Author Topic: cheap reusable rockets?  (Read 8077 times)

Offline michaelwy

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cheap reusable rockets?
« on: 10/02/2011 10:26 PM »
http://www.tgdaily.com/space-features/58793-can-reusable-rockets-help-us-get-to-mars

Space X boss Elon Musk has declared that he is going to build a re-usable rocket which can substantially reduce launch costs. I wonder what the safety of such a rocket would be?
If successful, this could be the most important development for space. The only thing that would be better than a reusable rocket is a space elevator.
In the future we would be able to travel to the Bigelow space hotels using Branson's Virgin galactic. Or perhaps we could travel from London to Sidney in 3 hours via his Spaceship three.

Offline Jim

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Re: cheap reusable rockets?
« Reply #1 on: 10/02/2011 11:15 PM »
The only thing that would be better than a reusable rocket is a space elevator.

Space Elevators are scifi and not practical.

Offline Jim

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Re: cheap reusable rockets?
« Reply #2 on: 10/02/2011 11:16 PM »

In the future we would be able to travel to the Bigelow space hotels using Branson's Virgin galactic. Or perhaps we could travel from London to Sidney in 3 hours via his Spaceship three.


Virgin galactic has done nothing about orbital flight and point to point is not viable as a business.

Offline CitabriaFlyer

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Re: cheap reusable rockets?
« Reply #3 on: 10/03/2011 12:29 AM »
How much fuel would it take for a Falcon 9 first stage to pull off that RTLS manuver?  Wouldn't this mean they would have to stage earlier in the flight?  I would think it would sacrifice a lot of performance.

But what do I know?  I am just an old country biologist who has given up calculus.

Offline michaelwy

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Re: cheap reusable rockets?
« Reply #4 on: 10/03/2011 02:01 AM »

In the future we would be able to travel to the Bigelow space hotels using Branson's Virgin galactic. Or perhaps we could travel from London to Sidney in 3 hours via his Spaceship three.


Virgin galactic has done nothing about orbital flight and point to point is not viable as a business.

Branson has said that if Spaceship Two is a success, and 400 people have already signed up for a trip, he would build an orbital Spaceship Three. Branson has the money to make it happen, and as long as Burt Rutan is alive, he also has the brains. Point to Point travel would be possible then. It would have to be about the price of a Concord ticket. The rich and famous can travel between Europe and Australia in a few hours.

As for the Space Elevator, it can be built of carbon nanotubes, according to Michio Kaku.

Offline Bill White

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Re: cheap reusable rockets?
« Reply #5 on: 10/03/2011 02:07 AM »
The lack of markets, not the lack of technology, is what stands between us and cheap access to space. IMHO.
« Last Edit: 10/03/2011 02:07 AM by Bill White »
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Offline scienceguy

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Re: cheap reusable rockets?
« Reply #6 on: 10/03/2011 02:18 AM »
The lack of markets, not the lack of technology, is what stands between us and cheap access to space. IMHO.

So what if there were people living on Mars? Then there would be a market for access to space. But we probably won't have people on Mars until there is cheap access to space...
e^(pi*i) = -1

Offline Jim

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Re: cheap reusable rockets?
« Reply #7 on: 10/03/2011 02:24 AM »

1. as long as Burt Rutan is alive, he also has the brains.

2 Point to Point travel would be possible then. It would have to be about the price of a Concord ticket. The rich and famous can travel between Europe and Australia in a few hours.

3.As for the Space Elevator, it can be built of carbon nanotubes, according to Michio Kaku.

1. Rutan has retired

2.  Not true, there are many issues with PTP that don't make viable

3.  One person's opinion doesn't mean it's true.
« Last Edit: 10/03/2011 02:24 AM by Jim »

Offline michaelwy

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Re: cheap reusable rockets?
« Reply #8 on: 10/03/2011 09:02 AM »

1. as long as Burt Rutan is alive, he also has the brains.

2 Point to Point travel would be possible then. It would have to be about the price of a Concord ticket. The rich and famous can travel between Europe and Australia in a few hours.

3.As for the Space Elevator, it can be built of carbon nanotubes, according to Michio Kaku.

1. Rutan has retired

2.  Not true, there are many issues with PTP that don't make viable

3.  One person's opinion doesn't mean it's true.

Rutan has retired? Well, that was sad. But I guess Branson has the funds to get a pretty good replacement.

What you say about PTP is interesting. Could you say something more about why you think it isn't viable?

Offline john smith 19

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Re: cheap reusable rockets?
« Reply #9 on: 10/03/2011 09:24 AM »

1. Rutan has retired
True. He was the public face of Scaled Composites. Time will tell how diligent Scaled have been in growing replacements. I suspect they have been quietly encouraging new talent in relative obscurity until now.

Quote
2.  Not true, there are many issues with PTP that don't make viable
As there used to be with transatlantic or transpacific flight without refueling or changing planes. The issues relate to market size, is there a *return* market (from there to here) and how far apart those points are. The massively dumb ITAR rules don't help. Beyond that is the question of building a vehicle which can pay for itself and deliver operating expenses which allow its operators to make a profit before end of life.

ELV designers have not historically had to deal with these issues.

Quote
3.  One person's opinion doesn't mean it's true.
True. Materials are the #1 issue with space elevator concepts. It's not enough the material has to be *theoretically* capable of the load/unit mass it's got be available in the *quantity* to do the job. I'm not sure how many elevator advocates realize how much of this they need.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.
So you're going to Mars to seek a better life. What does that mean to you? Always spot a fanbois by how they react to their idols failures.

Offline ANTIcarrot

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Re: cheap reusable rockets?
« Reply #10 on: 10/03/2011 02:12 PM »
Watching the video the first stage takes off from Kennedy, imparts some sideward velocity, and then lands back at Kennedy? Or is supposed to be launching from the west coast? (Tampa? Cape Coral?) Despite usually on the pro side or RLV and CATS, this looks overly optimistic even to me, and I feel the need to ask questions like, "Is that a beryllium heat shield on the second stage?" :o

The video is certainly representative of some technologies that SpaceX could use to reduce the cost space flight, but I get the impression they've either glossed over or hidden some details, or the artists making it didn't pay a lot of attention to the engineers advising them.
« Last Edit: 10/03/2011 02:15 PM by ANTIcarrot »

Offline Jim

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Re: cheap reusable rockets?
« Reply #11 on: 10/03/2011 02:16 PM »

True. Materials are the #1 issue with space elevator concepts. It's not enough the material has to be *theoretically* capable of the load/unit mass it's got be available in the *quantity* to do the job. I'm not sure how many elevator advocates realize how much of this they need.

There are other issues, like orbital debris, weather, interference with other spacecraft, etc

Offline Jim

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Re: cheap reusable rockets?
« Reply #12 on: 10/03/2011 02:17 PM »

1. Rutan has retired
True. He was the public face of Scaled Composites. Time will tell how diligent Scaled have been in growing replacements. I suspect they have been quietly encouraging new talent in relative obscurity until now.



He was more than that.

Offline Bill White

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Re: cheap reusable rockets?
« Reply #13 on: 10/03/2011 02:37 PM »

True. Materials are the #1 issue with space elevator concepts. It's not enough the material has to be *theoretically* capable of the load/unit mass it's got be available in the *quantity* to do the job. I'm not sure how many elevator advocates realize how much of this they need.

There are other issues, like orbital debris, weather, interference with other spacecraft, etc

There also are economic issues.

Back of the envelope calculations quickly reveal that if space elevator price points are to fall below $500 per pound, staggering amounts of mass need to be lifted to LEO on a regular basis in order to amortize the capital costs of building the elevator, even if all of the countless technical challenges can be solved.

A $10 billion space elevator with ten year service life "costs" $121 million per month merely for the capital. (I used a generic financial amortizatrion program). This figures also ignores ongoing operating costs.

At a $1,000 per pound price target, an elevator operator needs to loft 121,000 pounds per month. At a $500 per pound price target, an elevator operator needs to loft 242,000 pounds per month.

= = =

Yes, I did do this on the back of a business envelope and may have dropped a few orders of magnitude.

Others are encouraged to check my math.
EML architectures should be seen as ratchet opportunities

Offline Hop_David

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Re: cheap reusable rockets?
« Reply #14 on: 10/03/2011 02:49 PM »

True. Materials are the #1 issue with space elevator concepts. It's not enough the material has to be *theoretically* capable of the load/unit mass it's got be available in the *quantity* to do the job. I'm not sure how many elevator advocates realize how much of this they need.

There are other issues, like orbital debris, weather, interference with other spacecraft, etc

There also are economic issues.

Back of the envelope calculations quickly reveal that if space elevator price points are to fall below $500 per pound, staggering amounts of mass need to be lifted to LEO on a regular basis in order to amortize the capital costs of building the elevator, even if all of the countless technical challenges can be solved.

A $10 billion space elevator with ten year service life "costs" $121 million per month merely for the capital. (I used a generic financial amortizatrion program). This figures also ignores ongoing operating costs.

At a $1,000 per pound price target, an elevator operator needs to loft 121,000 pounds per month. At a $500 per pound price target, an elevator operator needs to loft 242,000 pounds per month.

= = =

Yes, I did do this on the back of a business envelope and may have dropped a few orders of magnitude.

Others are encouraged to check my math.

And elevator throughput is seldom discussed. What speed can the elevator cars achieve? (recall they must travel 36,000 km to reach geosynch) How many elevator cars can the bean stalk support?

In my opinion the elevator would be far from the panacea a lot of people wish for.

Offline Epis

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Re: cheap reusable rockets?
« Reply #15 on: 10/03/2011 05:01 PM »
few days ago new interesting concept appeared from DirectP2  see at page
http://www.launchcomplexmodels.com/DirectP2/leviathan140.html
and I made some calculation of how much acceleration could deliver underwater launch tunnel 50m long for Falcon9 54m high rocket placed at the depth of 100m underwater.
so operation is simple:
- sink rocket to 100m depth down the 5.2m diameter 50m long   tube
- push out all water with air pressure 0.5 Mpa,
-clamp rocket and tube to lake / pool bottom if in ocean then to some counterweight.
- release rocket and tube from counterweight
- blast off tube pressure cap to release air pressure
- and the rocket will take off from 100m water depth at the beginning with 30m/s2 acceleration then when rocket aligns with tube fire some small Solid rocket engines to create hot high pressure gases and blast out of tube with more than 30m/s so at the end total launch assist runway length would be 150m long  with average 20-30m/ss acceleration speeds of 77-94 m/s could be reached that would result in ~17% fuel saving of rocket first stage compared to launch without acceleration, that fuel saving bonus could then be used for first stage Vertical fly back and landing.
performance could be increased when launched at higher altitude mountain top lake, problem is that there are no deep high altitude lakes so I guess someone would need to find some >5km altitude volcano crater and make some digging, basically make small pool and pump in water, that would be then launch pad.
rockets first stage could fly back to high altitude pool and land there for next launch, so basically second stage + payload would be parts that will need transportation to launch place. if second stage could make trip around the earth and land back to pool then it will be more economical, will save time and money and high transportation costs to mountain top.
mountain spaceport infrastructure could be used in future for other mountain slope linear accelerator project research and development to reduce further cost of launches.

Offline Jim

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Re: cheap reusable rockets?
« Reply #16 on: 10/03/2011 05:10 PM »
few days ago new interesting concept appeared from DirectP2  see at page
http://www.launchcomplexmodels.com/DirectP2/leviathan140.html
and I made some calculation of how much acceleration could deliver underwater launch tunnel 50m long for Falcon9 54m high rocket placed at the depth of 100m underwater.
so operation is simple:


Again you fail.  It is not simple nor does it provide an advantage.

Offline A_M_Swallow

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Re: cheap reusable rockets?
« Reply #17 on: 10/03/2011 07:25 PM »
{snip}

And elevator throughput is seldom discussed. What speed can the elevator cars achieve? (recall they must travel 36,000 km to reach geosynch) How many elevator cars can the bean stalk support?

In my opinion the elevator would be far from the panacea a lot of people wish for.

The top speed is about 200 mph to 250 mph.  The speed limitation is the maximum force you can apply to the ribbon and the energy your solar panels can deliver.  The main acceleration is gravity which varies with height.

Throughput is likely to be 1 launch per day, timed 2 hours before sunrise.

The cargo vehicles will probably be expendable, the elevator has to stop launches during descents.

Offline michaelwy

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Re: cheap reusable rockets?
« Reply #18 on: 10/03/2011 09:00 PM »

1. as long as Burt Rutan is alive, he also has the brains.

2 Point to Point travel would be possible then. It would have to be about the price of a Concord ticket. The rich and famous can travel between Europe and Australia in a few hours.

3.As for the Space Elevator, it can be built of carbon nanotubes, according to Michio Kaku.

1. Rutan has retired

2.  Not true, there are many issues with PTP that don't make viable

3.  One person's opinion doesn't mean it's true.

I found this video interview with Burt Rutan in which he practically answers my questions. (He keeps saying that Al Gore created the internet.LOL)

http://bigthink.com/ideas/18881

But it looks like Rutan agrees with you about point to point flight.
« Last Edit: 10/03/2011 09:01 PM by michaelwy »

Offline gbaikie

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Re: cheap reusable rockets?
« Reply #19 on: 10/03/2011 09:46 PM »

In the future we would be able to travel to the Bigelow space hotels using Branson's Virgin galactic. Or perhaps we could travel from London to Sidney in 3 hours via his Spaceship three.


Virgin galactic has done nothing about orbital flight and point to point is not viable as a business.

Branson has said that if Spaceship Two is a success, and 400 people have already signed up for a trip, he would build an orbital Spaceship Three. Branson has the money to make it happen, and as long as Burt Rutan is alive, he also has the brains. Point to Point travel would be possible then. It would have to be about the price of a Concord ticket. The rich and famous can travel between Europe and Australia in a few hours.

Let's see after a dozen or so joyrides. Maybe we will see it in 2012.

"As for the Space Elevator, it can be built of carbon nanotubes, according to Michio Kaku. "

Carbon nanotubes would worth more than the high quality steel used in bridges, but at the price steel [or even if free] Space Elevators can not
get people into space cheaper than chemical rockets.

The fundamental problem is amount of payload and the time it takes to
get into orbit. How fast can a train go? And do trains travel faster if going straight up.
Or what is fastest elevator in the world? And if there was any need could one fairly easily double or triple it's speed?
Why isn't "space elevator technology" used in "normal" elevators. Such technology is cheap and energy efficient, no?

I think if there is any value to a space elevator it will be in bringing people and/or cargo [or stuff] from space to earth. Not a pressing problem at the moment.

Offline Jim

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Re: cheap reusable rockets?
« Reply #20 on: 10/03/2011 10:00 PM »

Why isn't "space elevator technology" used in "normal" elevators. Such technology is cheap and energy efficient, no?


no, it is not applicable to normal elevators.

Offline ANTIcarrot

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Re: cheap reusable rockets?
« Reply #21 on: 10/04/2011 11:08 AM »
The fundamental problem is amount of payload and the time it takes to get into orbit. How fast can a train go? And do trains travel faster if going straight up.

Maglev trains can reach 500kph at sea level, and possible higher speeds above the atmosphere. Top speed would be determined by how quickly you could turn the magnets on and off. Such a design would require magnets to be embedded in the stalk/ribbon - so you'd be trading off thousands of tons of cargo capacity for maybe a 90% reduction in journey time. You'd also want a compact nuclear power source to run the train, perhaps in a seperate 'power car' a mile removed from the actual cargo.

But it would still take three days to get to the top. And this is an idealised 'gen VI' design, and probably not something we can build in the next 100 years.

Chemical rockets are going to be the way things work for a long time to come.

Offline pippin

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Re: cheap reusable rockets?
« Reply #22 on: 10/04/2011 11:21 AM »
Errr... Could it be that you haven't understood the principal limitation of space elevators: You have to find a material that is strong enough to be able to support it's own weight (and not a lot more beyond that) when you build a structure 36.000 km tall.
The problem is that we don't know a material light or strong enough to even do THAT (whether carbon nanotubes are strong enough is subject to debates but most people believe they are not). Behind that background it doesn't really help to want to add tons of additional magnet structure to each meter of the elevator.
What you need is something that weights GRAMS per meter, not TONS or the concept is a non-starter.

Online Robotbeat

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Re: cheap reusable rockets?
« Reply #23 on: 10/04/2011 01:16 PM »
Just a note: Carbon Nanotubes are theoretically strong enough for a space elevator, but practically getting the practical, macroscopic tensile strength high enough is a significant challenge. There are advancements happening in that aspect, though.

And it's not a strict line between working an not working... If a material isn't strong enough, a "taper ratio" can allow a space elevator to still be constructed. If the strength is not high enough, though, the taper ratio is incredibly high and the total mass of the space elevator becomes unrealistic.

But even if a pure space elevator turns out not to be practical, other tether concepts still are feasible (and become more practical with higher tensile strength).
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Offline Epis

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Re: cheap reusable rockets?
« Reply #24 on: 10/05/2011 09:50 AM »
Just had new idea about that Space X Grasshopper, how it could increase payload, and reduce landing fuel/time.
Solution is simple:
 why not takeoff from 7-8km high mountain top ? 
and land on mountain top?
 and it wont cost much money to set up launch port on mountain Top because there would be no need for large infrastructures like road, transport, etc. because reusable rocket stages could fly from factory launch site (empty) to mountain top, by themselves, rocket payload/fuel could be delivered by helicopter or Aerial Tram, so infrastructure would be aerial tramway that will need to be built, and that's all.

today only obstacle form mountain top high altitude sites was heavy rocket delivery that would require extensive ground infrastructure and large workforce for assembly, but if rocket stage is VTVL then first is solved, and second is also solved if rocket is Reusable 100+ times, then some minor checking, inspection could be needed before sticking stages together with payload and fueling it up, that would all reduce needed crew at high altitude mountain top as much as possible.
that would be real game changing if launching from mountain top. :) 

Offline Jim

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Re: cheap reusable rockets?
« Reply #25 on: 10/05/2011 11:43 AM »
Just had new idea about that Space X Grasshopper, how it could increase payload, and reduce landing fuel/time.
Solution is simple:
 why not takeoff from 7-8km high mountain top ? 
and land on mountain top?
 and it wont cost much money to set up launch port on mountain Top because there would be no need for large infrastructures like road, transport, etc. because reusable rocket stages could fly from factory launch site (empty) to mountain top, by themselves, rocket payload/fuel could be delivered by helicopter or Aerial Tram, so infrastructure would be aerial tramway that will need to be built, and that's all.

today only obstacle form mountain top high altitude sites was heavy rocket delivery that would require extensive ground infrastructure and large workforce for assembly, but if rocket stage is VTVL then first is solved, and second is also solved if rocket is Reusable 100+ times, then some minor checking, inspection could be needed before sticking stages together with payload and fueling it up, that would all reduce needed crew at high altitude mountain top as much as possible.
that would be real game changing if launching from mountain top. :) 

Wrong.  It is not game changing.  It still needs extensive ground infrastructure.  "sticking stages together with payload and fueling it up"  is not simple. Still needs the same size ground crew.    Also, the payload cant flight to the mountain top.

The extra altitude is not that much of an advantage.
 
"in the end advantage if is, is so small, then whats a point ? "

Just give it up with the mountain top or tunnels.  They don't help.
« Last Edit: 10/05/2011 11:47 AM by Jim »

Offline Epis

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Re: cheap reusable rockets?
« Reply #26 on: 10/05/2011 02:07 PM »
Wrong.  It is not game changing.  It still needs extensive ground infrastructure.  "sticking stages together with payload and fueling it up"  is not simple. Still needs the same size ground crew.    Also, the payload cant flight to the mountain top.

The extra altitude is not that much of an advantage.
 
"in the end advantage if is, is so small, then whats a point ? "

Just give it up with the mountain top or tunnels.  They don't help.

Extra advantage will be high launching from high altitude, just make quick read on http://www.g2mil.com/high.htm  advantages are:
- higher rocket engine Thrust thanks to lower atmospheric pressure.
- No Max-Q so full engine throttle all the time = less gravity losses.
- less air drag losses.
- at least 50% payload to LEO improvement if launched from >5km mountain top at near equatorial location, or close to it.

basically that extra payload boost could be used to add mass to rocket, to make it not just more rugged, for re usability, but also to add extra hardware for easier stage assembly and even make it automated with external crane help. so goal is human free mountain top rocket stage assembly. also launch pad must be as simple as possible that would mean heavier grasshopper launch pads to hold full rocket weight on launch. all extra hardware weight to reduce launch assemble and pad complexity will eat mountain top payload surplus advantage, but cost from re usability will make it >20-30x cheaper than current launches.
rocket payload or 3 rocket stage could be assembled on sea level in some existing facility, then by helicopter transported to mountain top, at least it is in current helicopter payload capability range ( largest machine Mil V-12 has max 44,205 kg payload lift capability so entire 3 rocket stage could be delivered to launch site for Falcon 9 rocket with 10ton payload), for falcon heavy in future  more powerful helicopter could be  developed. or if large cargo capacity areal Tram be built then it could be used, but first business model can be started with smaller rockets (F9) using helicopter cargo transport services only, it succeeds then high infrastructural investments in heavy cargo lifting system could be more economical.

 in north America continent there is >5Km volcano mountain tops in Mexico for example Iztaccihuatl mountain http://en.wikipedia.org/wiki/Iztacc%C3%ADhuatl
height 5230m it has snow, glaciers from where to get Water for Oxygen/hydrogen fuel.

there is some rumor on net about spaceX f9 latest reusable launch video animation that some parts are not shown, maybe they don't show that rocket launches/lands on higher altitude launch pads, maybe not mountain top as high as 5-7-8km but 3.4-4km altitude pads could be that secret that is missing ??

I am definitely seeing this trend where reusable rockets will go to high altitude launch sites to squeeze missing performance boost to be able to cover for added re usability rocket weight penalty.

one more thing is that rocket must use Lox/Lh2 fuel in order to not pollute snow that is future water source and no one will allow tech that could pollute snow water. so electrical power line will be needed and snow water separator for rocket fuel. I quickly checked how high are temperatures at highest earth mountain (mount Everest) and in winter they have average -30 degrees (lowest record -60) i guess for cryogenic fuels like LOX and Lh2 it is much better than +20-30C on hot equatorial launch pad, so less thermal protection will be needed that means lighter stronger fuel tanks could be made. 
« Last Edit: 10/05/2011 02:38 PM by Epis »

Offline Jim

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Re: cheap reusable rockets?
« Reply #27 on: 10/05/2011 04:29 PM »
Wrong.  It is not game changing.  It still needs extensive ground infrastructure.  "sticking stages together with payload and fueling it up"  is not simple. Still needs the same size ground crew.    Also, the payload cant flight to the mountain top.

The extra altitude is not that much of an advantage.
 
"in the end advantage if is, is so small, then whats a point ? "

Just give it up with the mountain top or tunnels.  They don't help.

Extra advantage will be high launching from high altitude, just make quick read on http://www.g2mil.com/high.htm  advantages are:
 
- at least 50% payload to LEO improvement if launched from >5km mountain top at near equatorial location, or close to it.

There is nothing that shows 50% improvement in that website. 

And you don't know what you are talking about.

Better performance does not mean cheaper launch

Offline Jim

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Re: cheap reusable rockets?
« Reply #28 on: 10/05/2011 04:31 PM »
then by helicopter transported to mountain top, at least it is in current helicopter payload capability range ( largest machine Mil V-12 has max 44,205 kg payload lift capability so entire 3 rocket stage could be delivered to launch site for Falcon 9 rocket with 10ton payload),

No, a helicopter can not lift heavy loads at high altitudes.  The Mil V-12 could only lift that to less than 2250 meters. The Mil V-12 could only fly to 3,500 m empty.

See you don't know what you are talking about.  Your ideas are not viable or cheaper.  When will you learn that!!!

« Last Edit: 10/05/2011 04:35 PM by Jim »

Offline Jim

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Re: cheap reusable rockets?
« Reply #29 on: 10/05/2011 04:36 PM »

I am definitely seeing this trend where reusable rockets will go to high altitude launch sites to squeeze missing performance boost to be able to cover for added re usability rocket weight penalty.

Huh?  You are seeing things that are not there.

No, the cost of logistics out weighs the performance gains.
« Last Edit: 10/05/2011 04:36 PM by Jim »

Online Robotbeat

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Re: cheap reusable rockets?
« Reply #30 on: 10/05/2011 04:41 PM »
If you have to deliver stuff via helicopter, no way it's going to be cheap.

It's logistics, you guys... Remember, SpaceX recently essentially abandoned Kwaj, partly because of logistics reasons (partly because it is too small for anything much more than Falcon 1, for which there is only a small market).
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Offline ANTIcarrot

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Re: cheap reusable rockets?
« Reply #31 on: 10/06/2011 01:26 AM »
Errr... Could it be that you haven't understood the principal limitation of space elevators:
Could it be you've overlooked basic concepts of material science? Or maybe you skipped over parts of my post, and missed certain caveats? ::)

There is no scientific reason why we can't build a space elvator, and material limitations are usually temporary in the long term (sometimes very long term) so assuming that building a space elevator is possible at all...

Current semi-serious designs for space elevators envisage a very thin ribbon cable, which can only support a ton at most. Until additional climbers are sent up to thicken it, at which point it can support more weight. Taken to it's logical conclusion, a very thick cable with a CSA in the dozens of square meters (or more) could support hundreds or thousands of tons of cargo. Keep increasing the thickness and eventually you'll have a cable that can support a small fast car AND the weight of the magnets it needs to speed to orbit. This is why it's a trade off; and a pretty bad one at that.

Someone asked about maximum elevator speeds. Less than 200mph is true for wheel/friction near-term based designs. But it is not an absolute limit, as I explained. Rapid field switching is the next problem. Solve that litle nugget and you can use a slightly lighter car and get to GSO in ten hours or less at 0.1G all the way.

In summery: We can't build one today. We probably will be able to build one some day in the far future. Even though the early ones will be slow, we'll eventually be able to build a concorde equivolent if for some daft reason we wanted to. But baring a material breakthrough, for the next few decades, rockets will be the best way of getting into space.

Offline Epis

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Re: cheap reusable rockets?
« Reply #32 on: 10/06/2011 09:47 AM »
There is nothing that shows 50% improvement in that website. 
And you don't know what you are talking about.
Better performance does not mean cheaper launch
its not in that site, there could be find figures as high as <30% payload increase for concepts that are described there, but for Max TOp theoretical performance boost that could be possible at highest earth mountain top (like Everest 8820m ) 50% payload increase could be real, for proof lets take rocket equation where if we have LOX/RP-1 engine with 338s isp (3312.4m/s) and orbital LEO for 0m sea level will need 9756m/s then payload+rocket empty mass for SSTO would be 5.26%.
I predicted that 50% increas in payload could be possible so lets add 50% payload to 5.26% we get 7.89% and make backward calculation to get orbital speed that SSTO rocket could reach with previous engine and we get 8412.48m/s so if orbital speed is 7800m/s we have surplus of 612m/s for Gravity losses and Atmospheric drag. I think it will be enough because at such altitude there is 1/3 air pressure and it sharply drops (at 15km it is ~1/10) so air drag/pressure will be no problem, so high power engines could be used to fly with 3-4G acceleration that would mean large reduction in gravity losses .
1527m/s could be saved. of course that would be MAX available performance.
No, the cost of logistics out weighs the performance gains.
at current launch rates I agree there is no need for that, but if launch rates and demand increase to 1-2 launch per week then it will pay back fast, similar like airplanes fly each day and ticket prices are low, and plane/infrastructure cost is long term investments and more frequently it is used less it will cost.
I am not saying that now spaceX must go to >8km mountaintop  !, I say they would need to consider starting with 3.5-4km mountain tops or high altitude places preferably with all infrastructure already available like railway, roads,power lines.  and try to lower cost to 500$/kg to make at least 2 launches per month, with target 1 per week. and when market will develop they could plan for higher performance launch sites with more frequent launches as high as 1 per day.  that would be incremental development path and could take 10 years till next step.

speaking about helicopters then there are 9km altitude capable machines specially designed for Himalaya rescue   
here is pic
http://www.gizmag.com/go/6793/
that is not high payload capable but it shows that technology exist and it needs scaling up, and after 10-15+ years when there will be such need for extreme altitude mountain top Rocket launch such machines will already be developed.

See you don't know what you are talking about.  Your ideas are not viable or cheaper.  When will you learn that!!!
I think problem is time, these Ideas are >15-30 years in future, with clear development path which I try to show how rocket industry will get from now to future.
currently development path looks like this:
1. current rocket level. cost of launch 1000-3000$/kg
2. Reusable VTVL 2 stage rocket launched from 3.5-4km altitude. cost of launch 300-600$/kg  (LOX/RP-1) fuel
3. reusable  VTVL 1 or 2 stage rocket launched from 7-8km altitude cost of launch could be 100-250$/kg ( LOX/LH2 fuel )
4. Reusable SSTO rocket launched from Maglev- electric/chemical propulsion 5-6km long mountain (7-8km high) Slope  track at speeds Mach 2-3. launch cost 20-50$/kg.
5. Full Electrical Maglev Mach 8 vacuum tube track  15-20 km long on highest mountain TOp that is out there (>8Km exit altitude )  this in year 2150-2200  with launch rates as high as 2 in hour, for orbital civilization, and moon base+ mars base human transport cost to LEO is extremely low 7-10$/kg
at that final stage of development humans could start to think about building 100 year starship to make first mission to closest habitable exoplanet.
orbital elevator could be built starting at 4th stage, and it could decrease cost of 4 and 5th stage.

you can call this pure since fiction, speculation.

this list doesn't contain any plane style orbital vehicles, because they are not energy efficient, I think movies has created this type of imagination that future we will have orbital planes, or such style vehicles because they look cooler, has more style like virgin galactic SS2/WK2 but lows of physics say different thing, and path is going to mountain slope track style high energy efficient accelerators.
« Last Edit: 10/06/2011 09:48 AM by Epis »

Offline Kaputnik

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Re: cheap reusable rockets?
« Reply #33 on: 10/06/2011 10:40 AM »
On the subject of space elevators...

has any serious work gone into a *partial* elevator? i.e. one that does not go all the way to the ground. I'd envisage a landing/docking platform suspended from its tether just above the atmosphere; the speed over the ground would depend on how long you made the whole system and where its centre of mass was located. In operation, relatively low-tech single-stage RLVs would be able to boost up and rendezvous with the platform as it flew overhead. Payloads would be sent up the tether section and released into a higher orbit, having gained orbital velocity along the way.

Would such a thing be feasible with current technology?
Waiting for joy and raptor

Offline Jim

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Re: cheap reusable rockets?
« Reply #34 on: 10/06/2011 12:14 PM »

that is not high payload capable but it shows that technology exist and it needs scaling up,


Wrong.  Learn something instead of posting unrelated references from the internet.  Scaling up doesn't work for helicopters.   There is a limit on rotor tip speed and increasing rotor length "scaling up", quickly exceeds the limit.

Offline Jim

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Re: cheap reusable rockets?
« Reply #35 on: 10/06/2011 12:22 PM »

I think problem is time, these Ideas are >15-30 years in future, with clear development path which I try to show how rocket industry will get from now to future.
currently development path looks like this:
1. current rocket level. cost of launch 1000-3000$/kg
2. Reusable VTVL 2 stage rocket launched from 3.5-4km altitude. cost of launch 300-600$/kg  (LOX/RP-1) fuel
3. reusable  VTVL 1 or 2 stage rocket launched from 7-8km altitude cost of launch could be 100-250$/kg ( LOX/LH2 fuel )
4. Reusable SSTO rocket launched from Maglev- electric/chemical propulsion 5-6km long mountain (7-8km high) Slope  track at speeds Mach 2-3. launch cost 20-50$/kg.
5. Full Electrical Maglev Mach 8 vacuum tube track  15-20 km long on highest mountain TOp that is out there (>8Km exit altitude )  this in year 2150-2200  with launch rates as high as 2 in hour, for orbital civilization, and moon base+ mars base human transport cost to LEO is extremely low 7-10$/kg
at that final stage of development humans could start to think about building 100 year starship to make first mission to closest habitable exoplanet.
orbital elevator could be built starting at 4th stage, and it could decrease cost of 4 and 5th stage.


No, the problem is not time, these ideas not going to happen.  Your "path' will not be followed.  Each step is not viable nor worth the effort.  There won't be flight rates to support them. You have this crazy idea and wont let it go


Offline aquanaut99

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Re: cheap reusable rockets?
« Reply #36 on: 10/06/2011 12:28 PM »
Errr... Could it be that you haven't understood the principal limitation of space elevators: You have to find a material that is strong enough to be able to support it's own weight (and not a lot more beyond that) when you build a structure 36.000 km tall.

No. The principle limitation of a space elevator is that it won't survive. Even if some miracle material is found that could actually stand the tensile strength of being a 72'000 km long structure (not 36'000, since you have to build it twice as long so that the structure's center of gravity is in GSO), the cable will sooner or later be cut by the swirling cloud of debris (natual and man-made) circling Earth, especially in LEO. Also, after being severed, the falling half of that space elevator has the potential to cause immense (read: asteroid-strike-level) damage on Earth.

The space elevator concept will always remain science fiction.
« Last Edit: 10/06/2011 12:30 PM by aquanaut99 »

Offline pippin

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Re: cheap reusable rockets?
« Reply #37 on: 10/06/2011 01:17 PM »
No. The principle limitation of a space elevator is that it won't survive. Even if some miracle material is found that could actually stand the tensile strength of being a 72'000 km long structure (not 36'000, since you have to build it twice as long so that the structure's center of gravity is in GSO)
Well, no. You just need a sufficiently large counterweight just above GSO.

Of course, your point then still holds true, the elevator would still have to take that force and it's the same as for a 72'000 km structure.

That said, you can't build it straight up because of the different directions of the centripetal forces so you'll end up with something that is way longer than  72'000km AND has to have the counterweight.
And it has to be flexible because it will have to be able to move, quite a bit of wind, solar winds and magnetic forces out there. Which brings back my point about the excess weight you don't want to have.
Quote
The space elevator concept will always remain science fiction.
probably.

Offline RobLynn

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Re: cheap reusable rockets?
« Reply #38 on: 10/06/2011 01:20 PM »
I like high altitude (land based) launch, though most estimates I've seen put the payload gain at only about 10-15%.  The gains might be better for RLV vehicles with low payload fractions (like where SpaceX seems to be going).

There is no problem living and working at 4-5km altitude for people who are aclimatised (for most people takes a few days), and for short visits of a few hours it is not too much of a problem even if you are not aclimatised.  Close to the equator the temperature is not a problem either.

SpaceX Falcon9 charges about $50million for 10tonnes to LEO = $5000/kg.  Increasing that by 10% would be worth about $5million, which is probably far more than the marginal costs would be for mountain top launches.

Big problem is lack of suitable 4km+ mountains. Pikes Peak is too far north, Hawaii swarming with rich NIMBY environmentalists, Ecuador, Mexico, Chile and Kenya too unstable/unreliable and lacking infrastructure. 4.2km Mt Kinabalu on the equator in Malaysia close to major city could be good and I expect that China will eventually set up sites on the Tibetan Plateau.

Might be made easier using heavy duty radio mast - they apparently only cost about $500k per 100m (630m KVLY mast cost $500k in 1963), and might only cost a 1-200 million doallrs for a few km tall capable of supporting a large rocket.
I'm a "glass is twice as big as it needs to be" kinda guy

Offline aquanaut99

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Re: cheap reusable rockets?
« Reply #39 on: 10/06/2011 01:25 PM »
And it has to be flexible because it will have to be able to move, quite a bit of wind, solar winds and magnetic forces out there. Which brings back my point about the excess weight you don't want to have.

And it will still be cut by space debris, sooner or later...
« Last Edit: 10/06/2011 01:25 PM by aquanaut99 »

Offline pippin

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Re: cheap reusable rockets?
« Reply #40 on: 10/06/2011 01:40 PM »
And it has to be flexible because it will have to be able to move, quite a bit of wind, solar winds and magnetic forces out there. Which brings back my point about the excess weight you don't want to have.

And it will still be cut by space debris, sooner or later...
Well, if you can build a maglev around it the little excess weight for the strong laser cannons for the defense system can't be that much of an issue.  ;D

I wonder whether the power you can generate by moving the whole structure through the magnetosphere (relative to the sun) can contribute significantly to it's operation, otherwise it would be just too annoying to get rid of all the excess voltage...

Online Robotbeat

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Re: cheap reusable rockets?
« Reply #41 on: 10/06/2011 03:33 PM »
And it has to be flexible because it will have to be able to move, quite a bit of wind, solar winds and magnetic forces out there. Which brings back my point about the excess weight you don't want to have.

And it will still be cut by space debris, sooner or later...
And if it does, it'll float down relatively gently or burn up. It's a lightweight ribbon, after all.

You're ignoring several things. First of all, the timescale until being struck by debris matters quite a bit. If it's after 1 year (not at all likely), then the concept isn't viable. If it's 100 or 1000 years, then it is. Also, you can make the ribbon wide enough to survive strikes by small pieces of debris and able to dodge larger pieces. This may not be achieved in our lifetimes, but it's not as impossible as you make it seem.

That said, I don't think in the near-term it can be cheaper than RLVs can be near-term. Material science is not at the point where it's feasible (though I think that part will get there eventually... it's at least physically possible). Tethers make sense in other concepts. Mars, for instance, rotates just as fast as Earth but has much less gravity (making the material science case easier) and has big difficulties with EDL (which can also be solved by a tether). The concept has merit, even if not at Earth for 300 years (say).
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Offline pippin

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Re: cheap reusable rockets?
« Reply #42 on: 10/06/2011 03:47 PM »
And if it does, it'll float down relatively gently or burn up. It's a lightweight ribbon, after all.
Well, not with ANTIcarrot's few tons of maglev structure per meter of "ribbon"

Online Robotbeat

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Re: cheap reusable rockets?
« Reply #43 on: 10/06/2011 03:53 PM »
And if it does, it'll float down relatively gently or burn up. It's a lightweight ribbon, after all.
Well, not with ANTIcarrot's few tons of maglev structure per meter of "ribbon"
Okay, that's probably true.
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online douglas100

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Re: cheap reusable rockets?
« Reply #44 on: 10/06/2011 04:03 PM »
Just to add: if you're thousands of miles up the ribbon and it gets severed above you, your vehicle is certainly not going to float down. Hope you've got a heat shield, or you're toast. Above a certain height (16000 miles comes to mind, but probably wrong) you would end up in an elliptical orbit with a perigee above the atmosphere: not so bad, but not to be desired.

As far as magnetic fields are concerned, if the ribbon is a good conductor, you would have to take special care to ground it. Large currents could be induced in it by magnetic storms.

Like some other posters I don't see a system like this being developed near term. In principle it would work, given the right material, but in practice the investment would be very large for an uplift capacity that will not be needed for a long time.
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Offline aquanaut99

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Re: cheap reusable rockets?
« Reply #45 on: 10/06/2011 04:08 PM »
Just to be clear: With "space debris", I also mean every commercial, military and other satellite ever launched into LEO, active or not. Their paths will all eventually cross the elevator and crash into it, and in LEO they have the highest relative velocity to the elevator and therefore cause the most damage.

A space elevator should have been built pre-1957 if at all. Nowadays, it's impossible and it would also be a mortal threat to every commercial and military satellite up there.

Yet another reason why it will never be built even if the technical issues were solvable.

Online Robotbeat

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Re: cheap reusable rockets?
« Reply #46 on: 10/06/2011 04:41 PM »
Just to be clear: With "space debris", I also mean every commercial, military and other satellite ever launched into LEO, active or not. Their paths will all eventually cross the elevator and crash into it, and in LEO they have the highest relative velocity to the elevator and therefore cause the most damage.

A space elevator should have been built pre-1957 if at all. Nowadays, it's impossible and it would also be a mortal threat to every commercial and military satellite up there.

Yet another reason why it will never be built even if the technical issues were solvable.
That threat also applies to existing satellites running into each other.
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline kch

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Re: cheap reusable rockets?
« Reply #47 on: 10/06/2011 04:44 PM »

Yet another reason why it will never be built even if the technical issues were solvable.

"Never" is a long time -- could be as much as 100 trillion years, last I heard.  ;)

Offline Hop_David

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Re: cheap reusable rockets?
« Reply #48 on: 10/06/2011 05:00 PM »
Just to be clear: With "space debris", I also mean every commercial, military and other satellite ever launched into LEO, active or not. Their paths will all eventually cross the elevator and crash into it, and in LEO they have the highest relative velocity to the elevator and therefore cause the most damage.

A space elevator should have been built pre-1957 if at all. Nowadays, it's impossible and it would also be a mortal threat to every commercial and military satellite up there.

Yet another reason why it will never be built even if the technical issues were solvable.
That threat also applies to existing satellites running into each other.

Satellites have a much smaller cross sectional area than an elevator.

Also most of the debris in a satellite's orbit would be in roughly the same orbit, therefore the debris flux through the cross sectional area would be less. But with an elevator, relative velocity of debris will climb as the stalk becomes more distant from geosynch altitude.
« Last Edit: 10/06/2011 05:01 PM by Hop_David »

Offline Epis

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Re: cheap reusable rockets?
« Reply #49 on: 10/06/2011 08:02 PM »
I like high altitude (land based) launch, though most estimates I've seen put the payload gain at only about 10-15%.  The gains might be better for RLV vehicles with low payload fractions (like where SpaceX seems to be going).

There is no problem living and working at 4-5km altitude for people who are aclimatised (for most people takes a few days), and for short visits of a few hours it is not too much of a problem even if you are not aclimatised.  Close to the equator the temperature is not a problem either.

SpaceX Falcon9 charges about $50million for 10tonnes to LEO = $5000/kg.  Increasing that by 10% would be worth about $5million, which is probably far more than the marginal costs would be for mountain top launches.

Big problem is lack of suitable 4km+ mountains. Pikes Peak is too far north, Hawaii swarming with rich NIMBY environmentalists, Ecuador, Mexico, Chile and Kenya too unstable/unreliable and lacking infrastructure. 4.2km Mt Kinabalu on the equator in Malaysia close to major city could be good and I expect that China will eventually set up sites on the Tibetan Plateau.

Might be made easier using heavy duty radio mast - they apparently only cost about $500k per 100m (630m KVLY mast cost $500k in 1963), and might only cost a 1-200 million doallrs for a few km tall capable of supporting a large rocket.

there are 2 high altitude railway roads  that run at more than 4.5km altitudes and they are:
Quote
# Beijing-Lhasa Express, China, running at an altitude of 16,640 feet (5,072 meters) above sea level.
# Lima to Huancayo, through the Central Andes of Peru. It took nearly forty years to be completed, from 1870 to 1908.
The track's highest point is at La Galera, some 15,685 feet (4,781 meters) above sea level.
main argument was that extra payload boost by high altitude launch pad  close as possible to equator could compensate for extra weight penalty for each rocket stage re-usability fly back feature, that will need landing pads, extra return fuel, thermal protection, and etc.. that currently will cut payload weight making it less cost efficient and more hard to make such reusable fly back rocket stages.
Question is simple why complicate things?
here is Quote of recent Space X Elon Musk anouncment about reusable rocket.
Quote
"We have a design that on paper doing the calculations, doing the simulations it does work," Musk said. "Now we need to make sure those simulations and reality agree because generally, when they don't, reality wins."
so they don't know if it will work in reality, and why risk ?
if problem could be solved simply by going to high altitude launch site that will give missing performance, and they could build rocket with more rugged hardware instead of making it on the edge with low payload fraction.

and there is already example when rocket launch is taken to country far away like ESA went to French Guiana.

if high altitude close to equator launch pad could enable true 100+ times reusable/ fly back rocket design, then some one must do that, and in future someone will try that.

Offline Jim

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Re: cheap reusable rockets?
« Reply #50 on: 10/06/2011 08:36 PM »
1.  so they don't know if it will work in reality, and why risk ?

2.  if problem could be solved simply by going to high altitude launch site that will give missing performance, and they could build rocket with more rugged hardware instead of making it on the edge with low payload fraction.

3.  if high altitude close to equator launch pad could enable true 100+ times reusable/ fly back rocket design, then some one must do that, and in future someone will try that.

1.  Because the pay off is greater and rocket can be used in many more places.  That what will reduce costs.  Launching from a few isolated places for a little performance enhancement is not going to reduce costs.

2.  Because it isn't 'solved' and it isn't simple, you are trading one risk for another.  The high altitude has more risks and issues and cost.  The increase in performance is not offset buy the increase in logistics and infrastructure.

3. If, if, if, ends up being won't, won't, won't.  It won't enable and someone is not going to try it.  It will be the last place to enable an RLV.
The places that will enable RLV's are existing ones or ones that are easier to get to. 

Why do you keep this illogical line of thinking? 

Have you ever seen the process of preparing a launch vehicle or spacecraft for flight?  When you have done this then you can have some assertions about launch ops.
« Last Edit: 10/06/2011 08:39 PM by Jim »

Offline Jim

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Re: cheap reusable rockets?
« Reply #51 on: 10/06/2011 08:38 PM »

and there is already example when rocket launch is taken to country far away like ESA went to French Guiana.


It is not applicable to your argument.  It is on a sea coast and it is easily accessible.  And it has a large runway.  Hence, it is not far away

Offline Chris Bergin

Re: cheap reusable rockets?
« Reply #52 on: 10/06/2011 11:58 PM »
Strange thread. Seems to have nothing to do with the thread title for the most part. Locking.

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