Build a Hypersonic Orbital Sky Hook
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05-04-2013, 07:59 PM
RE: Build a Hypersonic Orbital Sky Hook
(05-04-2013 07:55 PM)DeepThought Wrote:  
(05-04-2013 07:50 PM)Heywood Jahblome Wrote:  I'm sure you could save a lot of fuel with a skyhook system. However if you are Verizon and you want a new satellite placed in geosynchronis orbit, its just cheaper to pay for a tried and true booster stage to take it there then it is to developed a skyhook system and hope it works.

The skyhook system works with the already well known laws of physics.

If it is used it saves fuel. ALLOT of fuel.

That's never been demonstrated. It should work is the best we can say.

Also my "hoping it works" isn't a comment about the physics but rather hoping the technology works as intended.

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06-04-2013, 03:26 AM
RE: Build a Hypersonic Orbital Sky Hook
A major deficiency with the skyhook system is that the skyhook itself requires fuel in order to work and this will have to be refueled priodically. Which means some sort of fuel shipments to it via surface or air launched rocket boosters. It's not a perfect panacea.

The system's biggest strength is in using a transport system utilizing air breathing engines to clear 99% of the atmosphere, leaving the final ascent to LEO in the vacuum of space, which requires a fraction of the fuel used by a standard ground launched rocket.

Given this, a hypersonic mothership / daughter craft would be much more feasible. The daughter craft could simply be a small disposable rocket booster carrying the payload.

A lot of people here are shitting on NASA's operation of the STS program. The Shuttle had its flaws but it was a technological marvel being a fully reusable spacecraft. Building a craft which can sustain multiple re entries through the atmosphere plus reusable rocket engines is a daunting challenge. If you wanted a real viable replacement for the shuttle, allocate $40 billion and ten years for development. You'll have a runway to orbit aerospace plane then, fully reusable, with greater reliability than any other space transport system.

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06-04-2013, 03:50 AM
RE: Build a Hypersonic Orbital Sky Hook
(06-04-2013 03:26 AM)Carlo_The_Bugsmasher_Driver Wrote:  A major deficiency with the skyhook system is that the skyhook itself requires fuel in order to work and this will have to be refueled priodically. Which means some sort of fuel shipments to it via surface or air launched rocket boosters. It's not a perfect panacea.

The system's biggest strength is in using a transport system utilizing air breathing engines to clear 99% of the atmosphere, leaving the final ascent to LEO in the vacuum of space, which requires a fraction of the fuel used by a standard ground launched rocket.

Given this, a hypersonic mothership / daughter craft would be much more feasible. The daughter craft could simply be a small disposable rocket booster carrying the payload.

A lot of people here are shitting on NASA's operation of the STS program. The Shuttle had its flaws but it was a technological marvel being a fully reusable spacecraft. Building a craft which can sustain multiple re entries through the atmosphere plus reusable rocket engines is a daunting challenge. If you wanted a real viable replacement for the shuttle, allocate $40 billion and ten years for development. You'll have a runway to orbit aerospace plane then, fully reusable, with greater reliability than any other space transport system.

There are a couple options to resolve the orbit degradation issue.

The main option is use the sky hook for return trips and boost the orbit that way. Hell, throw old satellites at it. Another satellite disposal option that provides some extra energy.

It could have solar panels and use the energy to run electromagnets that boost the orbit by pushing against Earths magnetic field. That reduces the need for conventional chemical thrusters. The electromagnets on each end could double as a docking/attachment mechanism for skyhook use.

The problem with the shuttle was that it was still outrageously expensive despite being reusable. The main reason for making it reusable is to reduce launch costs. In this regard NASA failed.

“Forget Jesus, the stars died so you could be born.” - Lawrence M. Krauss
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06-04-2013, 10:21 PM
RE: Build a Hypersonic Orbital Sky Hook
(06-04-2013 03:50 AM)DeepThought Wrote:  
(06-04-2013 03:26 AM)Carlo_The_Bugsmasher_Driver Wrote:  A major deficiency with the skyhook system is that the skyhook itself requires fuel in order to work and this will have to be refueled priodically. Which means some sort of fuel shipments to it via surface or air launched rocket boosters. It's not a perfect panacea.

The system's biggest strength is in using a transport system utilizing air breathing engines to clear 99% of the atmosphere, leaving the final ascent to LEO in the vacuum of space, which requires a fraction of the fuel used by a standard ground launched rocket.

Given this, a hypersonic mothership / daughter craft would be much more feasible. The daughter craft could simply be a small disposable rocket booster carrying the payload.

A lot of people here are shitting on NASA's operation of the STS program. The Shuttle had its flaws but it was a technological marvel being a fully reusable spacecraft. Building a craft which can sustain multiple re entries through the atmosphere plus reusable rocket engines is a daunting challenge. If you wanted a real viable replacement for the shuttle, allocate $40 billion and ten years for development. You'll have a runway to orbit aerospace plane then, fully reusable, with greater reliability than any other space transport system.

There are a couple options to resolve the orbit degradation issue.

The main option is use the sky hook for return trips and boost the orbit that way. Hell, throw old satellites at it. Another satellite disposal option that provides some extra energy.

It could have solar panels and use the energy to run electromagnets that boost the orbit by pushing against Earths magnetic field. That reduces the need for conventional chemical thrusters. The electromagnets on each end could double as a docking/attachment mechanism for skyhook use.

The problem with the shuttle was that it was still outrageously expensive despite being reusable. The main reason for making it reusable is to reduce launch costs. In this regard NASA failed.

In order to use transfer of momentum to accelerate, decelerate the skyhook, it would require an object the mass of the payload whic has a relative closure of 11,000 m/s, which works out to be faster than the escape velocity for the Earth! This would be an extremely difficult task to capture this object without destroying the skyhook and the payload in the process.

The solar electromagnetic propulsion scheme could work provided the following:

The skyhook was extremely massive ie >1000 times the mass of the payload to minimize the loss of speed and orbital decay the skyhook would suffer in capturing the payload.

A sufficiently large power plant and conductors could be used to generate the required force as the Earth's magnetic field is a mere 50 microTeslas in strength.

A sufficiently long time was available to accelerate the skyhook back up to orbital velocity.

All in all the system is impractical.

"IN THRUST WE TRUST"

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06-04-2013, 11:23 PM
RE: Build a Hypersonic Orbital Sky Hook
(06-04-2013 10:21 PM)Carlo_The_Bugsmasher_Driver Wrote:  
(06-04-2013 03:50 AM)DeepThought Wrote:  There are a couple options to resolve the orbit degradation issue.

The main option is use the sky hook for return trips and boost the orbit that way. Hell, throw old satellites at it. Another satellite disposal option that provides some extra energy.

It could have solar panels and use the energy to run electromagnets that boost the orbit by pushing against Earths magnetic field. That reduces the need for conventional chemical thrusters. The electromagnets on each end could double as a docking/attachment mechanism for skyhook use.

The problem with the shuttle was that it was still outrageously expensive despite being reusable. The main reason for making it reusable is to reduce launch costs. In this regard NASA failed.

In order to use transfer of momentum to accelerate, decelerate the skyhook, it would require an object the mass of the payload whic has a relative closure of 11,000 m/s, which works out to be faster than the escape velocity for the Earth! This would be an extremely difficult task to capture this object without destroying the skyhook and the payload in the process.

The solar electromagnetic propulsion scheme could work provided the following:

The skyhook was extremely massive ie >1000 times the mass of the payload to minimize the loss of speed and orbital decay the skyhook would suffer in capturing the payload.

A sufficiently large power plant and conductors could be used to generate the required force as the Earth's magnetic field is a mere 50 microTeslas in strength.

A sufficiently long time was available to accelerate the skyhook back up to orbital velocity.

All in all the system is impractical.

Where did you get those figures from? 1000x payload mass seems a massively exaggerated figure!

I guess if all this is true it would explain the lack of interest in the idea.

Was kinda hoping there was a practical idea out there that would enable cheap flights into LEO. Something doable with todays technology. I guess if there were we would already be doing it! Rolleyes

“Forget Jesus, the stars died so you could be born.” - Lawrence M. Krauss
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27-08-2014, 10:38 AM
RE: Build a Hypersonic Orbital Sky Hook
I have always found the concept of a gravity gradient stabilized skyhook very interesting. As I see it, they are a space elevator that can be built with existing technology.

http://web.archive.org/web/2007022116222...vator.html

https://www.dropbox.com/s/fp6q6eq9iky8vw...e,%201.pdf

http://skyhookorbiting.wordpress.com/
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27-08-2014, 12:30 PM
RE: Build a Hypersonic Orbital Sky Hook
(06-04-2013 11:23 PM)DeepThought Wrote:  Was kinda hoping there was a practical idea out there that would enable cheap flights into LEO. Something doable with todays technology. I guess if there were we would already be doing it! Rolleyes
There is - SpaceX

They have really shaken the launch industry and have redefined how to put payloads into LEO far cheaper than what was previously possible. They are on the verge of getting a reusable first stage that will drive costs down even further.

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27-08-2014, 03:38 PM
RE: Build a Hypersonic Orbital Sky Hook
The three ingredients for an affordable transportation system are: reusability, low propellant fraction, and high payload fraction.

The fact that SpaceX is working on the development of a reusable first stage is wonderful and will be a big step forward towards making spaceflight truly affordable. But it is not the end-all be-all solution.

Air-launching is a way to reduce the propellant fraction and increase the payload fraction. It also allows you to pick a launch point such that the reusable first stage will come down over land versus the ocean.

Ground accelerators are another way of reducing the propellant fraction and increasing the payload fraction. They are lower in cost to build than a stratolaunch aircraft.

Air-breathing for at least some part of the flight profile via a ramjet, scramjet, ducted rocket, or combination there-of does the same. This also works well with air-launching and ground accelerators as long as they get the launch vehicle up to ramjet ignition speed.

A skyhook reduces the velocity required at the upper end of the flight profile. When the skyhook is long enough it makes possible single stage to skyhook flight with a reusable first stage. Another way of thinking of a skyhook is as a reusable upper stage. It also allows for timing the re-entry so that the returning vehicle lands where you want it to.

Another advantage of the skyhook is that it gives low cost access to higher orbits and escape velocity, an item that none of the other options do.

Most likely the lowest cost solution will be some combination of all of these options as size of the investment is another issue that is rarely discussed but also of importance.

Another issue that could possible impact the final design is where we are going next. Is our primary interest low Earth orbit or beyond?
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