Stories
Slash Boxes
Comments

SoylentNews is people

posted by chromas on Tuesday April 24 2018, @06:02AM   Printer-friendly
from the \ dept.

"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


Original Submission

This discussion has been archived. No new comments can be posted.
Display Options Threshold/Breakthrough Mark All as Read Mark All as Unread
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
(1)
  • (Score: 0) by Anonymous Coward on Tuesday April 24 2018, @06:25AM (27 children)

    by Anonymous Coward on Tuesday April 24 2018, @06:25AM (#671047)

    So essentially races on those super earths would have to realize that when they try to leave the planet, they should do so with the intent of immediately setting up a permanent living structure/base/etc on a nearby moon/planet/etc since it would not be feasible to keep making trips to and from the planet itself. That's a lot of homework to do before the first flight.

    • (Score: 2) by mhajicek on Tuesday April 24 2018, @06:52AM (11 children)

      by mhajicek (51) on Tuesday April 24 2018, @06:52AM (#671053)

      I'm surprised the article makes no mention of space planes.

      --
      The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
      • (Score: 2) by zocalo on Tuesday April 24 2018, @07:06AM (10 children)

        by zocalo (302) on Tuesday April 24 2018, @07:06AM (#671057)
        Same problem. You need much more fuel to generate the necessary lift, even allowing for a potentially denser atmosphere (which is another challege to reach orbit - more atmospheric friction), which probably makes conventional aircraft, hot air balloons, and all the other methods that we use to get airbourne, unviable as well. To get a given mass to orbit, for a given gravity well, you either need to expend a given amount of energy which means a Great Pyramid's worth of fuel, a *much* higher energy density in your fuel, or some radically different technology than our chemical-reaction powered aircraft and rockets.
        --
        UNIX? They're not even circumcised! Savages!
        • (Score: 5, Insightful) by frojack on Tuesday April 24 2018, @08:32AM (9 children)

          by frojack (1554) on Tuesday April 24 2018, @08:32AM (#671076) Journal

          Same problem. You need much more fuel to generate the necessary lift, even allowing for a potentially denser atmosphere (which is another challege to reach orbit - more atmospheric friction), which probably makes conventional aircraft, hot air balloons, and all the other methods that we use to get airbourne, unviable as well.

          Wrong. It makes those methods MORE viable. A denser atmosphere (virtually a given on a high gravity planet) provides just as much (if not more) lift capability for a balloon. Helium is still lighter than nitrogen and oxygen. A bag of helium will still rise.

          Wings work better in dense air than they do in thin air. And combustion engines produce more power in dense air than thin air.

          Basically we've settled on vehicles that work on earth. Then we try out those formulas on what we imagine another planet might present, and make pronouncements about impossibility.

          Don't you suppose an intelligent life form on a high gravity planet would try different solutions than ours?
          Is ours box the only box within which all alien life forms have to think?

          --
          No, you are mistaken. I've always had this sig.
          • (Score: 3, Funny) by Anonymous Coward on Tuesday April 24 2018, @09:11AM

            by Anonymous Coward on Tuesday April 24 2018, @09:11AM (#671086)

            Getting altitude is only half the battle. the real trick is to be going fast enough so you can get a stable orbit.
            Source: Kerbal Space Program.

          • (Score: 2) by zocalo on Tuesday April 24 2018, @10:04AM (5 children)

            by zocalo (302) on Tuesday April 24 2018, @10:04AM (#671098)
            Yes, you're going to get more lift, but you're also going to be expending all that extra lift on the increased weight of the aircraft, fuel, passengers, cargo, etc. with the higher gravity, and that's before you factor in any increase in mass required to deal with the extra stresses that higher gravity and atmospheric density brings - you might have more lift from denser air, but you've still got to push the heavier aircraft through it. Plus, for aircraft, you've also got the initial issue of getting enough lift to get off the ground in the first place to overcome - which is where fuel burn is highest. That said, you're also going to have a fair bit of wiggle room depending on multiple atmospheric conditions like chemical makeup, temperature, pressure (possibly the main showstopper, since that could push the temperature up to Venus like levels), so it's probably actually impossible to say for sure either way without knowing the exact details.

            And no, I'm definitely not assuming terrestrial conditions/tech - see my other post below - but the problem with hypothetical alien tech is in the name; we have no way of knowing what it is or how it might work making it kind of hard to second guess, so all we can really do is extrapolate from what we do know. Even if aircraft would work on a given heavy Earth, I'd expect that you'd see either a radically different approach to deal with the specific conditions, or at the very least some fairly obvious changes in the relative size of the lifting surfaces and weight ratios.
            --
            UNIX? They're not even circumcised! Savages!
            • (Score: 4, Interesting) by Immerman on Tuesday April 24 2018, @02:24PM (4 children)

              by Immerman (3985) on Tuesday April 24 2018, @02:24PM (#671163)

              No need to burn fuel getting off the ground, balloons will do the job far more efficiently. All you need to do is contain enough helium or hydrogen to reduce your balloon + payload density below that of the surrounding atmosphere. Gravity is irrelevant, and the denser the atmosphere, the less lift-gas you need to accomplish the task, since your payload is more buoyant to begin with.

              Once you're above the vast bulk of the atmosphere, you can then worry about getting up to orbital speeds. If you try to do that with a traditional rocket then yes, you'll still have to spend enough energy to keep it from falling while it accelerates, and you're back to directly fighting a much greater gravity. However, an airship-to-orbit (http://www.jpaerospace.com/) giant high-altitude delta-wing -rocket propelled airship could still be feasible - aerodynamic enough that lift keeps it rising through the increasingly vacuous atmosphere as it accelerates. It might take you several weeks to accelerate to orbit, but lift and buoyancy are doing most of the work of keeping you up while you do so.

              Plus, since you're not relying on raw thrust to keep you in the air, you can use less powerful, more efficient rockets - even current ion drives typically have around 10x the specific impulse of chemical rockets.

              Yes, they might need need to be more technologically advanced before they could actually pull it off, but what's another century or two of technological development in the face of the thousands it took to reach the point where they could even start dreaming up solutions?

              • (Score: 2) by zocalo on Tuesday April 24 2018, @02:44PM (3 children)

                by zocalo (302) on Tuesday April 24 2018, @02:44PM (#671176)
                Assuming you can build a balloon large enough to lift the required payload, then sure. We've certainly been able to get balloons to the edge of space so that people can jump out of the capsule for the ultimate in freefall thrills. We've also launched aerospace craft from below other aircraft - X-15 through to Virgin Galactic - so again, it's not completely "out there". It's going to be an awfully large balloon though, and you're going to be going through a correspondingly large volume of helium (presumably) in the process, so unless helium is much more plentiful in their world (quite possible, if the higher gravity has limited the bleed to space) or they get very good at retrieval of the balloon and gas (also possible) then they might hit "peak-helium" rather quickly. Like all the other solutions, the specifics of the environment and technological path are the key, but it does seem like it might not be quite so gloomy a proposition as TFA makes out, provided that you're prepared to allow for some approaches that we might consider sub-optimal in our environment.
                --
                UNIX? They're not even circumcised! Savages!
                • (Score: 2) by Immerman on Tuesday April 24 2018, @07:47PM (2 children)

                  by Immerman (3985) on Tuesday April 24 2018, @07:47PM (#671289)

                  Why use helium? Hydrogen is a LOT more plentiful, slightly more potent, and not dramatically more dangerous as long as you treat it with due respect (LOTS of airships used hydrogen safely for years, the Hindenburg was never designed to do so - it was designed to use helium). There's also no particular reason to "use it up" - it's quite possible to have both a balloon and pressure tank, and pump your lift gas between them to control buoyancy.

                  And building a large enough balloon is a safe assumption for a species even 100 years more technologically advanced than us, we could probably do it today - heck, we've figured out how to mass-produce graphene, which is probably as good as it gets for balloons. If you want to lift a 1000kg point mass (to sidestep payload buoyancy considerations) on Earth you need a balloon large enough to hold a bit more than 1000kg of air - at 1.225 kg/m^3 that's 816 cubic meters, or a sphere roughly 12m across. On Venus air density is 67 kg/m^3, so to get the same lift you'd only need about 15m^3, or only 3m across. Of course you need a bigger balloon as you get closer to vacuum, but that's why the Airship-to-orbit folks plan a transfer from their "deep atmosphere" to their orbital one.

                  And again - it doesn't matter what the gravity is, your balloon just has to displace a greater than-payload mass of air, buoyancy does all the work. The only place the force of gravity factors in is the necessary strength of the balloon to support your payload - which if you're using graphene might have to be dozens of atoms thick.

                  • (Score: 0) by Anonymous Coward on Wednesday April 25 2018, @07:47AM (1 child)

                    by Anonymous Coward on Wednesday April 25 2018, @07:47AM (#671539)

                    The hydrogen wasn't the problem with the Hindenburg anyway. Hydrogen burns with a faint blue flame, not the large yellow-orange flames the Hindenburg burned with.

                    The Hindenburg was covered in a conductive paint due to problems with static discharges. That paint was basically thermite, which just happens to burn with huge yellow-orange flames.

                    • (Score: 2) by Immerman on Thursday April 26 2018, @02:48AM

                      by Immerman (3985) on Thursday April 26 2018, @02:48AM (#671994)

                      True, but the Hindenburg is pretty much why hydrogen, and airships for that matter, went out of style. Facts are irrelevant once the media adopts a narrative.

          • (Score: 2) by fadrian on Tuesday April 24 2018, @02:28PM

            by fadrian (3194) on Tuesday April 24 2018, @02:28PM (#671165) Homepage

            There are a lot of other ways to lift weight than rockets. A launch loop [wikipedia.org] would be feasible, for instance. Though, to be fair, having worked next to its inventor for a couple years, I do have a bit of an unfair advantage in thinking of this solution for our poor, gravity-bound aliens.

            --
            That is all.
          • (Score: 2) by HiThere on Tuesday April 24 2018, @04:50PM

            by HiThere (866) Subscriber Badge on Tuesday April 24 2018, @04:50PM (#671223) Journal

            I'm not sure that it makes those methods more viable, but it sure doesn't make them less viable.

            The problem is, once you get high enough, you still need to lift off against a greater gravitational pull. Orbital velocities are higher, escape velocity is higher, etc. You get this "higher velocity requirement" for free with a stronger gravity.

            OTOH, if the atmosphere were dense further out (lots further out) like that of Venus, then balloons might actually be a better first stage. But I'm having a hard time thinking of that kind of a planet as a Super-Earth. It would be more like a Hypo-Jupiter (except for having a necessary rocky core...but most of my life we didn't know that Jupiter didn't have one, and we're still not sure).

            With an atmosphere that reaches far enough from ground a nuclear powered plane might be a reasonable "one stage to orbit" vehicle. But that's not a SuperEarth.

            Still, with a SuperEarth I expect that you could get to orbit with a nuclear powered spaceplane. It just wouldn't be any trivial exercise. You'd basically need to get above orbital velocity while still in the atmosphere, where you could use the atmosphere as working material for your nuclear powered jet. I'm rather sure that no chemical fuel would be energetic enough to make this work.

            --
            Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
    • (Score: 4, Informative) by zocalo on Tuesday April 24 2018, @06:56AM (14 children)

      by zocalo (302) on Tuesday April 24 2018, @06:56AM (#671055)
      I suspect the article's conclusion is probably correct, but perhaps there are other technologies than chemical rockets they could use to overcome gravity instead and might eventually discover. Another issue might be the desire to go in the first place; in an environment that's not even particularly suited to the development of creatures capable of flight would ground based life even have any inspiration to atmospheric flight, let alone aspire to reach orbit? Depending on the gravity, it's doubtful whether any of our aviation tech would by viable either, and it's going to be kind of hard to try and run before you can even crawl - especially so when the price of failure is going to be considerably more painful and/or likely to be lethal.

      We got to space a whole bunch of intermediate experiments and developments in many fields other than aviation and aerospace over many decades, so even if there is some tech that would let them overcome gravity and reach orbit there would need to be some logical development path that drives them to discover it and all the other necessary technologies required - perhaps as part of the development of more efficient ground based travel - e.g. anti-grav based equivalents to our MagLev trains. Or maybe we've just overlooked something really fundamental about how gravity works that includes a means to negate it, an oversight that has been explored in several SciFi works such as The Road Not Taken [wikipedia.org], quite possible given that we still don't really understand the nature of gravity.
      --
      UNIX? They're not even circumcised! Savages!
      • (Score: 5, Insightful) by choose another one on Tuesday April 24 2018, @07:39AM (13 children)

        by choose another one (515) Subscriber Badge on Tuesday April 24 2018, @07:39AM (#671061)

        > perhaps there are other technologies than chemical rockets they could use to overcome gravity instead and might eventually discover.

        Yeah, the biggest hole in the article is that it assumes intelligent aliens living on alien (non-earthlike) planets would develop technology along the same lines as earthlings and then get awfully frustrated that it didn't work in their environment. Why assume that intelligent aliens would not have _alien_ technology?

        • (Score: 5, Touché) by qzm on Tuesday April 24 2018, @10:05AM (2 children)

          by qzm (3260) on Tuesday April 24 2018, @10:05AM (#671099)

          Nuclear rockets.
          We developed them, but not to use due to primarily to politics (not sure to radiation, investigateme designs are very clean, and most are cleaner than true open air testing we did do).

          This appears to be yet more 'science' since by people with no ability to investigate or research outside their starting assumptions.

          • (Score: 3, Funny) by bob_super on Tuesday April 24 2018, @04:44PM

            by bob_super (1357) on Tuesday April 24 2018, @04:44PM (#671220)

            > This appears to be yet more 'science' since by people with no ability to investigate or research outside their starting assumptions.

            Silly humans. One day you might understand how to properly use a Higgs Field Crawler and stop letting gravity keep you down.

          • (Score: 0) by Anonymous Coward on Tuesday April 24 2018, @08:17PM

            by Anonymous Coward on Tuesday April 24 2018, @08:17PM (#671303)

            You build a plain old fission reactor, fueled with uranium or plutonium. The cooling system is open; the goal is in fact to boil the coolant at minimum. The coolant is chosen to produce exhaust containing simple molecules (few degrees of freedom to steal energy) that have low molecular mass.

            Hydrogen is great. The mass is 2, or 1 if you heat it enough to make it monoatomic.

            Helium is great. The mass is 4. It is already monoatomic, which reduces degrees of freedom.

            Helium-3 is as above, but a mass of 3.

            Methane, nitrogen, water, cyanide, hydrogen fluoride, lithium, carbon monoxide, and ammonia are other choices. Some of them would be made monoatomic. The seemingly toxic ones might be perfectly fine for alien life forms, not that you can be fussy when trying to launch a rocket.

        • (Score: 5, Interesting) by JoeMerchant on Tuesday April 24 2018, @12:47PM (9 children)

          by JoeMerchant (3937) on Tuesday April 24 2018, @12:47PM (#671129)

          This "article" was pretty heavily covered in the Niven Known Space series by multiple authors. When a species gets into space is heavily dependent upon the technical challenges of getting into space from their planet. Thus, the less socially developed - more war-like races come from smaller gravity wells. Yeah, it's a lot of assumption, but it makes a great deal of sense that a highly technically challenging planet to leave will require cooperation of more or less the whole planet to do it, while an easy world could have multiple competing factions all independently launching and continuing their competition in space.

          --
          🌻🌻 [google.com]
          • (Score: 2) by Freeman on Tuesday April 24 2018, @05:17PM (1 child)

            by Freeman (732) on Tuesday April 24 2018, @05:17PM (#671233) Journal

            So, what you're saying is we're an easy world and we can expect WWIII to be "In Space!!!". We're definitely don't have the whole planet cooperating as a whole to achieve space flight. Our space program was actually brought about by competition with a potentially hostile force.

            --
            Joshua 1:9 "Be strong and of a good courage; be not afraid, neither be thou dismayed: for the Lord thy God is with thee"
            • (Score: 3, Interesting) by JoeMerchant on Tuesday April 24 2018, @10:16PM

              by JoeMerchant (3937) on Tuesday April 24 2018, @10:16PM (#671377)

              So, what you're saying is we're an easy world

              Not really. We were close to using space as a battleground in the Cold War, but... at this point in time, if we were to make a battleground of space we'd just be trashing Trillions of dollars of investment in navigation, communication and surveillance satellites - and I think the business interests of the world are powerful enough to prevent the politicians from doing that. Putting up shrapnel in a counter-directional orbit at geo-stationary altitude is not the same thing as bombing a rice patty or the desert - making geostationary un-usable would be like salting all the wheat and corn fields of the American Midwest.

              I think we have enough global social cohesion to keep from slugging it out throughout the solar system, but the future may prove me wrong.

              --
              🌻🌻 [google.com]
          • (Score: 2) by DannyB on Tuesday April 24 2018, @05:30PM (6 children)

            by DannyB (5839) Subscriber Badge on Tuesday April 24 2018, @05:30PM (#671240) Journal

            The more war-like races probably can't live or fight well in the higher gravity environments of the less war-like races.

            The less war-like races, having overcome higher technical challenges, probably know how to build better weapons and defenses.

            The more advanced race might have done away with marketing, advertising, lawyers and politicians in the sense that we think of such.

            --
            People today are educated enough to repeat what they are taught but not to question what they are taught.
            • (Score: 2) by JoeMerchant on Tuesday April 24 2018, @10:21PM (5 children)

              by JoeMerchant (3937) on Tuesday April 24 2018, @10:21PM (#671379)

              The more advanced race might have done away with marketing, advertising, lawyers and politicians in the sense that we think of such.

              You (and I) would hope so, but I think that marketing, advertising, lawyers, national defense forces, etc. are just as much a sign of an advanced society as particle accelerators, telescopes, and entertainment. If you're just scraping by, you can't afford all that crap. I would wish that we could focus our efforts in such a way that marketing, advertising and lawyers were mostly unneeded and unwanted, but we're still all going in too many different directions at once; which is healthy, from a diversity perspective, but disappointing from the perspective of what we could accomplish if we would all just agree to do it.

              --
              🌻🌻 [google.com]
              • (Score: 2) by DannyB on Wednesday April 25 2018, @05:56PM (4 children)

                by DannyB (5839) Subscriber Badge on Wednesday April 25 2018, @05:56PM (#671731) Journal

                Think marketing / advertising versus search.

                Does not scale: every single vendor in the world with a product to sell gets to put an ad in front of YOUR eyes. More than once. (Oh, and gets to call you during dinner time. And gets to erect a billboard on every road. Etc.)

                Does scale: when you want something, you search for it. Results include reviews, comparisons, vendor websites, etc.

                I think an advanced civilization would not need so much marketing / advertising as we have today. When I suddenly realize that I need house siding, I can find it and who sells it.

                --
                People today are educated enough to repeat what they are taught but not to question what they are taught.
                • (Score: 2) by JoeMerchant on Wednesday April 25 2018, @06:27PM (3 children)

                  by JoeMerchant (3937) on Wednesday April 25 2018, @06:27PM (#671766)

                  Some Sci-Fi flop of a movie I watched had a "aliens take over all the humans" basis, after they had control they kept all the stores, etc., but they were just marked as "Store" and people just walked in and took plain brown wrapper with simple label products as they needed them from the shelves, no payments.

                  Makes sense, not sure that people are wired to ever be able to work that way.

                  The innundation of crap that _still_ arrives at my mailbox every day is unbelievable... I'm pretty sure that more is spent on the paper that reaches us every year than we spend on products advertised in that paper, certainly more than we were influenced to buy by that paper, since almost all of it hits the trash can as soon as we're sure that nothing important got buried inside.

                  --
                  🌻🌻 [google.com]
                  • (Score: 2) by DannyB on Wednesday April 25 2018, @08:54PM (2 children)

                    by DannyB (5839) Subscriber Badge on Wednesday April 25 2018, @08:54PM (#671857) Journal

                    People could probably deal with not paying. Taking products that are wrapped in plain brown paper.

                    People will still have preferences. But probably not Brand preferences.

                    Do you want the Cherry Flavor or Orange Flavored . . . Brawndo! The Thirst Mutilator! It's Got Electrolytes. (Or without electrolytes)

                    Do you want the restroom tissue with Ronald Rump's face, or Killary Flinton's face?

                    --
                    People today are educated enough to repeat what they are taught but not to question what they are taught.
                    • (Score: 2) by JoeMerchant on Wednesday April 25 2018, @09:37PM (1 child)

                      by JoeMerchant (3937) on Wednesday April 25 2018, @09:37PM (#671881)

                      Do you want the restroom tissue with Ronald Rump's face, or Killary Flinton's face?

                      Funny you should mention this - I saw a Trump-Pence logo bumper sticker today and had the very same thought.

                      --
                      🌻🌻 [google.com]
                      • (Score: 2) by DannyB on Friday April 27 2018, @06:47PM

                        by DannyB (5839) Subscriber Badge on Friday April 27 2018, @06:47PM (#672726) Journal

                        I was referring to two hypothetical people. Not actual people. :-)

                        yeah, right

                        --
                        People today are educated enough to repeat what they are taught but not to question what they are taught.
  • (Score: -1, Troll) by Anonymous Coward on Tuesday April 24 2018, @06:45AM

    by Anonymous Coward on Tuesday April 24 2018, @06:45AM (#671050)

    Anything goes up here, eh?

  • (Score: 0, Flamebait) by Anonymous Coward on Tuesday April 24 2018, @07:30AM (4 children)

    by Anonymous Coward on Tuesday April 24 2018, @07:30AM (#671060)

    Many are the Terrans who are similarly tethered by the force of gravity, especially many Americans, who are too fat to even fit in a space ship, even if there was enough fuel to launch them out of the gravity well. Who wants "Fatties in Space"?

    • (Score: 3, Funny) by Gaaark on Tuesday April 24 2018, @10:47AM

      by Gaaark (41) on Tuesday April 24 2018, @10:47AM (#671106) Journal

      New reality TV weight loss channel: "Lost, in space"

      --
      --- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
    • (Score: 4, Insightful) by JoeMerchant on Tuesday April 24 2018, @12:50PM (2 children)

      by JoeMerchant (3937) on Tuesday April 24 2018, @12:50PM (#671130)

      Our missiles are powerful enough to lift our biggest and least healthy into space in comfort and safety.

      Therefore, they can also deliver terrifying weapons with a high rate of reliability. 2 shuttles blowing up is an embarrassment, but it's not a significant failure rate if you're talking about delivering nuclear warheads.

      --
      🌻🌻 [google.com]
      • (Score: 2) by bob_super on Tuesday April 24 2018, @11:21PM (1 child)

        by bob_super (1357) on Tuesday April 24 2018, @11:21PM (#671414)

        > Our missiles are powerful enough to lift our biggest and least healthy into space in comfort and safety.

        Sadly, most do not come with a fairing wide enough for a conference table, and the ample seats required for Mr Kim and Mr Trump.

        • (Score: 2) by DannyB on Wednesday April 25 2018, @08:59PM

          by DannyB (5839) Subscriber Badge on Wednesday April 25 2018, @08:59PM (#671859) Journal

          The fairing on the Falcon Heavy, with that car inside, looked pretty dang spacious. [google.com]

          It looked like you could put a couple of school busses in there filled with congress.

          --
          People today are educated enough to repeat what they are taught but not to question what they are taught.
  • (Score: 2, Insightful) by Anonymous Coward on Tuesday April 24 2018, @07:50AM (2 children)

    by Anonymous Coward on Tuesday April 24 2018, @07:50AM (#671063)

    It depends a lot on the atmosphere. When we launch a rocket, the first stage is basically to get it through the atmosphere, with the second (in a two-stage rocket) accelerating to orbital speed.

    A thinner atmosphere would allow the first stage to be smaller. A thicker atmosphere would make using an airplane as the first stage more viable.

    • (Score: 3, Funny) by realDonaldTrump on Tuesday April 24 2018, @09:23AM

      by realDonaldTrump (6614) on Tuesday April 24 2018, @09:23AM (#671088) Homepage Journal

      Walt Disney, tremendous builder, very smart guy. He saw so many rockets launching in Florida. He built Disney World in Florida. But, Florida is VERY FLAT (very hard to be a 10). So he built Space Mountain. Best place in our Country for rockets!

    • (Score: 1, Informative) by Anonymous Coward on Tuesday April 24 2018, @09:56AM

      by Anonymous Coward on Tuesday April 24 2018, @09:56AM (#671094)

      I should probably add that once you are above the atmosphere, orbital speed still depends on the size of the planet.

      A larger planet requires a larger orbit, which requires a higher speed. A larger planet is usually also more heavy, which means more gravity, which requires a higher speed to reach orbit. So even when you are through the atmosphere, we are probably still talking about something like (size difference) squared.

  • (Score: 3, Interesting) by inertnet on Tuesday April 24 2018, @11:31AM (4 children)

    by inertnet (4071) on Tuesday April 24 2018, @11:31AM (#671117) Journal

    I'm guessing that larger planets will have very high wind speeds at higher altitudes. If I were that alien, I'd design a ship that could take advantage of those speeds. It wouldn't be enough to get off the planet, but it would require a lot less fuel than the article is assuming.

    • (Score: 0) by Anonymous Coward on Tuesday April 24 2018, @11:54AM (3 children)

      by Anonymous Coward on Tuesday April 24 2018, @11:54AM (#671122)

      The only way I know to take advantage of wind (for flying) is to react against the ground, like a kite. The problem with kites for an initial "boost stage" is that they don't give you any orbital velocity (except whatever you get from planet rotation).

      • (Score: 0) by Anonymous Coward on Tuesday April 24 2018, @01:48PM

        by Anonymous Coward on Tuesday April 24 2018, @01:48PM (#671145)

        there are updrafts, that birds routinely use to climb up (just watch some hawks when you get a chance). relative to the air, they are falling in a spiral, but their terminal velocity is smaller than the upwards velocity of the air, so they go up. people in gliders also do this routinely.
        there are also horizontal winds, that can be taken advantage of with the right airship. in our atmosphere, I don't know that anyone tries to do this (I know that weather balloons get carried by these high altitude winds, but I don't know how much this is actually desired by the weather people).

        I don't know what you mean by "kite reacting against the ground", but this is the mechanism that GP is referring to: climb up through some means (not necessarily updrafts) until you reach the high winds, and the high winds will accelerate you to a large horizontal speed; afterwards you can start the rocket for the additional speed that you need to get off the planet.
        people in gliders do the following: find out how far you can get from a given height; given the distance you want to travel, deduce the height required, then use an updraft to get there, afterwards you get out of the updraft and just glide to wherever you want.

      • (Score: 2) by Immerman on Tuesday April 24 2018, @02:30PM

        by Immerman (3985) on Tuesday April 24 2018, @02:30PM (#671167)

        Hot air balloons do it all the time. In fact wind-speed is their *only* means of propulsion.

      • (Score: 2) by Fluffeh on Thursday April 26 2018, @01:27AM

        by Fluffeh (954) Subscriber Badge on Thursday April 26 2018, @01:27AM (#671986) Journal

        Almost all aeroplane flights take advantage of wind [wikipedia.org] where they can.

        Special routes known as ocean tracks are used across some oceans, mainly in the Northern Hemisphere, to increase traffic capacity on busy routes. Unlike ordinary airways, which change infrequently, ocean tracks change twice a day, so as to take advantage of favourable winds. Flights going with the jet stream may be an hour shorter than those going against it. Ocean tracks may start and finish about 100 miles offshore at named waypoints, to which a number of airways connect. Tracks across northern oceans are suitable for east–west or west–east flights, which constitute the bulk of the traffic in these areas.

        When you are flying, you are flying relative to the area around you and that is again relative to the ground. If your propulsion is able to move you at x velocity relative to the air around you, but the air is already moving at y velocity to the ground, you are moving at x + y velocity relative to the ground.

        This could assist in gaining orbital velocity. In out atmosphere, wind speeds can get up to around 300-ish miles (450-ish kilometers) per hour. While that may not be a huge compared to an orbital velocity speed, there have been far faster winds recorded [space.com] in the solar system:

        Uranus can blow clouds up to 560 miles per hour (900 kilometers per hour), while Neptune's winds can reach up to 1,500 miles per hour (2,400 kilometers per hour)

        That is starting to be a free kick in velocity worth looking at...

        *sips coffee*

  • (Score: 2, Informative) by Anonymous Coward on Tuesday April 24 2018, @02:00PM

    by Anonymous Coward on Tuesday April 24 2018, @02:00PM (#671151)

    This is old news. Any one who understands both the rocket equation, and the relationship between planetary mass and orbital velocity already knew all this.

  • (Score: 0) by Anonymous Coward on Tuesday April 24 2018, @02:24PM

    by Anonymous Coward on Tuesday April 24 2018, @02:24PM (#671162)

    I remember reading this a long time ago which nicely explains the impressive difficulties of getting to orbit.

    https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html [nasa.gov]

    In short, your current technology limits the maximum fuel ratio (fuel mass / total mass) which in turn limits the maximum dV / orbital height.

    It is not just an exponential increase in cost but also in the required technology.

  • (Score: 0) by Anonymous Coward on Tuesday April 24 2018, @04:15PM

    by Anonymous Coward on Tuesday April 24 2018, @04:15PM (#671210)

    ...they could carry the rocket rather high before launch...

    or?

    -zug

  • (Score: 3, Interesting) by bradley13 on Tuesday April 24 2018, @04:47PM (2 children)

    by bradley13 (3053) on Tuesday April 24 2018, @04:47PM (#671222) Homepage Journal

    Correspondingly, getting into space on a smaller planet would be easy. Look how easy it was for the Lunar Lander to launch from the moon - almost trivial.

    Perhaps we are the ones who are trapped...

    --
    Everyone is somebody else's weirdo.
    • (Score: 0) by Anonymous Coward on Tuesday April 24 2018, @10:07PM (1 child)

      by Anonymous Coward on Tuesday April 24 2018, @10:07PM (#671373)

      on smaller planets there's no atmosphere, so there's nobody to get off the planet anyway.

      • (Score: 2) by bob_super on Tuesday April 24 2018, @11:24PM

        by bob_super (1357) on Tuesday April 24 2018, @11:24PM (#671415)

        That was impressively short-sighted of you.

  • (Score: 2) by Virindi on Tuesday April 24 2018, @05:36PM (3 children)

    by Virindi (3484) on Tuesday April 24 2018, @05:36PM (#671243)

    This does seem not necessarily correct. Depending on the atmosphere it may be feasible to do a long, slow acceleration during high altitude flight, with high Isp propulsion. Such as, as previously mentioned, nuclear rockets...or ion style engines.

    Jeez, it's like these people have never played Kerbal Space Program!! :D

    • (Score: 0) by Anonymous Coward on Tuesday April 24 2018, @10:13PM (2 children)

      by Anonymous Coward on Tuesday April 24 2018, @10:13PM (#671376)

      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 Virindi (3484) on Wednesday April 25 2018, @02:34AM (#671478)

        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

          by Anonymous Coward on Wednesday April 25 2018, @09:32AM (#671564)

          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.

          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.

(1)