Author Topic: Earth to Orbit with a Space Bungee  (Read 3321 times)

Online bradjensen3

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Earth to Orbit with a Space Bungee
« on: 08/09/2017 05:59 AM »
Earth to Orbit with a Space Bungee- Yes, I'm serious.

The recent discovery that the Moon has vast quantities of water leads to a different method of taking payloads into orbit.

Imagine if you will a rocket that has a small nuclear reactor for its energy source, and vast quantities of water for reaction mass. This rocket starts from the Moon, and returns to low earth orbit.

Meanwhile you take your payload and haul it up to about 100,000 feet with a hydrogen balloon. On top of the payload there is a big handle like an easter basket. Or something much more sophisticated than that.

Now you take the rocket in low earth orbit, and slow it down while firing the rocket at an angle to retain its altitude. You drop a big, many miles long bungee cord down with something on the end of the cord that can maneuver and hook up to the payload. Then you accelerate the rocket back to orbital speed or even back to the moon, while reeling in the payload.

You don't have to lift the reaction mass from the Earth's surface.

You could burn some of the hydrogen to pressurize the remainder and reuse the balloon and hydrogen.

You could move a lot of mass into orbit quickly and cheaply this way.

Obviously I don't mean to use an actual elastic bungee cord, but you would use something that functions in a similar way.

Since the rocket remains in space, it operates efficiently and reduces drag losses to almost nothing.

Think about being able to put hundreds or thousands of people in orbit at once. Think of being able to stock a Moon colony and keep it supplied.

This is as close as we can get to a Space Elevator with current technology. We could start with inanimate payloads to make the engineering easier, and work our way up to moving people.

You could also park your rocket in a higher orbit and swing a much longer bungee as a pendulum thru the upper atmosphere  to pick up the payload.

The basic concept is to use water reaction mass obtained on the moon or elsewhere in space to do the work of accelerating payloads into orbit.
« Last Edit: 08/09/2017 06:05 AM by bradjensen3 »

Online Flying Beaver

Re: Earth to Orbit with a Space Bungee
« Reply #1 on: 08/09/2017 06:44 AM »
Besides all the other issues associated with plans likes these (massive heating, shock, weight of a self supporting cable over a 50-100km+ distance, and (slightly) dodgy method of propelling the lunar spacecraft) the energy required to accelerate the total system of the ballon payload, propellent and engines up to 7~km/s is still the exact same as it would be for say a high altitude air launched rocket (why need stop by the moon?). The force from the tether/payload/winch is still countered by the engines, so the payload is literally dragged up to orbital velocity by the lunar spacecraft on some sci-fi strength cable (on some equally massive winch (which would start, to save obliterating the payload from acceleration, by unspooling at a rate 7 km of cable, per second).

edit: i'm tired and didn't have too much time to write this. Other will be able to debunk more in-depth with lack of current cable tech.
« Last Edit: 08/09/2017 06:52 AM by Flying Beaver »
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Online Asteroza

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Re: Earth to Orbit with a Space Bungee
« Reply #2 on: 08/09/2017 09:16 AM »
Compared to a HASTOL or LEO rotovator paired with a popup rocket, this seems kinda hard to do. Search previous threads about reverse bomber/unbomber designs to get a feel for these kinds of designs, and the tradeoffs and assumptions regarding discrete vehicles servicing occasional payloads versus higher throughput "fixed" transport infrastructures like HASTOL. A lot of the assumptions don't line up well for reverse bombers.

A momentum exchange tether as infrastructure, using electrodynamic propulsion (effectively zero fuel), or waste rock mass delivered via mass driver from the moon (raw momentum exchange downwards), to recover momentum lost picking up payloads from earth, is much more efficient and stable but presupposes a large cargo stream to support that infrastructure. Note the rock mass can be used for shielding and concrete in orbit as well so it is not a true "waste" export from the moon. HASTOL can also be the first of many tethers in a "Lunar Railroad" network of momentum exchange tethers.

See Tran Cislunar Railroad

Water is a precious resource, I wouldn't want to blow it on earth local milkrun infrastructure where possible.

Online bradjensen3

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Re: Earth to Orbit with a Space Bungee
« Reply #3 on: 08/09/2017 03:31 PM »
There is nothing dodgy about heating water and using it as reaction mass.

Yes of course it takes the same energy to accelerate the payload into orbit, but you don't have to burn 95% of your propellant to get the rocket off the Earth if you start from the Moon.

As I said, the Space Bungee rocket would not be in free fall orbit. It could be travelling any speed you want. You don't have to hook up at 7 km per second. You could be going 50 miles an hour if you want.

I'm not talking about shooting a rocket to the Moon, filling up with reaction mass, then doing the space bungee thing. The Space Bungee rocket would start from the Moon, and return to the Moon for reaction mass refills.

If those guys are right about the millions of microcomets impacting the Earth, it might be possible to refill from then. But the safe bet is to use water from the Moon.

For that matter, if the payload had a nuclear rocket engine, you could use the Space Bungee rocket as a tanker and deliver a water reaction mass to the payload.

Since we now know there is subsurface water all over the Moon, not just fossil water in shaded craters at the poles, water is not a scarce item.


Online bradjensen3

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Re: Earth to Orbit with a Space Bungee
« Reply #4 on: 08/09/2017 08:00 PM »
Most hydrogen gas is made from methane.

Methane itself is a lifting gas, although not as good as hydrogen or helium.

However, about 3% of all methane is flared at the wellhead because it is in a place where there is no pipeline or gathering system for it.

You could drive your payload to that well head and lift it into the upper atmosphere for very few dollars since they can't sell the gas to anyone else.

You might even get the government to give the company a small tax credit for supplying you with the methane.

Offline Nomadd

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Re: Earth to Orbit with a Space Bungee
« Reply #5 on: 08/09/2017 08:09 PM »
 Is that you Dmitry?

Offline Jim

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Re: Earth to Orbit with a Space Bungee
« Reply #6 on: 08/09/2017 08:15 PM »

Now you take the rocket in low earth orbit, and slow it down while firing the rocket at an angle to retain its altitude. You drop a big, many miles long bungee cord down with something on the end of the cord that can maneuver and hook up to the payload. Then you accelerate the rocket back to orbital speed or even back to the moon, while reeling in the payload.


Not possible.  Rockets are not helicopters.  Can't "slow it down while firing the rocket at an angle to retain its altitude."

This is just nonsense

Online bradjensen3

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Re: Earth to Orbit with a Space Bungee
« Reply #7 on: 08/09/2017 08:35 PM »

Not possible.  Rockets are not helicopters.  Can't "slow it down while firing the rocket at an angle to retain its altitude."

This is just nonsense

Well I guess that explains all the Harrier crashes...

Of course a rocket can hover. It isn't what you would normally do.

There are certainly multiple ways to engage the payload.

If you think it is nonsense that a rocket can hover, we aren't speaking from the same physical framework.
« Last Edit: 08/09/2017 08:49 PM by bradjensen3 »

Offline meberbs

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Re: Earth to Orbit with a Space Bungee
« Reply #8 on: 08/09/2017 08:37 PM »
Yes of course it takes the same energy to accelerate the payload into orbit, but you don't have to burn 95% of your propellant to get the rocket off the Earth if you start from the Moon.

As I said, the Space Bungee rocket would not be in free fall orbit. It could be travelling any speed you want. You don't have to hook up at 7 km per second. You could be going 50 miles an hour if you want.

Trying to stay in "orbit" going 50 mph would run you out of propellant very quickly. You'd need way more propellant than just launching normally from Earth.

Since we now know there is subsurface water all over the Moon, not just fossil water in shaded craters at the poles, water is not a scarce item.
Where do you get that from? Last I checked any water outside the poles is very low concentration, and possibly they were detecting hydroxyl salts, not water.

You might even get the government to give the company a small tax credit for supplying you with the methane.
Why would there be a tax credit for this? Remember methane is a powerful greenhouse gas, so burning it is generally better than releasing it.

Offline Lar

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Re: Earth to Orbit with a Space Bungee
« Reply #9 on: 08/09/2017 08:37 PM »

Now you take the rocket in low earth orbit, and slow it down while firing the rocket at an angle to retain its altitude. You drop a big, many miles long bungee cord down with something on the end of the cord that can maneuver and hook up to the payload. Then you accelerate the rocket back to orbital speed or even back to the moon, while reeling in the payload.


Not possible.  Rockets are not helicopters.  Can't "slow it down while firing the rocket at an angle to retain its altitude."

This is just nonsense

Agreed, as written it's not workable at all. Let's see how gently and patiently we can debunk it, though... and perhaps all learn something? If not, back to dead threads (it was there once already) it goes. (feel free to just ignore the thread if you can't be bothered)
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Online whitelancer64

Re: Earth to Orbit with a Space Bungee
« Reply #10 on: 08/09/2017 08:42 PM »
The basic idea here is an old idea (unsurprisingly, there are only very rarely new ideas in space travel...)

https://en.wikipedia.org/wiki/Skyhook_(structure)

If you had a rocket that could "hover" relative to a stationary position on Earth for an indefinite period of time while remaining at an Earth-orbital altitude, you wouldn't need to bother with the complexity of a skyhook. That thing would have more than enough fuel capacity to be able to land on Earth and blast off back to the Moon without refueling.
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Offline Lar

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Re: Earth to Orbit with a Space Bungee
« Reply #11 on: 08/09/2017 08:45 PM »
Bradjensen: take a look at the post by Asteroza, and read the link they are pointing to. Also look up HASTOL and Rotavator, and the links others gave... and pay attention to the mass balances that have to be taken into account. Conservation of momentum can't be evaded.

Also when replying, it's good to quote posts (like this)

Let's see how gently and patiently we can debunk it, though

... the web interface posting mechanism gives you lots of tools, explore them. Helping your readers helps you too.
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Offline Ictogan

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Re: Earth to Orbit with a Space Bungee
« Reply #12 on: 08/09/2017 09:19 PM »
There is nothing dodgy about heating water and using it as reaction mass.

Yes of course it takes the same energy to accelerate the payload into orbit, but you don't have to burn 95% of your propellant to get the rocket off the Earth if you start from the Moon.

As I said, the Space Bungee rocket would not be in free fall orbit. It could be travelling any speed you want. You don't have to hook up at 7 km per second. You could be going 50 miles an hour if you want.

I'm not talking about shooting a rocket to the Moon, filling up with reaction mass, then doing the space bungee thing. The Space Bungee rocket would start from the Moon, and return to the Moon for reaction mass refills.

If those guys are right about the millions of microcomets impacting the Earth, it might be possible to refill from then. But the safe bet is to use water from the Moon.

For that matter, if the payload had a nuclear rocket engine, you could use the Space Bungee rocket as a tanker and deliver a water reaction mass to the payload.

Since we now know there is subsurface water all over the Moon, not just fossil water in shaded craters at the poles, water is not a scarce item.
You may not have to burn off any propellant to get the rocket off from the earth orbit, but you'll have to have more delta-V to get from the moon to LEO and back. And then you need the delta-V to tug something out of earth's atmosphere to LEO in addition to that...

Offline hop

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Re: Earth to Orbit with a Space Bungee
« Reply #13 on: 08/09/2017 09:35 PM »
There is nothing dodgy about heating water and using it as reaction mass.
Water can certainly be used as reaction mass, but it's generally a low performance option. You seem to be assuming that a nuclear reactor provides essentially unlimited performance, but this is not the case. Nuclear thermal only provides moderate improvement over chemical rockets in the best case, and water is not the optimal propellant.

If you want to convince anyone that your proposal is viable, you need to define the required performance of the rocket and show that credible designs are capable of achieving it. What is the required delta v? What are the assumed ISP, thrust and mass fraction, and how do they compare with real systems that have been built or designed?

If you haven't done this with actual numbers, then you have no basis to believe that your concept is viable.

Online bradjensen3

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Re: Earth to Orbit with a Space Bungee
« Reply #14 on: 08/09/2017 09:49 PM »

Trying to stay in "orbit" going 50 mph would run you out of propellant very quickly. You'd need way more propellant than just launching normally from Earth.

I am not suggesting that the rocket hover, or go 50 miles an hour for any period of time, if at all. My point is that the rocket doesn't need to be in free fall. The interaction between the Space Bungee rocket and the payload doesn't have to be at 7 km/second.

Once again, the underlying notion is to raise a payload using a balloon into the upper atmosphere. Then use a rocket coming form the Moon into low Earth orbit to basically swoop in and grab the payload, and accelerate it into orbit using fuel from the Moon.

I am sorry I got off into side discussions with people who think rockets can't hover and can only go one speed.

The basic idea here is to do the work of taking a payload into orbit using reaction mass not lifted off the Earth.

I agree that the amount of water on the Moon is not certain at this point. However recent news articles suggest it is relatively abundant.  I get much of my science news from phys.org.

It seems to me that there are two factors that lead to expense in putting a payload in orbit. The first is atmospheric drag, and the second is gravity.

You reduce the drag by raising the payload into the upper atmosphere with a balloon.

The expense of gravity is basically the expense of accelerating the mass of the payload to orbital speed.

The amount of work it takes to accelerate that mass is the same, but it is much cheaper to do that work using a rocket fuelled on the Moon, than using rocket fuel hauled from the Earth's surface.

By 'rocket fuelled on the Moon' I mean a rocket using water from the Moon as its reaction mass.

Thanks for the suggestion to look at the skyhook stuff. Sounds like a fantasy to me.



Offline meberbs

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Re: Earth to Orbit with a Space Bungee
« Reply #15 on: 08/09/2017 10:15 PM »

Trying to stay in "orbit" going 50 mph would run you out of propellant very quickly. You'd need way more propellant than just launching normally from Earth.

I am not suggesting that the rocket hover, or go 50 miles an hour for any period of time, if at all. My point is that the rocket doesn't need to be in free fall. The interaction between the Space Bungee rocket and the payload doesn't have to be at 7 km/second.

Once again, the underlying notion is to raise a payload using a balloon into the upper atmosphere. Then use a rocket coming form the Moon into low Earth orbit to basically swoop in and grab the payload, and accelerate it into orbit using fuel from the Moon.
See hop's post above for the list of things that you need to calculate to show that this is a viable concept.

I am sorry I got off into side discussions with people who think rockets can't hover and can only go one speed.
You missed the point of Jim's post, which was a more blunt way of saying what I did, what you described is not practical.

It seems to me that there are two factors that lead to expense in putting a payload in orbit. The first is atmospheric drag, and the second is gravity.
Neither of those is the primary factor, most of the energy of a rocket launch goes into getting orbital velocity more than fighting the atmosphere or gravity. Your "slow down then speed back up" concept just makes this worse, and the balloon portion does not help with the primary issue.

The amount of work it takes to accelerate that mass is the same, but it is much cheaper to do that work using a rocket fuelled on the Moon, than using rocket fuel hauled from the Earth's surface.
Again, work out the numbers. I can't see this helping if you don't keep the spacecraft carrying the fuel moving at orbital velocity, but this causes problems with the capture.

Thanks for the suggestion to look at the skyhook stuff. Sounds like a fantasy to me.
They at least have used real numbers, so while skyhook seems impractical to me, your concept is more of a fantasy than the skyhook concept.

Offline Jim

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Re: Earth to Orbit with a Space Bungee
« Reply #16 on: 08/09/2017 10:53 PM »

Well I guess that explains all the Harrier crashes...


A harrier is not rocket and does not hover above 5000ft


Of course a rocket can hover. It isn't what you would normally do.
 

A rocket basically can not hover at orbital altitudes


If you think it is nonsense that a rocket can hover, we aren't speaking from the same physical framework.

That is correct.  You don't understand the basic physical framework and orbital mechanism  There is no stopping in space without massive thrust and propellant quantities many times our capabilities.


Offline Jim

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Re: Earth to Orbit with a Space Bungee
« Reply #17 on: 08/09/2017 11:10 PM »

Once again, the underlying notion is to raise a payload using a balloon into the upper atmosphere. Then use a rocket coming form the Moon into low Earth orbit to basically swoop in and grab the payload, and accelerate it into orbit using fuel from the Moon.


Which is basically impossible. 

1.  Just starting from the point of grabbing the payload, the rocket is going close to the size of existing rockets to push the spacecraft and payload back "towards" the moon.  The altitude saves only a few percent propellant. 

2.  Conversely, the propellant to slow down the spacecraft propulsively* to grab the payload is also going to be near the same amount it took to get to the moon.

3.  So now but since the spacecraft which is on a (large) return rocket slowed down to pickup the payload, the rocket that is doing #2 has to be much more massive.

* ignoring any aerobraking

Online bradjensen3

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Re: Earth to Orbit with a Space Bungee
« Reply #18 on: 08/09/2017 11:45 PM »

Well I guess that explains all the Harrier crashes...

A harrier is not rocket and does not hover above 5000ft

And bananas are not papyas. A jet powered mechanism can hover. A rocket-powered mechanism can also hover.  The thing I am proposing is not designed to hover.


Of course a rocket can hover. It isn't what you would normally do.
 

A rocket basically can not hover at orbital altitudes

not for long, anyways.


If you think it is nonsense that a rocket can hover, we aren't speaking from the same physical framework.
That is correct.  You don't understand the basic physical framework and orbital mechanism  There is no stopping in space without massive thrust and propellant quantities many times our capabilities.

.I have no intention to 'stop in space' whatever that might mean.  I appreciate everyone explaining that I can't do what I never intended to do.

I understand the orbital mechanism well enough to realize that free fall orbit and hovering are not the only two choices for locomotion.

[/quote]

So let's say the bungee cord version is on hold. Instead we have a rocket on the Moon. It is nuclear powered. No I don't think nuclear power is magic and has unlimited energy. It uses water for reaction mass.

Now we move from the Moon's surface to low earth orbit. For efficiency sake we have a smaller stage, a skimmer, that decelerates in the upper atmosphere, hooks the payload and accelerates it back to orbital speed. The skimmer then connects back to the Moon rocket, perhaps to repeat its process several times.

It does not matter if the total work done is more than the work done by blasting the payload off the Earth's surface into orbit, because the fuel is far cheaper, the rocket is reusable,  and the effort of getting the rocket and reaction mass into orbit from the Moon is a tiny fraction of what it would be from the Earth's surface.

With abundant water on the Moon, the economics of space travel will change.



Offline Jim

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Re: Earth to Orbit with a Space Bungee
« Reply #19 on: 08/09/2017 11:58 PM »

Now we move from the Moon's surface to low earth orbit. For efficiency sake we have a smaller stage, a skimmer, that decelerates in the upper atmosphere, hooks the payload and accelerates it back to orbital speed. The skimmer then connects back to the Moon rocket, perhaps to repeat its process several times.

It does not matter if the total work done is more than the work done by blasting the payload off the Earth's surface into orbit, because the fuel is far cheaper, the rocket is reusable,  and the effort of getting the rocket and reaction mass into orbit from the Moon is a tiny fraction of what it would be from the Earth's surface.

With abundant water on the Moon, the economics of space travel will change.

 Doesnt matter about water on the moon, the link up wont work

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