Satellites : general discussion and musings

[simonshack]

*

Here's the second part of EUTELSAT's...

"THE MAGIC CIRCLE" - episode 2

I'm posting it for a reason. If you care to watch it, please note the constant depiction of satellites as 'world-saviors' - which "help save lives, prevent natural disasters and all sorts of lovely, humanitarian things" - bla bla bla." So I'll let you watch it now:


full link: http://www.youtube.com/watch?v=6zLD1vm-5fk


Well, I was curious to know who is the CEO of Eutelsat. I found out that his name is Michel De Rosen.

MICHEL DE ROSEN - current CEO of EUTELSAT - and...

Now, get this: From 1976 to 1982 de Rosen was auditor at the French Ministries of Finance and Defense. From 1982 to 1999 he held several positions at RHONE-POULENC, a huge French chemical/pharmaceutical company. He then became chairman of an infamous pharmaceutical company - ViroPharma ( between 2000-2008). Moreover, he is still today on the board of directors of ABB - the world's largest builder of electricity grids, which - between 1990 and 2001 - had one Donald Rumsfeld on board...


Of course, ABB is also a key player in the highly lucrative satellite/global-warming business:
http://www.abb.com/cawp/seitp202/5109c6 ... 7f1df.aspx

..and with the search for life on Mars...
http://www.abb.com/cawp/seitp202/14dc2c ... 90bdd.aspx

Enough said?

[lux]

^ Looks like a friendly chap too.

From pharma scams to satellite scams. Makes sense.

[reichstag fireman]

^ Looks like a friendly chap too.

Hehe!

Is it an optical illusion, or are his glasses really dirty? Could it be cosmic dust on them? And what's with the lip scar? It's on some photos but not others. So a fairly recent addition, maybe to boost his street cred?

Described as from an aristocratic French family, Michel de Rosen married Laurence Marie Solange, daughter of Count Charles Stanislas de Taisne de Raymonval. The family can claim amongst its ancestors, Philippe ("Felipe") V de Bourbon, King of Spain (1700 to 1746), King of Naples and Sicily (1700 to 13), and Henri IV de Bourbon, King of Navarre (1572 to 1610) and King of France (1589 to 1610).

http://www.william1.co.uk/b32.htm
http://en.wikipedia.org/wiki/Henry_IV_of_France
http://en.wikipedia.org/wiki/Philip_V_of_Spain

[reichstag fireman]

Gentlemen,

how about a tiny school trigonometry problem?

[..snippage..]

AFAIK, no one ever claimed to having found any ionosphere at 2199.7 km or above: 600 km is the upper limit.

All that numbers show the same simple fact: the ionospheric mirror is just too low for reichstag fireman's model to be adequate.

Thanks Dmitry for the trig lesson! I will enjoy studying it 'tomorrow'

[Dmitry]

Caption: "Astrounaut James Van Hoften repairing the LEASAT F3" :

http://www.astronautix.com/craft/syncom.htm

Now, the SYNCOM Wiki page tells us that these LEASAT barrels weighed "1.3 tonnes each (over 7 tonnes with launch fuel)." So...we are actually asked to believe that : NASA dropped that thing off at about 400km altitude. It failed to ignite. They later docked with it again with another Space Shuttle, got it fixed, than got it fired up in mid-air - and remotely steered/navigated/and braked it - all the way up into a 35,678km orbit. How do they do it? My head hurts!

I warmly welcome any (possibly sensible) clarifications from any rocket scientist on board - thank you very much!

Simon,

I am not really rocket scientist, but will do my best. Well, what do hurt your head?

1) That a barrel was dropped at 400 km above the Earth surface and didn't fall during some years? But the Earth itself didn't fall to the Sun. By the same reason: its velocity is too high to let it fall (http://en.wikipedia.org/wiki/Orbital_speed).

2) It failed to start (not completely ignite). It happens, I believe.

3) Later, another shuttle came, James Van Hoften stepped out and fixed the satellite. The credibility depends on the problem fixed. Repairing an engine in such conditions seems pure fantastic. But to hook up a cable (accessible from exterior) or to lift away some forgotten cap -- why not?

4) ...got it fired up in mid-air... There is no air there. The barrel rotated around the Earth at the orbital speed. The engine was started. The barrel started lifting up. No non-sense.

5) remotely steered/navigated/and braked it - all the way up into a 35,678km orbit. AFAIK, no one claim to having remotely navigated this craft in manual mode in real time. This might be done by an automatic control system.

6) Or the number of (35,678 - 400) = 35 278 km seems too big? But at such altitude, the drag force is near zero. At the orbital velocity, you can apply tiniest force and go very far: nothing stops you. This is very unlike our everyday experience where there are always a lot of dissipative forces (friction, drag etc.)

7) Maybe you agree that 35,678 km is accessible, but suspect that the ascension must take millenniums? Let's recall that the barrel had (7-1.3) = 5.7 tonnes of fuel that was completely ejected -- right to speed up first and then brake down 1.3 tonnes of material. By the law of conservation of linear of momentum, roughly speaking, having ejected 3.5 tonnes with the velocity v and weighting yourself 3.5 tonnes, you fly with v the in opposite direction. Then, you can slow down the same way.

In fact, the mass varies as the fuel goes away and this happens not instantly. So we face the differential equation (by I. Meshchersky, http://www.encyclopedia.com/doc/1G2-2830902925.html). Solved by Tsiolkovsky (http://en.wikipedia.org/wiki/Tsiolkovsk ... t_equation) more than a century ago. I don't know in what exact time the satellite is said to be lifted to the geostationary orbit and what are the official performances of its propulsion system (first of all -- the speed of ejected gas). But if you find some sources -- you can explicitly check it with well known physics formulas.

[simonshack]

*

Dear Dmitry,

Since you seem keen to believe in these NASA space fables, and since you are in Russia, would you do me a favour?

Could you please read this thread about the absolutely hilarious fable of BURAN - and comment on it? As you'll see, I've spent a fair amount of time looking at the BURAN (Russia's Space Shuttle 'clone') and I am very eager to get some Russian feedback from my patient work on that subject. ( I will now reply to your above post).

Thanks in advance!

[simonshack]

Simon,

I am not really rocket scientist, but will do my best. Well, what do hurt your head?

The SYNCOM "barrel" satellite

Dear Dmitry,

Here is a series of questions (A, B, C) which are hurting my head. As you'll see, all of those questions will faithfully address your above replies. I of course wish to get some answers to my questions - so I will keep it all nicely on topic.

A: Since there is no air up there (as you rightly point out), how exactly do these thrusters exert motion on / and accurately steer any spacecraft up there? How can a Space Shuttle recapture/ and accurately dock with another object left orbiting (at 27,000km/h) around the F-region of the ionosphere - (aka the APPLETON layer) ? You make it all sound so simple - but that doesn't satisfy me, Dmitry. As far as I know (but I'm certainly no rocket scientist), you can't apply thrust in a vacuum.

B: Likewise, how did the SYNCOM's propel itself in any given direction - AND MOST IMPORTANTLY, orientate that thrust upwards - in order to reach the desired 36km geostationary altitude? When NASA remotely ignited the SYNCOM's thruster - how did they make sure that barrel wasn't pointing down towards Earth - thus plunging it to its death - like a burning meteor?

C: If - as you say - all this was handled by "an automatic control system", can you point me to some NASA data explaining how such an automatic control system works? Like, what sort of sensors would tell that system how to navigate that SYNCOM barrel up (with utmost precision) to its desired geostationary position? And how it would be braked - in order to stop it from proceeding up in outer space? As you say - there's no AIR up there, right? So HOW does NASA make it stop at 36km ???

Lastly, how do they make sure their satellite doesn't collide with the other 350 geostationary satellites placed around that "265.000km-long belt" (& distanced by a mere 1500km!) as stated by this EUTELSAT video? (watch at 12:00) :


full link: http://www.youtube.com/watch?v=j8jtpyW6ATM

Thanks!

[Gauging]

As an aside, there's a discussion on GLP about the question of rockets in a vacuum:

http://www.godlikeproductions.com/forum1/message1791934/pg14

Naturally, there's a lot of condescension - "didn't you know that the rocket thrusts against itself!?"

[Maat]

This answer & example re Newton's 3rd Law might help: http://www.straightdope.com/columns/rea ... m-of-space

Q: My understanding of space is that it is a vacuum, i.e., devoid of pretty much all matter, just empty space. Also from my amazingly limited knowledge of physics I understand that in order for a force to create movement it must act upon something. So if a spacecraft fires its rockets into space, a vacuum, what is this force is acting upon? If there is nothing there, what are the rockets pushing against to cause the ship to move?..

A: … The truth is that the rocket does have something to push against: namely, its own fuel. Let's illustrate with an example you kids can try at home. First, you need to get yourself into some sort of frictionless situation. Wearing ice skates on a slippery ice rink would be good, or maybe your office has a chair that rolls really well on a hard surface. Next, you'll need a medicine ball. You are the rocket and the medicine ball is your fuel. Toss the medicine ball. You'll notice that as you shove the medicine ball forwards, you yourself lurch backwards. Ta-da, the miracle of physics! (If you think this is because the medicine ball pushed on the air, then try the experiment without the medicine ball--just push on the air with your hands, see how far you lurch backwards.)

Newton's Third Law is usually expressed as, "For every action there is an equal and opposite reaction," and you can also think of it as "Forces always come in pairs." While you are pushing on the medicine ball, Newton's Third Law says that the medicine ball is also pushing on you. Thus, you are accelerated by the force acting (backward) on you by the medicine ball. Never mind that it was you who decided to start the pushing in the first place; you can't push on the ball without having the ball push back. Forces always come in pairs.

Of course, rockets work on more sophisticated principles than just tossing fuel out the back. First, the fuel is burned and its hot exhaust gases are expelled at very high velocity (if you toss the medicine ball faster, your body experiences greater backward force). And the rocket's exhaust nozzle has a narrowing so as to squirt the exhaust gasses out even faster, like putting your thumb over the end of a garden hose. Exhaust from chemical propulsion (i.e., fuel-burning propulsion) is typically expelled at 2 km/s (= 4500 mph), and your average rocket mass at launch is 80-85% propellant (fuel + oxidizer), most of which eventually gets squirted out.

[simonshack]

Ok, Maat

So what the thrust acts upon - to make that thing move - is its own fuel. Fine.

But how did NASA tell this (1984) satellite barrel where to go? Can my question get any simpler?


SYNCOM/Leasat 3 (1984)

*********************
And if I need to make my point any clearer, here's an image depicting the 1963 "SYNCOM 2" satellite (a 39kg miniature version of the above) - and reportedly the VERY FIRST satellite to be placed in geostationary orbit:


SYNCOM 2 (1963)

How did even THIS old precursor get properly navigated to its intended destination? What guided it?

And on a common sense / aside note: are we really supposed to believe that the design of this SYNCOM, barrel-shaped satellite remained virtually unaltered for over 20 years (1963 to 1984) ?

[Maat]

I don't buy any of NASA's fairy tales for a second, Simon. Not even Newton's 3rd can make any of their crap believable to me.

[brianv]

I must admit that one has always baffled me too! How do rockets work in space?

If a human is sitting on wheelie chair in space and she throws a ball, would she move in the opposite direction - for ever? An object traveling in a straight line will continue unless some force acts against it! Newton Motion 1.

So with no force to stop her, what force is present to propel her in the first place? In the pool, if I push my hands against the water, im pushed backways, the same water stops me from continuing to go backways!

In space what force do rockets thrust against to propel them forward? If you are pushing against nothing there is no reciprocal push! If I put my two fists against a wall and start pushing, the wall pushes back with the same force, until I'm overcome by pain! The system collapses. Same as airplanes flying against steel buildings, the building hits the plane with the same force the plane hits the building!

When a rocket lifts off, the ground is pushing it up. I'm guessing, as it climbs the rockets have to fire harder proportional to the distance travelled from the ground. I'm thinking you would run out of fuel quickly. So you take more fuel next time, making the craft bigger and heavier, so you need even more fuel, making the craft even heavier, so more fuel ad infinitum... Didnt Von Clown say something about needing a rocket-ship the size of the ESB to get to the Moon?

Just thinking out loud!

[lux]

Here is my understanding ...

The combustion within the rocket motor causes a force in all directions. Most of these forces cancel each other out except for the force moving toward the nose. That is because the opposite end of the rocket is open (the nozzle). Thus the rocket moves forward.

It's not that the rocket pushes against anything behind it, it's that it doesn't push against anything behind it (due to the opening at the rear) so the combustion force pushing toward the nose isn't canceled out.

Rotating propellers, on the other hand, do push against the air behind them in a sense so they do require air to work.

[Farcevalue]

I am picturing two ice skaters at edge of a frozen pond. One has a medicine ball, the other has his arms on a large tree, bent and flexed to push himself backward.

Anybody want to put money on the medicine ball?

(later, there willl be a pumpkin cannon demonstration and someone lecturing about parallax)

[whatsgoingon]

a