Wired question request some pro help

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Discussion Overview

The discussion revolves around a hypothetical scenario involving a rocket with infinite fuel and constant mass, exploring its ability to reach space and achieve orbit under specific conditions. The focus includes concepts of thrust, acceleration, escape velocity, and the mechanics of entering orbit.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant posits that a rocket with constant mass and sufficient thrust can reach space, arguing that escape velocity does not apply in this scenario.
  • Another participant agrees, suggesting that if the rocket ascends at a constant speed, it can continue to rise indefinitely, but acknowledges that achieving a circular orbit would require additional sideways velocity.
  • A participant expresses frustration over being misunderstood and seeks ways to convince others of their viewpoint regarding Newton's laws and the nature of escape velocity.
  • One participant clarifies that escape velocity is defined as the speed needed to leave a gravitational field without propulsion, implying that the original scenario may not require this concept.

Areas of Agreement / Disagreement

Participants appear to agree that the rocket can ascend into space under the given conditions, but there is contention regarding the requirements for achieving orbit and the relevance of escape velocity in this context. The discussion remains unresolved on how to effectively communicate these ideas to skeptics.

Contextual Notes

Participants express uncertainty about the implications of Newton's laws and the definitions of escape velocity, indicating a need for clearer explanations and potentially more rigorous mathematical support for their claims.

jacobgong
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I have a question that is not present in any physics book I've ever seen:
Supose I have a rocket with infinite fuel, but it's mass is constant. This rocket's power is limited and can only provide enugh thrust to accelerate it self at a rate of just over 9.81M/s. If I were to lunch this rocket straight up into the air with a equipment onboard(with zero mass) that will absolutly keep the rocket from changing direction.(reletive to Earth's rotation axis)
The question is, is this rocket able to get into space (higher than the lowest stable Earth orbit).
The second question is, without increasing it's power, is it possible to enter an Earth orbit after it's in space.
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this question is driving me crazy trying to convince people that the escape velocity and so on don't apply to this situation... They just keep saying I make no sense and nothing can go into space without a minimum orbit velocity.
I know I'm right that this thing can go into space but looks like most people don't even understand what do the words in those physics textbooks mean. too bad I'm not good at school physics and can't explane with super pro-looking equations...
 
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Welcome to PF!

jacobgong said:
The question is, is this rocket able to get into space (higher than the lowest stable Earth orbit).
The second question is, without increasing it's power, is it possible to enter an Earth orbit after it's in space.
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this question is driving me crazy trying to convince people that the escape velocity and so on don't apply to this situation... They just keep saying I make no sense and nothing can go into space without a minimum orbit velocity.
I know I'm right that this thing can go into space …

Hi jacobgong! Welcome to PF! :smile:

You're right, of course, that it can go into space …

if you rise at a constant speed of one metre per second for a million seconds, you'll obviously go a million metres (1000 Km) …

keep going long enough, and you can go as far as you want! :smile:

But getting into circular orbit will be more difficult … I suppose you could use the extra acceleration (you'll need less and less as you go higher, so there'll be some over :wink:) to go sideways a little, and gradually build up the sideways velocity until you reach orbital velocity.
btw, H. G. Wells had the identical idea …
in The First Men in the Moon, a Professor Cavor invented cavorite, an gravity-blocking device which took him to the moon at roughly that speed. :biggrin:
 
Thanks, I thought so...
But the problem remains, without a super mind-blowing and eye catching list of equations, my reputations remains as knowing nothing about physics and ignores the laws of gravity, escape velocity and so on and so forth... So, how can I convince people that I'm right about it? cause they're taking what I said as a joke and posting them on forums to make fun of me...
I just want to prove to them that I've been right and they didn't understand what Newton's laws ment. and don't worry it's not cyber bullying...:smile:
 
What "they" appear to be missing is that escape velocity is the velocity you need to escape without propulsion.
 

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