Satellites : general discussion and musings

If NASA faked the moon landings, does the agency have any credibility at all? Was the Space Shuttle program also a hoax? Is the International Space Station another one? Do not dismiss these hypotheses offhand. Check out our wider NASA research and make up your own mind about it all.

Re: Satellites : general discussion and musings

Unread postby SacredCowSlayer on Sat Sep 29, 2018 12:31 am

simonshack » September 28th, 2018, 6:24 pm wrote:
So the question is: HOW exactly could any man-made satellite survive (for years & years on end, as we are told) in the midst of such constant bombardment? Have we ever heard of any of those precious satellites being hit by any space debris? And please, spare me from the standard, idiotic answer that "space is sooo vast that it is unlikely that any of our satellites get hit by any meteors/comets/asteroids/space debris". Thanks.


According to the “experts,” these man made behemoths have been launched into the vacuum since Sputnik in 1957. :rolleyes:

I find this to be a good time to remind our readers of the story of “The Big Bounce,” featuring Echo One (claimed to be a whopping “ten stories tall” :blink:) found here:


full link: http://www.youtube.com/watch?v=sY8MeZ6lpwI

It is truly difficult to take the “real satellites” seriously when the whole thing began with silly things like Sputnik and Echo One.

Moreover, it’s rare that modern day WiFi can be maintained without some kind of disruption (requiring physical access to the equipment) even in my own house (complete with atmosphere) for two weeks straight in the year 2018.
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Re: Satellites : general discussion and musings

Unread postby Mansur on Sat Sep 29, 2018 9:31 pm

simonshack » September 28th, 2018, 11:15 pm wrote:
TripleSpeak wrote: EDIT: One more question that I think would be useful to readers of this thread: what are those seemingly far away, fast-moving blinking lights you can see with the naked eye in the skies at night (official sources say are satellites)?


To my knowledge, in the pre-satellites era, which is a considerable time interval, people, even "official sources" titled them as "falling stars".
I've never laid on my back for more than 10 minutes under a clear sky and not spotted one.

This could have been said, I think, by all our forefathers. (And mothers.)
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Re: Satellites : general discussion and musings

Unread postby simonshack on Fri Jun 21, 2019 3:37 pm

*

I know, this article is over four years old - yet you've gotta wonder what this is all about... :mellow:

"DARPA to re-invent GPS navigation without the use of satellites"

https://www.extremetech.com/extreme/202 ... satellites

Image
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Re: Satellites : general discussion and musings

Unread postby Kham on Thu Jun 27, 2019 4:14 am

Thanks Simon,

Fun read. Consider this quote from the article discussing how DARPA is investing in radically new technologies that have the potential to deliver GPS-quality position:

“Ground-based systems may seem like a good alternative, but there are pitfalls. One design would involve hundreds of thousands of transmitters, which would be ridiculously difficult to build and maintain.”

Hahaha, yes, cell phone towers, aka thousands of transmitters, are quite tricky to build and maintain? I think not. The 4.7 billion uninterrupted cell phone users world wide might say the system is already in place. Hey secret military, how about this, use cell phone towers for gps.

or

Just admit you have been using cell phone towers for gps location the entire time.

(Just like satellite radio in cars are using cell phone towers, heard it from Sirius xm technician as he was installing a Sirius xm transmitter on a local cell tower.)
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Re: Satellites : general discussion and musings

Unread postby anonjedi2 on Fri Jun 28, 2019 3:15 am

Kham » June 26th, 2019, 9:14 pm wrote:Thanks Simon,

Fun read. Consider this quote from the article discussing how DARPA is investing in radically new technologies that have the potential to deliver GPS-quality position:

“Ground-based systems may seem like a good alternative, but there are pitfalls. One design would involve hundreds of thousands of transmitters, which would be ridiculously difficult to build and maintain.”

Hahaha, yes, cell phone towers, aka thousands of transmitters, are quite tricky to build and maintain? I think not. The 4.7 billion uninterrupted cell phone users world wide might say the system is already in place. Hey secret military, how about this, use cell phone towers for gps.

or

Just admit you have been using cell phone towers for gps location the entire time.

(Just like satellite radio in cars are using cell phone towers, heard it from Sirius xm technician as he was installing a Sirius xm transmitter on a local cell tower.)


Ahh, yes. Ground based systems would be ridiculously difficult to build and maintain, but building and maintaining 75,000+ satellites in "Earth's orbit" is no problem. :D
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Re: Satellites : general discussion and musings

Unread postby simonshack on Fri Jun 28, 2019 10:22 am

*

Indeed, dear Kham and anonjedi, indeed...


You may enjoy reading this ridiculous article :

https://www.vox.com/2015/1/20/7558681/space-junk

"There are 300,000 pieces of garbage orbiting earth, and it's a big problem"

Image
Caption: "An illustration of space junk — not to scale. (ESA)" :rolleyes:


Image
Caption: "A NASA graphic shows the 19,000 pieces of trackable debris in Earth's orbit. (NASA)" :rolleyes:
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Re: Satellites : general discussion and musings

Unread postby nokidding on Sun Jul 14, 2019 8:47 am

Pure speculation, but when one considers all the (impossible) difficulties of navigating to and entering an orbit around a planet or the Moon, you begin to realise that some of the same difficulties are presented when entering Earth orbit (from Earth).

When a satellite is launched it follows the Great Circle by default as it falls towards the centre of gravity, and shares Earths velocity through stellar space, unlike with Moon/planets. However to be in orbit it requires that speed, direction and altitude are all spot on. Orbit may be theoretically possible but it may be much harder to achieve than is made out.

Once the rocket engine thrust stops, motion becomes ballistic. Timing of this moment is critical as the rocket is accelerating. The vector dynamics include direction which needs to be tangential. If below the tangent it will eventually crash. If too slow for the altitude it will eventually crash. (Ignore the issues of separating and braking the rocket.) This may be a long slow spiral but over time it is still a failure for a satellite.

If too fast then we are told the orbit becomes elliptical. Gravity slows it down until it is pulled back, and it enters into an orbit. Or does it perhaps fall back to Earth in a parabolic arc? In the early Explorer program there are several that ‘failed to enter orbit’. (6 out of first 11 Explorer missions 'failed to enter orbit'. Then there are none. Wikilies)

Whilst a rocket engine does maintain thrust in a vacuum its speed and direction probably cannot be accurately controlled. We can be fairly sure that when the rocket engines are stopped speed / direction / altitude will have significant errors. Orbit conditions are precise. Do satellites now have thrust and control and instrumentation to correct for final rocket ballistic errors?

Maybe in the early days it was a case of ‘Light the blue touch paper and retire’ but today rockets surely have sophisticated monitoring and control systems. However whatever the processing power these can be no better than the instruments on board. How do you measure altitude and speed above the atmosphere? GPS would be the best answer if it’s not satellite based (haha)! Aeroplanes still rely on barometric altimeters and Pitot tubes.

Apart from the question of instrumentation the rocket is steered by quite crude means: The nozzles are gimballed or the exhaust is deflected with rudder paddles, or the engines are selectively throttled. Once above the atmosphere any rotational moment imparted must be counteracted. This means continuous attitude control. The early X-15 and NF-104A rocket planes were equipped with a reaction flight control system. Michael J Adams was killed in a hypersonic spin and break up.

This is not about manned space flight, but is it possible that the Mercury project where the capsules did not go into orbit (and so fell back without the re-entry heat), were genuine? Gemini and everything thereafter are obvious frauds due to re-entry speed from orbit.

Although we can believe nothing we read, exploration programs in the late Fifties / early Sixties were probably genuine to some extent. Were the data from the Explorer missions on the Van Allen Belt faked? There seems no reason why a single parabolic trajectory into space could not be achieved. These orbits are drawn as long ellipses. Too many ‘failed to enter orbit’ missions would not have been acceptable. What changed to make achieving orbit straightforward?

‘Radiation Effects on Electronic Instruments’ by Henning Lind Olesen (perhaps shouldn’t link to libgen) is an academic paper from 1966 - when I was doing Physics at school– surprising how primitive. I was looking for early numbers on radiation in space.

Satellites seem to have turned out to be a great disappointment both commercially and militarily, perhaps scientifically too. Solid state electronics were fried or zapped. Communication Satellites weren’t practical or even needed due to refractive properties of the Ionosphere (thank you reichstag fireman!). Aeroplanes, cruise missiles / drones precision bomb and photograph your back yard much better.

I guess Space created a ‘river of gold’. The show business side was primarily to boost the funding appropriation, it was a closed cycle racket engine.

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Re: Satellites : general discussion and musings

Unread postby Altair on Sun Jul 14, 2019 6:15 pm

A satellite launcher would be no different than an ICBM or even a WWII V-2 rocket, just with some more muscle. They could be guided to the destination before the digital era by just a primitive analog computer that takes inputs from gyroscopes and maybe accelerometers, no more. Obviously, those inputs were very imprecise and prone to error accumulation. This sufficed to send bombs to London with a wide margin of error, or maybe even to send a nuclear missile, but it wouldn't provide the precision needed for placing an object in orbit (think also about the vibrations & so on).
In control automatics, that would fit into what's called a closed loop system: you've got a set of inputs from sensors, a set of outputs connected to actuators, and the goal is to place the system in a state where the inputs match a given set of values. In the case of a satellite, you'd be limited to get your rocket to a state where the inputs of the gyros match the desired values... and that means just a known orientation around the x-y-z axes.
GPS wasn't available (if it was at all) until the 90's, so placing a satellite in orbit just with the input of mechanical gyros seems quite of a stretch. So think about getting to the Moon...

EDIT: After writing this first part I was puzzled so as how early rockets could achieve a reasonable targetting accuracy given the primitive technology of the time. Most probably, they used just an attitude control system that allowed the rocket to fly in a straight line and stable direction until it ran out of fuel, and then continued in a ballistic trajectory. So it would be little more than a self-propelled shell.
Now, the issue is that there were no technology breakthroughs in this area until the 70's, so all the control technology employed in the 'space race' had to be essentially the same as in the V2. Simply put, as nokidding noted, a launcher would have no way to know where it was nor what speed was it travelling at, so any guidance systems would have to be blind. Even with good position/velocity feedback, achieving a reasonable accuracy would be quite difficult, so go imagine if all you have is a bunch of mechanical gyroscopes.
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Re: Satellites : general discussion and musings

Unread postby patrix on Sun Jul 14, 2019 9:05 pm

After writing this first part I was puzzled so as how early rockets could achieve a reasonable targetting accuracy given the primitive technology of the time.

The biggest problem for satellites (as the first page in the "Rocketry" thread explains) is however that it is physically impossible (confirmed by controlled experiments) for rockets to create propulsion in space.
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Re: Satellites : general discussion and musings

Unread postby Altair on Mon Jul 15, 2019 9:44 am

Lies rarely go alone. While the ability for rockets to work in vacuum is the main issue, even if they worked we'd got also the technical unfeasibility of positioning a satellite exactly in the required orbit without a precise position & velocity feedback. Just imagine you're the "pilot" of a rocket and your only input consists of three pitch/roll/yaw indicators. You can steer the rocket just by directing thrust sideways. Then, go and put this thing in the required orbit.
Even a small Cessna has a lot more sensors that are used as inputs for its autopilot: compass, airspeed, vertical speed, attack angle, and many others. The only way I can figure for a rocket guidance system to work would be by being constantly tracked by radar and then sending back the telemetry data. Even so, that would depend a lot upon atmospheric conditions and radio reception issues, and should be done in digital format (which over radio has very low througput).
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Re: Satellites : general discussion and musings

Unread postby simonshack on Tue Jul 16, 2019 2:01 pm

*

Russian musical intermezzo...

"Surprise!"


full link: http://www.youtube.com/watch?v=4ltTnQu2BNI

Beep beep beep ! ^_^
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Re: Satellites : general discussion and musings

Unread postby nokidding on Wed Jul 17, 2019 5:30 am

Wonderful thank you Simon! Here’s a paper all about the Explorer satellites going beep-beep-beep: ‘Vehicle Motions as Inferred from Radio-signal- Strength Records’

https://ntrs.nasa.gov/archive/nasa/casi ... 073999.pdf

I think it gives a glimpse of some real engineering before everything got buried by the scam. The paper includes background info on staged launch, attitude control and stability, temperature averaging, ground station monitoring, ionosphere effects, telemetry. Interesting to see the long ‘coasting’ period after Stage 1 burns out where the rocket continues up ballistically, angling over to the horizontal. The following three ‘high speed rocket stages’ (small concentrically mounted solid fuel rockets) take it into orbit. The satellite including the spent final stage rocket is 14Kg and 2m long.
https://en.wikipedia.org/wiki/Explorer_1

It seems early ballistic rockets could enter orbit just by exceeding the required velocity for a circular orbit at a given altitude. The resulting elliptical orbit might not be known but it achieved the objectives. Explorer-1 is said to have stayed in orbit for 12 years - but the identical Explorer-3 decayed from orbit in 93 days. Periapsis was lower than planned on Explorer-3 (186Km). Not sure how a satellite gone silent is monitored.

R&D obviously continued (it’s hard to comprehend a real and fake program co-existiing) but we don’t have much idea (or have faith in) what satellites are capable of. It tells us something that the U-2 spy plane program continued to operate, now being replaced by high altitude drones. https://en.wikipedia.org/wiki/Lockheed_U-2

The West Ford Needles experiment https://en.wikipedia.org/wiki/Project_West_Ford was to try and improve the skywave. HAARP officially is to research the Ionosphere (using EM induced changes). Comms satellites were also an early idea that looks like science fiction. As has been pointed out we now have a world wide cable and tower based infrastructure.

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