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"Super-Earth" planets are giant-size versions of Earth, and some research has suggested that they're more likely to be habitable than Earth-size worlds. But a new study reveals how difficult it would be for any aliens on these exoplanets to explore space.
To launch the equivalent of an Apollo moon mission, a rocket on a super-Earth would need to have a mass of about 440,000 tons (400,000 metric tons), due to fuel requirements, the study said. That's on the order of the mass of the Great Pyramid of Giza in Egypt.
"On more-massive planets, spaceflight would be exponentially more expensive," said study author Michael Hippke, an independent researcher affiliated with the Sonneberg Observatory in Germany. "Such civilizations would not have satellite TV, a moon mission or a Hubble Space Telescope."
https://www.space.com/40375-super-earth-exoplanets-hard-aliens-launch.html
[Also Covered By]: GIZMODO
[Paper]: Spaceflight from Super-Earths is difficult
[Related]: 10 Exoplanets That Could Host Alien Life
(Score: 0) by Anonymous Coward on Tuesday April 24 2018, @10:13PM (2 children)
If by flight, you mean atmosphere breathing engines, that might help, but is insanely hard to do even at your planets lower speed requirements. (check out the SABRE engine https://en.wikipedia.org/wiki/SABRE_(rocket_engine) [wikipedia.org]
Otherwise, the most efficient way to burn your focket fuel is as fast as possible, You get more benefit from it the lower you are in the gravity well, (basically by not having to lift it as far).
You're right about nuclear rockets though. Even the basic ones developed 50 years ago had an Isp three times that of the best chemical rocket humans have produced.
(Score: 2) by Virindi on Wednesday April 25 2018, @02:34AM (1 child)
By flight I mean horizontal launch style spaceplane.
Accelerating at the top of the atmosphere using high Isp but low thrust engines while wings keep you aloft. As you go faster, you need less lift from the wings and you can go higher which also reduces drag. Naturally, the composition of the atmosphere will determine how well this can be done (if at all).
And note that there is no reason a spaceplane has to be single stage. You could just as easily have multiple nested winged craft of varying size (some early Space Shuttle designs looked like this).
(Score: 0) by Anonymous Coward on Wednesday April 25 2018, @09:32AM
It looks good at first sight, but there are reasons no serious rocket engineer proposes this. There is a big jump from going fast enough to get hot, to fast enough to get into orbit. That speed gap would be even wider on a heavier planet and your plane would melt long before it got into orbit.
(As an example, the SR-71 Blackbird gets to Mach 3, and its skin heats to 300 celsius. That's about 1 km/s. You need to go 7 times as fast to get into orbit.)
The Skylon that is using that SABRE engine wouldn't make it on a heavier planet. The wikipedia article doesn't tell you, but that 'revolutionary' heat exchanger they are using is something like 25 km of 1 mm metal tubing with walls thinner than home al-foil, all crammed in the front of the engine. It's awesome, but extreme engineering.
Lofting a rocket stage on a lifting body first stage probably wouldn't get you to orbit on a world twice as heavy as this one. Two stages might get you there, but either your craft is huge or your payload is tiny.
I think they would still do it, satellites are just too useful, but it would be later in their development. You aren't going to get there using 50's/60's tech.