9 ms·

Beyond all the theoretical implementation complexities of space elevators, we don't even know of a single material with the required tensile strength. Graphene

Beyond all the theoretical implementation complexities of space elevators, we don't even know of a single material with the required tensile strength. Graphene was thought to be strong enough, but recent research found practical graphene had defects that significantly reduces its strength below that required for a space elevator. Space elevators aren't scrapped, just on the shelf until we even have a material that let's us think they might be feasible. That said, Lunar space elevators could be done with lower-strength materials, like Kevlar, and there are some people working on them. For Earth orbit, I think the centrifuge concept (e.g. SpinLaunch) has some promise. Still some huge implementation hurdles, but could be a huge step forward to put all of the energy for the first stage on the ground.

wombatpm 5y ago
Spin Launch for cargo. Can’t imagine being a passenger
- qayxc 5y ago
  At about 10,000Gs of acceleration (as per their claims¹ ~2200m/s in a 100m vacuum chamber, e.g. a=v²/r ≈ 97,000m/s² or roughly 10,000Gs) any human passenger would be liquified and form a nice smooth film on the inner surfaces of the vehicle. ¹https://www.spinlaunch.com/orbital#p2 https://www.spinlaunch.com/orbital#p2
- panick21_ 5y ago
  How many SpinLaunch to launch the same amount of Cargo compared to a single Starship. With a 100m arm, the will launch only like a few 100kg, a single Starship can launch 150tons. Why in the world would anybody use spin launch?
moron4hire 5y ago
SpinLaunch is easily the dumbest thing I've seen this year, and I got to become aware of NFTs this year. It's going to end up in the long list of grifts designed to bleed investors.
- spanktheuser 5y ago
  Curious about your reasoning. I immediately wondered what type of cargo would be suitable for this sort of launch system. I came up with a fairly short list. Fuel/water/perhaps food for interplanetary spacecraft destined for Luna or Mars. I imagine one could design some types of cubesats to withstand the tremendous acceleration forces. That was about it. Is your skepticism based on cargo suitability or other factors.
  - NikolaeVarius 5y ago
    Who the fuck cares about cargo before trying to figure out if any second stage rocket that isn't a rock can reasonably survive the extended application of high G-forces
    - robszumski 5y ago
      They have some data that indicates most off the shelf electronics survive or need very minor modifications to withstand the G forces. That's better than no data at all but they do have a ways to go.
      - mayama 5y ago
        It's not just g forces. It's combination of g forces and atmosphere drag. Drag forces during launch could be bigger issue.
  - avmich 5y ago
    Some classification considers 3 types of cargo - bulk materials (metals, fuel); complex electronics; humans. The majority of weight is in the 1st type. Unless first two types have complex mechanical structure, where loads can't be distributed into supports - which is an important issue - the first two groups are candidates.
    - jhgb 5y ago
      But this launch system still needs the projectile itself to be a fairly complex rocket capable of delivering several km/s of delta V and of steering the payload onto a desired orbit. That still implies electronics and mechanical systems onboard even if you're carrying only bulk cargo.
Ajedi32 5y ago
Spinlaunch is potentially okay for cargo, assuming they can overcome limitations imposed by atmospheric drag, and scale up sufficiently to make it practical; but the G forces involved make it impossible to use for human spaceflight. IMO the closest thing to a space elevator realistically achievable with today's technology would be a Skyhoook: https://en.wikipedia.org/wiki/Skyhook_(structure) https://en.wikipedia.org/wiki/Skyhook_(structure)
- jhgb 5y ago
  Is something like spinlaunch (centrifugal force) even better than a hydrogen gun (linear acceleration) from the perspective of g forces? For example Quicklaunch (6 km/s speed, 1100 m barrel) would require ~1700g of acceleration. Spinlaunch appears to be significantly more demanding while providing even smaller initial velocity. Even if it's just cargo applications, surely there's still a difference between 1000g and 10000g.
  - Ajedi32 5y ago
    The main advantages of spin launch's approach over a more conventional mass driver are that it takes up less space (Quicklaunch's proposed driver is over 1km long), and that it requires less peak power to get up to speed (Spinlaunch accelerates over a period of one and half hours).
    - jhgb 5y ago
      One could argue that Quicklaunch doesn't practically require much peak power either since you have means to store hydrogen and oxygen in tanks over time if you generate them in trickles. The fact that firing it generates high peak power is no more relevant for practicality than the fact that firing a handgun generates high peak power. It's just combustion. As for size, honestly, that doesn't seem to be much of a problem. You still have exclusion zones, and I'd argue that the exclusion zone around a spinning device like Spinlaunch proposes would have to be fairly large in all directions. Quicklaunch doesn't have a failure mode where the payload goes sideways at its full speed. Even if Quicklaunch were on land (which it wasn't planned to be), it would still probably require a smaller exclusion area.
jjk166 5y ago
Space elevators don't work on the moon. While gravity is weaker, the moon's rotation period is also much lower. To build a space elevator, its center of mass must be in a stationary orbit over the body. A geostationary orbit around the moon (selenostationary) would be about 88,000 km. The moon's Hill sphere, the region where its gravity dominates and thus things can stay in stable orbit around it, is only about 58,000 km. Basically a lunar space elevator would be so tall that Earth's gravity would yoink it off the moon. You could potentially build a skyhook on the moon, which a space elevator is merely a special case of, but you lose a lot of the advantages of a space elevator - namely you still need something to blast off the surface to reach the skyhook, and you have to carefully time it because everything's moving at extremely high speed. Saves a lot of fuel though.
- Valgrim 5y ago
  On the moon, you'd need a mass driver in conjunction with a skyhook.
  - jhgb 5y ago
    But why not just build a mass driver, then? It's a somewhat large horizontal structure, compared to a space elevator which is an absolutely humongous vertical structure. If you can reach 2 km/s on magnetic rails, you don't need anything else to launch from the Moon -- or even land on it.
    - Valgrim 5y ago
      Because unless you reach escape velocity, you still need to adjust your trajectory to insert into orbit, or else you're just going to crash back on the surface. If you use a rocket that's fine you just point in a different direction and burn, but if you're trying to launch, say, a few trillion tons of stuff, you need something a tad more efficient
      - jhgb 5y ago
        It's not like you need no maneuvering when you use a space elevator. At some point you have to detach from it. You'll always need course corrections afterwards.
panick21_ 5y ago
SpinLaunch is a terrible idea. You need to build a non reusable rocket upper stage for every couple 100kg or material you want to launch. Starship fully reusable will end up with 150t per launch. How many spin launches do you need to get the same cargo as a single Starship launch. 300 Upper-stages you need to build and launch or launch literally one Starship. Good luck with your competition. Almost all of those alternative launch things make almost no sense once you make fully reusable rockets work.

wombatpm 5y ago

Spin Launch for cargo. Can’t imagine being a passenger

qayxc 5y ago
At about 10,000Gs of acceleration (as per their claims¹ ~2200m/s in a 100m vacuum chamber, e.g. a=v²/r ≈ 97,000m/s² or roughly 10,000Gs) any human passenger would be liquified and form a nice smooth film on the inner surfaces of the vehicle. ¹https://www.spinlaunch.com/orbital#p2 https://www.spinlaunch.com/orbital#p2
panick21_ 5y ago
How many SpinLaunch to launch the same amount of Cargo compared to a single Starship. With a 100m arm, the will launch only like a few 100kg, a single Starship can launch 150tons. Why in the world would anybody use spin launch?

moron4hire 5y ago

SpinLaunch is easily the dumbest thing I've seen this year, and I got to become aware of NFTs this year. It's going to end up in the long list of grifts designed to bleed investors.

spanktheuser 5y ago
Curious about your reasoning. I immediately wondered what type of cargo would be suitable for this sort of launch system. I came up with a fairly short list. Fuel/water/perhaps food for interplanetary spacecraft destined for Luna or Mars. I imagine one could design some types of cubesats to withstand the tremendous acceleration forces. That was about it. Is your skepticism based on cargo suitability or other factors.
- NikolaeVarius 5y ago
  Who the fuck cares about cargo before trying to figure out if any second stage rocket that isn't a rock can reasonably survive the extended application of high G-forces
  - robszumski 5y ago
    They have some data that indicates most off the shelf electronics survive or need very minor modifications to withstand the G forces. That's better than no data at all but they do have a ways to go.
    - mayama 5y ago
      It's not just g forces. It's combination of g forces and atmosphere drag. Drag forces during launch could be bigger issue.
- avmich 5y ago
  Some classification considers 3 types of cargo - bulk materials (metals, fuel); complex electronics; humans. The majority of weight is in the 1st type. Unless first two types have complex mechanical structure, where loads can't be distributed into supports - which is an important issue - the first two groups are candidates.
  - jhgb 5y ago
    But this launch system still needs the projectile itself to be a fairly complex rocket capable of delivering several km/s of delta V and of steering the payload onto a desired orbit. That still implies electronics and mechanical systems onboard even if you're carrying only bulk cargo.

Ajedi32 5y ago

Spinlaunch is potentially okay for cargo, assuming they can overcome limitations imposed by atmospheric drag, and scale up sufficiently to make it practical; but the G forces involved make it impossible to use for human spaceflight. IMO the closest thing to a space elevator realistically achievable with today's technology would be a Skyhoook: https://en.wikipedia.org/wiki/Skyhook_(structure) https://en.wikipedia.org/wiki/Skyhook_(structure)

jhgb 5y ago
Is something like spinlaunch (centrifugal force) even better than a hydrogen gun (linear acceleration) from the perspective of g forces? For example Quicklaunch (6 km/s speed, 1100 m barrel) would require ~1700g of acceleration. Spinlaunch appears to be significantly more demanding while providing even smaller initial velocity. Even if it's just cargo applications, surely there's still a difference between 1000g and 10000g.
- Ajedi32 5y ago
  The main advantages of spin launch's approach over a more conventional mass driver are that it takes up less space (Quicklaunch's proposed driver is over 1km long), and that it requires less peak power to get up to speed (Spinlaunch accelerates over a period of one and half hours).
  - jhgb 5y ago
    One could argue that Quicklaunch doesn't practically require much peak power either since you have means to store hydrogen and oxygen in tanks over time if you generate them in trickles. The fact that firing it generates high peak power is no more relevant for practicality than the fact that firing a handgun generates high peak power. It's just combustion. As for size, honestly, that doesn't seem to be much of a problem. You still have exclusion zones, and I'd argue that the exclusion zone around a spinning device like Spinlaunch proposes would have to be fairly large in all directions. Quicklaunch doesn't have a failure mode where the payload goes sideways at its full speed. Even if Quicklaunch were on land (which it wasn't planned to be), it would still probably require a smaller exclusion area.

jjk166 5y ago

Space elevators don't work on the moon. While gravity is weaker, the moon's rotation period is also much lower. To build a space elevator, its center of mass must be in a stationary orbit over the body. A geostationary orbit around the moon (selenostationary) would be about 88,000 km. The moon's Hill sphere, the region where its gravity dominates and thus things can stay in stable orbit around it, is only about 58,000 km. Basically a lunar space elevator would be so tall that Earth's gravity would yoink it off the moon. You could potentially build a skyhook on the moon, which a space elevator is merely a special case of, but you lose a lot of the advantages of a space elevator - namely you still need something to blast off the surface to reach the skyhook, and you have to carefully time it because everything's moving at extremely high speed. Saves a lot of fuel though.

Valgrim 5y ago
On the moon, you'd need a mass driver in conjunction with a skyhook.
- jhgb 5y ago
  But why not just build a mass driver, then? It's a somewhat large horizontal structure, compared to a space elevator which is an absolutely humongous vertical structure. If you can reach 2 km/s on magnetic rails, you don't need anything else to launch from the Moon -- or even land on it.
  - Valgrim 5y ago
    Because unless you reach escape velocity, you still need to adjust your trajectory to insert into orbit, or else you're just going to crash back on the surface. If you use a rocket that's fine you just point in a different direction and burn, but if you're trying to launch, say, a few trillion tons of stuff, you need something a tad more efficient
    - jhgb 5y ago
      It's not like you need no maneuvering when you use a space elevator. At some point you have to detach from it. You'll always need course corrections afterwards.

panick21_ 5y ago

SpinLaunch is a terrible idea. You need to build a non reusable rocket upper stage for every couple 100kg or material you want to launch. Starship fully reusable will end up with 150t per launch. How many spin launches do you need to get the same cargo as a single Starship launch. 300 Upper-stages you need to build and launch or launch literally one Starship. Good luck with your competition. Almost all of those alternative launch things make almost no sense once you make fully reusable rockets work.