Author Topic: Earth to Orbit with a Space Bungee  (Read 3320 times)

Online Asteroza

  • Full Member
  • ****
  • Posts: 443
  • Liked: 47
  • Likes Given: 2
Re: Earth to Orbit with a Space Bungee
« Reply #40 on: 08/11/2017 03:32 AM »
...It is nuclear powered...

Of course, my whole argument and proposal is based on the idea that water is not precious and scarce on the Moon...

... The water is too useful for the general space economy as a hydrogen source

Why use the hydrogen?  Oxygen is a gas and it expands when heated.  The ISP would be lower but there is more than 1022kg of oxygen.

Oxygen propellant through an NTR?

Do you WANT oxidation? Because that's how you get oxidation...

Online bradjensen3

  • Member
  • Posts: 27
  • Tulsa, Oklahoma, USA
  • Liked: 2
  • Likes Given: 0
Re: Earth to Orbit with a Space Bungee
« Reply #41 on: 08/11/2017 05:38 AM »
You said you know some math, stopped short of doing calculus. 

Actually I said I stopped studying math after doing calculus, unless you consider statistics for psychology and multiple regression for ecnometrics more math.

All of that was in the late 1960s and early 1970s so I am a bit rusty.

My calculus was college prep in high school, and while I derived a lot of personal satisfaction from it, it was not integral to my further success.

I remember Newton stole it from Leibniz , but then Newton was accused of stealing lots of things.

Online bradjensen3

  • Member
  • Posts: 27
  • Tulsa, Oklahoma, USA
  • Liked: 2
  • Likes Given: 0
Re: Earth to Orbit with a Space Bungee
« Reply #42 on: 08/11/2017 06:11 AM »
From what I am now reading about Nerva (tested with specific impulse of 850 seconds) and later NTRs, they are so poisonous you could never use them in or near the Earth's atmosphere.

There's almost no carbon on the Moon, so you would have to use liquid H2 and LOX, which doesn't provide nearly as much thrust. Also it's a lot harder to fuel up. 

It has been suggested that I learn all the formulas for orbital changes etc, so I will spend some time doing that, which sounds like a lot of fun.

I assume if someone actually had web site for calculating all these things, all of my helpful listeners would be rushing to point them out to me.

So you guys still don't think someone could launch a rocket from the Moon and pick up a payload in the upper atmosphere of the Earth?

It seems to me that you are pulling one of my tentacles but I don't know for sure which one.

I'm sure you all can all do the math in your head while blowing your nose, but it is going to take me a bit longer.

There are people planning to build balloons that can transition to space now.  Still early planning stages I believe.

Online Asteroza

  • Full Member
  • ****
  • Posts: 443
  • Liked: 47
  • Likes Given: 2
Re: Earth to Orbit with a Space Bungee
« Reply #43 on: 08/11/2017 09:03 AM »
JP Aerospace , their Ascender LTO, and their Orbital Ascender are very different beasts. Orbital Ascender takes about a week to get to orbital speeds and altitude after launching from a floating station located at 140K feet.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 31028
  • Cape Canaveral Spaceport
  • Liked: 9187
  • Likes Given: 295
Re: Earth to Orbit with a Space Bungee
« Reply #44 on: 08/11/2017 10:51 AM »

So you guys still don't think someone could launch a rocket from the Moon and pick up a payload in the upper atmosphere of the Earth?


Not think but know it is not possible.   It borders on crazy.

You were the one who said they understood orbital mechanics but the used the terms:  hover, 50mph,  and then slammed us for not understanding.
« Last Edit: 08/11/2017 11:00 AM by Jim »

Offline Stan-1967

  • Full Member
  • ****
  • Posts: 445
  • Denver, Colorado
  • Liked: 230
  • Likes Given: 151
Re: Earth to Orbit with a Space Bungee
« Reply #45 on: 08/11/2017 04:12 PM »

It seems to me that you are pulling one of my tentacles but I don't know for sure which one.


==> BradJensen3,

It takes some high heat to make the toughest steel! 

Don't be discouraged if you feel some sharp elbows in response to your ideas.   You jumped into the fire pretty quick with your first comments & ideas being the start of this thread topic.  Don't be discouraged, people here generally offer criticisms in very tactful & constructive ways.  Rules of this board are to be excellent to each other.

This is a great place to come to learn, and also to contribute if you want to do that.  Welcome to NSF & I hope to see you commenting elsewhere.

Offline hop

  • Senior Member
  • *****
  • Posts: 3139
  • Liked: 341
  • Likes Given: 655
Re: Earth to Orbit with a Space Bungee
« Reply #46 on: 08/11/2017 04:27 PM »
So you guys still don't think someone could launch a rocket from the Moon and pick up a payload in the upper atmosphere of the Earth?
No, not even close with current technology, and if you had the technology to do it, you wouldn't need to because RLVs from Earth would be easy.

What you are suggesting requires that you send a full sized orbital LV (think of something like Falcon 9, Atlas 5, Soyuz...) from the moon, fully fueled and bring it to stop in the upper atmosphere. If you want to do it without dropping stages every mission, it needs to be an SSTO, which is something we've never built.

You have suggested aerobraking, but coming from the moon, that means you need heat shielding equivalent to the Apollo vehicles. Even from LEO, you need shielding equivalent to the Shuttle. But your vehicle still needs a mass ratio on a par with things like Falcon 9 (or much better, if it's single stage), which have no heat shield.

If you decide to brake propulsively instead, your braking rocket needs performance equivalent to putting that fully fueled LV into orbit.

There are a whole lot of other problems, but hopefully that gives you an idea why people like Jim who actually work on this stuff dismiss it out of hand.



Online bradjensen3

  • Member
  • Posts: 27
  • Tulsa, Oklahoma, USA
  • Liked: 2
  • Likes Given: 0
Re: Earth to Orbit with a Space Bungee
« Reply #47 on: 08/11/2017 07:43 PM »
So you guys still don't think someone could launch a rocket from the Moon and pick up a payload in the upper atmosphere of the Earth?
No, not even close with current technology, and if you had the technology to do it, you wouldn't need to because RLVs from Earth would be easy.

What you are suggesting requires that you send a full sized orbital LV (think of something like Falcon 9, Atlas 5, Soyuz...) from the moon, fully fueled and bring it to stop in the upper atmosphere.If you want to do it without dropping stages every mission, it needs to be an SSTO, which is something we've never built.

You have suggested aerobraking, but coming from the moon, that means you need heat shielding equivalent to the Apollo vehicles. Even from LEO, you need shielding equivalent to the Shuttle. But your vehicle still needs a mass ratio on a par with things like Falcon 9 (or much better, if it's single stage), which have no heat shield.

If you decide to brake propulsively instead, your braking rocket needs performance equivalent to putting that fully fueled LV into orbit.

There are a whole lot of other problems, but hopefully that gives you an idea why people like Jim who actually work on this stuff dismiss it out of hand.

If I don't need a rocket nearly that big to get to the Moon from Earth orbit, why would I need one that big to get back, particularly when I can use aerobraking to slow it down when I get to Earth orbit.

Why would you ever want to bring something to a stop in the atmosphere?  I made the comment that you don't have to capture the payload at 7 km/second, and now we are talking about coming to a stop in the atmosphere?

And yes, I said a rocket can go at any speed, even down to 50 miles and hour, but that doesn't mean I want to do that. I was just reacting to the seeming assertion that the pickup vehicle could only go at free fall orbit speed.

Hey and for that matter, the payload could accelerate before pickup.

Oh yeah, I know. I'm surrounded by engineers but I should learn to be one myself.  I Kant expect you guys to all become philosophy majors overnight.

If I am not planning to do a re-entry of the entire rocket, why do I have to do heavy duty aerobraking all at once? Can't I do something simpler by aerobraking on multiple orbits?

Of course I would not want to bring the entire rocket into the atmosphere, that after all was why I started by talking about bungees.

Hey maybe it would be fun to have the Bungee mothership in orbit around the Earth AND Moon, drop a skimmer as it approaches near Earth, which then aerobrakes into the upper atmosphere down below Mach 1, snatches the payload, accelerates back to above orbital speed, and joins the Mothership on the next orbit a couple of days later. 

Then you would just need to expend enough fuel to run the skimmer and maybe adjust the momentum of the mothership and skimmer a bit on each orbit.

Send some more fuel up as you pass the Moon every couple of orbits.

Super Virtual Bungee Cislunar Conveyor Belt!

Why bother with the mothership? Because human beings work better in groups on a stable platform. And this would be much better preparation for human interplanetary exploration than sitting with your ass in the air on the ISS.

Not that there's anything wrong with that.

You could also launch H2O from the moon and make liquid H2 and O2 on the mothership while it is zipping along in its weeklong orbit. Well about 4 to 5 days, right? I remember it took 2.something days to basically coast to the Moon back in Apollo days.

Hey you could use this setup even without the balloons and the skimmer.

I think the first one should be called "Bozo' for 'beautiful orbiter zipping overhead.'

So pi in the sky momentum based systems make sense to you, but this doesn't. Wow.

No I don't know why 'people who work with this stuff' would dismiss it out of hand.

There is a lot for me to learn in hearing 'you can't because.' Some of your objections I agree with. Others I do not, because in part we are not working from the same assumptions. You assume there isn't much water on the Moon because that's what you have been told. I am assuming, for the sake of this proposal, that lunar water is plentiful, not just enough to grow a few potatoes.

You are telling me that even if the Moon was full of free rocketfuel, it still wouldn't be worthwhile to lift stuff out of the Earth's atmosphere with it.

From what I have read, something like 95% of the rocket fuel used on an Earth based rocket is spent getting the payload to the point where it can be accelerated to orbital speeds.

To me that says rocket fuel in orbit is worth 20 times as much as rocket fuel on the Earth's surface.

Therefore unless it costs 20 times as much to make rocket fuel on the Moon and deliver it to Earth orbit, the idea has merit.

And that's only the cost of the fuel.

« Last Edit: 08/11/2017 08:12 PM by bradjensen3 »

Offline Stan-1967

  • Full Member
  • ****
  • Posts: 445
  • Denver, Colorado
  • Liked: 230
  • Likes Given: 151
Re: Earth to Orbit with a Space Bungee
« Reply #48 on: 08/11/2017 08:27 PM »

Oh yeah, I know. I'm surrounded by engineers but I should learn to be one myself.  I Kant expect you guys to all become philosophy majors overnight.


Well I guess if we are to approach this from a philosophy perspective, the thread should be moved to the section for "Spaceflight Entertainment & Hobbies/Disney's Star Wars Theme Park" section.

Since you Kant define your problem in terms an engineer can respond to, I'll leave a few helpful "Kant" quotes:

"It is beyond a doubt that all our knowledge begins with experience."

"Thoughts without content are empty, intuitions without concepts are blind."



Offline meberbs

  • Full Member
  • ****
  • Posts: 957
  • Liked: 874
  • Likes Given: 257
Re: Earth to Orbit with a Space Bungee
« Reply #49 on: 08/11/2017 08:51 PM »
From what I have read, something like 95% of the rocket fuel used on an Earth based rocket is spent getting the payload to the point where it can be accelerated to orbital speeds.

To me that says rocket fuel in orbit is worth 20 times as much as rocket fuel on the Earth's surface.

Therefore unless it costs 20 times as much to make rocket fuel on the Moon and deliver it to Earth orbit, the idea has merit.

And that's only the cost of the fuel.
No, you got your facts backwards, the 95% is mostly spent accelerating it to orbital speeds, not getting it to the point where it can be accelerated.

The 20x price only applies to refueling in LEO using lunar sourced propellants, which is not a new idea.

Your concept involves either slowing down, which doesn't save fuel, or a high speed rendezvous, which you have proposed no practical method of. And yes, there are in between options if you want the worst features of both concepts.

Offline hop

  • Senior Member
  • *****
  • Posts: 3139
  • Liked: 341
  • Likes Given: 655
Re: Earth to Orbit with a Space Bungee
« Reply #50 on: 08/11/2017 08:57 PM »
If I don't need a rocket nearly that big to get to the Moon from Earth orbit, why would I need one that big to get back, particularly when I can use aerobraking to slow it down when I get to Earth orbit.

Why would you ever want to bring something to a stop in the atmosphere?  I made the comment that you don't have to capture the payload at 7 km/second, and now we are talking about coming to a stop in the atmosphere?
I was describing what would be required for the concept presented in http://forum.nasaspaceflight.com/index.php?topic=43538.msg1711276#msg1711276

You've thrown out so many variations of the concept, I picked one that had obvious, insurmountable problems that didn't require a bunch of calculations to demonstrate.

Quote
If I am not planning to do a re-entry of the entire rocket, why do I have to do heavy duty aerobraking all at once? Can't I do something simpler by aerobraking on multiple orbits?
Because that's not how orbits work. Once you get below orbital velocity, you aren't in orbit any more. You can get down to LEO velocity in multiple passes (provided you're OK with multiple passes through the Van Allen belts), but after that you are all-in for the equivalent of Shuttle, Soyuz etc. Only going to a few thousand km/h instead of zero really doesn't help much, the peak heating is in the earlier parts of re-entry.

Quote
You are telling me that even if the Moon was full of free rocketfuel, it still wouldn't be worthwhile to lift stuff out of the Earth's atmosphere with it.
Propellant is by far the cheapest part of most existing rockets, so yeah, probably not. A re-usable tug going between LEO and higher orbits using lunar propellant would likely be a much more practical use of theoretical free Lunar fuel.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 31028
  • Cape Canaveral Spaceport
  • Liked: 9187
  • Likes Given: 295
Re: Earth to Orbit with a Space Bungee
« Reply #51 on: 08/11/2017 10:02 PM »


Although I am now wondering if that is what the Apollo lunar lander did with the command module since the lunar lander then impacted back on the Moon's surface. When it reached the command module it must have reduced its speed temporarily, which was regained when the command module ditched the lunar lander and then accelerated back to orbital and eventual lunar escape velocity.

I don't remember Walter Cronkite explaining it in that much detail at the time.

No, Not that at all.  The lunar module flew to the exact same stable orbit that the command module was in and then docked.   After the crew transfer, the lunar module was undocked ( With it and the command module still in a stable orbit) and thrusters fired to cause it to impact the moon. The command module stayed in the stable orbit for awhile (hours and then later missions, days) before firing to go back to earth.

Online Req

  • Full Member
  • ***
  • Posts: 336
  • Liked: 228
  • Likes Given: 2455
Re: Earth to Orbit with a Space Bungee
« Reply #52 on: 08/11/2017 10:46 PM »
From what I have read, something like 95% of the rocket fuel used on an Earth based rocket is spent getting the payload to the point where it can be accelerated to orbital speeds.

To me that says rocket fuel in orbit is worth 20 times as much as rocket fuel on the Earth's surface.

Therefore unless it costs 20 times as much to make rocket fuel on the Moon and deliver it to Earth orbit, the idea has merit.

And that's only the cost of the fuel.
No, you got your facts backwards, the 95% is mostly spent accelerating it to orbital speeds, not getting it to the point where it can be accelerated.

The 20x price only applies to refueling in LEO using lunar sourced propellants, which is not a new idea.

Your concept involves either slowing down, which doesn't save fuel, or a high speed rendezvous, which you have proposed no practical method of. And yes, there are in between options if you want the worst features of both concepts.

This belongs in the Q&A section, but it seems like a quick mspaint may help.  Things only orbit because they are going so fast that they never hit the ground.  Imagine throwing rocks at various speeds, from slow(red line) to green(fast enough to reach orbit.)  You don't just fly up there and then you're floating around in space, you will fall if you slow down.

This makes a few things clear:

1)  Most of the energy is spent gaining that velocity(throwing the rock.)
2)  It takes a lot of energy to counteract that velocity.
3)  There's a lot of energy saying that you are going this direction at this speed.  It takes a lot of energy to fight it in any other way(plane/inclination changes and etc.)
« Last Edit: 08/11/2017 10:59 PM by Req »

Online bradjensen3

  • Member
  • Posts: 27
  • Tulsa, Oklahoma, USA
  • Liked: 2
  • Likes Given: 0
Re: Earth to Orbit with a Space Bungee
« Reply #53 on: 08/14/2017 06:07 PM »
I'm not sure why I seem like such a dunce to you guys. Of course I know how a free fall orbit works. Basically the object in orbit is moving away from the earth at the same speed it is falling towards the earth as a component of its angular velocity.

Unless it runs into something (including a bit of atmosphere in low earth orbit) it will continue to do so forever.

Typical low earth orbit is about 90 minutes. Geosynchronous orbit is about 24 hourswhich is why the satellite seems to stay in the same place.

The period of the orbit is basically set by the force of gravity at the distance from the center of the mass that is being orbited, along with the total distance travelled in the orbit, which is roughly 6.28 * the radius of the orbit.. At Earth sea level is 9.8 meters per second per second. The higher you go the longer the orbit takes, until at the distance of the moon which is somewhat less than a quarter million miles, it takes almost 28 days.

The moon is not in a stable orbit. It is gradually leaving the Earth's orbit because it is being accelerated thru gravitational interaction with the Earth's oceans in the form of tides. The Earth's rotation is also slowing for the same reason. Basically the Earth rotation is slowing and the energy is being used to accelerate the Moon.

In the 1960s we learned this stuff in elementary school thru jr. high.

Someone said if you shed delta V thru aerobraking you end up inside the atmosphere and then you are basically doomed to reentry.

So you shed MOST of your delta V thru aerobraking and the last bit while outside the atmosphere using your cheap rocket fuel.

Of course my final desire has nothing to do with Earth orbits or the Moon. I really want to do this with Ceres, escape velocity .51 km/second,  Vast quantities of water available. Lots of other resources including carbon.

Think about re-engineering space exploration so it is not dependent on general public enthusiasm and politicians' promises.

That's where I am trying to go with this. Is it most efficient way to get stuff of the ground?  Almost certainly not. Is it the most sustainable way to do it? I think so.

« Last Edit: 08/14/2017 06:14 PM by bradjensen3 »

Offline stefan r

  • Member
  • Posts: 33
  • pennsylvania
  • Liked: 0
  • Likes Given: 9
Re: Earth to Orbit with a Space Bungee
« Reply #54 on: 08/14/2017 06:52 PM »
... Is it most efficient way to get stuff of the ground?  Almost certainly not.  Is it the most sustainable way to do it? I think so.

Use your asteroid materials to manufacture solar panels (or mirrors aimed at generator).   Beam energy to earth.  Use electricity to split water.  Use a reusable H2/LOx rocket to launch to space (can also use H2 for methane production).  This is sustainable and all energy originated from space.  But I would never call it a "space bungee". 

If an idea requires lots of infrastructure in space it will not get very far on this forum.  There are lots of options once(if) humans transition into space.  But there first needs to be a way to launch that initial infra-structure. 

Online bradjensen3

  • Member
  • Posts: 27
  • Tulsa, Oklahoma, USA
  • Liked: 2
  • Likes Given: 0
Re: Earth to Orbit with a Space Bungee
« Reply #55 on: 08/14/2017 07:10 PM »
PS Thank you Jim for all your helpful posts. Also Stan and others.

I know you mean the best for me, and I appreciate it.

Part of the problem with this discussion from my point of view is that you aren't accepting my central premise for the point of this discussion, that water is plentiful on the Moon. I understand this is not currently an Established Fact, but I think the possibility that it soon will be is enough to start thinking about what to do with it.

The other part is that I don't know the formulas for orbital dynamics or the method of applying them. I promise to learn those soon. A nice engineer across the street who owes me some time, and I'll ask him to help me learn.  We trade time and resources from time to time. I believe he thinks I am a bit crazy too, but he is extremely polite about it.  With him, I discuss my ideas about nuclear synthetic oil.

I am not a nuts and bolts engineer, but I am a software engineer for the last 40+ years and I do understand that things have to work in a practical fashion.

It is not enough for things to work mechanically, they must also function economically, and behind all economics is politics.

It has been almost 50 years since a man first walked on the Moon. That man is now dead. The reason space exploration proceeds at such a snail's pace is because it is an expensive luxury, not a self-supporting economic activity.

I think we can change this in the next two or three decades.

So how would you guys get things off the Earth, using non-Earth-based resources?

Online whitelancer64

Re: Earth to Orbit with a Space Bungee
« Reply #56 on: 08/14/2017 07:17 PM »
Even if water was plentiful on the Moon, to the point that it could be used freely, and for things like propulsion, it wouldn't be a good use of it to fly nearly all the way back to Earth, reduce velocity a great deal, drop a tether, and pick up a payload from high in the atmosphere, and accelerate again to go back to the Moon.

There are a whole bunch of complex technical issues in there that could probably be solved, but ultimately it would be both much simpler, and a better use of (and would use less) fuel to land on Earth, then launch back to the Moon.
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 31028
  • Cape Canaveral Spaceport
  • Liked: 9187
  • Likes Given: 295
Re: Earth to Orbit with a Space Bungee
« Reply #57 on: 08/14/2017 07:55 PM »

So how would you guys get things off the Earth, using non-Earth-based resources?

You don't.  You use Earth-based resources to get things off the Earth.  Bringing non-Earth-based resources into the Earth's gravity well to get out of the gravity well makes no sense.

Online bradjensen3

  • Member
  • Posts: 27
  • Tulsa, Oklahoma, USA
  • Liked: 2
  • Likes Given: 0
Re: Earth to Orbit with a Space Bungee
« Reply #58 on: 08/14/2017 08:52 PM »

So how would you guys get things off the Earth, using non-Earth-based resources?

You don't.  You use Earth-based resources to get things off the Earth.  Bringing non-Earth-based resources into the Earth's gravity well to get out of the gravity well makes no sense.

"Under current constraints and circumstances."

I thought this part of the forum was for advanced topics.

I'm a disaster recovery guy in real life.

So far I hear people telling me 'it's impossible' when I think what they mean is 'it's not economically sensible in current conditions.'

Maybe you do mean it is impossible to make a water based rocket that can lift from the Moon, reach lunar escape velocity, partially aerobrake in the Earths atmosphere, send a skimmer into the atmosphere to retrieve a payload hanging from a balloon or launched ballistically from a balloon (or maybe an Airbus!) and accelerate it to orbit.



Offline meberbs

  • Full Member
  • ****
  • Posts: 957
  • Liked: 874
  • Likes Given: 257
Re: Earth to Orbit with a Space Bungee
« Reply #59 on: 08/14/2017 09:51 PM »
So far I hear people telling me 'it's impossible' when I think what they mean is 'it's not economically sensible in current conditions.'
Close, but replace "current conditions" with "any conceivable conditions."

Tags: