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A comment on Starship Update. Parent comment

Re:Starship Update by nearbuy on Sunday September 29, 2019 @12:19AM (#21105052)
That's not really how it works. If Earth's gravity were 1.3% stronger, you'd need about 0.6% (√1.013) more delta-v to escape Earth, or about an extra 70m/s. That's not hard to achieve. Increasing the total mass to dry mass ratio by about 0.6% would do it (and the Saturn 5 was about 85% fuel) since ln(x*1.006) = ln(x) + ln(1.006) ≈ ln(x) + 0.006.

Someone else posted somewhere that if the Earth was about 3x heavier, we wouldn't be able to use chemical rockets to escape.

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Re:Starship Update by CobrastanJorji on Sunday September 29, 2019 @02:23AM (#21105458)
If the Earth were 3x heavier, birds wouldn't be able to fly, at least not the way they are now. Sparrows can barely get airborne when they're full, let alone at triple their weight.
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Re:Starship Update by ars on Sunday September 29, 2019 @02:52AM (#21105538)
Air density would be three times higher though. So they might still be able to fly.
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Re:Starship Update by CobrastanJorji on Tuesday October 01, 2019 @01:29PM (#21128087)
Ooo, that's a good point!
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Re:Starship Update by icebraining on Sunday September 29, 2019 @07:18AM (#21106411)
> at least not the way they are now.

Yeah, but they wouldn't be, because the extra mass would have influenced their evolution.

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Re:Starship Update by rexer on Sunday September 29, 2019 @01:11PM (#21108232)
Extra weight. If gravity is the only thing changed, mass would remain constant.
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Re:Starship Update by icebraining on Sunday September 29, 2019 @01:31PM (#21108347)
Since the discussion is about "earth's gravity", I'm assuming the change would be in its mass, not in the universal gravitational constant, which is not Earth-specific.
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Re:Starship Update by rocqua on Sunday September 29, 2019 @05:29AM (#21106056)
Did that take into account the possibility of an air breathing first stage?
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Re:Starship Update by jccooper on Sunday September 29, 2019 @12:09PM (#21107843)
Probably not. But, while an air-breather would be more useful on a larger planet, it would still be the case that almost all of the space launch system's work must be done outside the sensible atmosphere. Air breathing would only add the tiniest margin to "chemically escapable planets."
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