Evidence of water observed on exoplanet

Originally published at: https://boingboing.net/2019/09/13/evidence-of-water-observed-on.html


It’s amazing how fast you have to go before time dilation becomes a meaningful part of this calculation.


Correction to the post - the planet in question is NOT a “super-earth”, it’s a mini-neptune. That means that no, there is zero chance that it would even slightly resemble earth’s environment. It’s not a big rocky ball with oceans, it’s a big gas ball, and there’s water vapour in that gas.


For an astronaut flying with constant 1g it would be a little over 20 years round trip. That’s perfectly doable considering you can pull constant 1g.


Well except for the fact that it would require an amount of fuel something like the volume of the Atlantic Ocean.
Edited to add. Well it looks like I was off by a FEW orders of magnitude

edited to add: And that doesn’t account for staging. As the rocket consumes propellent and becomes lighter, acceleration for a given amount of thrust increases. To the point where it becomes uneconomical to built it heavy enough to withstand the G forces, to say nothing of the Astronauts. The first stage of the Saturn V had to turn off the center engine before it finished to keep the G forces down. Which is why rockets use stages, to throw away and not have to accelerate engines and tankage that you’re not using anymore. And they do that OFTEN. The second stage of the Saturn V fired for ~367 seconds. If we divide 10 yeas by 367 seconds we have close to a million staging events, and each stage is two to four times as heavy as the one before it. Even if we improve things with a higher Isp using Nerva engines that is still an impossible project.

Constant accelerations engines, as featured in The Expanse and Traveller are just as implausible as FTL drives. They are based on plot requirements and not physics.


Call me when there’s beer.

I think internal combustion engine would also not work. Steam engine might. Though wait… that won’t work either.

What if the ship and fuel(s) were assembled in space?

I was rather assuming that. Although assembled in space does not help much unless it is actually MANUFACTURED in space. But constant high acceleration requires constant staging. There are a few possibilities for very high Isp engines that make much more sense for LONG voyages, but they tend to have VERY LOW thrust. 1 G for years at a time requires truly stupendous numbers of stages. Even if we assume more efficient engines than the J-2 used in the Saturn and we ARE assuming lower acceleration, you still need to push large amounts of propellant out the back. And as you consume fuel, the acceleration increases as the weight decreases. High acceleration inevitably means that most of the ship is propellant. Which means that the mass changes greatly over a short period of time. Which means lots of stages, each one a multiple in size of the next one.


Or we can just let them come to us. Much more straight forward!


I’m pulling 1 g right now!


I’ve been formulating a short story involving time dilation and you really do have to be going very close to light speed to get a nice dramatic discrepancy.


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