Calculating Force and Energy Requirements for a Reactionless Drive in Space

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Discussion Overview

The discussion revolves around the theoretical calculations of force and energy requirements for a hypothetical reactionless drive in space, specifically focusing on moving a massive object (a 40 billion ton rock) to a speed of one mile per hour. It includes considerations of physics principles, such as Newton's laws, and the implications of a drive that operates without equal and opposite forces.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant queries the force required to move a 40 billion ton rock without external contact, suggesting a reactionless drive concept.
  • Another participant references Newton's 2nd law to indicate that net force is necessary to produce acceleration, implying a need for force calculations.
  • A different participant emphasizes the importance of impulse (force multiplied by time) in achieving a change in momentum, providing calculations for the required impulse and energy needed for the velocity change.
  • One participant estimates a force requirement of approximately 150,000 pounds for the reactionless drive, questioning the energy calculations provided earlier.
  • Another participant challenges the feasibility of the energy figure, arguing that a reactionless drive could theoretically require no energy, highlighting the complexities of reference frames in such scenarios.

Areas of Agreement / Disagreement

Participants express differing views on the implications of a reactionless drive, with some supporting the need for force and energy calculations based on Newton's laws, while others argue that such a drive could operate outside these laws, leading to unresolved disagreements about the nature of the drive and its requirements.

Contextual Notes

The discussion includes assumptions about the nature of the reactionless drive and its operational principles, which remain undefined. The calculations presented depend on specific reference frames, which are not universally agreed upon among participants.

MIKESMIND
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If I have a drive that works in space without the need of any out side contact.
In other words there is no equal and opposite force. How many pounds of force would I need to move a 40 billion ton rock to a speed of one mile an hour? If there is a program to work it out that would be great as well.
Also what would be the best high temp and high strain insulators? I would like something what would work with molten copper or aluminum.
 
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MIKESMIND said:
If I have a drive that works in space without the need of any out side contact.
In other words there is no equal and opposite force.
Oh really?
How many pounds of force would I need to move a 40 billion ton rock to a speed of one mile an hour?
Newton's 2nd law will tell you the net force needed to produce a given acceleration.
 
I'm not sure how your hypothetical drive is supposed to work so I won't address that.

Use as much or as little force as you want. The more force you use, the less time it will take to achieve your desired change in velocity.

What's important is the amount of energy needed, or impulse- which is more convenient in this case.

An impulse (I), which is Force • time, will result in an equivalent change in momentum (mass • velocity). Both are measured in units of Newton seconds:

Ft = m\Delta v​

The total change in velocity is 0.447 m/s. Multiply that by the mass of your 40 billion ton rock (3.629×10^13 kg) to get the change in momentum:

Ft = 1.622×10^{13} N s​

From here, you can either pick the amount of force to use and solve for t, or choose an arbitrary time in seconds and solve for F which is measured in Newtons.

In terms of energy, you'll need 3.624×10^12 Joules to change the velocity by .447 m/s (1 mile/hour).

E = \frac{I^2}{2m}​
 
Thank You
I did a bit of fast math and that would come out about a 150000 pounds of h and the o2 to burn it minus boiler and electrical loss for each mile an hour of change sound right?
 
MIKESMIND said:
Thank You
I did a bit of fast math and that would come out about a 150000 pounds of h and the o2 to burn it minus boiler and electrical loss for each mile an hour of change sound right?

How did you come up with that figure?

You have postulated a reactionless drive. A reactionless drive need not require any energy at all. The figure of 3.624×10^12 Joules would imply that the reaction mass is infinitely large and is at rest in your chosen reference frame.

Choose a different referrence frame and the energy delta changes. That's one reason why reactionless drives do not fit well with Newton's laws.
 

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