A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » Technology
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Space Solar Power – Recent Conceptual Progress



 
 
Thread Tools Display Modes
  #12  
Old June 25th 11, 03:04 PM posted to sci.space.tech
Keith Henson
external usenet poster
 
Posts: 34
Default Space Solar Power ? Recent Conceptual Progress

On Jun 21, 7:50 pm, Jeff Findley wrote:

snip

Henry Spencer has posted specific stages which meet the above criteria

in postings to these newsgroups. A Google search of these newsgroups

ought to turn up these postings. Of course, these stages were all

expendable. Making a reusable SSTO is quite a bit more difficult.

Jeff


Taking "orbit" as 9,000 m/s and SSME as 4,500 m/s, the mass fraction
is 1/7.4 or 13.5%

Gary Hudson has informally said that a mass fraction of 15% is about
as low as you can go for "reusable."

Skylon C1 design was 17.8% structure, (and ~4% payload) but they
cheat. Counting the rotation of the earth, they get to 1/4 of orbital
speed with an equivalent exhaust velocity of 10.5 km/s.

I have a graph of beamed energy exhaust velocity vs cost if I can
figure out how to make it into something I can put on a wiki.

Keith

  #13  
Old July 13th 11, 03:59 AM posted to sci.space.tech
Jeff Findley
external usenet poster
 
Posts: 5,012
Default Space Solar Power ? Recent Conceptual Progress



In article , lid

says...



Nothing would ever get built if nothing was ever built before it had


been built.




On paper, Sabre has the characteristics required for an SSTO, and Skylon


itself isn't designed around unobtanium. So far no show stoppers have


been identified.




On paper.



The show stoppers are the flight rate and reliability of bleeding edge

technologies. In order to make a profit (and pay off development

costs), Skylon will have to fly quite often and have an extremely high

reliability (hardware losses will be very expensive for such a complex

engine/vehicle).



A more conventional approach to reusable SSTO using VTVL and plain old

liquid fueled rocket engines would be a far more sane approach when you

take into account economics. That said, even SpaceX didn't use this

approach, instead choosing to build an expendable in order to minimize

development costs and time.



There are no existing markets which would require the high flight rates

needed to justify the development costs for Sabre and Skylon. It's a

research project which belongs in Popular Science magazine.



Jeff

--

" Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry

Spencer 1/28/2011




  #14  
Old July 14th 11, 01:14 AM posted to sci.space.tech
Keith Henson
external usenet poster
 
Posts: 34
Default Space Solar Power ? Recent Conceptual Progress

On Jul 12, 7:59 pm, Jeff Findley wrote:
In article ,

says...



Nothing would ever get built if nothing was ever built before it had
been built.


On paper, Sabre has the characteristics required for an SSTO, and Skylo

n
itself isn't designed around unobtanium. So far no show stoppers have
been identified.


On paper.

The show stoppers are the flight rate and reliability of bleeding edge

technologies. In order to make a profit (and pay off development

costs), Skylon will have to fly quite often and have an extremely high

reliability (hardware losses will be very expensive for such a complex

engine/vehicle).


The engine doesn't have any more moving parts than a conventional
aircraft turbine. True, the vehicle is big, but not as heavy as a
747.

A more conventional approach to reusable SSTO using VTVL and plain old

liquid fueled rocket engines would be a far more sane approach when you

take into account economics.


How do you get it back? If you put wings on it and land, then the
structure mass eats the whole mass budget.

That said, even SpaceX didn't use this

approach, instead choosing to build an expendable in order to minimize

development costs and time.

There are no existing markets which would require the high flight rates

needed to justify the development costs for Sabre and Skylon.


I agree entirely with you statement. There is only one projected
market I know about where Skylon makes sense (SBSP) and even for that
market it takes something extreme for the second stage.

Power satellites really need $100/kg to GEO to make economic sense.

Keith

It's a

research project which belongs in Popular Science magazine.

Jeff

--

" Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry

Spencer 1/28/2011


  #15  
Old July 15th 11, 03:26 AM posted to sci.space.tech
Jeff Findley
external usenet poster
 
Posts: 5,012
Default Space Solar Power ? Recent Conceptual Progress



In article 01609aef-2c20-43b4-a553-9c84cb346892

@m3g2000pre.googlegroups.com, says...



On Jul 12, 7:59 pm, Jeff Findley wrote:


In article ,




says...








Nothing would ever get built if nothing was ever built before it had


been built.




On paper, Sabre has the characteristics required for an SSTO, and Skylo


n


itself isn't designed around unobtanium. So far no show stoppers have


been identified.




On paper.




The show stoppers are the flight rate and reliability of bleeding edge




technologies. In order to make a profit (and pay off development




costs), Skylon will have to fly quite often and have an extremely high




reliability (hardware losses will be very expensive for such a complex




engine/vehicle).




The engine doesn't have any more moving parts than a conventional


aircraft turbine. True, the vehicle is big, but not as heavy as a


747.




Development costs are still high and it's very unlikely that a Skylon

would have the high flight rate of a 747. The 747 needs that high

flight rate in order to justify the high development and operational

costs of its engines.



A more conventional approach to reusable SSTO using VTVL and plain old




liquid fueled rocket engines would be a far more sane approach when you




take into account economics.




How do you get it back? If you put wings on it and land, then the


structure mass eats the whole mass budget.




I said VTVL: vertical take off and vertical landing.



In other words, land the thing like DC-X on liquid fueled rocket engine

power and on vertical landing gear. This approach is simple (no wings

needed) and has been proven to work "in the real world".



That said, even SpaceX didn't use this




approach, instead choosing to build an expendable in order to minimize




development costs and time.




There are no existing markets which would require the high flight rates




needed to justify the development costs for Sabre and Skylon.




I agree entirely with you statement. There is only one projected


market I know about where Skylon makes sense (SBSP) and even for that


market it takes something extreme for the second stage.




Power satellites really need $100/kg to GEO to make economic sense.




Even then I'm not sure they make sense. They've got to compete with all

other alternative sources of terrestrial power. As fossil fuel prices

continue to rise, terrestrial alternatives become more attractive and

investment in them may yield reductions in cost such that space based

power never makes economic sense.



Jeff

--

" Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry

Spencer 1/28/2011




  #16  
Old July 15th 11, 04:30 PM posted to sci.space.tech
Keith Henson
external usenet poster
 
Posts: 34
Default Space Solar Power ? Recent Conceptual Progress

On Jul 14, 7:26 pm, Jeff Findley wrote:
In article 01609aef-2c20-43b4-a553-9c84cb346892

@m3g2000pre.googlegroups.com, says...

On Jul 12, 7:59 pm, Jeff Findley wrote:
In article ,


says...


Nothing would ever get built if nothing was ever built before it ha

d
been built.


On paper, Sabre has the characteristics required for an SSTO, and S

kylo
n
itself isn't designed around unobtanium. So far no show stoppers ha

ve
been identified.


On paper.


The show stoppers are the flight rate and reliability of bleeding edg

e

technologies. In order to make a profit (and pay off development


costs), Skylon will have to fly quite often and have an extremely hig

h

reliability (hardware losses will be very expensive for such a comple

x

engine/vehicle).


The engine doesn't have any more moving parts than a conventional
aircraft turbine. True, the vehicle is big, but not as heavy as a
747.


Development costs are still high and it's very unlikely that a Skylon

would have the high flight rate of a 747. The 747 needs that high

flight rate in order to justify the high development and operational

costs of its engines.

A more conventional approach to reusable SSTO using VTVL and plain ol

d

liquid fueled rocket engines would be a far more sane approach when y

ou

take into account economics.


How do you get it back? If you put wings on it and land, then the
structure mass eats the whole mass budget.


I said VTVL: vertical take off and vertical landing.

In other words, land the thing like DC-X on liquid fueled rocket engine

power and on vertical landing gear. This approach is simple (no wings

needed) and has been proven to work "in the real world".


That's not entirely true. Nobody has ever gone to orbit with a DC-X
approach. It's possible new materials like carbon nanotubes or
graphene would get the structure fraction down far enough to have some
payload.

That said, even SpaceX didn't use this


approach, instead choosing to build an expendable in order to minimiz

e

development costs and time.


There are no existing markets which would require the high flight rat

es

needed to justify the development costs for Sabre and Skylon.


I agree entirely with you statement. There is only one projected
market I know about where Skylon makes sense (SBSP) and even for that
market it takes something extreme for the second stage.


Power satellites really need $100/kg to GEO to make economic sense.


Even then I'm not sure they make sense. They've got to compete with al

l

other alternative sources of terrestrial power. As fossil fuel prices

continue to rise, terrestrial alternatives become more attractive and

investment in them may yield reductions in cost such that space based

power never makes economic sense.


That's possible. But it will take a conceptually different approach,
like solar collectors that grow themselves like Kudzu. It seems
unlikely that earth based solar power will ever get down to 2 cents
per kWh, and that's the target I set for power satellites.
(StratoSolar might be an exception.)

Keith

Jeff

--

" Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry

Spencer 1/28/2011


  #17  
Old July 16th 11, 04:25 AM posted to sci.space.tech
Jeff Findley
external usenet poster
 
Posts: 5,012
Default Space Solar Power ? Recent Conceptual Progress



In article 41f2ea4f-47ee-4f68-b980-399f7e714df0

@j14g2000prn.googlegroups.com, says...



On Jul 14, 7:26 pm, Jeff Findley wrote:


In article 01609aef-2c20-43b4-a553-9c84cb346892




Even then I'm not sure they make sense. They've got to compete with


all other alternative sources of terrestrial power. As fossil fuel


prices continue to rise, terrestrial alternatives become more


attractive and investment in them may yield reductions in cost such


that space based power never makes economic sense.




That's possible. But it will take a conceptually different approach,


like solar collectors that grow themselves like Kudzu. It seems


unlikely that earth based solar power will ever get down to 2 cents


per kWh, and that's the target I set for power satellites.


(StratoSolar might be an exception.)




Perhaps advances similar to this?



Photovoltaic Breakthroughs Brighten Outlook for Cheap Solar Power

Novel materials might make harvesting sunlight for electricity

affordable

http://www.scientificamerican.com/ar...=photovoltaic-

breakthroughs-brighten-outlook-for-cheap-solar-power



And there are always other renewable sources, like wind, wave,

hydroelectric, thermal, and etc.



Jeff

--

" Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry

Spencer 1/28/2011




  #18  
Old July 16th 11, 02:50 PM posted to sci.space.tech
Keith Henson
external usenet poster
 
Posts: 34
Default Space Solar Power ? Recent Conceptual Progress

On Jul 15, 8:25 pm, Jeff Findley wrote:
In article 41f2ea4f-47ee-4f68-b980-399f7e714df0

@j14g2000prn.googlegroups.com, says...



On Jul 14, 7:26 pm, Jeff Findley wrote:
In article 01609aef-2c20-43b4-a553-9c84cb346892


Even then I'm not sure they make sense. They've got to compete wit

h
all other alternative sources of terrestrial power. As fossil fuel
prices continue to rise, terrestrial alternatives become more
attractive and investment in them may yield reductions in cost such
that space based power never makes economic sense.


That's possible. But it will take a conceptually different approach,
like solar collectors that grow themselves like Kudzu. It seems
unlikely that earth based solar power will ever get down to 2 cents
per kWh, and that's the target I set for power satellites.
(StratoSolar might be an exception.)


Perhaps advances similar to this?

Photovoltaic Breakthroughs Brighten Outlook for Cheap Solar Power

Novel materials might make harvesting sunlight for electricity

affordable

http://www.scientificamerican.com/ar...=photovoltaic-

breakthroughs-brighten-outlook-for-cheap-solar-power


Frankly, no. This is not particularly reliable information. Shame
too, I grew up on Scientific American, started reading it in 1957,
read back issues to 1948 and read every issue till the editorial
policy changed and it got "fluffy."

And there are always other renewable sources, like wind, wave,

hydroelectric, thermal, and etc.


Wind will not scale large enough, wave is much worse. Hydroelectric
is mostly exploited. Geothermal isn't large enough either.

You might want to look he Sustainable Energy — Without the Hot
Air. http://en.wikipedia.org/wiki/David_J._C._MacKay It's available
online.

Keith



Jeff

--

" Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry

Spencer 1/28/2011


 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Rename Space Solar Power to " Wireless Power Transmission"! John M Policy 8 June 11th 10 05:32 PM
..Space Energy Inc plans to launch prototype Space Solar Power Satellite Jonathan History 10 December 22nd 09 05:17 AM
Solar power from space... Brian Gaff Space Shuttle 1 May 29th 09 12:56 PM
Space Solar Power Gets A Boost [email protected] Policy 26 October 21st 07 03:57 PM
Zubrin's panning of space solar power in Entering Space TomRC Technology 10 February 25th 04 12:26 PM


All times are GMT +1. The time now is 02:47 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.