Orbital maneuver by applying a thrust in the radial direction

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Discussion Overview

The discussion revolves around the effects of applying thrust in the radial direction on a spacecraft's orbit, particularly at perigee. Participants explore the implications for energy and angular momentum, considering both theoretical and practical aspects of orbital mechanics.

Discussion Character

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

Main Points Raised

  • One participant notes that thrust in the radial direction at perigee increases the spacecraft's energy without changing its angular momentum, as described by the relationship between eccentricity and energy.
  • Another participant argues that radial thrust adds a vertical component to the velocity, thus increasing total energy.
  • Some participants challenge the assertion that radial thrust does not do work, questioning the reasoning behind the claim that the thrust vector and displacement vector are orthogonal.
  • There is a discussion about the implications of maintaining thrust perpendicular to the velocity vector, with some asserting that this does not add energy to the orbit.
  • Several participants discuss the shifting nature of perigee when radial thrust is applied, suggesting that continuous adjustment of thrust direction would be necessary to maintain a specific orbital path.
  • One participant introduces the concept of an impulse applied at perigee, suggesting that this would change the orbit and energy, while also raising questions about the effects on angular momentum.
  • Another participant reflects on the ambiguity of the term "radial direction," noting that interpretations may vary between inward and outward thrusts.

Areas of Agreement / Disagreement

Participants express differing views on the effects of radial thrust on energy and angular momentum, with no consensus reached. Some agree that thrust can alter the orbit and energy, while others maintain that it does not affect angular momentum under certain conditions.

Contextual Notes

Participants highlight the importance of definitions and assumptions regarding thrust direction and its application, as well as the conditions under which energy and angular momentum are considered. The discussion remains unresolved regarding the precise mechanics of thrust effects.

  • #61
jbriggs444 said:
If I were less lazy,
You wouldn't know a short fellow called Tom Sawyer would you ?...
Anyhow I took what @DrStupid did and made a little graph which I find useful. First I will choose some natural units ##r_0,g_0, m=1## to write the effective potential$$V_{eff}(r)=\frac 1 {2r^2}-\frac 1 r -a(r-1)$$ where I have changed the zero for the "added" radial potential . The graph and a "blown up" version near the minimum show the potential for various values of a. I think it comports with all the analyses.
I need pictures.
 

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  • #62
hutchphd said:
You wouldn't know a short fellow called Tom Sawyer would you ?...
ROFL. Only a really smart person is good enough to do those boards.
 
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  • #63
hutchphd said:
Anyhow I took what @DrStupid did and made a little graph which I find useful. First I will choose some natural units ##r_0,g_0, m=1## to write the effective potential$$V_{eff}(r)=\frac 1 {2r^2}-\frac 1 r -a(r-1)$$ where I have changed the zero for the "added" radial potential . The graph and a "blown up" version near the minimum show the potential for various values of a. I think it comports with all the analyses.
I need pictures.
Yes, thank you! This is what I envisioned in post #56. I added some additional marks to your plot. For thrust higher than 0.125 the right maximum of the potential will drop below the value of the circular orbit (dotted red line) and can be overcome to escape.

eff_pot.png
 
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