Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 421853 times)

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1100 on: 12/18/2015 12:01 PM »


AFAIK there are no stats for damage to satellites on the Shuttle. It never happened.

No stats are required for shuttle.  The payloads were just required to survive an abort landing.  The capability to be operable after an abort landing is s different story.

Offline Space OurSoul

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1101 on: 12/18/2015 10:34 PM »
It is designed to cruise (at Mach 3) on bypass ram engines alone, enabling intact abort to a wide range of destinations late in the launch phase even with both sets of rockets out of action.

Well I have been interested in Skylon for a long time and never come across that gem of info before. That's quite something. With all main engines out it can still propel itself with the bypass ramjets? Is this a fact?

Well, I suppose there is some inference on my part that might not be warranted. There's a comment from an REL person in one of the videos where it's mentioned that it's expected to sustain Mach 3 "on the bypass burners alone", but granted that could very well mean merely that the burners produce enough thrust to do so, rather than meaning that it's a fully-supported mode of operation.


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Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1102 on: 12/19/2015 02:03 AM »
I believe that's part of the abort procedure for a failure early in rocket mode.

Offline Robotbeat

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1103 on: 12/19/2015 02:22 AM »
Uh, how far would it hobble Skylon operators to ban traditional toxic hypergols in payloads? Considering all the moves to electric thrusters as it is, what specific scenarios end up essentially needing hypergolic propellants? The missions that come to mind is any kind of short, high thrust scenario where a solid kick stage is undesirable, so some manned systems perhaps?
Almost every single spacecraft uses hypergols. Crewed, uncrewed, science, military, commercial, etc. All pretty much use hypergols (except a handful of special design).
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Offline Patchouli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1104 on: 12/19/2015 04:27 AM »

Well I have been interested in Skylon for a long time and never come across that gem of info before. That's quite something. With all main engines out it can still propel itself with the bypass ramjets? Is this a fact?

Well, I suppose there is some inference on my part that might not be warranted. There's a comment from an REL person in one of the videos where it's mentioned that it's expected to sustain Mach 3 "on the bypass burners alone", but granted that could very well mean merely that the burners produce enough thrust to do so, rather than meaning that it's a fully-supported mode of operation.



[/quote]

Seems it's abort modes are a lot better then a VTOL rocket.
Such as being able to handle a rejected take off after roll and even make it to a landing site with half it's engines inoperative.
http://www.reactionengines.co.uk/tech_docs/JBIS_v57_22-32.pdf

Makes sense loose half your thrust on a conventional LV it's coming back down but since Skylon operates as an aircraft during the first part of it's flight an engine failure should be similar to other fixed wing aircraft.
« Last Edit: 12/19/2015 04:32 AM by Patchouli »

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1105 on: 12/23/2015 06:55 AM »


AFAIK there are no stats for damage to satellites on the Shuttle. It never happened.

No stats are required for shuttle.  The payloads were just required to survive an abort landing.  The capability to be operable after an abort landing is s different story.
IIRC the 4 satellites of the Cluster mission that flew on the first Ariane 5 were re flown after recovery from the Guyianan jungle.

I would expect most Skylon failure modes to be more benign (in terms of acceleration and heating) than a 1st stage engine explosion and subsequent ELV RUD.
"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.

Offline Archibald

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1106 on: 12/24/2015 09:47 AM »
I don't think so. Do you have a source for that claim ? I think they were completely destroyed and new spacecrafts had to be build. 

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1107 on: 12/24/2015 04:21 PM »
1.  IIRC the 4 satellites of the Cluster mission that flew on the first Ariane 5 were re flown after recovery from the Guyianan jungle.

2. I would expect most Skylon failure modes to be more benign (in terms of acceleration and heating) than a 1st stage engine explosion and subsequent ELV RUD.

1.  Nonsense. 

2.  Meaningless comparison, because the payload in both cases is unusable.

There is a major difference in design for surviving an abort landing vs being a 100% capable of use after one.


Offline Alpha_Centauri

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1108 on: 12/24/2015 05:18 PM »
I don't think so. Do you have a source for that claim ? I think they were completely destroyed and new spacecrafts had to be build. 
Yes new spacecraft were built; IIRC at least one was made using spare parts from the first mission which is perhaps the source of confusion.
« Last Edit: 12/24/2015 05:19 PM by Alpha_Centauri »

Offline Vultur

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1109 on: 12/24/2015 06:08 PM »
Uh, how far would it hobble Skylon operators to ban traditional toxic hypergols in payloads? Considering all the moves to electric thrusters as it is, what specific scenarios end up essentially needing hypergolic propellants? The missions that come to mind is any kind of short, high thrust scenario where a solid kick stage is undesirable, so some manned systems perhaps?

There isn't "all the moves", it has only been GEO comsats that have done it.  The issue is for attitude control and not orbit changing.  Most spacecraft need thrusters with more power than electric ones.

Yeah. You'd have to talk spacecraft manufacturers into using less toxic propellants like hydrogen peroxide/something, hydrogen peroxide and the new "green" monoprops instead of hydrazine family/N2O4 and hydrazine.

Offline Vultur

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1110 on: 12/24/2015 06:15 PM »
They compute only a one-off count, not a recylce of the acquisition each 10 launches. Basically, it is like buying one skylon and using it 200 times, or buying a falcon 9 and using it 200 times. which is wrong.

Where does the assumption that a F9 first stage will only have a life of 10 flights come from? Is this a SpaceX number?

Offline Elmar Moelzer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1111 on: 12/24/2015 10:57 PM »
They compute only a one-off count, not a recylce of the acquisition each 10 launches. Basically, it is like buying one skylon and using it 200 times, or buying a falcon 9 and using it 200 times. which is wrong.

Where does the assumption that a F9 first stage will only have a life of 10 flights come from? Is this a SpaceX number?
Indeed, last I heard Elon Musk was optimistic that a booster could be launched 20 times before major refurbishment would be necessary (like taking the stage apart and cleaning and checking every piece of it). I do not remember anything about 10 being the limit (even with refurbishment).

Offline Dalhousie

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1112 on: 12/25/2015 12:07 AM »
They compute only a one-off count, not a recylce of the acquisition each 10 launches. Basically, it is like buying one skylon and using it 200 times, or buying a falcon 9 and using it 200 times. which is wrong.

Where does the assumption that a F9 first stage will only have a life of 10 flights come from? Is this a SpaceX number?
Indeed, last I heard Elon Musk was optimistic that a booster could be launched 20 times before major refurbishment would be necessary (like taking the stage apart and cleaning and checking every piece of it). I do not remember anything about 10 being the limit (even with refurbishment).

Probably his usual excessive optimism.
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Offline Robotbeat

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1113 on: 12/25/2015 12:14 AM »
Probably there is no hard limit to what could be done.
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Offline Elmar Moelzer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1114 on: 12/25/2015 03:13 AM »
Indeed, last I heard Elon Musk was optimistic that a booster could be launched 20 times before major refurbishment would be necessary (like taking the stage apart and cleaning and checking every piece of it). I do not remember anything about 10 being the limit (even with refurbishment).
Probably his usual excessive optimism.
Well, so far he has done everything he claimed he would do... taking a bit longer than anticipated but he did it.
Also I am sure that this estimate is based on their experiences gained during their engine test program and the grasshopper tests. So if he is not the one who is in the position to make a prediction about this, who is?

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1115 on: 12/25/2015 08:47 PM »
I don't think so. Do you have a source for that claim ? I think they were completely destroyed and new spacecrafts had to be build. 
Yes new spacecraft were built; IIRC at least one was made using spare parts from the first mission which is perhaps the source of confusion.
I re-checked the history and indeed they did build a new group launched on a pair of Soyuz.

I had equated recovery with reuse. My mistake.
Yeah. You'd have to talk spacecraft manufacturers into using less toxic propellants like hydrogen peroxide/something, hydrogen peroxide and the new "green" monoprops instead of hydrazine family/N2O4 and hydrazine.
The question is how big a threat of leakage does a satellite pose if adequately sealed and how do other operators deal with these problem?
Probably there is no hard limit to what could be done.
Probably not, however there is likely a number of cycles where the probability of failure rises substantially, effectively the tail end of the "bathtub" reliability curve.

An interesting question would be if this remains the same regardless of payload size and wheather they are GSO or LEO missions.

Only time will tell what those numbers are will but they will have a major effect on how cost effective reuse can be for F9SR.
Well, so far he has done everything he claimed he would do... taking a bit longer than anticipated but he did it.
Not quite. He's eventually found a way to do most of what he's talked about. The original airbags + parachutes plan was abandoned. Upper stage reuse of the F9 (and FH) has also been abandoned.

While this is very pragmatic approach (something is better than nothing) the problem it demonstrates no clear path to the ultimate goal, or even that there is a clear path to it.
Quote
Also I am sure that this estimate is based on their experiences gained during their engine test program and the grasshopper tests. So if he is not the one who is in the position to make a prediction about this, who is?
While SX obviously has the best available data for their stage reuse Grasshopper had a key goal of working out how to land in the first place. It's structure and flight trajectories were so different there is little to connect the two vehicles.

10 or 20 is an informed guess.

When a 1st stage  flies that number of launches then they will be on much firmer ground.

Now could we return to discussing REL, SABRE and Skylon?
"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.

Offline Vultur

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1116 on: 12/26/2015 01:39 AM »
Upper stage reuse of the F9 (and FH) has also been abandoned.

It was abandoned at one time, but there was IIRC a more recent comment (in one of the news articles on this site, IIRC) that that might no longer be the case in view of the satellite constellation.

(Musk said that it didn't make sense before because of the low Isp of kerolox and most payloads want GTO. But with a lot of LEO demand...)

Offline pippin

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1117 on: 12/26/2015 02:16 AM »
THIS THREAD IS NOT ABOUT SPACEx!

Offline Vultur

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1118 on: 12/26/2015 02:24 AM »
True, but the question of Skylon's ability to attract enough investment to be built, and profitability if it is built and works, is strongly affected by what other reusable launch vehicles/systems are around.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1119 on: 12/26/2015 05:59 AM »
True, but the question of Skylon's ability to attract enough investment to be built, and profitability if it is built and works, is strongly affected by what other reusable launch vehicles/systems are around.
Current answer. None.

Future answer. None.

SX have a superb PR machine but for most normal people "reusable" means fully reusable.

Getting a first stage of a 2 stage vehicle down is an amazing achievement, but (provided it can be re-flown) it's still half of a reusable rocket.

Changing the definition of a word to have a more limited meaning borrows from another Silicon Valley company, Microsoft. 

Do you want to view SX as the new Microsoft?  :(

Now can we return to a positive discussion of REL?
"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.

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