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Aerospike engine to be tested at high altitude (Finally!)
The new start-up Arca Space Corporation will test this year for the very
first time, more than 50 years after the aerospike was developed, the high altitude performance of an aerospike on their liquid-fueled demonstrator for their planned SSTO: Flight of the Aerospike: Episode 1. https://www.youtube.com/watch?v=L1hnImvI2gw ARCA to perform historic space flight of aerospike engine. Published by Klaus Schmidt on Sat Jun 17, 2017 9:30 am Quote:
Rocket engine nozzles now are of a fixed bell shape. However, it is known a bell nozzle is most efficient at a certain altitude and less efficient at other altitudes. As an example, the SpaceX Merin engines for sea level use have an Isp of 312 s. But the Merlin Vacuum optimized for vacuum use given a much longer nozzle has a vacuum Isp of 348 s. Since all orbital rockets operate in stages, this lack of efficiency at varying altitudes was considered acceptable. But the SSTO concept (single-stage-to-orbit) would use a single engine all the way to orbit. So there were investigated methods such as the aerospike that could maintain high efficiency at all altitudes. However, it came to be believed that SSTO's were not feasible, either technically or economically. So little research went into the aerospike. This is extremely unfortunate. In fact, the aerospike can increase payload for all rockets including staged ones. If the aerospike or other altitude compensation had been used for existing rockets, it would have been observed that at the increased Isp, several *existing* first stages could be SSTO's. For instance, the famous Saturn 1C first stage of the of the Saturn V could be SSTO with altitude compensation to give it a max vacuum Isp of 360 s instead of its 304 s. As I said this increase in payload using the aerospike can be significant. I estimated it could be 25% for the Falcon 9. How much is the increase is dependent on the individual rocket. But for a solid rocket launch system I was investigating I found the aerospike doubled the payload to orbit! This is because solid rocket motors typically get about 285 s vacuum ISP. But using a rocket simulation program, I found the vacuum Isp could get as as high as 325 s and above. The required bell size though would be quite large, and would extend far outside the width of the rocket body, making it impractical. But the aerospike could do this without extending outside the rocket body's width. In short the reason why the aerospike hasn't been used for any rocket liquid or solid is because of the idea it is only useful for SSTO's and because of the idea that SSTO's aren't useful. Both of these ideas are incorrect. Bob Clark ---------------------------------------------------------------------------------------------------------------------------------- Finally, nanotechnology can now fulfill its potential to revolutionize 21st-century technology, from the space elevator, to private, orbital launchers, to 'flying cars'. This crowdfunding campaign is to prove it: Nanotech: from air to space. https://www.indiegogo.com/projects/n...ce/x/13319568/ ---------------------------------------------------------------------------------------------------------------------------------- |
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Aerospike engine to be tested at high altitude (Finally!)
JF Mezei wrote:
On 2017-06-21 09:58, Robert Clark wrote: The new start-up Arca Space Corporation will test this year for the very first time, more than 50 years after the aerospike was developed, the high Would an aerospike engine be inherently more complex/costly to build? or it is more or less a conventional engine with different engine bell? You've confused. An aerospike engine essentially doesn't have an engine bell. That's the point of the 'spike'. In the case of linear aerospike, is there a single combustion chamber with manifolds that direct thrust left/right (to provide steering), or is there a single turbopump but multiple combustion chambers with manifolds to direct fuel/oxidizer to the combustion chambers? No. And in terms of steering in the other axis, does the whole thing rotate? What 'other axis' are you referring to? Couldn't they make an engine bell in X shape at which point thrust could be vectors in both axis? I don't know what you're talking about now, but it's not an aerospike. In the case of a round aerospike, is it just the inner portion which moves to steer or does the whole kit move? If by 'round' you mean 'annular aerospike', you steer them by using one or more of the same techniques used to steer any other rocket. -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
#3
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Aerospike engine to be tested at high altitude (Finally!)
"Robert Clark" wrote in message news
================================================== ============== The new start-up Arca Space Corporation will test this year for the very first time, more than 50 years after the aerospike was developed, the high altitude performance of an aerospike on their liquid-fueled demonstrator for their planned SSTO: Flight of the Aerospike: Episode 1. https://www.youtube.com/watch?v=L1hnImvI2gw ARCA to perform historic space flight of aerospike engine. Published by Klaus Schmidt on Sat Jun 17, 2017 9:30 am Quote:
Rocket engine nozzles now are of a fixed bell shape. However, it is known a bell nozzle is most efficient at a certain altitude and less efficient at other altitudes. As an example, the SpaceX Merin engines for sea level use have an Isp of 312 s. But the Merlin Vacuum optimized for vacuum use given a much longer nozzle has a vacuum Isp of 348 s. Since all orbital rockets operate in stages, this lack of efficiency at varying altitudes was considered acceptable. But the SSTO concept (single-stage-to-orbit) would use a single engine all the way to orbit. So there were investigated methods such as the aerospike that could maintain high efficiency at all altitudes. However, it came to be believed that SSTO's were not feasible, either technically or economically. So little research went into the aerospike. This is extremely unfortunate. In fact, the aerospike can increase payload for all rockets including staged ones. If the aerospike or other altitude compensation had been used for existing rockets, it would have been observed that at the increased Isp, several *existing* first stages could be SSTO's. For instance, the famous Saturn 1C first stage of the of the Saturn V could be SSTO with altitude compensation to give it a max vacuum Isp of 360 s instead of its 304 s. As I said this increase in payload using the aerospike can be significant. I estimated it could be 25% for the Falcon 9. How much is the increase is dependent on the individual rocket. But for a solid rocket launch system I was investigating I found the aerospike doubled the payload to orbit! This is because solid rocket motors typically get about 285 s vacuum ISP. But using a rocket simulation program, I found the vacuum Isp could get as as high as 325 s and above. The required bell size though would be quite large, and would extend far outside the width of the rocket body, making it impractical. But the aerospike could do this without extending outside the rocket body's width. In short the reason why the aerospike hasn't been used for any rocket liquid or solid is because of the idea it is only useful for SSTO's and because of the idea that SSTO's aren't useful. Both of these ideas are incorrect. --- ================================================== ============= Flight of the Aerospike: Episode 2 - The Propellant Tank. https://www.youtube.com/watch?v=-lGJz1i7VxQ Very informative video. They mention in the video that the tank will be at 20 bar for their pressure-fed vehicles. This is fine their suborbital demonstrator, but will be problematical for their SSTO vehicle. The problem is a SSTO has to be highly weight optimized. A tank pressure of 20 bar is about 10 times higher than that for typical orbital rockets, commonly pump-fed. They expect to reduce tank weight by using composites, but this can cut the tank weight by only 1/2. Yet by having the pressure 10 times higher than normal for an orbital rocket, the result is still a tank 5 times heavier than for usual orbital rockets. Since an SSTO is already skating on the edge of what is feasible, this makes it even more difficult for their SSTO to succeed. Still, for this suborbital demonstrator it will be important to prove it can get the high vacuum Isp that theory suggests. I expect though when they move to the full orbital SSTO, they'll switch to pump-fed engines. Bob Clark ---------------------------------------------------------------------------------------------------------------------------------- Finally, nanotechnology can now fulfill its potential to revolutionize 21st-century technology, from the space elevator, to private, orbital launchers, to 'flying cars'. This crowdfunding campaign is to prove it: Nanotech: from air to space. https://www.indiegogo.com/projects/n...ce/x/13319568/ ---------------------------------------------------------------------------------------------------------------------------------- |
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