Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 421922 times)

Offline Elmar Moelzer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1520 on: 05/14/2016 03:46 PM »
The Shuttle had growth problems throughout its development, wasn't it originally supposed to get 29.5 tons into LEO, but couldn't in practice?
The Shuttle is a special case to me and also only ONE example for this. You said "often". One is not "often".
If I was to take one, then I could use Falcon 9 which is now way beyond the original designs capabilities.

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1521 on: 05/14/2016 04:48 PM »
The Shuttle had growth problems throughout its development, wasn't it originally supposed to get 29.5 tons into LEO, but couldn't in practice?
The Shuttle is a special case to me and also only ONE example for this. You said "often". One is not "often".
If I was to take one, then I could use Falcon 9 which is now way beyond the original designs capabilities.

A.  It applies to all rockets, not just shuttle, most fail to meet original specs.   And it applies Falcon 9 too

b.  There were upgrades left on the table to help the shuttle meet original requirements. 

c.  All vehicles have gone through upgrades.  Nothing new about that.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1522 on: 05/14/2016 05:12 PM »
I am aware I was extremely conservative. However, consider that prices were expressed in 2008 values, so inflation also is to be taken into account. Still, the numbers are higher than their own estimates precisely because I wanted to test whether the model is sustainable even in case of substantial costs overshots.
I see.
Quote
the verdict is that yes, it looks sustainable, as long as operators mantain an high price (spaceX 1R levels). If prices go substantially below, then each Skylon will need to launch much more frequently . The bottom price any commercial Skylon operator looks to be a price of 16M/flight, at the conditions they manage to fly it at least 7 times per year (for 30 years). this is the minimal condition to operate without losses. below that, the company is in red.
Ideally, if a Skylon operator would charge 25M/flight and fly 10 times per year, it would completely repay the investment in about 8-9 years, leaving  more than the half of the vehicle capaity for pure profit.
in that case, total expected revenue is about 5Bn in 18 years.
My cost modelling game reckons the with enough launches the customer price for an F9SR will converge to the replacement cost of the upper stage, the refurb costs and the profit SX charge.

Currently Shotwell reckons $3m in all in will cover refurb and the upper stage is somewhere around $17m. With a 20% gross profit margin that gives a price of $27m/launch.

SX will say that FH will be cheaper on a $/Kg basis and (in principal) have all lower stages fully recoverable, but the mission cost goes up a lot.

The interesting thing about a state buying a Skylon is that while it won't have the launch site restrictions of a 2000 Km missile range to drop stages over it will have exactly the same political restrictions. In that those payloads funded by governments or government controlled institutions will not be allowed to launch from certain countries and vice versa.

However Skylon is the only architecture that lets each state do that and still give the supplier a profit.

Of course if that state were someone like New Zealand I could imagine quite a lot of people would be happy to have their payload launched by "NZ Space."  :)
"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 Elmar Moelzer

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1523 on: 05/14/2016 06:40 PM »
The Shuttle had growth problems throughout its development, wasn't it originally supposed to get 29.5 tons into LEO, but couldn't in practice?
The Shuttle is a special case to me and also only ONE example for this. You said "often". One is not "often".
If I was to take one, then I could use Falcon 9 which is now way beyond the original designs capabilities.

A.  It applies to all rockets, not just shuttle, most fail to meet original specs.   And it applies Falcon 9 too

b.  There were upgrades left on the table to help the shuttle meet original requirements. 

c.  All vehicles have gone through upgrades.  Nothing new about that.
Falcon 9 exceeded the original specs, from all we know. No one said that vehicles don't go through upgrades. Upgrades are fine. My point was that the OP said that rockets often don't meet their design capabilities. My point was that while it might happen, it is not often. They get there, at least after upgrades.

Offline Alf Fass

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1524 on: 05/14/2016 10:51 PM »
The statistics I quoted 5 years ago are different to those I'm seeing today, most notably engine thrust, my original post had it at 270 "tons" thrust at a T/W of 14, wiki now has 2000 kN per engine, still at T/W of "up to 14"

That difference would mean an increase in engine weight from 19 tons to over 28 tons, empty weight is still given as 53.4 tons, so that shrinks non engine empty weight from 34 to 25 tons.

Maybe I've misinterpreted something, or maybe wiki's got it wrong, or maybe those growth problems are happening for Skylon.
« Last Edit: 05/14/2016 10:53 PM by Alf Fass »
When my information changes, I alter my conclusions. What do you do, sir?
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Offline Alf Fass

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1525 on: 05/14/2016 11:14 PM »
. . . They get there, at least after upgrades.

Or they don't and are abandoned.


When my information changes, I alter my conclusions. What do you do, sir?
John Maynard Keynes

Offline Star One

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1526 on: 05/15/2016 08:38 AM »
The statistics I quoted 5 years ago are different to those I'm seeing today, most notably engine thrust, my original post had it at 270 "tons" thrust at a T/W of 14, wiki now has 2000 kN per engine, still at T/W of "up to 14"

That difference would mean an increase in engine weight from 19 tons to over 28 tons, empty weight is still given as 53.4 tons, so that shrinks non engine empty weight from 34 to 25 tons.

Maybe I've misinterpreted something, or maybe wiki's got it wrong, or maybe those growth problems are happening for Skylon.

You're using wiki as a source for something like this.....

Offline Alf Fass

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1527 on: 05/15/2016 09:19 AM »
The statistics I quoted 5 years ago are different to those I'm seeing today, most notably engine thrust, my original post had it at 270 "tons" thrust at a T/W of 14, wiki now has 2000 kN per engine, still at T/W of "up to 14"

That difference would mean an increase in engine weight from 19 tons to over 28 tons, empty weight is still given as 53.4 tons, so that shrinks non engine empty weight from 34 to 25 tons.

Maybe I've misinterpreted something, or maybe wiki's got it wrong, or maybe those growth problems are happening for Skylon.

You're using wiki as a source for something like this.....

The Reaction Engines site seems to have a lot less details about Skylon and Sabre on it these days, I can confirm that as of May 2014 the Skylon dry mass and engine thrust are as Wiki states, the T/W for the engines isn't stated on the RE document I'm looking at, but hey, maybe they're working on it going up from 14 to 20, that would keep the engine weight under control  ::) .

http://www.reactionengines.co.uk/tech_docs/SKYLON_Users_Manual_Rev_2.1.pdf
« Last Edit: 05/15/2016 09:20 AM by Alf Fass »
When my information changes, I alter my conclusions. What do you do, sir?
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Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1528 on: 05/15/2016 10:14 AM »
The statistics I quoted 5 years ago are different to those I'm seeing today, most notably engine thrust, my original post had it at 270 "tons" thrust at a T/W of 14, wiki now has 2000 kN per engine, still at T/W of "up to 14"

That difference would mean an increase in engine weight from 19 tons to over 28 tons, empty weight is still given as 53.4 tons, so that shrinks non engine empty weight from 34 to 25 tons.

Maybe I've misinterpreted something, or maybe wiki's got it wrong, or maybe those growth problems are happening for Skylon.
Or we could use the figures from V 2.0 of the Skylon Users Manual figures.

That has a GTOW of 325 Tonnes  with air breathing minimum thrust of 163 tonnes up to 407 tonnes and a rocket thrust of 407 tonnes.

Given this is a HTO vehicle thrust does not have to exceed mass. Typically GTOW for aircraft is 3x thrust. For Skylon it's about 2x thrust, given a substantially faster acceleration profile. 
"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 Alf Fass

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1529 on: 05/15/2016 10:28 AM »
The statistics I quoted 5 years ago are different to those I'm seeing today, most notably engine thrust, my original post had it at 270 "tons" thrust at a T/W of 14, wiki now has 2000 kN per engine, still at T/W of "up to 14"

That difference would mean an increase in engine weight from 19 tons to over 28 tons, empty weight is still given as 53.4 tons, so that shrinks non engine empty weight from 34 to 25 tons.

Maybe I've misinterpreted something, or maybe wiki's got it wrong, or maybe those growth problems are happening for Skylon.
Or we could use the figures from V 2.0 of the Skylon Users Manual figures.

That has a GTOW of 325 Tonnes  with air breathing minimum thrust of 163 tonnes up to 407 tonnes and a rocket thrust of 407 tonnes.

Given this is a HTO vehicle thrust does not have to exceed mass. Typically GTOW for aircraft is 3x thrust. For Skylon it's about 2x thrust, given a substantially faster acceleration profile.

Umm, yeah, it's TO speed is around 500 km/hr!
The figures you quote offer no explanation as to how TO weight can increase by 50 tons, engine thrust can increase by 48% and yet dry mass remains the same as it was in the earlier C1 version.
When my information changes, I alter my conclusions. What do you do, sir?
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Offline Alf Fass

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1530 on: 05/15/2016 10:33 AM »
wiki now has 2000 kN per engine, still at T/W of "up to 14"


Maybe I've misinterpreted something, or maybe wiki's got it wrong, or maybe those growth problems are happening for Skylon.
I take it you failed to notice the "citation needed" note on the 14:1 statement in wikipedia's Skylon article?

Why would they not have a citation? Is it perhaps because with RE failing to provide a T/W ratio for the engines they've done the sensible thing and had to assume its the same as for the previous engine?

If you think that an air breathing engine as complex as Sabre is can have a thrust ratio as high as 20/1, which would be far higher than any turbojet, well . . .
« Last Edit: 05/15/2016 11:02 AM by Alf Fass »
When my information changes, I alter my conclusions. What do you do, sir?
John Maynard Keynes

Offline lkm

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1531 on: 05/15/2016 01:12 PM »
Sabre 3 engine mass was 10870 kg for both engines, Sabre 4 isn't necessarily a heavier engine as it losses the frost control mass.
SABRE T/W is up to 14 over the air breathing mode as it varies with velocity and altitude, peeking around Mach 2. SABRE rocket mode is substantially higher thrust with a T/W of 28.
That's my understanding from the information we have available to us.


Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1532 on: 05/15/2016 05:08 PM »
I take it you failed to notice the "citation needed" note on the 14:1 statement in wikipedia's Skylon article?

Why would they not have a citation? Is it perhaps because with RE failing to provide a T/W ratio for the engines they've done the sensible thing and had to assume its the same as for the previous engine?

If you think that an air breathing engine as complex as Sabre is can have a thrust ratio as high as 20/1, which would be far higher than any turbojet, well . . .
Firstly AFAIK it doesn't need to be better than 14:1 to do the job. I don't think anyone has suggested 20:1 is needed.

Is this another of your "Well I don't know any better, but I'm sure it can't be possible" views then?

As it happens experimental turbojet lift engines in the 1960's for some VTOL designs had T:W ratios of 16:1. They had short continuous operating lives but they were expected to only be operating in horizontal to vertical flight transition, a period of minutes with plenty of recovery time during flight.

The ones I'm aware of were designed by Rolls Royce.

There's the common state of practice, the state of the art and the theoretical maximum based on physics and thermochemistry.

The 3 are very rarely close to each other.
"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 Alf Fass

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1533 on: 05/15/2016 06:49 PM »
Sabre 3 engine mass was 10870 kg for both engines, Sabre 4 isn't necessarily a heavier engine as it losses the frost control mass.
SABRE T/W is up to 14 over the air breathing mode as it varies with velocity and altitude, peeking around Mach 2. SABRE rocket mode is substantially higher thrust with a T/W of 28.
That's my understanding from the information we have available to us.

Thanks, that makes more sense.
When my information changes, I alter my conclusions. What do you do, sir?
John Maynard Keynes

Offline lkm

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1534 on: 05/15/2016 11:44 PM »

SABRE T/W is up to 14 over the air breathing mode as it varies with velocity and altitude, peeking around Mach 2. SABRE rocket mode is substantially higher thrust with a T/W of 28.
That's my understanding from the information we have available to us.
Which SABRE? do you have a source?
Skylon user Manual 2.1 shows 2MN peak thrust for air breathing and 2MN thrust for rocket.




The manual is stating gross thrust but I was quoting net T/W which explains the difference. During rocket mode the net thrust is much higher as atmospheric drag is removed. I should have been clearer.

Just to correct myself, I stated the wrong rocket mode, a T/W of 28 is what SABRE 3 seems to have but SABRE 4 looks like it reaches a T/W of 35 during rocket mode.
« Last Edit: 05/15/2016 11:56 PM by lkm »

Offline francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1535 on: 05/16/2016 12:14 PM »
Britain to announce the location of its first spacesport after tomorrow.

http://www.parabolicarc.com/2016/05/15/reports-britain-announce-location-spaceport-wednesday/

I believe that the only suited for Skylon is CampbellTown, right?

Offline francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1536 on: 05/16/2016 03:17 PM »
The EU has launched a public consultation on its 2030 Space Strategy.

It will inform the next EU Strategy on space to be developed next year, and also will lead allocation of EU resources.

You can freely participate here: https://ec.europa.eu/eusurvey/runner/SpaceStrategy

Don't forget to cite SABRE development as a priority :)

Offline knowles2

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1537 on: 05/16/2016 07:56 PM »
Britain to announce the location of its first spacesport after tomorrow.

http://www.parabolicarc.com/2016/05/15/reports-britain-announce-location-spaceport-wednesday/

I believe that the only suited for Skylon is CampbellTown, right?

I got a feeling it will be Newquay through. Cornwall is a economic deprive area so using a spaceport to drive investment make sense. I don't think it will the two scottish sites.

It will be interest to see if any backers are reveal tomorrow. Virgin Galactic, Reaction Engines or BAE Systems.
150 million is a bit low for Skylon through, construction and modifications to the runway is likely to cost substantially more than that.
« Last Edit: 05/16/2016 08:02 PM by knowles2 »

Offline Alpha_Centauri

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1538 on: 05/17/2016 10:36 AM »
The spaceport isn't directly related to Skylon in any way, it's about developing the UK space sector through space tourism (virgin galactic etc) and eventually potential for a small polar launcher. Of course REL may well make use of the site for small-scale testing.

Offline francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1539 on: 05/17/2016 03:50 PM »
The spaceport isn't directly related to Skylon in any way, it's about developing the UK space sector through space tourism (virgin galactic etc) and eventually potential for a small polar launcher. Of course REL may well make use of the site for small-scale testing.

I wouldn't say they are not related in any way. Sure, they are not dependent on each other. But a appropriately sized space-port would actually boost skylon chances.

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