For Questions That Don't Merit Their Own Thread

[steve9728]

2 hours ago, miklkit said:

Interesting topic.  I recently found that archeologists have discovered some similarities between Sumerian cuneiform and Chinese writing.  Some characters not only look the same but have the same sounds attached to them. 

Little more interesting line of study: you could look at Greco-Buddhist art.

And a little interesting detail probably is easy to be ignored: check out link of the tablet about the Church of the East I shared above - Cross on lotus base.

The Chinese script of the same period, around 3000 BC, is oracle-bone script. To be honest, I don’t see any correlation between the two in terms of structure and writing style. The exchange between Central Asians and Chinese must have existed, but it is a “little” too early in terms of the time dimension.

Edited June 2, 2023 by steve9728

[miklkit]

I should have clarified.  They were comparing ancient Sumerian cuneiform to current Chinese writing.    Cuneiform predates everything.

[steve9728]

1 hour ago, miklkit said:

I should have clarified.  They were comparing ancient Sumerian cuneiform to current Chinese writing.    Cuneiform predates everything.

Even worse if he compares modern writing. I'm really curious about who made this comparison. One thing is for sure that guy can't write at least one of two languages between them.

Chinese characters are made up of characters that can be placed one by one in squares of the same size. Early or not didn't make it looks similar have to say.

[JoeSchmuckatelli]

If you put rockets at the top of a landing craft and cant them at 45 degrees (or whatever is optimal to land/not burn the craft) I'd assume there is some performance loss. 

Anyone know what that is? 

Also, does doing this restrict the ability to lift off and rendezvous with the moon-earth ship? 

[Terwin]

2 hours ago, JoeSchmuckatelli said:

If you put rockets at the top of a landing craft and cant them at 45 degrees (or whatever is optimal to land/not burn the craft) I'd assume there is some performance loss. 

Anyone know what that is? 

Also, does doing this restrict the ability to lift off and rendezvous with the moon-earth ship? 

I believe I have heard it called cosine losses, so presumably the cos of the angle (0.71 for 45 degrees) should be the effective thrust multiplier(so almost 30% loss at 45 degrees)

It would only prevent liftoff if you do not have enough thrust after accounting for the loss due to the angle.

Presumably you would switch to the main engine once you were an appropriate height above the surface, so hopefully the total wastage is not too bad.

[kerbiloid]

So...

Late XIX century. The archaeologists from various countries (Europe, China, Egypt, Mesopotamia) were talking to each other without understanding each other's language, so they were helping themselves by drawing primitive pictograms with stick on ground. Everyone was impressed and inspired, and the drawings were looking like a cuneiform.
When they had returned to home, everyone kept drawing same "writings" in his own manner, with his own materials.

Early XX century, The museums of the world are full of the archaeologists' pictorial graphomaniac inscriptions, looking suspiciously similar...
"Ancient Mesopotamian" on the clay tablets, "Ancient Egyptian" on the papyrus and stone, "Ancient Chinese" on the rice paper, "Medieval Gothic" on parchment.

The "Medieval Gothic" are the most dull, because they are just routine texts, written in a stylish manner.

Others are more funny, but they are just funny pictures. So, as these pictures aren't connected to the languages to any degree, the "Ancient Egyptian", "Ancient Mesopotamian", "Ancient Chinese" archaeologists start thinking out funny stories on these funny pictures. The "hieroglyphic writing" is born!

The linguists of the Middle East languages also do not lag behind. They suffer from backhurt, that the archaeologists do have this, while they don't.
While the Chinese still speak Chinese, and are happy with these pictures and stories, the "Ancient Egyptian" and "Ancient Mesopotamian" are mute, nobody speaks in them.

Bingo! They take Coptic (because using Arabian would look too revealing), tune it, and invent the "Ancient Egyptian".
Also they say to the Copts that they are former Ancient Egyptians, and that's why they differ from others.
The Copts understand it as "They called us Pagans! Go fake yourself, archaeologists, the pyramids aren't ours, you built them yourselves, we saw it! We're good Christians! Go home, mummyfakers, and take your mummies with you!" 
(And they took).
But who cares, what the Copts think? Did you see a Copt to ask if he had seen a pharaoh? So, they are Ancient Egyptians. See, the languages are same!

But Mesopotamia...
"We have funny cuneiform pictures, we have written funny stories for them, but what's the language?... Bingo! Let's mix Hebrew and Arabian, change some sounds to sound weird, say "Z" and "Tz" in every word, and call it... Akkadian!"
"Wait, wait, colleagues! I have constructed a language before you, I call it Sumerian. As it's constructed, it's not like others."
"Okay, let your Sumerian be an mystic orphan language of The Elders, who came from nowhere. But it's too lazy to invent another writing, let it use the same cuneiform as in our Akkadian!"

Meanwhile, in the "Ancient Egyptian" camp...
"Colleagues, don't you think that the 5 000 year long history we declared is too much for writing? Look, our "Ancient Mesopotamian" partners already have screwed their Babylon, Assyria, and Sumeria, and declared them dead long ago. I'm tired of rolling dice even to generate the random pharaoh names. Johnhotep, Bobhotep, Billhotep...  Now I just use numbers. Ramesses #7, Thutmose #3 (btw, see a funny joke, it sounds almost like Moses), Ptholemei #17, Cleopatra #13, etc."

Late XX century.
"Now look to the right, please. You can see an Ancient Egyptian mummy of the pharaoh Jebediah-Ra #4. our museum is proud to keep it, it's a real gem of our collection."

Edited June 4, 2023 by kerbiloid

[SunlitZelkova]

Three questions-

1. Does a space program need to start with automated spaceflight, or could it have theoretically started with crewed spaceflight in the same way we went from small gliding models to airplanes?

2. Are computers necessary for spaceflight, or would it be possible without them? Just more difficult and dangerous of course.

3. How did Pioneer 10 perform course correction maneuvers? It had a Star-37E solid booster which is not throttable, and in pictures I don’t see RCS.

[DDE]

1 hour ago, SunlitZelkova said:

2. Are computers necessary for spaceflight, or would it be possible without them? Just more difficult and dangerous of course.

AFAIK early WWII electromechanics are roughly sufficient, with most of the advancement being in soecialized gyros. Most orbital computation work was double-checked by humans, so early XXth century tech was adequate. So, I'd say yes.

Therefore,

1 hour ago, SunlitZelkova said:

1. Does a space program need to start with automated spaceflight, or could it have theoretically started with crewed spaceflight in the same way we went from small gliding models to airplanes?

Technologically, this seems possible. But evolutionarily? There are two big hurdles to clear: first, the leap from small model rockets to V-2 or something else large enough to carry humans, and then the leap from V-2 to effective surborbital and orbital rockets. That's a heck of a lot to leapfrog through in order for crewed spaceflight to have an advantage. What's more, funding becomes an issue: V-2 only hapenned because someone throw money at it as a military technology; without it, it's not immediately clear how amateur rocket societies would have evolved out of small rocketry.

[kerbiloid]

8 hours ago, SunlitZelkova said:

1. Does a space program need to start with automated spaceflight, or could it have theoretically started with crewed spaceflight in the same way we went from small gliding models to airplanes?

Sputnik-3 mass is 1.3 t, so it could be used to launch something Mercury-like. 

And R-7 is irl the first rocket which had put something into orbit, while much lighter Vanguard was enough. This strange, weird world...
Just because USSR didn't have a lot of bombers, and needed an ICBM more than USA. Geography matters.

8 hours ago, SunlitZelkova said:

2. Are computers necessary for spaceflight, or would it be possible without them? Just more difficult and dangerous of course.

R-7 family didn't use computers in Soviet time, pure electromechanics. On-board computers became a thing in late 1960s,, and the main of them, Argon-16 is in use since 1973. 

https://ru-m-wikipedia-org.translate.goog/wiki/Аргон_(компьютер)?_x_tr_sl=ru&_x_tr_tl=en&_x_tr_hl=ru&_x_tr_pto=wapp

8 hours ago, SunlitZelkova said:

3. How did Pioneer 10 perform course correction maneuvers? It had a Star-37E solid booster which is not throttable, and in pictures I don’t see RCS.

According to wiki, it has 3 pairs of hydrazine thrusters and 36 kg of propellant.

[Superluminal Gremlin]

Attempting to find the total force applied to an egg when dropped (Egg drop challenge basically).

I'm confused about how mathematically you are supposed to find time to stop (decelerate). I have Mass (0.05kg), Velocity Initial(3.11m/s) and Velocity Final (0). How are you supposed to find the total time to stop assuming the floor is perfectly hard?

I've tried calculating Kinetic energy, and then dividing it by time to stop, which I have just substituted values in, which is messy but works.

Could someone with an actual understanding of basic Physics help me? Is calculus needed? Or am I missing something so simple I could kick my self (Like forgetting to pack enough batteries )

 

[magnemoe]

On 6/11/2023 at 6:58 AM, kerbiloid said:

Sputnik-3 mass is 1.3 t, so it could be used to launch something Mercury-like. 

And R-7 is irl the first rocket which had put something into orbit, while much lighter Vanguard was enough. This strange, weird world...
Just because USSR didn't have a lot of bombers, and needed an ICBM more than USA. Geography matters.

R-7 family didn't use computers in Soviet time, pure electromechanics. On-board computers became a thing in late 1960s,, and the main of them, Argon-16 is in use since 1973. 

Note that lots of the high end electromechanics stuff was analogue computers and they was good. 
Back in the 1980's then the US reactivated the Iowa class battleships, they found that the WW 2 electromechanics fire control computers was as good at their current digital ones, probably as the digital was based on them, yes the digital was much cheaper and you could easy change them. 
This goes back over 100 years the battleships fighting at Jutland compensated for the earth rotation and curvature.

[kerbiloid]

56 minutes ago, magnemoe said:

Note that lots of the high end electromechanics stuff was analogue computers and they was good. 

They were good, but big and slow, as usually hydraulic or pneumatic. So, the complexity of their tasks was proportional to their hugeness.

[JoeSchmuckatelli]

If / when we decide to send something interstellar (as it's purpose, as opposed to the Voyagers and New Horizons) - would we originate from Earth's orbit? 

Or - Would we start at a place like Mercury which has ~ half again the orbital velocity of the Earth... Or just drop in for a flyby of the Sun? 

What's the plan for interstellar levels of delta v? 

(current tech, not sci fi) 

[AckSed]

The normal, slow way would be to use gravity assists.

One fun way is a proposal that uses a very light solar sail to catch the light pressure at very short range: The beryllium hollow-body solar sail: exploration of the Sun's gravitational focus and the inner Oort Cloud.

We would probably build it in orbit around Earth, as the sail is a disc-shaped 'air mattress' of sub-micron-thick beryllium foil. (It's hollow because it's inflated with a tiny amount of hydrogen to stiffen it.) We don't quite have the manufacturing capability to make that on Earth and bring it up the gravity well. It would be sent into a 0.1 AU perhelion before the sail is deployed. Because of the extreme ratio of mass to sail area (the disc would be 1.874 km wide, yet only mass 150 kg, leaving space for a 150 kg payload), combined with the light pressure so close to the Sun, it would gain impressive amounts of acceleration.

Quote

For a 0.1 AU perihelion, a 937 m radius sail with a sail mass of 150 kg and a payload mass of 150 kg, perihelion sail temperature is about 1000 K, peak acceleration is about 0.6 g, and solar-system exit velocity is about 400 km/s.

After sail deployments, the craft reaches the 200 AU heliopause in 2.5 years, the Sun's inner gravitational focus at 550 AU in about 6.5 years and 2,550 AU in 30 years.

Note this was a modification of an earlier proposal to make a probe (or 10,000 ton generation ship, which is a bit of a jump) that flew even closer (0.05AU) and went even faster:

Quote

If fully inflated at the 0.05 AU perihelion of an initially parabolic solar orbit, both had a peak radiation-pressure acceleration of 36.4 m/s2 and exited the solar system at 0.00264c after an acceleration duration less than one day.

I.e. one day of constant acceleration later, it would be going 2,851,200 km/h. In comparison, New Horizons has, with the gravity assist off Jupiter, managed to clock 84,000 km/h as it flew past Pluto. The Parker Solar Probe, the fastest human-made object, gleaned enough speed from Venus flybys to skim the Sun at 586,800 km/h.

This isn't the only proposal: NASA has funded a Stage II (i.e. 'seems interesting, here's money to investigate further') study of sun-grazing solar sails: https://www.nasa.gov/directorates/spacetech/niac/2021_Phase_I/Extreme_Solar_Sailing_for_Breakthrough_Space_Exploration/

Edited June 15, 2023 by AckSed
Additional link

[kerbiloid]

7 hours ago, JoeSchmuckatelli said:

Mercury which has ~ half again the orbital velocity of the Earth

The Mercury's orbital velocity is 1.6 times greater than the Earth's one.

Because gravity well.

So, it takes much greater delta-V to depart.

[Jacke]

20 hours ago, kerbiloid said:

The Mercury's orbital velocity is 1.6 times greater than the Earth's one.

Because gravity well.

So, it takes much greater delta-V to depart.

There's also the Oberth effect.

[darthgently]

6 minutes ago, Jacke said:

9 minutes ago, Jacke said:

There's also the Oberth effect.

 

And the intent is a flyby and grav assist (if I'm following correctly).  It isn't like the probe would going into a closed Mercury orbit, then breaking orbit, so it would be a good Oberth at closest approach making the already hyperbolic encounter have an even higher velocity on the outward leg

[mikegarrison]

On 6/14/2023 at 7:20 PM, Superluminal Gremlin said:

Attempting to find the total force applied to an egg when dropped (Egg drop challenge basically).

I'm confused about how mathematically you are supposed to find time to stop (decelerate). I have Mass (0.05kg), Velocity Initial(3.11m/s) and Velocity Final (0). How are you supposed to find the total time to stop assuming the floor is perfectly hard?

I've tried calculating Kinetic energy, and then dividing it by time to stop, which I have just substituted values in, which is messy but works.

Could someone with an actual understanding of basic Physics help me? Is calculus needed? Or am I missing something so simple I could kick my self (Like forgetting to pack enough batteries )

 

How fast it stops is basically what you are trying to achieve in the first place. It's a design target, not a fixed quantity.

[SunlitZelkova]

On 6/15/2023 at 1:16 PM, JoeSchmuckatelli said:

If / when we decide to send something interstellar (as it's purpose, as opposed to the Voyagers and New Horizons) - would we originate from Earth's orbit? 

Or - Would we start at a place like Mercury which has ~ half again the orbital velocity of the Earth... Or just drop in for a flyby of the Sun? 

What's the plan for interstellar levels of delta v? 

(current tech, not sci fi) 

I highly recommend this book to you:

https://www.amazon.com/Centauri-Dreams-Imagining-Interstellar-Exploration/dp/038700436X

[JoeSchmuckatelli]

Apparently, I am now a quantum physicist. 

Hopefully youtube sends my diploma soon 

[Rocket Witch]

Apparently the Gemini astronauts used the Eye of the Sahara as a landmark "to track the progress of their [docking] sequences". Does anyone know HOW this was done? Since one will pass over it very quickly while in low orbit, it's not immediately obvious what utility a planetary landmark has as a visual aid for docking, especially since I doubt the Agena's orbit passed directly over the Eye every time. It sounds like a myth made up to make the discovery of the Eye seem more meaningful, to be honest, but if they did actually use it I'm sure the story is interesting.

Edited June 21, 2023 by Rocket Witch

[monophonic]

15 hours ago, Rocket Witch said:

Apparently the Gemini astronauts used the Eye of the Sahara as a landmark "to track the progress of their [docking] sequences". Does anyone know HOW this was done? Since one will pass over it very quickly while in low orbit, it's not immediately obvious what utility a planetary landmark has as a visual aid for docking, especially since I doubt the Agena's orbit passed directly over the Eye every time. It sounds like a myth made up to make the discovery of the Eye seem more meaningful, to be honest, but if they did actually use it I'm sure the story is interesting.

I hear and the captions read them talking about the landing sequence. It would actually make sense as the spacecraft would pass approximately over the Eye (guesstimated) one orbit before the planned splashdown area in the Atlantic. So seeing the Eye would somewhat accurately match to a specific stage in the landing sequence and predict splashdown in less than two hours.

[sevenperforce]

Not thread-meriting, but a friend of mine asked me if the people on board the Oceangate sub would have felt or heard anything, and I'm pretty sure the answer is no.

At 375 atmospheres, any pressure vessel failure would be immediately catastrophic. I calculate implosion time at 3.42 milliseconds. Roughly the equivalent of a 100-foot-wide iron cube hitting you at 1600 mph.

Right? Or is it possible they had some sort of warning?

[SunlitZelkova]

1 hour ago, sevenperforce said:

Not thread-meriting, but a friend of mine asked me if the people on board the Oceangate sub would have felt or heard anything, and I'm pretty sure the answer is no.

At 375 atmospheres, any pressure vessel failure would be immediately catastrophic. I calculate implosion time at 3.42 milliseconds. Roughly the equivalent of a 100-foot-wide iron cube hitting you at 1600 mph.

Right? Or is it possible they had some sort of warning?

It depends on how the implosion occurred. Perhaps there was some warning sign separate to what caused the actual implosion, and then they went instantly.

[JoeSchmuckatelli]

Um... 

So, NASA plans to launch a space based telescope to prove the existence of DM. 

https://roman.gsfc.nasa.gov/dark_matter.html

It's got a 2.4 my mirror and observes in the IR. 

... I thought Webb was already tasked with that?