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Rigorous Science

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Rigorous Science What is the highest theoretical escape velocity a 2 billion metric ton vehicle can achieve using a >20$^{\circ}$ gravitational slingshot?

I want to send a flying saucer (a $\frac{1}{10}$ scale Independence Day City Destroyer - calculated as a sphere cap 112m high with 1.2km segment radius, $\rho$ about 43.3kg/m3) away from the sun as...

1 answer  ·  posted 5y ago by Vogon Poet‭  ·  edited 4y ago by HDE 226868‭

#2: Post edited by user avatar HDE 226868‭ · 2020-06-02T18:33:32Z (over 4 years ago)
#1: Post edited by user avatar HDE 226868‭ · 2020-06-02T18:33:18Z (over 4 years ago)
More formatting fun.
  • <p>I want to send a flying saucer (a <span class="math-container">$\frac{1}{10}$</span> scale <a href="https://medium.com/@brandonweigel/the-largest-ships-in-science-fiction-d3dc9c2da3f" rel="nofollow noreferrer"><em>Independence Day</em> City Destroyer</a> - calculated as a sphere cap 112m high with 1.2km segment radius, <span class="math-container">$ ho$</span> about 43.3kg/m<sup>3</sup>) away from the sun as fast as possible, accelerating it from some initial velocity <span class="math-container">$V_i$</span> to escape velocity <span class="math-container">$V_f$</span> by <a href="https://en.m.wikipedia.org/wiki/Gravity_assist" rel="nofollow noreferrer">gravity assist</a>, and learn the <span class="math-container">$\Delta V$</span> gained. It's mass is about <span class="math-container">$2\times 10^9$</span> metric tons. Parameters are:</p>
  • <ul>
  • <li><p>The assist will deflect the initial trajectory by no less than 20° (<span class="math-container">$\Delta$</span>V is <span class="math-container">$\delta$</span> or the angle between the hyperbolic asymptotes). This allows a useable steering benefit.</p></li>
  • <li><p>The entry vector <span class="math-container">$V_i$</span> is an indeterminate variable with less velocity than the exit vector.</p></li>
  • <li><p>Any celestial body in our solar system can be used for the assist except the sun (the sun's gravity can't assist something escaping itself?)</p></li>
  • <li><p>The mass cannot enter any atmosphere (no friction calculations or concerns) so <span class="math-container">$\text r_0 = $</span> the assist planet's upper atmosphere.</p></li>
  • <li><p>No thrust burn, no Oberth effect.</p></li>
  • </ul>
  • <p>The entire problem is centered around the sun's frame of reference, so the plot needs an answer with the largest rate of separation from the sun <em>as it's trajectory approaches that asymptote</em>, not the assist planet. So there's a little vector translation I need to figure out.</p>
  • <p>I suppose the most useful solution has the <span class="math-container">$V_f = f(m)$</span> and <span class="math-container">$V_i = f(m)$</span> allowing for more diverse applications. This way we know the required initial velocity along with the exit velocity achieved.</p>
  • <p>I believe the problem can be stated, find the maximum translated V<span class="math-container">$_f$</span> with <span class="math-container">$ ho > 20°$</span> as <span class="math-container">$r_0$</span> approaches the upper atmosphere from above.</p>
  • <hr>
  • <h1>Premises:</h1>
  • <ul>
  • <li><p>The saucer is an interstellar bulk carrier that wants to save fuel and travel time.</p></li>
  • <li><p>This is for an opportunistic use not routine benefit. It's an energy cost benefit analysis.</p></li>
  • <li><p>I realize the diminishing returns from steering the vehicle along a vector inclined to the planet's orbital plane.</p></li>
  • <li><p>Jupiter seems to be the obvious choice but I don't know if getting closer to a fast-moving planet with less atmosphere, like Mercury, gives more oomph?</p></li>
  • <li><p>I also realize a smaller angle will allow a greater <span class="math-container">$V_f$</span>, but the <span class="math-container">$V_i$</span> I feel will be prohibitive (<span class="math-container">$\Delta$</span>V will get too small).</p></li>
  • </ul>
  • <p>I want to send a flying saucer (a <span class="math-container">$\frac{1}{10}$</span> scale <a href="https://medium.com/@brandonweigel/the-largest-ships-in-science-fiction-d3dc9c2da3f" rel="nofollow noreferrer"><em>Independence Day</em> City Destroyer</a> - calculated as a sphere cap 112m high with 1.2km segment radius, <span class="math-container">$ ho$</span> about 43.3kg/m<sup>3</sup>) away from the sun as fast as possible, accelerating it from some initial velocity <span class="math-container">$V_i$</span> to escape velocity <span class="math-container">$V_f$</span> by <a href="https://en.m.wikipedia.org/wiki/Gravity_assist" rel="nofollow noreferrer">gravity assist</a>, and learn the <span class="math-container">$\Delta V$</span> gained. It's mass is about <span class="math-container">$2\times 10^9$</span> metric tons. Parameters are:</p>
  • <ul>
  • <li><p>The assist will deflect the initial trajectory by no less than 20$^{\circ}$ (<span class="math-container">$\Delta$</span>V is <span class="math-container">$\delta$</span> or the angle between the hyperbolic asymptotes). This allows a useable steering benefit.</p></li>
  • <li><p>The entry vector <span class="math-container">$V_i$</span> is an indeterminate variable with less velocity than the exit vector.</p></li>
  • <li><p>Any celestial body in our solar system can be used for the assist except the sun (the sun's gravity can't assist something escaping itself?)</p></li>
  • <li><p>The mass cannot enter any atmosphere (no friction calculations or concerns) so <span class="math-container">$\text r_0 = $</span> the assist planet's upper atmosphere.</p></li>
  • <li><p>No thrust burn, no Oberth effect.</p></li>
  • </ul>
  • <p>The entire problem is centered around the sun's frame of reference, so the plot needs an answer with the largest rate of separation from the sun <em>as it's trajectory approaches that asymptote</em>, not the assist planet. So there's a little vector translation I need to figure out.</p>
  • <p>I suppose the most useful solution has the <span class="math-container">$V_f = f(m)$</span> and <span class="math-container">$V_i = f(m)$</span> allowing for more diverse applications. This way we know the required initial velocity along with the exit velocity achieved.</p>
  • <p>I believe the problem can be stated, find the maximum translated V<span class="math-container">$_f$</span> with <span class="math-container">$ ho > 20^{\circ}$</span> as <span class="math-container">$r_0$</span> approaches the upper atmosphere from above.</p>
  • <hr>
  • <h1>Premises:</h1>
  • <ul>
  • <li><p>The saucer is an interstellar bulk carrier that wants to save fuel and travel time.</p></li>
  • <li><p>This is for an opportunistic use not routine benefit. It's an energy cost benefit analysis.</p></li>
  • <li><p>I realize the diminishing returns from steering the vehicle along a vector inclined to the planet's orbital plane.</p></li>
  • <li><p>Jupiter seems to be the obvious choice but I don't know if getting closer to a fast-moving planet with less atmosphere, like Mercury, gives more oomph?</p></li>
  • <li><p>I also realize a smaller angle will allow a greater <span class="math-container">$V_f$</span>, but the <span class="math-container">$V_i$</span> I feel will be prohibitive (<span class="math-container">$\Delta$</span>V will get too small).</p></li>
  • </ul>