Artemis Project

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rabinoz

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Re: Artemis Project
« Reply #30 on: July 26, 2019, 03:52:27 AM »
They needed to get the craft traveling at 7 miles per second in straight light relationship from the center of the earth. It doesn't matter what they had to do to do that. It's the rules. Many other proposals and ship designs had different dynamics.
No they do not have to "to get the craft traveling at 7 miles per second in straight light relationship from the center of the earth".
  • The Apollo missions were never leaving earth's gravitational field.
    They simply had to reach the earth-moon L1 Lagrangian point with enough velocity to orbit the moon at required periapsis.

  • The 'best trajectory' is not simply "in straight flight relationship from the center of the earth".
    Why would you claim that they should do that?
    Though the 'best trajectory' depends on the requirements - such as minimum fuel, minimum time or a compromise with a free-return orbit,  as the earlier Apollo missions did.
Quote from: Tom Bishop
Yes, they did claim that the final stage of the Saturn V reached escape velocity.
Who claimed that because the post flight data from the the Apollo 10 mission does not confirm that.

The maximum velocity of the Saturn V on the Apollo 10 mission was 10,840 m/s (or 6.74 miles/second) at the end of the TLI burn 333 km above earth.
As noted above it was not attempting to escape the earth's gravitational field but reach the moon's.

The escape velocity from 333 km above earth is 10,904 m/s (or 6.78 miles/second), lower than from the earth's surface.
And the maximum velocity was never quite as high as the escape velocity.
These values are from page 3-29 of Document Apollo/Saturn V Postflight Trajectory AS-505.

Quote from: Tom Bishop
Derived by mathematicians regarding possible space travel long before NASA. Newton postulated escape velocities, in fact.
Would your care to post these calculations showing where they insist that the rocket must leave the earth "in straight flight relationship from the center of the earth"?

<< Sorry I screwed up a link. >>
« Last Edit: July 26, 2019, 05:12:42 AM by rabinoz »

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Tom Bishop

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Re: Artemis Project
« Reply #31 on: July 26, 2019, 04:53:07 AM »
It clearly says the following on NASA's website.

https://history.nasa.gov/SP-368/s1ch2.htm

"The crew checked out the spacecraft, and, after approximately three hours in Earth orbit, the Saturn IV-B stage was fired for approximately five minutes to accelerate the spacecraft to an Earth-gravity escape velocity of 40 233 km/hr (25 000 mph) to begin its 370 149 km (230 000 mile) coast to the moon. Following the translunar injection maneuver, the Apollo spacecraft was separated from the Saturn IV-B stage."

https://images.nasa.gov/details-0100983.html

"The S-IVB restarted to speed the Apollo spacecraft to escape velocity injecting it and the astronauts into a moon trajectory."

https://www.nasa.gov/feature/50-years-ago-the-journey-to-the-moon-begins

"Two hours and 44 minutes after liftoff, the third stage engine ignited for the six-minute TLI burn, increasing the spacecraft’s velocity to more than 24,000 miles per hour, enough to escape Earth’s gravity."

Apollo 15 Flight Journal https://history.nasa.gov/afj/ap15fj/03tde.html

The stack is 40 metres long and 6.6 metres at its widest, weighing over 65 metric tonnes; not an insubstantial load to have propelled away from Earth at escape velocity.

Popular mechanics:

Instead, the remaining structure continued to orbit Earth until a "go/no-go" decision was made by Mission Control in Houston. At that time, the third-stage rocket, technically known as an S-IVB, reignited and achieved "translunar injection." Once escape velocity, the speed needed to overcome Earth's gravity, or 24,500 mph, was achieved, the S-IVB was discarded as well.

...

They are clearly claiming to reach escape velocity of the Earth's gravity to inject into a trans lunar orbit. In order to reach escape velocity, it must be done in relation to the center of the earth.
« Last Edit: July 26, 2019, 05:26:52 AM by Tom Bishop »

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Tom Bishop

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Re: Artemis Project
« Reply #32 on: July 26, 2019, 05:29:18 AM »
I saw that you fixed your link. On page 3-29 of that document you refer to it says "space-fixed velocity".

Re: Artemis Project
« Reply #33 on: July 26, 2019, 05:42:55 AM »
What part of everyones explanation are you failing to comprehend.
You even quoted it yourself.

Re: Artemis Project
« Reply #34 on: July 26, 2019, 05:44:49 AM »
It clearly says the following on NASA's website.

https://history.nasa.gov/SP-368/s1ch2.htm

"The crew checked out the spacecraft, and, after approximately three hours in Earth orbit, the Saturn IV-B stage was fired for approximately five minutes to accelerate the spacecraft to an Earth-gravity escape velocity of 40 233 km/hr (25 000 mph) to begin its 370 149 km (230 000 mile) coast to the moon. Following the translunar injection maneuver, the Apollo spacecraft was separated from the Saturn IV-B stage."

https://images.nasa.gov/details-0100983.html

"The S-IVB restarted to speed the Apollo spacecraft to escape velocity injecting it and the astronauts into a moon trajectory."

https://www.nasa.gov/feature/50-years-ago-the-journey-to-the-moon-begins

"Two hours and 44 minutes after liftoff, the third stage engine ignited for the six-minute TLI burn, increasing the spacecraft’s velocity to more than 24,000 miles per hour, enough to escape Earth’s gravity."

Apollo 15 Flight Journal https://history.nasa.gov/afj/ap15fj/03tde.html

The stack is 40 metres long and 6.6 metres at its widest, weighing over 65 metric tonnes; not an insubstantial load to have propelled away from Earth at escape velocity.

Popular mechanics:

Instead, the remaining structure continued to orbit Earth until a "go/no-go" decision was made by Mission Control in Houston. At that time, the third-stage rocket, technically known as an S-IVB, reignited and achieved "translunar injection." Once escape velocity, the speed needed to overcome Earth's gravity, or 24,500 mph, was achieved, the S-IVB was discarded as well.

...

They are clearly claiming to reach escape velocity of the Earth's gravity to inject into a trans lunar orbit. In order to reach escape velocity, it must be done in relation to the center of the earth.

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Tom Bishop

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Re: Artemis Project
« Reply #35 on: July 26, 2019, 05:48:33 AM »
What part of everyones explanation are you failing to comprehend.
You even quoted it yourself.

I quoted five instances of descriptions of needing to reach earth-gravity escape velocity. The velocity rab posted says "space-fixed velocity" in the document.

And then you bolded "three hours in earth orbit" for some reason? Escape Velocity has only to do with the speed away from the center of the earth, not any particular method of application.
« Last Edit: July 26, 2019, 06:00:01 AM by Tom Bishop »

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rabinoz

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Re: Artemis Project
« Reply #36 on: July 26, 2019, 06:19:51 AM »
Your link leads nowhere. That's not what we see on NASA's website.
Sorry about that and the values I gave were actual measurements from the Apollo 10 mission!
The maximum velocity of the Saturn V on the Apollo 10 mission was 10,840 m/s (or 6.74 miles/second) at the end of the TLI burn 333 km above earth.
As noted above it was not attempting to escape the earth's gravitational field but reach the moon's.

The escape velocity from 333 km above earth is 10,904 m/s (or 6.78 miles/second), lower than from the earth's surface.
And the maximum velocity was never quite as high as the escape velocity.
These values are from page 3-29 of Document Apollo/Saturn V Postflight Trajectory AS-505.

It clearly says the following on NASA's website.

https://history.nasa.gov/SP-368/s1ch2.htm

"The crew checked out the spacecraft, and, after approximately three hours in Earth orbit, the Saturn IV-B stage was fired for approximately five minutes to accelerate the spacecraft to an Earth-gravity escape velocity of 40 233 km/hr (25 000 mph) to begin its 370 149 km (230 000 mile) coast to the moon. Following the translunar injection maneuver, the Apollo spacecraft was separated from the Saturn IV-B stage."

https://images.nasa.gov/details-0100983.html

"The S-IVB restarted to speed the Apollo spacecraft to escape velocity injecting it and the astronauts into a moon trajectory."

https://www.nasa.gov/feature/50-years-ago-the-journey-to-the-moon-begins

"Two hours and 44 minutes after liftoff, the third stage engine ignited for the six-minute TLI burn, increasing the spacecraft’s velocity to more than 24,000 miles per hour, enough to escape Earth’s gravity."

Apollo 15 Flight Journal https://history.nasa.gov/afj/ap15fj/03tde.html

The stack is 40 metres long and 6.6 metres at its widest, weighing over 65 metric tonnes; not an insubstantial load to have propelled away from Earth at escape velocity.
[/quote]
But look at the actual velocities given:
Quote
Apollo 15 Transposition, Docking and Extraction
Public Affairs Officer - "Velocity dropped off somewhat from the initial cut-off velocity of 35,000 and some odd feet per second [10,600 m/s] down to 30,436 feet per second [9,276.9 m/s].
is 2,3712 mph.

Quote from: Tom Bishop
Popular mechanics:

Instead, the remaining structure continued to orbit Earth until a "go/no-go" decision was made by Mission Control in Houston. At that time, the third-stage rocket, technically known as an S-IVB, reignited and achieved "translunar injection." Once escape velocity, the speed needed to overcome Earth's gravity, or 24,500 mph, was achieved, the S-IVB was discarded as well.
to the center of the earth.
Note that the Popular Mechanics gives "the speed needed to overcome Earth's gravity, or 24,500 mph" not the "25,000 mph" quoted earlier for escape velocity.

I think I'll go by the actual velocities quoted and not information as in the document for Apollo 11: APOLLO/SATURN V POSTFLIGHT TRAJECTORY - AS-506

That 10,843 m/s is 24,255 mph still below, but close to escape velocity.

Quote from: Tom Bishop
...
They are clearly claiming to reach escape velocity of the Earth's gravity to inject into a trans lunar orbit. In order to reach escape velocity, it must be done in relation to the center of the earth.
I'll grant that some public statements do say that they have to reach "escape velocity" and the figures I found were close.

But I'm more concerned with your claims of "in straight flight relationship from the center of the earth" because there is no such requirement.
A spacecraft could, and many do, leave the earth from a near-circular orbit by applying a burn to achieve a velocity high enough to leave earth.

Where do they say this?
They needed to get the craft traveling at 7 miles per second in straight light relationship from the center of the earth.
And that "7 miles per second" you keep quoting is only an approximate figure for the escape velocity from the earth's surface but no spacecraft would do that.

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markjo

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Re: Artemis Project
« Reply #37 on: July 26, 2019, 07:14:45 AM »
What part of everyones explanation are you failing to comprehend.
You even quoted it yourself.

I quoted five instances of descriptions of needing to reach earth-gravity escape velocity. The velocity rab posted says "space-fixed velocity" in the document.

And then you bolded "three hours in earth orbit" for some reason? Escape Velocity has only to do with the speed away from the center of the earth, not any particular method of application.
Tom, I'm not disputing you interpretation of escape velocity as much as I'm disputing your interpretation of "straight up".  Spacecraft move in lots of trajectories.  None of them are "straight up", especially in an environment where "up" loses its meaning and "straight" isn't really a thing anymore.
Science is what happens when preconception meets verification.
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Re: Artemis Project
« Reply #38 on: July 26, 2019, 08:10:17 AM »
What part of everyones explanation are you failing to comprehend.
You even quoted it yourself.

I quoted five instances of descriptions of needing to reach earth-gravity escape velocity. The velocity rab posted says "space-fixed velocity" in the document.

And then you bolded "three hours in earth orbit" for some reason? Escape Velocity has only to do with the speed away from the center of the earth, not any particular method of application.

It does make a difference though, because once you are in orbit, you can use most of your tangential velocity towards your escape velocity if you burn at the right moment.

The first 2 stages of the Saturn V (and I believe a bit of the third stage) were just used to get into Earth orbit.  Escape velocity from here isn’t that much less than at the surface, but the craft is already traveling at enormous speed, so they just needed to burn enough to make up the difference.

Apparently this is much more efficient than just trying to launch straight up.

This is quite a good explanation if you’re interested:

https://www.school-for-champions.com/science/gravitation_escape_velocity_saturn_v.htm#.XTsNoqQo-Ed

But I’m still not sure exactly what point you are making?

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Tom Bishop

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Re: Artemis Project
« Reply #39 on: July 26, 2019, 10:46:41 AM »
It is just how we are taught about Escape Velocity. Look at this page from Georgia State:

http://hyperphysics.phy-astr.gsu.edu/hbase/vesc.html



Disregarding any and all applications which any space agency claims to use, how would you describe this image if you had to put it into a sentence?

One way to phrase it is that the object needs to go straight up, or away from the earth, at 7 miles per second. It is simply what needs to be done. A description of Escape Velocity as commonly taught and nothing more. I can change the "straight up" in the sentence to "away from the earth" if it makes it more clear.

I think I'll go by the actual velocities quoted and not information as in the document for Apollo 11: APOLLO/SATURN V POSTFLIGHT TRAJECTORY - AS-506

That 10,843 m/s is 24,255 mph still below, but close to escape velocity.

What you quoted says space-fixed velocity.
« Last Edit: July 26, 2019, 11:36:36 AM by Tom Bishop »

Re: Artemis Project
« Reply #40 on: July 26, 2019, 11:38:58 AM »

Disregarding any and all applications which any space agency claims to use, how would you describe this image if you had to put it into a sentence?

Stuff flat earthers don’t believe.

Re: Artemis Project
« Reply #41 on: July 26, 2019, 11:55:38 AM »
correct
if you were to stand on the ground and jump straight up, how fast would you need to jump?
that fast as you mentioned.

if you were designing an efficient as possible to leave the earth using a rocket system and yaadyayadayayada - it's not straight up as per what you quoted, and what everyone else is trying to tell you.

but do go on, holding onto this ONE issue.

Re: Artemis Project
« Reply #42 on: July 26, 2019, 12:07:57 PM »
It is just how we are taught about Escape Velocity. Look at this page from Georgia State:

http://hyperphysics.phy-astr.gsu.edu/hbase/vesc.html



Disregarding any and all applications which any space agency claims to use, how would you describe this image if you had to put it into a sentence?

One way to phrase it is that the object needs to go straight up, or away from the earth, at 7 miles per second. It is simply what needs to be done. A description of Escape Velocity as commonly taught and nothing more. I can change the "straight up" in the sentence to "away from the earth" if it makes it more clear.

I think I'll go by the actual velocities quoted and not information as in the document for Apollo 11: APOLLO/SATURN V POSTFLIGHT TRAJECTORY - AS-506

That 10,843 m/s is 24,255 mph still below, but close to escape velocity.

What you quoted says space-fixed velocity.

If you stood on a high mountain and threw a rock horizontally at 25,000 mph it would escape the Earth as well. (disregarding air resistance of course)  It does not have to be "straight up"

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Tom Bishop

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Re: Artemis Project
« Reply #43 on: July 26, 2019, 12:50:47 PM »
What's your definition of up in RET?

This is mine:


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Stash

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Re: Artemis Project
« Reply #44 on: July 26, 2019, 01:27:44 PM »
What's your definition of up in RET?

This is mine:



What's your issue here? That:

A) For a rocket (we'll use Apollo) to leave earth's gravitational pull, it must be fired straight up from the Earth's center of gravity, and
B) It must have a velocity of greater than 7 miles per second, 25,000 mph

Versus our contention that:

A) For a rocket (we'll use Apollo) to leave earth's gravitational pull, it does NOT need to be fired straight up from the Earth's center of gravity, and
B) It does not need a velocity of greater than 7 miles per second, 25,000 mph, just shy of that, around 23,000 mph, using TLI and the moon's gravitational pull

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markjo

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Re: Artemis Project
« Reply #45 on: July 26, 2019, 01:29:30 PM »
It is just how we are taught about Escape Velocity. Look at this page from Georgia State:
Tom, as is often the case, how things work in theory is often very different from how they work in practice.  Just because escape velocity is 7 miles per second away from the center of the earth does not mean that any spacecraft has ever been launched and accelerated to 7 miles per second in a straight line away from the center of the earth.  They always launch to a circular orbit first and then accelerate to escape velocity following a parabolic or hyperbolic trajectory.  Sometimes they even use gravitational assist flybys to accelerate to escape velocity. 
Science is what happens when preconception meets verification.
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Tom Bishop

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Re: Artemis Project
« Reply #46 on: July 26, 2019, 01:56:06 PM »
It is just how we are taught about Escape Velocity. Look at this page from Georgia State:
Tom, as is often the case, how things work in theory is often very different from how they work in practice.  Just because escape velocity is 7 miles per second away from the center of the earth does not mean that any spacecraft has ever been launched and accelerated to 7 miles per second in a straight line away from the center of the earth.  They always launch to a circular orbit first and then accelerate to escape velocity following a parabolic or hyperbolic trajectory.  Sometimes they even use gravitational assist flybys to accelerate to escape velocity.

It needs to end up going seven miles per second away from the center of gravity. This holds if they stop at a space station and install a nuclear powered scram engine along the way. It doesn't matter how they do it.

There is a difference between how they did it and what needs to be done. You seem to think a single sentence is describing orbital meneuver when it is describing escape velocity

What's your definition of up in RET?

This is mine:



What's your issue here? That:

A) For a rocket (we'll use Apollo) to leave earth's gravitational pull, it must be fired straight up from the Earth's center of gravity, and
B) It must have a velocity of greater than 7 miles per second, 25,000 mph

Versus our contention that:

A) For a rocket (we'll use Apollo) to leave earth's gravitational pull, it does NOT need to be fired straight up from the Earth's center of gravity, and
B) It does not need a velocity of greater than 7 miles per second, 25,000 mph, just shy of that, around 23,000 mph, using TLI and the moon's gravitational pull

The quotes say that the third stage reached escape velocity. The quotes you guys provided specify space-fixed velocity.
« Last Edit: July 26, 2019, 02:12:01 PM by Tom Bishop »

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Stash

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Re: Artemis Project
« Reply #47 on: July 26, 2019, 02:19:38 PM »
The quotes say that the third stage reached escape velocity. The quotes you guys provided specify space-fixed velocity.

Apollos, 8-17:
Earth Fixed Velocity (ft/sec)

34,140.1

34,217.2

34,195.6

34,020.5

34,195.3

34,151.5

34,202.2

34,236.6

34,168.3


https://history.nasa.gov/SP-4029/Apollo_18-24_Translunar_Injection.htm

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Tom Bishop

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Re: Artemis Project
« Reply #48 on: July 26, 2019, 02:48:05 PM »
The quotes say that the third stage reached escape velocity. The quotes you guys provided specify space-fixed velocity.

Apollos, 8-17:
Earth Fixed Velocity (ft/sec)

34,140.1

34,217.2

34,195.6

34,020.5

34,195.3

34,151.5

34,202.2

34,236.6

34,168.3


https://history.nasa.gov/SP-4029/Apollo_18-24_Translunar_Injection.htm

And what makes you think that the tranlunar injection was the fastest point on the way to the moon?

"The next event was trans-lunar injection, at which point of time the crew re-ignited the single J-2 engine to accelerate the vehicle to escape velocity" (source)

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Stash

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Re: Artemis Project
« Reply #49 on: July 26, 2019, 02:57:23 PM »
The quotes say that the third stage reached escape velocity. The quotes you guys provided specify space-fixed velocity.

Apollos, 8-17:
Earth Fixed Velocity (ft/sec)

34,140.1

34,217.2

34,195.6

34,020.5

34,195.3

34,151.5

34,202.2

34,236.6

34,168.3


https://history.nasa.gov/SP-4029/Apollo_18-24_Translunar_Injection.htm

And what makes you think that the tranlunar injection was the fastest point on the way to the moon?

"The next event was trans-lunar injection, at which point of time the crew re-ignited the single J-2 engine to accelerate the vehicle to escape velocity" (source)

Because that's what NASA says.

If you want a real hard hitting reputable source of data, none other than the Guinness Book of World Records:

"According to the 2002 Guinness World Records, Apollo 10 set the record for the highest speed attained by a crewed vehicle: 39,897 km/h (11.08 km/s or 24,791 mph) on May 26, 1969, during the return from the Moon."

That was upon return from the moon and it still isn't breaking the 25,000 mph mark.

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Tom Bishop

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Re: Artemis Project
« Reply #50 on: July 26, 2019, 03:12:12 PM »
It doesn't have to be exactly 25,000 for escape velocity.

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

"The escape velocity from Earth is about 11.186 km/s (6.951 mi/s; 40,270 km/h; 36,700 ft/s; 25,020 mph; 21,744 kn) at the surface."

Perhaps we should take all of these sources, including NASA, at their word that the goal was escape velocity.

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Stash

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Re: Artemis Project
« Reply #51 on: July 26, 2019, 03:30:23 PM »
It doesn't have to be exactly 25,000 for escape velocity.

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

"The escape velocity from Earth is about 11.186 km/s (6.951 mi/s; 40,270 km/h; 36,700 ft/s; 25,020 mph; 21,744 kn) at the surface."

Perhaps we should take all of these sources, including NASA, at their word that the goal was escape velocity.

Maybe not a bad idea. Though I'm pretty proud of finally using The GBofWR's as a source...

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rabinoz

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Re: Artemis Project
« Reply #52 on: July 26, 2019, 04:04:17 PM »
The quotes say that the third stage reached escape velocity. The quotes you guys provided specify space-fixed velocity.

Apollos, 8-17:
Earth Fixed Velocity (ft/sec)

34,140.1
34,217.2
34,195.6
34,020.5
34,195.3
34,151.5
34,202.2
34,236.6
34,168.3

https://history.nasa.gov/SP-4029/Apollo_18-24_Translunar_Injection.htm

And what makes you think that the tranlunar injection was the fastest point on the way to the moon?

"The next event was trans-lunar injection, at which point of time the crew re-ignited the single J-2 engine to accelerate the vehicle to escape velocity" (source)
I suggest that you read:
Descanso2_S06.pdf: SECTION 6 SPACE-FIXED POSITION, VELOCITY, AND ACCELERATION VECTORS OF A LANDED SPACECRAFT RELATIVE TO CENTER OF MASS OF PLANET, PLANETARY SYSTEM, OR THE MOON.

Note that the "SPACE-FIXED POSITION, VELOCITY, AND ACCELERATION VECTORS OF A LANDED SPACECRAFT" are "RELATIVE TO CENTER OF MASS OF PLANET, PLANETARY SYSTEM, OR THE MOON".

Note that:
  • Stash gave Earth-Fixed Velocities (ft/sec)
  • The difference between Space-Fixed Velocities and Earth-Fixed Velocities is always 1346 ft/sec.
  • The maximum of even the Space-Fixed Velocities is 35579 ft.sec for Apollo 15 was below the usually quoted escape velocity of "about 11.2 km/s" (36745 ft/sec).

And there is no doubt that on the journey to the moon the highest velocity was at the end of the TLI burn. Higher velocities were reached just before re-entry into the earth's atmosphere.
Quote
DOCUMENT NO. D5-15560-6: TITLE APOLLO/SATURN V POSTFLIGHT TRAJECTORY - AS-506, page 1-1
The vehicle was inserted into a parking orbit at 709.33 seconds at an altitude of 191.1 km (103.2 n mi) and a total space-fixed velocity of 7,793.1 m/s (25,567.9 ft/s).

The vehicle remained in orbit for approximately one and one-half revolutions. The S-IVB stage was restarted during the second revolution approximately midway between Australia and Hawaii, at 9,856.2 seconds.

At 10,213.03 seconds, the vehicle was injected onto a circumlunar trajectory at an altitude of 334.4 km (180.6 n mi) and a total space-fixed velocity of 10,834.3 m/s (35,545.6 ft/s).

At 11,723 seconds, the CSM separated from the launch vehicle at an altitude of 7,065.7 km (3,815.2 n mi) and a total space-fixed velocity of 7,608.6 m/s (24,962.6 ft/s).

And please note that:
The usually quoted escape velocity of "about 11.2 km/s" (36745 ft/sec) only applies to a projectile fired from the surface of the earth with that velocity.
This type of trajectory is quite impossible to achieve and the initial acceleration would kill anyone onboard and the spacecraft.

Spacecraft can leave the earth for any destination by gradually raising the altitude.
This can be achieved by first using a "chemical rocket engine" to achieve LEO and then a low thrust engine (maybe an ion thruster or ion drive) to gradually increase the altitude of the orbit.

How Do Ion Engines Work? The Most Efficient Propulsion System Out There by Fraser Cain.


In practical terms, the velocity would be finally increased far higher than escape velocity simply to get to the destination in a shorter time.

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markjo

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Re: Artemis Project
« Reply #53 on: July 26, 2019, 05:24:26 PM »
It is just how we are taught about Escape Velocity. Look at this page from Georgia State:
Tom, as is often the case, how things work in theory is often very different from how they work in practice.  Just because escape velocity is 7 miles per second away from the center of the earth does not mean that any spacecraft has ever been launched and accelerated to 7 miles per second in a straight line away from the center of the earth.  They always launch to a circular orbit first and then accelerate to escape velocity following a parabolic or hyperbolic trajectory.  Sometimes they even use gravitational assist flybys to accelerate to escape velocity.

It needs to end up going seven miles per second away from the center of gravity. This holds if they stop at a space station and install a nuclear powered scram engine along the way. It doesn't matter how they do it.

There is a difference between how they did it and what needs to be done. You seem to think a single sentence is describing orbital meneuver when it is describing escape velocity
All I'm saying is that the phrase "accelerate 100 tons of matter straight up at 7 miles per second" is very misleading and a claim that NASA never made.
Science is what happens when preconception meets verification.
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Tom Bishop

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Re: Artemis Project
« Reply #54 on: July 26, 2019, 05:35:45 PM »
It might be reaching escape velocity, Rab. Look at the calculator I posted:

http://hyperphysics.phy-astr.gsu.edu/hbase/vesc.html

If you put in 1 and 1 for the Mass and Radius the escape velocity is 25008.493 mph

If you put in 1 and 1.1 for the Mass and Radius then the escape velocity drops to 23844.662 mph.



Adjust the radius down from there. The earth is also "moving," etc. There are plenty of ways they could be claiming to reach escape velocity as advertised.
« Last Edit: July 26, 2019, 06:05:21 PM by Tom Bishop »

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rabinoz

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  • Real Earth Believer
Re: Artemis Project
« Reply #55 on: July 26, 2019, 07:24:13 PM »
It might be reaching escape velocity, Rab. Look at the calculator I posted:

http://hyperphysics.phy-astr.gsu.edu/hbase/vesc.html

If you put in 1 and 1 for the Mass and Radius the escape velocity is 25008.493 mph

If you put in 1 and 1.1 for the Mass and Radius then the escape velocity drops to 23844.662 mph.



Adjust the radius down from there. The earth is also "moving," etc. There are plenty of ways they could be claiming to reach escape velocity as advertised.
But the fact is that they didn't quite reach the escape velocity at any of the altitudes they were at.
They highest velocity was for Apollo 15 and that was for a Space-Fixed Velocity of 35,579 ft/sec (10,845 m/s) at 1,055,296 ft (322 km).
That altitude is 1.052 × earth's radius where the escape velocity is 39,240 km/hr (10,900 m/s or 24,383 mph).

But it's so close that it doesn't matter. So let's forget whether they did or did not achieve the escape velocity from earth.

The far more important issues are:
  • The usually quoted escape velocity, be it from earth or higher, assumed that no further thrust will be applied.
    It is quite feasible to escape from the earth by first achieving Low Earth Orbit and then applying a small continuous thrust.

  • When a single large thrust is applied to escape the direction does not matter as long as the craft does not impinge on the atmosphere or worse impact the planetary body:

    From: CalcTool: Escape velocity Calculator

The escape velocity does not have to be directly away from centre of the earth. It can and usually is a tangential velocity.
And "Note that a powered object may escape the gravity of a body at any velocity desired.".

Re: Artemis Project
« Reply #56 on: July 27, 2019, 07:00:05 AM »
It might be reaching escape velocity, Rab. Look at the calculator I posted:

http://hyperphysics.phy-astr.gsu.edu/hbase/vesc.html

If you put in 1 and 1 for the Mass and Radius the escape velocity is 25008.493 mph

If you put in 1 and 1.1 for the Mass and Radius then the escape velocity drops to 23844.662 mph.



Adjust the radius down from there. The earth is also "moving," etc. There are plenty of ways they could be claiming to reach escape velocity as advertised.

I’ll ask again, Tom.  Where are you going with this, if anywhere?

You keep quoting escape velocity numbers, fine, but why?

Re: Artemis Project
« Reply #57 on: July 27, 2019, 12:27:47 PM »
It might be reaching escape velocity, Rab. Look at the calculator I posted:

http://hyperphysics.phy-astr.gsu.edu/hbase/vesc.html

If you put in 1 and 1 for the Mass and Radius the escape velocity is 25008.493 mph

If you put in 1 and 1.1 for the Mass and Radius then the escape velocity drops to 23844.662 mph.



Adjust the radius down from there. The earth is also "moving," etc. There are plenty of ways they could be claiming to reach escape velocity as advertised.

I’ll ask again, Tom.  Where are you going with this, if anywhere?

You keep quoting escape velocity numbers, fine, but why?

In case you guys haven't noticed, Tom is simply derailing the thread by causing everyone to go round in circles saying the same thing over and over. He is fully aware of what you are all saying. But he will keep hammering at one line of semantics to prevent the discussion going anywhere by getting bogged down in more detailed technicalities and minutiae while not addressing any point.
« Last Edit: July 27, 2019, 07:34:33 PM by SpaceCadet »

Re: Artemis Project
« Reply #58 on: July 27, 2019, 12:35:16 PM »
Yes we have noticed.
But really, is there any other option for them?
You can't fix FE.

*

Tom Bishop

  • Flat Earth Believer
  • 17920
Re: Artemis Project
« Reply #59 on: July 30, 2019, 04:35:59 PM »
The far more important issues are:
  • The usually quoted escape velocity, be it from earth or higher, assumed that no further thrust will be applied.
    It is quite feasible to escape from the earth by first achieving Low Earth Orbit and then applying a small continuous thrust.

  • When a single large thrust is applied to escape the direction does not matter as long as the craft does not impinge on the atmosphere or worse impact the planetary body:

    From: CalcTool: Escape velocity Calculator

The escape velocity does not have to be directly away from centre of the earth. It can and usually is a tangential velocity.
And "Note that a powered object may escape the gravity of a body at any velocity desired.".

Your own source contradicts you. The image you shared with us says that it's in relation from the body center of mass.

« Last Edit: July 30, 2019, 04:41:53 PM by Tom Bishop »