The 21st century may never top this and it's only 2015.

[fast]

I'm thinking the amount of fuel needed would be less than expected, but there's a calculus issue here I can't reconcile. The fuel to get us 100 (or even 200) miles up is substantially lowered when there is no intent to get into or stay in orbit. There's no need for great acceleration to combat gravitational pull beyond the mile marker. If I don't need the fuel for that acceleration, I can start out with less fuel.

Wonder what it would be like to go up to a distance where a satellite was in orbit and flew by. Like walking across the lanes of an interstate, I guess.

 

[Bomb#20]

What is the energy output required for stasis? If we launched a spaceship (with no goal of going into space) with the sole intention of it hovering at 50 miles above the ground, how much energy is required to maintain no to very little velocity as it fights gravity? Not the energy to get it there...just to keep it there.

It depends solely on the amount of mass you want hanging there. The force required would be whatever is necessary to impart 1G acceleration (exactly countering the 1G of Earth's gravity) for that mass. How much energy is required to hold 1 pound straight out at arm's length for however many hours you want? 10 pounds? 100 pounds?

ETA:
For a small, five ton craft you would need a sustained 10,000 pounds of thrust from its jets (or rockets) directed straight down for it to remain stationary. A more massive craft would need proportionally more thrust.

There's no simple answer to that. The trouble is, you're using fuel both as an energy source and as reaction mass. In order to not run out you have to use the fuel efficiently; but using your energy source efficiently and using your reaction mass efficiently are diametrically opposed goals. The amount of upward force you get from a given amount of reaction mass goes up in proportion to how fast you blast it downward; but E=1/2mv², which means the amount of energy it takes to do it goes up as the square of how fast you blast it downward. So using your reaction mass efficiently means shooting it out your nozzle going as quickly as you can make it go, while using your energy source efficiently means shooting your reaction mass out your nozzle going as slowly as you can get away with while still holding yourself up. A practical rocket design is always a compromise between the two requirements. So to get a numerical answer to how much energy it takes per second to hold up a five ton craft, first you have to choose a rocket exhaust speed.

Maybe we should apply what's-his-name's third law to something other than fuel.

Well, sure. That's how airplanes work -- they apply what's-his-name's third law to the air. That's why airplanes have no trouble doing everything you described except the going to space part. Funny thing about space -- no air there. Not much of anything there. Kind of the defining characteristic. What did you have in mind for applying what's-his-name's third law to?

We just need to use cavorite.

Unobtainium will solve most physical problems like this.

I loved that movie!

 

[fast]

Well, sure. That's how airplanes work -- they apply what's-his-name's third law to the air. That's why airplanes have no trouble doing everything you described except the going to space part. Funny thing about space -- no air there. Not much of anything there. Kind of the defining characteristic. What did you have in mind for applying what's-his-name's third law to?

I don't know, uranium.

ETA: recall, I did say no safety inspections

 

[Bomb#20]

I'm thinking the amount of fuel needed would be less than expected, but there's a calculus issue here I can't reconcile. The fuel to get us 100 (or even 200) miles up is substantially lowered when there is no intent to get into or stay in orbit. There's no need for great acceleration to combat gravitational pull beyond the mile marker. If I don't need the fuel for that acceleration, I can start out with less fuel.

Absolutely. Here's your baby:

(Although SpaceShipOne only went up 70 miles.) But it still needed to go 2000 mph, and it was only able to stay in space for two minutes.

Wonder what it would be like to go up to a distance where a satellite was in orbit and flew by. Like walking across the lanes of an interstate, I guess.

More like being shot at. The satellite's coming at you at 18,000 mph.

 

[fast]

Interesting factoid: The achievements of SpaceShipOne are more comparable to the X-15 than orbiting spacecraft like the Space Shuttle. Accelerating a spacecraft to orbital speed requires more than 60 times as much energy as accelerating it to Mach 3. It would also require an elaborate heat shield to safely dissipate that energy during re-entry.[1]

Just curious, but did moon missions have a need to enter earths orbit?

 

[Bomb#20]

What did you have in mind for applying what's-his-name's third law to?

I don't know, uranium.

ETA: recall, I did say no safety inspections

There's no uranium in space. You'd have to take it with you. That means it's fuel.

Yes, powering a rocket with a nuclear reactor is possible and theoretically has higher performance than a chemical rocket, but not enough higher to get what you're describing. You can get a lot higher if you use the uranium in the form of atomic bombs instead of a nuclear reactor. That has been seriously studied as a potential technology for powering Mars missions; it has obvious disadvantages for use on Earth. So I guess what you'd need is a way to build micro-atomic-bombs. For an atomic bomb to detonate you need a critical mass, which puts a lower limit on how big an explosion you get -- they're measured in kilotons of TNT. But critical mass depends on density, so in principle if you could compress a little bit of uranium enough you might be able to get a much smaller nuclear blast. I have no idea how to run the numbers on that...

Interesting factoid: The achievements of SpaceShipOne are more comparable to the X-15 than orbiting spacecraft like the Space Shuttle. Accelerating a spacecraft to orbital speed requires more than 60 times as much energy as accelerating it to Mach 3. It would also require an elaborate heat shield to safely dissipate that energy during re-entry.[1]

Just curious, but did moon missions have a need to enter earths orbit?

Well, since the moon is in Earth's orbit, yes.

I take it you mean did they have to first go into "parking orbit" before heading out to the moon. Theoretically, no, they didn't absolutely need to. But there were a variety of practical advantages to it, so they did.

 

[Bronzeage]

Interesting factoid: The achievements of SpaceShipOne are more comparable to the X-15 than orbiting spacecraft like the Space Shuttle. Accelerating a spacecraft to orbital speed requires more than 60 times as much energy as accelerating it to Mach 3. It would also require an elaborate heat shield to safely dissipate that energy during re-entry.[1]

Just curious, but did moon missions have a need to enter earths orbit?

It's the same need that an expedition to the top of Mt. Everest has for a base camp, half way up the mountain. Earth orbit also gives the advantage of the slingshot effect of coming around Earth in a trajectory toward the Moon.

 

[Loren Pechtel]

Going to space without refueling? To go to space you need about 90% of your craft as fuel. To do it again you'll still need 90% of your craft as fuel--that means your initial launch must have been 99% fuel.

Now, mass ratios that high are just barely possible--but not without discarding an awful lot of the craft in the process.

Maybe we should apply what's-his-name's third law to something other than fuel.

Do that and you'll get a trip to Stockholm.

 

[Loren Pechtel]

That last part is your biggest obstacle. NASA defines "space" as 60 miles up.

Old school! The line is 62 miles up--100km to be more precise.

Your jet helicopter engines will stop working around 10 miles up, meaning your rocket is going to have to hold you up against gravity for the top 50 miles. At 300 mph it's going to take you 10 minutes to go up 50 miles. (It will take another 10 minutes to go back down 50 miles, but let's say you have a futuristic super-parachute that can slow your descent to 300 mph even in near-vacuum.)

Note, also, that the edge of space is defined by the altitude where wings can no longer hold you up no matter what--the stall speed of a ideal craft is faster than the orbital speed.

You want to do it twice without refueling, so that means your rocket has to support its weight against gravity for 20 minutes. Your rocket is mostly fuel, which means your fuel has to support itself against gravity for 20 minutes. (It also has to support your rocket engine, tanks, crew, helicopter rotors, etc., but those only make the problem harder so let's neglect those.) There's a term of art for how long a particular rocket fuel can support its own weight against gravity, Specific Impulse. So, even neglecting everything else your fuel has to hold up, the absolute minimum requirement for what you want is some kind of rocket fuel with a specific impulse of 20 minutes. The best chemical rocket fuel specific impulse ever discovered is 9 minutes. A nuclear rocket will get you about 14 minutes.

Yup. You need an ISP of 2,400 even if your craft is made of pure fuel.

Only a few rockets with this kind of ISP have ever been flown--and they're ion engines. Ion engines are totally useless at holding you even on a small moon. For a rocket powerful enough to actually hold you up the best is about 450. Even Orion--the best high-trust booster we have any idea of how to build--only has an ISP of 2000.

 

[Loren Pechtel]

Going to space without refueling? To go to space you need about 90% of your craft as fuel. To do it again you'll still need 90% of your craft as fuel--that means your initial launch must have been 99% fuel.



Now, mass ratios that high are just barely possible--but not without discarding an awful lot of the craft in the process.

Oh come on. Nuclear plane. There was some research done in the nineties on multi-function jets. The problem there would be in generating material for propulsion near the atmosphere/space boundary for scram jet configuration.

You can't hover in an airplane. A plane that gets into space is in orbit anyway.

 

[barbos]

That's not levitation, that's electromagnetic propulsion.

The launch loop provides the physical support to hold the track out of the atmosphere. You would use a maglev system on the track in order to accelerate, though.

That's not relevant detail.

 

[barbos]

What is the energy output required for stasis? If we launched a spaceship (with no goal of going into space) with the sole intention of it hovering at 50 miles above the ground, how much energy is required to maintain no to very little velocity as it fights gravity? Not the energy to get it there...just to keep it there.

453 seconds, Space Shuttle consisting mostly of fuel can hover for 453 seconds and then crash back to Earth.

 

[Loren Pechtel]

I'm thinking the amount of fuel needed would be less than expected, but there's a calculus issue here I can't reconcile. The fuel to get us 100 (or even 200) miles up is substantially lowered when there is no intent to get into or stay in orbit. There's no need for great acceleration to combat gravitational pull beyond the mile marker. If I don't need the fuel for that acceleration, I can start out with less fuel.

Wonder what it would be like to go up to a distance where a satellite was in orbit and flew by. Like walking across the lanes of an interstate, I guess.

You can think the moon is flat, also.

Hovering on a rocket on Earth needs 1g of acceleration--that's what we were basing our math on. That's why both Blue Origin and SpaceX did suicide burns to land their rockets. (Not to mention that SpaceX doesn't even have a choice--the Falcon 9 can't be throttled low enough to hover.)

 

[Loren Pechtel]

Interesting factoid: The achievements of SpaceShipOne are more comparable to the X-15 than orbiting spacecraft like the Space Shuttle. Accelerating a spacecraft to orbital speed requires more than 60 times as much energy as accelerating it to Mach 3. It would also require an elaborate heat shield to safely dissipate that energy during re-entry.[1]

Just curious, but did moon missions have a need to enter earths orbit?

No, not only did they not have a need to enter Earth's orbit but they didn't have the capability to enter Earth's orbit. The fuel tanks were pretty much spent at that point--they certainly didn't hold the 7,000 mph of Δv needed to enter LEO. The service module only produced 1,500 mph Δv leaving the moon and a like amount on lunar insertion. The 7,000 mph Δv needed to go from Earth orbit to the moon came from the third stage which was emptied by that burn and then discarded.

 

[Loren Pechtel]

Yes, powering a rocket with a nuclear reactor is possible and theoretically has higher performance than a chemical rocket, but not enough higher to get what you're describing. You can get a lot higher if you use the uranium in the form of atomic bombs instead of a nuclear reactor. That has been seriously studied as a potential technology for powering Mars missions; it has obvious disadvantages for use on Earth. So I guess what you'd need is a way to build micro-atomic-bombs. For an atomic bomb to detonate you need a critical mass, which puts a lower limit on how big an explosion you get -- they're measured in kilotons of TNT. But critical mass depends on density, so in principle if you could compress a little bit of uranium enough you might be able to get a much smaller nuclear blast. I have no idea how to run the numbers on that...

It doesn't even matter--note my post. Orion wouldn't do it.

 

[Underseer]

I don't understand what are you trying to say here, but rockets are multi-stage because chemical propellants are not powerful enough for single stage, you need rocket consisting mostly of fuel.

Then chemical propellants not being powerful enough is the unwon challenge that redirected us from the path of (solving the other problems that would have arisen had we sought to perfect single stage rocket design) to the path of (solving the other problems that did arise as we sought to perfect the multi stage design). So, we're not on the path we would have preferred, as we would have preferred to have been on the original path. It's nice that we're solving the problems that we come across on this path, but it's going to be nicer once we solve the original unwon challenge and get back on the path it would have been nice to never have had the need to diverge from. Then, we can get to solving the future problems that will arise on that more preferred path.

Then I don't think you understand how this works.

Mass is the most critical part of reaching escape velocity. You know, force equals mass times acceleration? Get rid of mass, and you get more acceleration.

 

[fromderinside]

Oh come on. Nuclear plane. There was some research done in the nineties on multi-function jets. The problem there would be in generating material for propulsion near the atmosphere/space boundary for scram jet configuration.

You can't hover in an airplane. A plane that gets into space is in orbit anyway.

That's a leap. A plane can get out of the atmosphere at about 150-200 mile up on thrust and inertia at speeds well under those required to maintain an orbit there. It's a suborbital vehicle. Once in space the space plane can launch a rocket carrying a payload that can achieve orbit and rendezvous with such as a space station. The idea is to increase delivered payload and to have a re-usable transport platform. Whatever frame holds the delivery rocket to the payload is much less mass disposed - I believe uses can be found for it in the vicinity of the space stations such as part of an interstellar ship - of to get the job done.

 

[Loren Pechtel]

You can't hover in an airplane. A plane that gets into space is in orbit anyway.

That's a leap. A plane can get out of the atmosphere at about 150-200 mile up on thrust and inertia at speeds well under those required to maintain an orbit there. It's a suborbital vehicle. Once in space the space plane can launch a rocket carrying a payload that can achieve orbit and rendezvous with such as a space station. The idea is to increase delivered payload and to have a re-usable transport platform. Whatever frame holds the delivery rocket to the payload is much less mass disposed - I believe uses can be found for it in the vicinity of the space stations such as part of an interstellar ship - of to get the job done.

The edge of space is defined as the point where an optimal plane would have to be going faster to fly than it would to orbit, thus rendering flight meaningless.

 

[fromderinside]

That's a leap. A plane can get out of the atmosphere at about 150-200 mile up on thrust and inertia at speeds well under those required to maintain an orbit there. It's a suborbital vehicle. Once in space the space plane can launch a rocket carrying a payload that can achieve orbit and rendezvous with such as a space station. The idea is to increase delivered payload and to have a re-usable transport platform. Whatever frame holds the delivery rocket to the payload is much less mass disposed - I believe uses can be found for it in the vicinity of the space stations such as part of an interstellar ship - of to get the job done.

The edge of space is defined as the point where an optimal plane would have to be going faster to fly than it would to orbit, thus rendering flight meaningless.

The only definition of edge of space that even remotely mentioned orbiting is:

from: http://www.ask.com/science/far-edge-space-earth-e3f3ef46b7bdb91f

The Kármán Line, which was first proposed by scientist Theodore von Kármán in the 1950s, lies within the thermosphere, the layer of the atmosphere where the International Space Station orbits. The United States Air Force defines the edge of space as 50 miles above mean sea level, and international law does not specify an exact boundary but uses the lowest perigee of an orbiting space vehicle to define the boundary.

and

The edge of space is generally recognized internationally to be at the Kármán Line, which is 62 miles from the surface of Earth. While the exact boundary of space is open to interpretation, this is the definition recognized by the Federation Aeronautique Internationale and National Aeronautics and Space Administration

The reason orbiting is mention is it is at that altitude of orbit perigee where atmosphere does not cause significant degradation of orbit (maintainable orbit). It is considered an altitude and it really has little to do with how fast the object passing it is traveling beyond sufficient for the vehicle to achieve that altitude. Its obviously not required to be orbiting velocity since suborbital and below escape velocity speed craft have achieved that altitude in suborbital flight.

 

[Loren Pechtel]

The edge of space is defined as the point where an optimal plane would have to be going faster to fly than it would to orbit, thus rendering flight meaningless.

The only definition of edge of space that even remotely mentioned orbiting is:

from: http://www.ask.com/science/far-edge-space-earth-e3f3ef46b7bdb91f

The Kármán Line, which was first proposed by scientist Theodore von Kármán in the 1950s, lies within the thermosphere, the layer of the atmosphere where the International Space Station orbits. The United States Air Force defines the edge of space as 50 miles above mean sea level, and international law does not specify an exact boundary but uses the lowest perigee of an orbiting space vehicle to define the boundary.

and

The edge of space is generally recognized internationally to be at the Kármán Line, which is 62 miles from the surface of Earth. While the exact boundary of space is open to interpretation, this is the definition recognized by the Federation Aeronautique Internationale and National Aeronautics and Space Administration

The reason orbiting is mention is it is at that altitude of orbit perigee where atmosphere does not cause significant degradation of orbit (maintainable orbit). It is considered an altitude and it really has little to do with how fast the object passing it is traveling beyond sufficient for the vehicle to achieve that altitude. Its obviously not required to be orbiting velocity since suborbital and below escape velocity speed craft have achieved that altitude in suborbital flight.

https://en.wikipedia.org/wiki/Kármán_line