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A few simple misconceptions about space flight

 
Dr. Moran
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User ID: 73391481
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02/21/2018 06:50 AM
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A few simple misconceptions about space flight
I've seen these misconceptions in many space related threads, and they've given me an itch that I just have got to scratch...

1) A rocket does not simply climb up (vertically) to the orbit. Yes, the rocket needs to go up, but soon after the launch the trajectory must also tilt more parallel to the Earth's surface. You see it in video footage of launches like the recent Falcon launch. If you'd simply try to "fly up" (i.e. increase radial speed only) and did not achieve escape velocity (which would not put you into the orbit), you'd would fall back to Earth after the fuel runs out. No. Speed parallel to the Earth's surface (tangential speed) is essential in obtaining a stable orbit around the Earth. You need about 7-8 km/s of horizontal speed to make it.

2) There is zero gravity because you're far away from the Earth. Wrong. When you're orbiting the Earth you are in a constant free fall. Earth's gravity has not been significantly reduced. Imagine being on an elevator and the cables snap. While falling towards your inevitable death, you would also experience near zero-g - if we neglect acceleration from the drag and friction, that is. The difference between an orbital flight and the elevator example is that when you're orbiting the Earth, you have enough tangential velocity to keep you from falling back to the surface, but the elevator will crash sooner or later.

3) To increase the altitude of your orbit, you fire your thrusters towards the Earth. Nope. If you want to increase your altitude, you need to increase your tangential speed (i.e. fire thrusters). If you want to lower your altitude, you need to decrease your tangential speed (i.e. fire thrusters in the opposite direction to your orbital velocity). This will move you up or down the gravity well.

4) Removing heat from a space suit/space station to space is not possible in the vacuum. Wrong. Radiative heat transfer works in vacuum, and you can also use phase transitions to remove excess heat. A sublimator works on the principle of sublimation, that is, the process by which a solid turns directly into a vapor, bypassing the liquid phase. This phase change removes a lot of heat. In space applications, ice is formed on the sublimator evaporator sieve and is allowed to vaporize to space, removing heat with it. Air and cooling water are passed through fins in the sublimator, which extracts heat from the suit system. This requires, of course, water that can be vented to space, but it is very effective.

Now all this is in very simplistic terms. For orbital mechanics, I refer you here: [link to www.braeunig.us]

Last Edited by Dr. Moran on 02/21/2018 06:57 AM
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Anonymous Coward
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02/21/2018 07:05 AM
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Re: A few simple misconceptions about space flight
You do realize that the people here who don't already know all that also don't want to know? The flat earth tards, in particular, have impenetrable minds. They will believe only what they want to believe.
Anonymous Coward
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02/21/2018 07:06 AM
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Re: A few simple misconceptions about space flight
Everyone should purchase the game "Simple Rockets" on Steam.

It's a great 2d representation of how it works, and they use actual logistics. The game is damn hard.
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02/21/2018 07:11 AM
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Re: A few simple misconceptions about space flight
I will slightly disagree with #3, As a prograde burn towards the earth will increase the periapsis further from the planet on the otherside. It however does tighten the orbit into a more oval shape, but once you've reached the periapsis you could burn out towards the moon and create a new orbit.
Dr. Moran  (OP)

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02/21/2018 07:14 AM
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Re: A few simple misconceptions about space flight
I will slightly disagree with #3, As a prograde burn towards the earth will increase the periapsis further from the planet on the otherside. It however does tighten the orbit into a more oval shape, but once you've reached the periapsis you could burn out towards the moon and create a new orbit.
 Quoting: WrightWingConservative

Yeah, I was just trying to outline the basic principles.
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Anonymous Coward
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02/21/2018 07:21 AM
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Re: A few simple misconceptions about space flight
Mhd doesnt need those principles,generally speaking.plus why waste water.just concentrate the heat as another form of radiation and expel it.or recycle it back into a storage vessel.
Anonymous Coward
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06/27/2018 06:57 AM
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Re: A few simple misconceptions about space flight
bump
Anonymous Coward
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06/27/2018 07:08 AM
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Re: A few simple misconceptions about space flight
all rockets just crash into the ocean. OP is a bad liar with nothing to do.

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