8 ms·

We need a better way to get to space

48 points by vishaldpatel 11y ago

Amorymeltzer 11y ago
Space planes should absolutely be part of our strategy, but their effectiveness diminishes once you get past LEO. An effective program would have different vehicles for different purposes, using the right tool for each job.
- nickff 11y ago
  Taking mass to low earth orbit (LEO) is the gating item to increased space travel and exploration; Skylon, SpaceX, Blue Origin, and Orbital Sciences are all focused on reducing this cost. It is quite well understood that outside of plans like Mars Direct and Semi-direct, interplanetary and interstellar travel will require other technologies such as novel electric and nuclear drives, but we are simply not at a point where that is an issue yet.[1][2] [1] https://en.wikipedia.org/wiki/Ion_thruster https://en.wikipedia.org/wiki/Ion_thruster [2] https://en.wikipedia.org/wiki/Nuclear_thermal_rocket https://en.wikipedia.org/wiki/Nuclear_thermal_rocket
lmm 11y ago
Much as I love to cheer for British engineering, I don't understand the logic here. A rocket would require an expensive inspection before reuse but a spaceplane wouldn't? Why? Also not one SABRE engine has even been built yet, whereas SpaceX has got very close to landing their rockets.
- dredmorbius 11y ago
  SpaceX have landed their rockets. Just not ... in one piece.
  - charlesdenault 11y ago
    They've landed their rockets in one piece, which proceeded to tip over and explode. An important distinction.
    - dredmorbius 11y ago
      A most excellent and nuanced distinction, sir! Capital!
aggieben 11y ago
Giant railguns. That is all.
- iwwr 11y ago
  Light-gas guns may be a good contender while railguns are sorted out. https://en.wikipedia.org/wiki/Light-gas_gun https://en.wikipedia.org/wiki/Light-gas_gun
  - chris_va 11y ago
    Surprisingly, I actually did a fair bit of research into this field. Both rail guns and light gas guns cap out at around 6km/s, and you really want 8km/s (more actually, for hypersonic drag loss) for this to be economical. Otherwise you need to launch a large enough rocket to make up the 2km/s difference, and you stuck solving the rocket equation again. Except you've subjected your rocket to 1000g, and the odds of it being reusable are really small. For rail guns, the plasma discharge on the rails limits your speed. Around 6km/s. For light gas guns, the working temperature of the gas cannot exceed the melting point of the barrel (or get close), otherwise tungsten/steel will get into the working gas and slow down the speed of sound. With hydrogen+tungsten, also around 6km/s. There is a better solution, though :).
    - rakoo 11y ago
      > and you stuck solving the rocket equation again Yes, but only for 2km/s, so there's that. Also this system can be used on other bodies such as Mars and the Moon. But yeah, I'm more worried about the 1000g than anything.
      - chris_va 11y ago
        2km/s means you are limited to about 20% payload. 20% is 10x better than a normal rocket, but there are actually easier ways to get 20%. The beamed power method gets about 20%, and works for humans (no g load). Escape Dynamics is trying it: http://escapedynamics.com/edispacelaunch/ http://escapedynamics.com/edispacelaunch/. The difficulty here is more technical/scientific than engineering. Synchronizing microwave beams is hard, and if you don't you get destructive interference. I don't know if they have solved that problem yet (there have been a few proposed solutions, we'll see if any work). Edit: Yes, rail would work great on the moon/mars. Actually there was a movie (Moon, with Sam Rockwell) where fuel is harvested on the moon and shot into orbit. Fun, crazy movie.
rikkus 11y ago
20 years ago, I remember dreaming up a train pulling a cable with a glider at the far end. I'm sure there are many technical issues with this approach, possibly including the cable needing to be incredibly strong, light and flexible. Please tell me it would work, though, as I still enjoy the mental image.
- nickff 11y ago
  Reaching orbit is mostly an issue of velocity, not altitude. This is why balloons can get very high, above of almost all earth's atmosphere, while being far from orbit. Rockets spend most of their ascent traveling nearly horizontal to the ground (they only go straight up at the beginning to get out of the densest part of the atmosphere).
  - mmastrac 11y ago
    Exactly. The most expensive part of getting to orbit is circularization. It takes a delta-vee of ~9.4km/s to reach LEO from earth. If you could lift yourself into LEO altitude without any thrust, you'd still have to circularize to the orbital velocity of ~8km/s [!]. That's still the majority of your delta-vee! [!] I am not a rocket scientist, so I haven't taken into account the orbital velocity you'd get from being rooted on the earth at takeoff, but it should be at most ~500m/s.
  - baldfat 11y ago
    The train would glide the aircraft to the mesosphere (50 km or 31 miles) and than rocket to orbit? So you would need 62+ miles of track going hundreds of miles an hour at 45 degree angle with the tow rope?
  - rthomas6 11y ago
    What about geostationary orbit wrt balloons? Do the balloons slow down horizontally a lot during the ascent? If not, what if we floated a rocket up most of the way and let the rocket do the rest?
    - mynegation 11y ago
anon8764 11y ago
www.et3.com gradually leading up to the top of everest, jettisoning the capsule (6,500 km/h (4,000 mph)) to break out of the atmosphere. I have not done the math, physics, etc on this, but it's an interesting idea worth exploring. But that said, do we really belong in space when we cannot care for our own? Wouldn't that be akin to giving sugar to ants? only multiplying suffering and cruelty exponentially in space? Perhaps a refactoring of our culture and our methods of using/allocating/expending resources should be our first priority.
- grogenaut 11y ago
  If people had waited to leave Europe until the 1970s the culture had been "refactored" enough for the masses, I doubt the world would have advanced as far as it had and the pressure of the population growth from industrialization would have caused some real issues. Actually I think it might be refactored even worse for the masses. Letting the average person go out and build new things helped a lot. Also, do you really think we can only fix one problem at a time? Did the birth of the transistor stop the civil rights movement?
  - anon8764 11y ago
    Perhaps technology has advanced too fast for the "culture". Perhaps we should design our intentions before we build the tech, and not the other way around. Look at NASA for inspiration on design and forethought.
    - grogenaut 11y ago
      The problem with this is you're designing based on your current world view and assumptions. When does this type of planning ever work and actually stand up to 20 years of history? 40? 100? In the 50's the us was DESIGNED around the car and suburbs. That worked well.
      - anon8764 11y ago
        My logic is based on numbers. Earth Population, Imaginary lines in the sand, War over money. These are not signs of intelligence, especially when they have only 1 planet to survive on that gets more populated every day with little regard to long-term resource management, although I am proud of the Svalbard Global Seed Vault. :) This type of planning worked for Voyager (NASA/JPL). fyi: cars suck. Dirty, inefficient, and it follows the same logic of giving every person in a 200 person hotel an individual elevator. It makes no sense, when you can instead design cities and transportation to be like the site I linked above (www.et3.com). It's their choice though, if they want faster horses instead of cars, so be it. If they want faster cars instead of et3, so be it. They prop and fall on their own sword I suppose.
skizm 11y ago
So is infertility in astronauts still a problem? I could be totally wrong, but I was under the impression we haven't solved the problem of increased radiation negatively affecting fertility in both male and female astronauts.
- simonh 11y ago
  I'd have thought sperm/egg freezing would do the trick.
drewg123 11y ago
I was hoping the article would talk about space elevators, and not space planes. I'm eagerly awaiting materials science and geo-politics to mature enough to allow the construction of space elevators. https://en.wikipedia.org/wiki/Space_elevator https://en.wikipedia.org/wiki/Space_elevator
- jcfrei 11y ago
  I don't really see the benefits of space elevators, to be honest. At an altitude of 100km the gravity is still virtually the same. And you still need a huge amount of fuel in order to put your rocket/plane into orbit. Unless you build an elevator with a height of 42'164km (geostationary orbit) - but that seems unrealistic to me.
  - ZenoArrow 11y ago
    > "I don't really see the benefits of space elevators, to be honest. At an altitude of 100km the gravity is still virtually the same." You would have made the first 100km of the journey more fuel efficient, is that not a good enough reason?
    - jcfrei 11y ago
      I think it's just prohibitively expensive at the moment. 100km (I think it would have to be a lot more anyway) is not much in terms of space exploration. And even then you will always use the majority of your fuel for acceleration towards and deceleration at your destination (however fuel needs for deceleration might be much lower if you can do some sort of atmospheric braking).
  - thedufer 11y ago
    > Unless you build an elevator with a height of 42'164km (geostationary orbit) - but that seems unrealistic to me. Actually, much of the point is to build one that is significantly taller than that. The idea is that, if the center of mass sits at geostationary orbit, the elevator doesn't actually have to hold itself up. Centripetal forces do the heavy lifting. Try the wikipedia link posted by gp - the first thing you'll see is a very clear diagram.
rm_-rf_slash 11y ago
I'm no rocket scientist but I could imagine rockets having a place in regular space travel. Lets assume that we can harness solar power efficiently and safely store the extra energy in hydrogen and oxygen gas. Then let's say that we could construct sturdy and modular components that can be disassembled and re-assembled at some kind of orbital station, so that the boosters that take people into orbit for whatever reason could be rebuilt in orbit to carry a load of asteroid-mined metals back to the surface. Again, I don't know any of the mechanics or physics, but if energy was abundant and parts could be reused, would rockets really be all that bad?
- 7952 11y ago
  Sea Dragon [1] is slightly similar to that. Fuel is a small part of the cost of a rocket, most of the cost is in the engines and structures. Cheap production of hydrogen or oxygen is unlikely to make things much cheaper. Also, any mass left over at engine cut-off requires a large quantity of fuel at lift-off and possibly necessitating a larger more expensive rocket. This would make re-purposing of boosters in orbit less likely. [1] https://en.wikipedia.org/wiki/Sea_Dragon_(rocket) https://en.wikipedia.org/wiki/Sea_Dragon_(rocket)
blisterpeanuts 11y ago
It's a slick looking video, but what about reentry? It's not that hard to get a ship up there (the X-15 was flying to the edge of space 50 years ago), and launching like a jet plane obviously has many advantages over rockets, but when it comes back down it's going to hit the atmosphere at a pretty high velocity, unless it's carrying enough fuel to gradually lower itself back into airspace where the jets can kick in. The craft in the video does not appear to have VTOL capability. But, if they can solve such problems, great. I'm thinking that eventually we'll have some kind of electrical or hybrid mass driver (catapult) system for getting non-human cargo into low orbit[1], much cheaper (and quieter) and obviously could accomplish many launches a day for one-way missions. You could get a large space station or interplanetary craft up there rather affordably using this approach. Specialized reentry vehicles as well. Launch the parts cheaply, robots assemble the parts in orbit, then launch the humans expensively. 1. https://en.wikipedia.org/wiki/Mass_driver https://en.wikipedia.org/wiki/Mass_driver
7952 11y ago
This thread [1] gives a good explanation of why Skylon should be treated with scepticism. [1] https://m.reddit.com/r/engineering/comments/2wstn6/i_am_very_interested_in_reaction_engines_and/ https://m.reddit.com/r/engineering/comments/2wstn6/i_am_very...
Mvandenbergh 11y ago
For all that effort to reduce oxidiser mass by using atmospheric oxygen, it's still 80% propellant by mass. Saturn V was 85%. Still impressive if they can make it work, since of course Saturn V wasn't reusable.
- avmich 11y ago
  So, with Saturn-5 only 15% was dry mass - and with Skylon 20%? That's 33% increase. Moreover, Saturn-5 was staged - and Skylon is single-stage, and have single stage to orbit with 20% dry mass looks somewhat like a miracle.

48 points by vishaldpatel 11y ago

Space planes should absolutely be part of our strategy, but their effectiveness diminishes once you get past LEO. An effective program would have different vehicles for different purposes, using the right tool for each job.

nickff 11y ago
Taking mass to low earth orbit (LEO) is the gating item to increased space travel and exploration; Skylon, SpaceX, Blue Origin, and Orbital Sciences are all focused on reducing this cost. It is quite well understood that outside of plans like Mars Direct and Semi-direct, interplanetary and interstellar travel will require other technologies such as novel electric and nuclear drives, but we are simply not at a point where that is an issue yet.[1][2] [1] https://en.wikipedia.org/wiki/Ion_thruster https://en.wikipedia.org/wiki/Ion_thruster [2] https://en.wikipedia.org/wiki/Nuclear_thermal_rocket https://en.wikipedia.org/wiki/Nuclear_thermal_rocket

lmm 11y ago

Much as I love to cheer for British engineering, I don't understand the logic here. A rocket would require an expensive inspection before reuse but a spaceplane wouldn't? Why? Also not one SABRE engine has even been built yet, whereas SpaceX has got very close to landing their rockets.

dredmorbius 11y ago
SpaceX have landed their rockets. Just not ... in one piece.
- charlesdenault 11y ago
  They've landed their rockets in one piece, which proceeded to tip over and explode. An important distinction.
  - dredmorbius 11y ago
    A most excellent and nuanced distinction, sir! Capital!

aggieben 11y ago

Giant railguns. That is all.

iwwr 11y ago
Light-gas guns may be a good contender while railguns are sorted out. https://en.wikipedia.org/wiki/Light-gas_gun https://en.wikipedia.org/wiki/Light-gas_gun
- chris_va 11y ago
  Surprisingly, I actually did a fair bit of research into this field. Both rail guns and light gas guns cap out at around 6km/s, and you really want 8km/s (more actually, for hypersonic drag loss) for this to be economical. Otherwise you need to launch a large enough rocket to make up the 2km/s difference, and you stuck solving the rocket equation again. Except you've subjected your rocket to 1000g, and the odds of it being reusable are really small. For rail guns, the plasma discharge on the rails limits your speed. Around 6km/s. For light gas guns, the working temperature of the gas cannot exceed the melting point of the barrel (or get close), otherwise tungsten/steel will get into the working gas and slow down the speed of sound. With hydrogen+tungsten, also around 6km/s. There is a better solution, though :).
  - rakoo 11y ago
    > and you stuck solving the rocket equation again Yes, but only for 2km/s, so there's that. Also this system can be used on other bodies such as Mars and the Moon. But yeah, I'm more worried about the 1000g than anything.
    - chris_va 11y ago
      2km/s means you are limited to about 20% payload. 20% is 10x better than a normal rocket, but there are actually easier ways to get 20%. The beamed power method gets about 20%, and works for humans (no g load). Escape Dynamics is trying it: http://escapedynamics.com/edispacelaunch/ http://escapedynamics.com/edispacelaunch/. The difficulty here is more technical/scientific than engineering. Synchronizing microwave beams is hard, and if you don't you get destructive interference. I don't know if they have solved that problem yet (there have been a few proposed solutions, we'll see if any work). Edit: Yes, rail would work great on the moon/mars. Actually there was a movie (Moon, with Sam Rockwell) where fuel is harvested on the moon and shot into orbit. Fun, crazy movie.

rikkus 11y ago

20 years ago, I remember dreaming up a train pulling a cable with a glider at the far end. I'm sure there are many technical issues with this approach, possibly including the cable needing to be incredibly strong, light and flexible. Please tell me it would work, though, as I still enjoy the mental image.

nickff 11y ago
Reaching orbit is mostly an issue of velocity, not altitude. This is why balloons can get very high, above of almost all earth's atmosphere, while being far from orbit. Rockets spend most of their ascent traveling nearly horizontal to the ground (they only go straight up at the beginning to get out of the densest part of the atmosphere).
- mmastrac 11y ago
  Exactly. The most expensive part of getting to orbit is circularization. It takes a delta-vee of ~9.4km/s to reach LEO from earth. If you could lift yourself into LEO altitude without any thrust, you'd still have to circularize to the orbital velocity of ~8km/s [!]. That's still the majority of your delta-vee! [!] I am not a rocket scientist, so I haven't taken into account the orbital velocity you'd get from being rooted on the earth at takeoff, but it should be at most ~500m/s.
- baldfat 11y ago
  The train would glide the aircraft to the mesosphere (50 km or 31 miles) and than rocket to orbit? So you would need 62+ miles of track going hundreds of miles an hour at 45 degree angle with the tow rope?
- rthomas6 11y ago
  What about geostationary orbit wrt balloons? Do the balloons slow down horizontally a lot during the ascent? If not, what if we floated a rocket up most of the way and let the rocket do the rest?
  - mynegation 11y ago

anon8764 11y ago

www.et3.com gradually leading up to the top of everest, jettisoning the capsule (6,500 km/h (4,000 mph)) to break out of the atmosphere. I have not done the math, physics, etc on this, but it's an interesting idea worth exploring. But that said, do we really belong in space when we cannot care for our own? Wouldn't that be akin to giving sugar to ants? only multiplying suffering and cruelty exponentially in space? Perhaps a refactoring of our culture and our methods of using/allocating/expending resources should be our first priority.

grogenaut 11y ago
If people had waited to leave Europe until the 1970s the culture had been "refactored" enough for the masses, I doubt the world would have advanced as far as it had and the pressure of the population growth from industrialization would have caused some real issues. Actually I think it might be refactored even worse for the masses. Letting the average person go out and build new things helped a lot. Also, do you really think we can only fix one problem at a time? Did the birth of the transistor stop the civil rights movement?
- anon8764 11y ago
  Perhaps technology has advanced too fast for the "culture". Perhaps we should design our intentions before we build the tech, and not the other way around. Look at NASA for inspiration on design and forethought.
  - grogenaut 11y ago
    The problem with this is you're designing based on your current world view and assumptions. When does this type of planning ever work and actually stand up to 20 years of history? 40? 100? In the 50's the us was DESIGNED around the car and suburbs. That worked well.
    - anon8764 11y ago
      My logic is based on numbers. Earth Population, Imaginary lines in the sand, War over money. These are not signs of intelligence, especially when they have only 1 planet to survive on that gets more populated every day with little regard to long-term resource management, although I am proud of the Svalbard Global Seed Vault. :) This type of planning worked for Voyager (NASA/JPL). fyi: cars suck. Dirty, inefficient, and it follows the same logic of giving every person in a 200 person hotel an individual elevator. It makes no sense, when you can instead design cities and transportation to be like the site I linked above (www.et3.com). It's their choice though, if they want faster horses instead of cars, so be it. If they want faster cars instead of et3, so be it. They prop and fall on their own sword I suppose.

skizm 11y ago

So is infertility in astronauts still a problem? I could be totally wrong, but I was under the impression we haven't solved the problem of increased radiation negatively affecting fertility in both male and female astronauts.

simonh 11y ago
I'd have thought sperm/egg freezing would do the trick.

drewg123 11y ago

I was hoping the article would talk about space elevators, and not space planes. I'm eagerly awaiting materials science and geo-politics to mature enough to allow the construction of space elevators. https://en.wikipedia.org/wiki/Space_elevator https://en.wikipedia.org/wiki/Space_elevator

jcfrei 11y ago
I don't really see the benefits of space elevators, to be honest. At an altitude of 100km the gravity is still virtually the same. And you still need a huge amount of fuel in order to put your rocket/plane into orbit. Unless you build an elevator with a height of 42'164km (geostationary orbit) - but that seems unrealistic to me.
- ZenoArrow 11y ago
  > "I don't really see the benefits of space elevators, to be honest. At an altitude of 100km the gravity is still virtually the same." You would have made the first 100km of the journey more fuel efficient, is that not a good enough reason?
  - jcfrei 11y ago
    I think it's just prohibitively expensive at the moment. 100km (I think it would have to be a lot more anyway) is not much in terms of space exploration. And even then you will always use the majority of your fuel for acceleration towards and deceleration at your destination (however fuel needs for deceleration might be much lower if you can do some sort of atmospheric braking).
- thedufer 11y ago
  > Unless you build an elevator with a height of 42'164km (geostationary orbit) - but that seems unrealistic to me. Actually, much of the point is to build one that is significantly taller than that. The idea is that, if the center of mass sits at geostationary orbit, the elevator doesn't actually have to hold itself up. Centripetal forces do the heavy lifting. Try the wikipedia link posted by gp - the first thing you'll see is a very clear diagram.

rm_-rf_slash 11y ago

I'm no rocket scientist but I could imagine rockets having a place in regular space travel. Lets assume that we can harness solar power efficiently and safely store the extra energy in hydrogen and oxygen gas. Then let's say that we could construct sturdy and modular components that can be disassembled and re-assembled at some kind of orbital station, so that the boosters that take people into orbit for whatever reason could be rebuilt in orbit to carry a load of asteroid-mined metals back to the surface. Again, I don't know any of the mechanics or physics, but if energy was abundant and parts could be reused, would rockets really be all that bad?

7952 11y ago
Sea Dragon [1] is slightly similar to that. Fuel is a small part of the cost of a rocket, most of the cost is in the engines and structures. Cheap production of hydrogen or oxygen is unlikely to make things much cheaper. Also, any mass left over at engine cut-off requires a large quantity of fuel at lift-off and possibly necessitating a larger more expensive rocket. This would make re-purposing of boosters in orbit less likely. [1] https://en.wikipedia.org/wiki/Sea_Dragon_(rocket) https://en.wikipedia.org/wiki/Sea_Dragon_(rocket)

blisterpeanuts 11y ago

It's a slick looking video, but what about reentry? It's not that hard to get a ship up there (the X-15 was flying to the edge of space 50 years ago), and launching like a jet plane obviously has many advantages over rockets, but when it comes back down it's going to hit the atmosphere at a pretty high velocity, unless it's carrying enough fuel to gradually lower itself back into airspace where the jets can kick in. The craft in the video does not appear to have VTOL capability. But, if they can solve such problems, great. I'm thinking that eventually we'll have some kind of electrical or hybrid mass driver (catapult) system for getting non-human cargo into low orbit[1], much cheaper (and quieter) and obviously could accomplish many launches a day for one-way missions. You could get a large space station or interplanetary craft up there rather affordably using this approach. Specialized reentry vehicles as well. Launch the parts cheaply, robots assemble the parts in orbit, then launch the humans expensively. 1. https://en.wikipedia.org/wiki/Mass_driver https://en.wikipedia.org/wiki/Mass_driver

7952 11y ago

This thread [1] gives a good explanation of why Skylon should be treated with scepticism. [1] https://m.reddit.com/r/engineering/comments/2wstn6/i_am_very_interested_in_reaction_engines_and/ https://m.reddit.com/r/engineering/comments/2wstn6/i_am_very...

Mvandenbergh 11y ago

For all that effort to reduce oxidiser mass by using atmospheric oxygen, it's still 80% propellant by mass. Saturn V was 85%. Still impressive if they can make it work, since of course Saturn V wasn't reusable.

avmich 11y ago
So, with Saturn-5 only 15% was dry mass - and with Skylon 20%? That's 33% increase. Moreover, Saturn-5 was staged - and Skylon is single-stage, and have single stage to orbit with 20% dry mass looks somewhat like a miracle.