacing, while commercial airlines are private companies, and that's the corner stone of the free enterprise society?

Aeronautics and Space 

[JoeSchmuckatelli]

Moar efficient than Xenon (and on)?

Promising new electric iodine thruster passes key test in orbit (msn.com)

Iodine: it's not just for putting in your water any more.

Yum!

 

Quote

 iodine is not only a viable propellant, but can also achieve nearly 50% more efficient propulsion than xenon, because of factors such as how iodine is easier to electrify than xenon.

 

Edited November 27, 2021 by JoeSchmuckatelli

[kerbiloid]

7 hours ago, JoeSchmuckatelli said:

Aeronautics and Space 

Yes (though for Aeronautics there was NACA and is FASA), but still haven't heard about NASA Airlines stewardesses.

8 hours ago, DDE said:

Commercial supersonic in 15 years!

",  again."

Like it's 1969-15 = 1954 on calendar.

Wait... Oh, ...

2 hours ago, JoeSchmuckatelli said:

iodine is not only a viable propellant, but can also achieve nearly 50% more efficient propulsion than xenon, because of factors such as how iodine is easier to electrify than xenon.

As the iodine is for space, let's rename it into yodine.

[K^2]

6 hours ago, JoeSchmuckatelli said:

Moar efficient than Xenon (and on)?

Promising new electric iodine thruster passes key test in orbit (msn.com)

Yes, even taking into account the energy required to sublime iodine into a gas, you get lower energy requirement to produce I₂⁺ than Xe⁺ ions. But Iodine is still going to be molecular in an iodine thruster, so you are looking at about 30% loss of I_SP when everything else is kept the same. If you're building something like a cube sat, the low cost of Iodine, the fact that it can be kept as a solid until needed, and lower ionization energy, are probably the deciding factor. And in fact, a lot of the simplest RF-based ions for cube sats are already Iodine based for this exact reason.

On the other hand, if you are building something for a long duration interplanetary mission, I_SP is generally a greater factor, meaning that you want to go with the lighter elements. And here, noble gasses give you a very significant advantage of being monoatomic. Basically, whatever your specs are, you can probably find a noble gas that matches the profile, but is much lighter than diatomic alternatives. Xenon, of course, being most directly comparable to Iodine, but same can be said about Krypton or Argon thrusters in their own respective categories.

[SOXBLOX]

9 hours ago, kerbiloid said:

Yes (though for Aeronautics there was NACA and is FASA), but still haven't heard about NASA Airlines stewardesses.

NASA is working on a technology demonstrator / X-plane with almost no sonic boom. After that, I think the idea is that any company is free to use the basic design or research to build their own aircraft. NASA itself wouldn't build an airliner and fly it commercially.

9 hours ago, kerbiloid said:

As the iodine is for space, let's rename it into yodine.

Blend the two and you have юdine. 

[JoeSchmuckatelli]

Just some cool stuff to share 

https://www.nasa.gov/specials/landsat/#timeline_bg_6_a

 

[kerbiloid]

Now they can track the growth of the recreational manioc.

Spoiler

 

P.S.
It's indeed manioc, from wiki.

[ARS]

In space, if you use an extremely powerful directional microwave emitter (more than what spacecraft hazard protection designed for), could you actually blow up incoming target (fighters, missiles, ships, etc.) by cooking up their warhead/ ammunition? Or for the short version, could you cause ammo cook-off by using directional microwave? (which in turn, caused magazine detonation)

[JoeSchmuckatelli]

Apologies to ARS - answer the above question if possible... 

 

But:

 https://www.cnn.com/2021/11/29/americas/xenobots-self-replicating-robots-scn/index.html

You gotta see this. 

Read the article. 

Still processing 

[kerbiloid]

39 minutes ago, ARS said:

In space, if you use an extremely powerful directional microwave emitter (more than what spacecraft hazard protection designed for), could you actually blow up incoming target (fighters, missiles, ships, etc.) by cooking up their warhead/ ammunition? Or for the short version, could you cause ammo cook-off by using directional microwave? (which in turn, caused magazine detonation)

Possible, but makes not much sense due to the long wave length.

The beam divergence angle (rad) is ~ 1.22 * wavelength / optics_aperture (the mirror diameter or so)

So, the softer is the radiation, the wider is the beam, and you need as short wavelength as possible (preferrably, Xray or gamma). 
The IR emitter is used just due to the technical possibility, not because its long waves are in any sense good.

Also, a microwave advantage can be that the mist and clouds are transparent for it, but also only for short ranges.

10 minutes ago, JoeSchmuckatelli said:

https://www.cnn.com/2021/11/29/americas/xenobots-self-replicating-robots-scn/index.html

Xenobots → Xenobits → Xenobytes

Soon.

[JoeSchmuckatelli]

1 hour ago, kerbiloid said:

Xenobots → Xenobits → Xenobytes

-> *XenoBites!*  Yum!

 

(now with extra gut churning power!) 

 

 

 

* Do not consume XenoBites if allergic to XenoBites. 

Persons who enjoy personal autonomy should consult with a doctor, a priest and their financial advisor before ingesting XenoBites. 

Joking aside, I'm kinda creeped out by this. 

It's both fascinating and ethically ambiguous. 

[kerbiloid]

1 hour ago, JoeSchmuckatelli said:

XenoBites!

Thx. I had mistyped this for reasons, but now they know that we're talking about them...

1 hour ago, JoeSchmuckatelli said:

Joking aside, I'm kinda creeped out by this. 

It's both fascinating and ethically ambiguous. 

They should be crossed with flu to spread around, infiltrate in every human, and replace its cells with xenobot copies.

After that the humans will be ready for...hmm..  perfectization? perfectification?

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

Wait... Oh, ...

Can they into 5G?

Edited November 30, 2021 by kerbiloid

[ARS]

2 hours ago, JoeSchmuckatelli said:

 

 https://www.cnn.com/2021/11/29/americas/xenobots-self-replicating-robots-scn/index.html

 

It's the grey goo!!

[DDE]