Rama Set

Re: FE and ICBMs
« Reply #280 on: July 07, 2021, 01:31:34 PM »
Showing this mathematically would be extremely compelling.
I agree.

Kindly demonstrate the compelling mathematical evidence that a missile, under no engine power, traveling at a rate of 16,000km/h, at an altitude of 250km, subject to a g=slightly above 9m/s2, will continue to gain altitude to an apogee of 4500km.

By the way, how was your trip to outer space?

I see you are having trouble distinguishing between an assertion and showing the mathematical truth behind your claims.

Offline Action80

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Re: FE and ICBMs
« Reply #281 on: July 07, 2021, 01:41:12 PM »
Showing this mathematically would be extremely compelling.
I agree.

Kindly demonstrate the compelling mathematical evidence that a missile, under no engine power, traveling at a rate of 16,000km/h, at an altitude of 250km, subject to a g=slightly above 9m/s2, will continue to gain altitude to an apogee of 4500km.

By the way, how was your trip to outer space?

I see you are having trouble distinguishing between an assertion and showing the mathematical truth behind your claims.
What happened to the burden being on the OP and its supporters being responsible to demonstrate the reality of their claims?

But go ahead, post the math, which you claim has already been posted in this thread, demonstrating the reality of ICBM's.

As simple as posting a link to the post.
To be honest I am getting pretty bored of this place.

SteelyBob

Re: FE and ICBMs
« Reply #282 on: July 07, 2021, 02:10:00 PM »
^The entirety of this post just above mine here gets a big thumbs down, especially that last feeble attempt at trying to brush away the fact that 250km traveled in 5 minutes = 3000km/h average speed over those 5 minutes.

Just pitiful.

Really pitiful.

Moving on.

No, not moving on. You keep saying it's wrong, but you are completely unable to back up that claim with any evidence whatsoever. Nobody is saying that 3000km/h isn't the average speed. Of course it's the average speed. And that is entirely consistent with the final velocity being 16,000km/h. The final velocity could be anything at all. As long as the velocity-time profile is such that the area under the graph is 250km, then the average speed will be 3000km/h. It could finish at 16,000km/h, or 100,000km/h, or at a standstill. The totality of the profile is all that matters.

This is somewhat painful.

Offline Action80

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Re: FE and ICBMs
« Reply #283 on: July 07, 2021, 03:12:18 PM »
^Incorrect.

In order to to achieve the figure of 250km altitude in 5 minutes resulting in a 3000 km/h average rate of travel, the velocities contained between the 0 and the 16,000 over the five minutes would average out to 3000 km/h.

They cannot, as (final velocity + initial velocity)/2 = average velocity.

https://www.calculatorsoup.com/calculators/physics/velocity_avg.php#:~:text=The%20sum%20of%20the%20initial,u)%2C%20divided%20by%202.

One, if they would, you would have shown it by now, which is incumbent on the person making the initial claim, which you did, not me.

Two, if the missile is no longer under additional power at an altitude of 250km, and is being subjected to g=slightly over 9m/s2, you would have shown how it is possible for the missile to continue to gain 4250 km of additional altitude while decelerating, which is also your claim, not mine.
« Last Edit: July 07, 2021, 04:51:52 PM by Action80 »
To be honest I am getting pretty bored of this place.

SteelyBob

Re: FE and ICBMs
« Reply #284 on: July 07, 2021, 06:56:50 PM »
^Incorrect.

In order to to achieve the figure of 250km altitude in 5 minutes resulting in a 3000 km/h average rate of travel, the velocities contained between the 0 and the 16,000 over the five minutes would average out to 3000 km/h.
They cannot, as (final velocity + initial velocity)/2 = average velocity.

Hallelujah…finally, some maths so we can actually understand what it is that you don’t understand.

That statement above is simply incorrect. It would work as a calculation if and only if the velocity profile was linear which, as you’ve agreed previously, it isn’t - the fuel burns down, so mass reduces, but thrust is constant.

Average velocity is not necessarily the average of the start and end velocity.

It’s easy to prove that to yourself - just consider my 30mph car example. Your calculation would have the average velocity as the average of 30 and, say, 100mph even though the car only did 100mph for a few seconds after an hour at 30mph. Average speed is clearly not 65mph, as per your maths.

Or imagine a situation where start and end velocity are the same, but there’s a burst of increased velocity in the middle somewhere. Again, it wouldn’t work.

For general cases you need the area under the velocity time graph. If the slope is linear, your equation works - the area under a triangle is half the base times the height, which is, if you think about it, exactly what your equation is. But our graph here isn’t linear - it’s exponential, so you can’t calculate that simply.

Are we finally in agreement in this point at least?

Offline Action80

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Re: FE and ICBMs
« Reply #285 on: July 08, 2021, 12:20:18 PM »
^Incorrect.

In order to to achieve the figure of 250km altitude in 5 minutes resulting in a 3000 km/h average rate of travel, the velocities contained between the 0 and the 16,000 over the five minutes would average out to 3000 km/h.
They cannot, as (final velocity + initial velocity)/2 = average velocity.

Hallelujah…finally, some maths so we can actually understand what it is that you don’t understand.

That statement above is simply incorrect. It would work as a calculation if and only if the velocity profile was linear which, as you’ve agreed previously, it isn’t - the fuel burns down, so mass reduces, but thrust is constant.

Average velocity is not necessarily the average of the start and end velocity.

It’s easy to prove that to yourself - just consider my 30mph car example. Your calculation would have the average velocity as the average of 30 and, say, 100mph even though the car only did 100mph for a few seconds after an hour at 30mph. Average speed is clearly not 65mph, as per your maths.

Or imagine a situation where start and end velocity are the same, but there’s a burst of increased velocity in the middle somewhere. Again, it wouldn’t work.

For general cases you need the area under the velocity time graph. If the slope is linear, your equation works - the area under a triangle is half the base times the height, which is, if you think about it, exactly what your equation is. But our graph here isn’t linear - it’s exponential, so you can’t calculate that simply.

Are we finally in agreement in this point at least?
I already agree it is exponential, but I do not agree there would necessarily be a drastic difference in calculation.

According to the sources, the missile was fired in a near vertical trajectory from launch site. The attainment of 250km does not veer significantly from the vertical within the span of five minutes. 250km would, given an apogee of 4500km achieved downrange at approximately 450km, fall within a measure of approximately 50km or so. Not much of an interval to calculate and it remains very close to a linear calculation of average velocity.

0 - 16,000km/h within 5 minutes results also in a relatively straight line in what turns out to be roughly a tenth of total flight time according to your sources.

« Last Edit: July 08, 2021, 01:14:29 PM by Action80 »
To be honest I am getting pretty bored of this place.

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Offline Iceman

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Re: FE and ICBMs
« Reply #286 on: July 08, 2021, 12:58:20 PM »
Average velocity calculations have been accurate, but they are entirely irrelevant to the question at hand. The final velocity at the end of the burn is the only significant number here.

Talking about average is like saying that since I was 8lbs 8 oz at birth, and weight 185 now, my average weight over my lifetime would be just shy of 97 pounds.
Or like measuring a formula 1 car's lap time - you can have an average time but it's not going to tell you anything about its velocity going into a turn or at the end of a straightaway.
It's a meaningless calculation that offers nothing.

Offline Action80

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Re: FE and ICBMs
« Reply #287 on: July 08, 2021, 01:22:27 PM »
Average velocity calculations have been accurate, but they are entirely irrelevant to the question at hand. The final velocity at the end of the burn is the only significant number here.

Talking about average is like saying that since I was 8lbs 8 oz at birth, and weight 185 now, my average weight over my lifetime would be just shy of 97 pounds.
Or like measuring a formula 1 car's lap time - you can have an average time but it's not going to tell you anything about its velocity going into a turn or at the end of a straightaway.
It's a meaningless calculation that offers nothing.
When the average velocity doesn't match the velocity profiles over the given time of flight, it is certainly relevant.

I have no doubt of your other statements, but could care less as they are in no way related to the discussion here and are meaningless and totally fraudulent analogies. Not even close to the issue here.

We are talking about achievement of a goal in a certain period of time. What it took to achieve that goal is certainly averaged out.

Since you acknowledge the average velocity calculations as correct, that means 8000km/h is just shy of 2 minutes to travel 250km, which doesn't match the 5 minute burn time, or if you wish to keep the 5 minute burn time which would almost certainly be necessary (as it stands, the remainder of the flight is at jeopardy), the missile would have been a lot higher than 250km. Which would get you closer to the 4500km required for apogee, but attainment would likely be doomed by the g-forces at the new altitude figure of 667 km, which would be around 8m/s2.
« Last Edit: July 08, 2021, 01:55:38 PM by Action80 »
To be honest I am getting pretty bored of this place.

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Offline AATW

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Re: FE and ICBMs
« Reply #288 on: July 08, 2021, 02:20:51 PM »
We are talking about achievement of a goal in a certain period of time. What it took to achieve that goal is certainly averaged out.

Since you acknowledge the average velocity calculations as correct, that means 8000km/h is just shy of 2 minutes to travel 250km, which doesn't match the 5 minute burn time, or if you wish to keep the 5 minute burn time which would almost certainly be necessary (as it stands, the remainder of the flight is at jeopardy), the missile would have been a lot higher than 250km.
If it's travelled 250km in 5 minutes then the average is 3,000km/h.
It starting at 0 and ending at 16,000km/h doesn't mean the average is 8000. That's not how the calculation works. You could sit still for 4 minutes and then go at 15,000km/h for the final minute and you'd travel 250km. Your average would still be 3,000km/h.
I suggested an acceleration which would work and actually travel less than 250km, not more. You could obviously tweak it to be bang on if you really care.
Tom: "Claiming incredulity is a pretty bad argument. Calling it "insane" or "ridiculous" is not a good argument at all."

TFES Wiki Occam's Razor page, by Tom: "What's the simplest explanation; that NASA has successfully designed and invented never before seen rocket technologies from scratch which can accelerate 100 tons of matter to an escape velocity of 7 miles per second"

SteelyBob

Re: FE and ICBMs
« Reply #289 on: July 08, 2021, 02:31:36 PM »
We are talking about achievement of a goal in a certain period of time. What it took to achieve that goal is certainly averaged out.

Since you acknowledge the average velocity calculations as correct, that means 8000km/h is just shy of 2 minutes to travel 250km, which doesn't match the 5 minute burn time, or if you wish to keep the 5 minute burn time which would almost certainly be necessary (as it stands, the remainder of the flight is at jeopardy), the missile would have been a lot higher than 250km.
If it's travelled 250km in 5 minutes then the average is 3,000km/h.
It starting at 0 and ending at 16,000km/h doesn't mean the average is 8000. That's not how the calculation works. You could sit still for 4 minutes and then go at 15,000km/h for the final minute and you'd travel 250km. Your average would still be 3,000km/h.
I suggested an acceleration which would work and actually travel less than 250km, not more. You could obviously tweak it to be bang on if you really care.

And I suggested a velocity profile which also (coincidentally) gave a 250km distance over 5 minutes.

But we are, I think, wasting our collective time, as A80 doesn't actually appear to be reading what we write.

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Offline AATW

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Re: FE and ICBMs
« Reply #290 on: July 08, 2021, 02:33:14 PM »
But we are, I think, wasting our collective time, as A80 doesn't actually appear to be reading what we write.
Correct. We've shown our workings, he's refused to show his.
Until he does I don't think there's much more scope for discussion.
Tom: "Claiming incredulity is a pretty bad argument. Calling it "insane" or "ridiculous" is not a good argument at all."

TFES Wiki Occam's Razor page, by Tom: "What's the simplest explanation; that NASA has successfully designed and invented never before seen rocket technologies from scratch which can accelerate 100 tons of matter to an escape velocity of 7 miles per second"

SteelyBob

Re: FE and ICBMs
« Reply #291 on: July 08, 2021, 02:39:04 PM »
I already agree it is exponential, but I do not agree there would necessarily be a drastic difference in calculation.

So you agree that your 'start + end v divided by two' equation is wrong, but now we're in to a discussion about how wrong it is?

According to the sources, the missile was fired in a near vertical trajectory from launch site. The attainment of 250km does not veer significantly from the vertical within the span of five minutes. 250km would, given an apogee of 4500km achieved downrange at approximately 450km, fall within a measure of approximately 50km or so. Not much of an interval to calculate and it remains very close to a linear calculation of average velocity.

0 - 16,000km/h within 5 minutes results also in a relatively straight line in what turns out to be roughly a tenth of total flight time according to your sources.

What on earth does that bit in bold actually mean?

Why aren't you looking at either the example velocity profiles that AATW or I gave you - they both illustrate the point that you seem to be consistently missing. You're even accepting that your calculation is wrong...why not accept that the follow-on from that, ie that it's perfectly possible to accelerate to 16000km/h in 5 minutes and have an average velocity of 3000km/h over that same time period? For the - I've-lost-count-of-how-many-times time, if most of the acceleration happens in the last minute, it's not surprising at all that the average velocity is a lot less than the final velocity.

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Offline AATW

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Re: FE and ICBMs
« Reply #292 on: July 08, 2021, 02:59:28 PM »
it's perfectly possible to accelerate to 16000km/h in 5 minutes and have an average velocity of 3000km/h over that same time period?
It's not just possible, we've both given examples. And it's obvious that you can almost finish at any final velocity.
You could stay still for almost all the time and then in the last 0.000833333 seconds go at the speed of light.
You'll have travelled 250km and your average speed would have been 3,000km/h.
Obviously that's not realistic, I tried to do something more realistic.
If Lackey is struggling with the idea that there is no real link between final speed and average speed then we're a bit stuck.
Tom: "Claiming incredulity is a pretty bad argument. Calling it "insane" or "ridiculous" is not a good argument at all."

TFES Wiki Occam's Razor page, by Tom: "What's the simplest explanation; that NASA has successfully designed and invented never before seen rocket technologies from scratch which can accelerate 100 tons of matter to an escape velocity of 7 miles per second"

Offline Action80

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Re: FE and ICBMs
« Reply #293 on: July 08, 2021, 03:30:38 PM »
I already agree it is exponential, but I do not agree there would necessarily be a drastic difference in calculation.

So you agree that your 'start + end v divided by two' equation is wrong, but now we're in to a discussion about how wrong it is?
Evidently you are missing the point that while it is exponential, the calculation of the average velocity is such that it would not differ substantially from the result of a linear solution.
According to the sources, the missile was fired in a near vertical trajectory from launch site. The attainment of 250km does not veer significantly from the vertical within the span of five minutes. 250km would, given an apogee of 4500km achieved downrange at approximately 450km, fall within a measure of approximately 50km or so. Not much of an interval to calculate and it remains very close to a linear calculation of average velocity.

0 - 16,000km/h within 5 minutes results also in a relatively straight line in what turns out to be roughly a tenth of total flight time according to your sources.

What on earth does that bit in bold actually mean?

Why aren't you looking at either the example velocity profiles that AATW or I gave you - they both illustrate the point that you seem to be consistently missing. You're even accepting that your calculation is wrong...why not accept that the follow-on from that, ie that it's perfectly possible to accelerate to 16000km/h in 5 minutes and have an average velocity of 3000km/h over that same time period? For the - I've-lost-count-of-how-many-times time, if most of the acceleration happens in the last minute, it's not surprising at all that the average velocity is a lot less than the final velocity.
It means what I just pointed out.

You demand the area under the curve be calculated, which is fine and good, and I am stating there isn't much of a curve to be considered and the result would be much the same as a linear result.

Remember, the displacement is a total of 250km at t+5, with not much variance from the y-axis within that space. The difference in the resulting measures is not going to be that significant.
« Last Edit: July 08, 2021, 04:25:23 PM by Action80 »
To be honest I am getting pretty bored of this place.

Offline Action80

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Re: FE and ICBMs
« Reply #294 on: July 08, 2021, 03:56:54 PM »
We are talking about achievement of a goal in a certain period of time. What it took to achieve that goal is certainly averaged out.

Since you acknowledge the average velocity calculations as correct, that means 8000km/h is just shy of 2 minutes to travel 250km, which doesn't match the 5 minute burn time, or if you wish to keep the 5 minute burn time which would almost certainly be necessary (as it stands, the remainder of the flight is at jeopardy), the missile would have been a lot higher than 250km.
If it's travelled 250km in 5 minutes then the average is 3,000km/h.
It starting at 0 and ending at 16,000km/h doesn't mean the average is 8000. That's not how the calculation works. You could sit still for 4 minutes and then go at 15,000km/h for the final minute and you'd travel 250km. Your average would still be 3,000km/h.
I suggested an acceleration which would work and actually travel less than 250km, not more. You could obviously tweak it to be bang on if you really care.
Now your just throwing bogus numbers and argumentation in the mix. 15000 doesn't even get you to, what was it again? 7.17 m/s, right?
To be honest I am getting pretty bored of this place.

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Offline AATW

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Re: FE and ICBMs
« Reply #295 on: July 08, 2021, 04:10:37 PM »
Now your just throwing bogus numbers and argumentation in the mix. 15000 doesn't even get you to, what was it again? 7.17 m/s, right?
"you're".

And all I'm doing is explaining that final speed and average speed are not related. 15,000 is arbitrary as is the speed of light in my other example.
I was just making the point that you could travel 250km in 5 minutes and end up at pretty much any final speed.
Tom: "Claiming incredulity is a pretty bad argument. Calling it "insane" or "ridiculous" is not a good argument at all."

TFES Wiki Occam's Razor page, by Tom: "What's the simplest explanation; that NASA has successfully designed and invented never before seen rocket technologies from scratch which can accelerate 100 tons of matter to an escape velocity of 7 miles per second"

Offline Action80

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Re: FE and ICBMs
« Reply #296 on: July 08, 2021, 04:23:55 PM »
Now your just throwing bogus numbers and argumentation in the mix. 15000 doesn't even get you to, what was it again? 7.17 m/s, right?
"you're".

And all I'm doing is explaining that final speed and average speed are not related. 15,000 is arbitrary as is the speed of light in my other example.
I was just making the point that you could travel 250km in 5 minutes and end up at pretty much any final speed.
I am not denying that and sorry for the typo.

If you travel 250km in 5 minutes, you would certainly need to end up at some final velocity.

But given a starting velocity of 0 and a final velocity of whatever you choose it to be (in your example it was 16000km/h), that currently results in an 8000km/h average velocity.

That is a fact.

It is also a fact if the average velocity of 8000km/h is distributed over a period of time = 5 minutes, that does not = 250km traveled.

It is also a given that at 250km, RET demands g=9.08m/s2. A missile under no further engine power will certainly not continue its parabolic trajectory in order to gain an additional 4250 km in altitude while decelerating.
To be honest I am getting pretty bored of this place.

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Offline AATW

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Re: FE and ICBMs
« Reply #297 on: July 08, 2021, 04:33:46 PM »
If you travel 250km in 5 minutes, you would certainly need to end up at some final velocity.
Yes

Quote
But given a starting velocity of 0 and a final velocity of whatever you choose it to be (in your example it was 16000km/h), that currently results in an 8000km/h average velocity.

That is a fact.

It is literally the opposite of a fact. That only works if the acceleration was constant over the 5 minutes, which in the case of a rocket it is not.

The average velocity is simply the distance travelled divided by the time it took.

250km / 5minutes = 50 (kilometers per minute). To get to km/h multiply by the 60 minutes in an hour 50 x 60 = 3000km/h

Quote
It is also a fact if the average velocity of 8000km/h is distributed over a period of time = 5 minutes, that does not = 250km traveled.

That is a meaningless statement, you don't "distribute" an average over a period of time, the average is just what it is, and I've explained how to calculate it.

Quote
It is also a given that at 250km, RET demands g=9.08m/s2. A missile under no further engine power will certainly not continue its parabolic trajectory in order to gain an additional 4250 km in altitude while decelerating.

I am less sure about this. I found an online calculator for projectiles and that appears to be correct BUT I don't know if that was clever enough to take into account how g varies with altitude. This stuff is complicated, to be honest the maths is beyond me and, with respect, from this conversation I think it's beyond you too.
« Last Edit: July 08, 2021, 05:02:32 PM by AllAroundTheWorld »
Tom: "Claiming incredulity is a pretty bad argument. Calling it "insane" or "ridiculous" is not a good argument at all."

TFES Wiki Occam's Razor page, by Tom: "What's the simplest explanation; that NASA has successfully designed and invented never before seen rocket technologies from scratch which can accelerate 100 tons of matter to an escape velocity of 7 miles per second"

Offline Action80

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Re: FE and ICBMs
« Reply #298 on: July 08, 2021, 05:36:17 PM »
It is literally the opposite of a fact. That only works if the acceleration was constant over the 5 minutes, which in the case of a rocket it is not.

The average velocity is simply the distance travelled divided by the time it took.

250km / 5minutes = 50 (kilometers per minute). To get to km/h multiply by the 60 minutes in an hour 50 x 60 = 3000km/h
If you think you are somehow claiming that on the one hand, I am wrong by giving the average velocity of 8000km/h derived by your figures, then only to provide the displacement/t as the correct figure, then you would need to counter this: https://www.calculatorsoup.com/calculators/physics/velocity_avg.php
Type in 0 for initial velocity and 16,000 km/h for final velocity.

See what you get.
Quote
It is also a fact if the average velocity of 8000km/h is distributed over a period of time = 5 minutes, that does not = 250km traveled.

That is a meaningless statement, you don't "distribute" an average over a period of time, the average is just what it is, and I've explained how to calculate it.
Incorrect. The average rate is indeed distributed over time to ascertain total displacement.
Quote
It is also a given that at 250km, RET demands g=9.08m/s2. A missile under no further engine power will certainly not continue its parabolic trajectory in order to gain an additional 4250 km in altitude while decelerating.

I am less sure about this. I found an online calculator for projectiles and that appears to be correct BUT I don't know if that was clever enough to take into account how g varies with altitude. This stuff is complicated, to be honest the maths is beyond me and, with respect, from this conversation I think it's beyond you too.
I appreciate your thinking and I agree that it is beyond you.

Thank you for your participation.
To be honest I am getting pretty bored of this place.

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Offline AATW

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Re: FE and ICBMs
« Reply #299 on: July 08, 2021, 05:40:22 PM »
If you think you are somehow claiming that on the one hand, I am wrong by giving the average velocity of 8000km/h derived by your figures, then only to provide the displacement/t as the correct figure, then you would need to counter this: https://www.calculatorsoup.com/calculators/physics/velocity_avg.php
Type in 0 for initial velocity and 16,000 km/h for final velocity.

See what you get.

I get exactly what I would expect if the acceleration is constant.
The acceleration is not constant in the scenario we are discussing. This is the thing you are continually failing to understand.
And if you don't understand that - which is the fairly simple bit - the idea that you have the ability to calculate the other stuff given the constantly changing value of g with height is a little far fetched. You need calculus for this sort of thing.
Tom: "Claiming incredulity is a pretty bad argument. Calling it "insane" or "ridiculous" is not a good argument at all."

TFES Wiki Occam's Razor page, by Tom: "What's the simplest explanation; that NASA has successfully designed and invented never before seen rocket technologies from scratch which can accelerate 100 tons of matter to an escape velocity of 7 miles per second"