Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 420810 times)

Offline adrianwyard

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #300 on: 05/24/2015 07:44 PM »
There are a number of new things that need to be developed. These include
...
6. super lightweight tanks that are 1% of the mass of the propellant.
...

I don't believe I've seen this 1% tank mass requirement before. Can you point us to a source? (Or is this your own assessment?)

Offline Seer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #301 on: 05/24/2015 10:25 PM »
If you search for "skylon hotol" then go the top link on the second page of results. The tank is a balloon tank so that helps, but the hydrogen fraction is twice that of a normal vehicle and the tanks are split into two sets of tanks, which is more inefficient.

Offline adrianwyard

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #302 on: 05/25/2015 12:19 AM »
Those search terms revealed a number of interesting links (including videos of the Kerbal Space Program Skylon model that I'd not seen before) but not tank specs.

url?

Offline Seer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #303 on: 05/25/2015 12:50 AM »

Online hkultala

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #304 on: 05/25/2015 01:20 AM »
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.

Offline adrianwyard

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #305 on: 05/25/2015 01:34 AM »
I think we're all referring to the mass budget for the C1 design on pages 32-33? That shows 2,736kg budgeted for “main tankage, cryo Insulation & supports” to carry 216,630kg of propellant.

2.7 metric tonnes for tanks does sound light, but as hkultula points out more mass for the tank can be bought from elsewhere. Also, the C1 design/budget is at least one generation out of date (two if D1 is taken forward). The optimists among us will guess that later designs have wider margins.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #306 on: 05/25/2015 02:49 AM »
Those search terms revealed a number of interesting links (including videos of the Kerbal Space Program Skylon model that I'd not seen before) but not tank specs.

url?
For those interested in tank design John Whiteheads paper makes very interesting reading.
http://www.osti.gov/scitech/servlets/purl/379977

Whitehead's team developed the first positive displacement pumps for what people now call micro launchers. Whitehead was (is?) looking at what it takes to build an SSTO 2 people could carry in the back of a pickup truck.

They note that "1%" tanks IE tank mass 1% of contents are possible over several orders of magnitude. LH2 is the exception but that's reduced to maybe 3% of contents mass. Tankage on LH2 vehicles is always highly deceptive. Those little red tanks on Skylon are much heavier than the huge LH2 tanks that fill most of the fuselage.

"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 john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #307 on: 05/25/2015 02:55 AM »
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.
Doubtful. That rule applies when the tanks of the LV are virtually all of the dry mass (which for ELV stages they often are)

But for Skylon you'd need to figure that as a % of the dry mass, which IIRC is something like 46 tonnes, so it's 48/46 tonnes, IE about a 4% payload hit.

Tank mass is just a much smaller fraction of dry mass in Skylon than normal ELV's.
"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 Seer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #308 on: 05/25/2015 03:24 AM »
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.


It is 1.27% but I rounded down because there are two sets of tanks, so its as difficult as 1%. The problem with saying only a 2.7 tonne hit to payload is that all the mass margins look light. The tanks are just the most blatant. What if the structure, TPS, secondary systems, engines etc are too?

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #309 on: 05/25/2015 04:00 AM »
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.

It is 1.27% but I rounded down because there are two sets of tanks, so its as difficult as 1%. The problem with saying only a 2.7 tonne hit to payload is that all the mass margins look light. The tanks are just the most blatant. What if the structure, TPS, secondary systems, engines etc are too?
It's been a while since it was mentioned but Skylon is designed to AIAA guidelines with a 15% margin for hardware weight growth overall. However some of those will be tighter as there is quite a lot of data on horizontal cryogenic tanks for road and rail tankers. [EDIT Likewise large parts of the turbo machinery are well understood, so the margins for their design are narrower than they would have been say 40 or even 20 years ago. The less well understood sections have wider margins. ]
« Last Edit: 05/25/2015 04:11 AM by john smith 19 »
"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 Seer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #310 on: 05/25/2015 04:02 AM »
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.

It is 1.27% but I rounded down because there are two sets of tanks, so its as difficult as 1%. The problem with saying only a 2.7 tonne hit to payload is that all the mass margins look light. The tanks are just the most blatant. What if the structure, TPS, secondary systems, engines etc are too?
It's been a while since it was mentioned but Skylon is designed to AIAA guidelines with a 15% margin for hardware weight growth. However some of those will be tighter as there is quite a lot of data on horizontal cryogenic tanks for road and rail tankers.

road and rail tankers? Seriously?

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #311 on: 05/25/2015 09:29 AM »
It's been a while since it was mentioned but Skylon is designed to AIAA guidelines with a 15% margin for hardware weight growth overall.

You sure?  I know C1's truss structure had a 15% margin, and I know D1 was said to be designed with margins "consistent with" AIAA guidelines which implies at least 15% and probably more for the stage I tentatively judged the design to be at when I last attempted to figure this out, but I'm not aware of a concrete official number for the overall mass margin.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #312 on: 05/25/2015 09:42 AM »
There are a number of new things that need to be developed. These include
Drawing from various REL presentations I'll mention when REL looked at a particular area.
Quote
1. The transitioning inlet
Ongoing since 2012. Inlets with moving centre bodies have been around since the late 50's.
Quote
2. lox cooled chamber
2010. Also the use of air cooling for the cooling while the vehicle is air breathing.
Quote
3. heat exchangers, both the primary one and the high temperature silicon carbide one.
Under study since 2002.
Quote
4. active thermal protections systems on the canards and winds and perhaps the inlet.
Not mentioned. However transpiration cooled rentry vehicles have flown in flight tests in the late 1970's and reports are available in the open literature.
Quote
5. an aerodynamic configuration that can fly at hypersonic speeds (mach 5), re-entry and low landing speeds.
Under development since the late 80's. Making  your fuselage circular, contouring it front to back for low supersonic drag and sticking the major point masses in the middle makes life a lot easier right from the first moment. Although cross range was not (AFAIK) a design driver it's given got most (if not all) of the Shuttles target (but never achieved) cross range.
Quote
6. super lightweight tanks that are 1% of the mass of the propellant.
Outside of LH2 a tank weighing 1% of its payload is not that difficult in the aerospace field.
Quote
Having a high number of active systems increases the probability that one of them will fail during flight and also increases the maintenance and inspection burden between flights.
Which logically makes the Wright Flyer the safest aircraft every built, as there's so little to wrong, right?  :)
Or maybe not.

You might like to look out the window at the leading edge of an airliner when it lands or takes off.

There's a lot of "active systems" in play during that period, and  if any of them move in the wrong way (or fail to move at all) you're going to have a  very bad day.

And yet every day millions of passengers risk their lives to those active systems without thinking about it.
"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 pmcaerospacefreighter

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #313 on: 05/25/2015 04:31 PM »

The pre cooler at the front of the engine decouples the air temperature (cryogenic) and velocity (about M0.5) from the ambient environment (up to 1000c and M5.5)


So what you are telling me is that the first Skylon prototype will take off from a runway and proceed onto test flights at regimes that progressively get closer and closer to space flight?
i would love to see that happen.  But it sounds like a great risk to test the whole airframe-engine combination over such large range of regimes, when we are not talking about a relatively simple rocket but a RBCC or whatever they're using.

Online hkultala

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #314 on: 05/25/2015 08:21 PM »
Its a pdf, does this work? https://www.aiaa.org/WorkArea/DownloadAsset.aspx?id=14414

it's 1.27%.

And it's not a hard requirement, doubling the tank mass would hurt payload to LEO by only 2.7 tonnes.
Doubtful. That rule applies when the tanks of the LV are virtually all of the dry mass (which for ELV stages they often are)

But for Skylon you'd need to figure that as a % of the dry mass, which IIRC is something like 46 tonnes, so it's 48/46 tonnes, IE about a 4% payload hit.

Tank mass is just a much smaller fraction of dry mass in Skylon than normal ELV's.

What rule are you talking about?

What goes to orbit is (dry mass + payload).

If either grows, another must shrink. By same absolute amount, not any percentage.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #315 on: 05/25/2015 08:40 PM »
road and rail tankers? Seriously?
One of the hallmarks of solid engineering is a focus on using advanced technology only where necessary.  A similar example would have been the pilots position for the SR71.  The vehicle set the standard for materials, engine cycles and sensors for at least a decade yet the core flying and engine controls were, AFAP, those of a standard twin jet aircraft of the time.

Despite 20+ years of work composite LH2 tanks still seem to have significant leakage levels.

If you don't need them, why use them?
"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 Soundbite

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #316 on: 05/26/2015 02:36 PM »
Hi All,

I dont' know if anyone noticed the patents that Reaction Engines has filed on 1 December 2014.  There are two that I can see but I haven't searched for anymore

They are found on page https://www.ipo.gov.uk/p-gcp?lastResult=40&perPage=10&filter=&sort=GCP+Request+Date

The Details are found here https://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318111.0 and here ://www.ipo.gov.uk/p-ipsum/Case/ApplicationNumber/GB1318108.6 and then by clicking on the "Documents" link on the right hand side of these pages in the Window titled Select case view

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Offline Citizen Wolf

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #318 on: 05/26/2015 07:42 PM »
That's interesting news regarding the patents. I thought I heard somewhere that REL didn't want to patent the tech because they didn't want the information in the public domain. Is that memory of mine mistaken?
The only thing I can be sure of is that I can't be sure of anything.

Online momerathe

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #319 on: 05/26/2015 08:14 PM »
I haven't gone over them in detail (patent-ese makes my eyes bleed), but one thing jumped out at me - there are two separate patents for two different engine configurations, and one of the says:

Quote
A rocket engine is provided. The engine comprises: a rocket combustion chamber [...] and and air-breathing combustion chamber [...]. [They] are configured to be operated indepedently

That's new, isn't it? judging from the diagrams, they're concentric, sharing the same nozzle. Poss connected to the Valkyrie work?

There also seems to be some changes to the cooling loops in this version from the diagrams we've seen before, but I haven't puzzled out what the practical difference is.
thermodynamics will get you in the end

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