Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 440283 times)

Offline QuantumG

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #440 on: 07/22/2015 12:01 AM »
It's hard to see how flying through the atmosphere for longer, in an SSTO, is going to make a space plane safer.
« Last Edit: 07/22/2015 12:01 AM by QuantumG »
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline RobLynn

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #441 on: 07/22/2015 02:30 AM »
Is it not possible, even likely, that Lapcat/A2 was simply the wrong requirement? Yes ESA had good reasons for creating a future aircraft study and REL did a fine job of meeting their study needs, but that doesn't mean it's the best idea.

I don't think M5 is really needed or a good idea.  Why not make it way easier on yourself and just go Mach 3 - then you can use simple titanium structure and skins, cheap turbo ramjets without high risk heat exchangers, bascially little new tech requried, also an L/D of 7-8 (probably 15-30% lower fuel burn than L/D~6 Lapcat), and still get antipodial range in 6 hours.  For total trip time of probably 11-12 hours door to door vs 9-10 hours for Mach5 and 30 hours for conventional subsonic.

At the end of the day seat-mile cost for such an aircraft is likely to be half the estimated $4-5k antipodal ticket cost of Lapcat.  And demand curves being what they are that probably increases your market by an order of magnitude and the potential commercial viability from no-chance, to maybe.
I'm a "glass is twice as big as it needs to be" kinda guy

Offline flymetothemoon

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #442 on: 07/22/2015 02:37 AM »
It's hard to see how flying through the atmosphere for longer, in an SSTO, is going to make a space plane safer.

I am not a space expert. What I meant was flying a Skylon-like trajectory to get you to your destination - I meant absolutely not staying in the atmosphere and therefore avoiding those heating issues. Clearly re-entry has to be considered too, but that would already be worked through to some extent should Skylon-like craft actually get built.

I also wasn't implying any of that made it safer, but there is no reason why at some future date such a thing couldn't be relatively safe.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #443 on: 07/22/2015 06:59 AM »
Is it not possible, even likely, that Lapcat/A2 was simply the wrong requirement? Yes ESA had good reasons for creating a future aircraft study and REL did a fine job of meeting their study needs, but that doesn't mean it's the best idea.
ESA didn't issue this requirement.

LAPCAT was a research project from the EU under one of their FRAMEWORK R&D schemes, which encourage pan European co operation to solve common problems to a pre competitve stage. You might think of them as being like the sort of thing that the US DARPA and E-DARPA do, but including Canada and Mexico. FRAMEWORK programmes have supported everything from next generation chip lithography to domestic heat and power concepts using natural gas fuel cells. :)
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Once SABREs are shown to be effective and robust (here's hoping!) the entire focus of long-distance high speed air travel may well switch to sub-orbital hopping in a passenger vehicle with SABRE like engines. Why spend 5 hours getting from Europe to Australia (very impressive) when you can do it in 45 minutes - AND avoid all those really very difficult to solve skin heating issues.
It's an interesting idea but misses a few factors. Hempsell said a sub orbital Skylon flight could carry 30 tonnes, but passenger wise I think the payload bay is volume limited, not mass limited.

What Concorde demonstrated (and what the Boeing SST got right) was you need to carry a lot of passengers (in substantial comfort) to make it worthwhile. Most (all) post flight analysis of Concorde's economics said it was too small, and should have been 2x or 3x bigger (and the French wanted it smaller  :( )
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Currently, people just don't think of a safe 'space' plane with high passenger numbers as a realistic option because it "isn't possible".
REL are quit clear that LAPCAT/A2 is not a space plane but a very fast conventional airliner, designed to carry large number of passengers (not "spaceflight participants") with minimal special training and incorporating things like powered landings. Like getting on any large general aviation aircraft, but for less time.

It's pretty clear if a > M2.2 transport gets built it will be a very different beast from Concorde, due to thermal considerations alone. It's also likely to different from Skylon.

I don't think M5 is really needed or a good idea.  Why not make it way easier on yourself and just go Mach 3 - then you can use simple titanium structure and skins, cheap turbo ramjets without high risk heat exchangers, bascially little new tech requried, also an L/D of 7-8 (probably 15-30% lower fuel burn than L/D~6 Lapcat), and still get antipodial range in 6 hours.  For total trip time of probably 11-12 hours door to door vs 9-10 hours for Mach5 and 30 hours for conventional subsonic.
Perhaps you should ask the EU that question.

They set the requirements.
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At the end of the day seat-mile cost for such an aircraft is likely to be half the estimated $4-5k antipodal ticket cost of Lapcat. 
Based on what exactly?
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And demand curves being what they are that probably increases your market by an order of magnitude and the potential commercial viability from no-chance, to maybe.
I've flown on those $5k business class tickets.

They did not seem to have any trouble filling seats, or rather individual "pods"

At a certain level of business the key constraint is no  longer money it's time, and M5 means you spend less of it in the air.
"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 francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #444 on: 07/22/2015 08:04 AM »
there is another problem with a suborbital skylon- the pricing would be totally out of reach for everyone but the wealthiest. A LEO Skylon launch, in the best scenario possible, could lower the kg/price down to 350$. Even assuming lower costs for suborbital flights (let's say 150$ kg) and assuming it could carry 60 people (the double of a LEO flight) it would still be almost 40k $ per ticket. not much compared to the 200.000$/ticket it would cost to bring one passenger to LEO in the best-case scenario, but still....

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #445 on: 07/22/2015 12:11 PM »
there is another problem with a suborbital skylon- the pricing would be totally out of reach for everyone but the wealthiest. A LEO Skylon launch, in the best scenario possible, could lower the kg/price down to 350$. Even assuming lower costs for suborbital flights (let's say 150$ kg) and assuming it could carry 60 people (the double of a LEO flight) it would still be almost 40k $ per ticket. not much compared to the 200.000$/ticket it would cost to bring one passenger to LEO in the best-case scenario, but still....
Exactly.

Using a Skylon for occasional point to point delivery of high value goods may be viable as part of an operators business case (probably not an early adopter, but in a later wave of buyers) but it's not what Skylon is designed to do.

Such a transporter, flying either a sub orbital or a cruise trajectory, would need to be a very different vehicle. The upside is the maximum powered velocity would be lower (shrinking the vehicle) it would be all air breathing (eliminating the LOX tanks, also shrinking the vehicle), but then you need to make the payload bay much bigger. An early REL estimate was the Skylon design could carry 30 passengers but that was scaled down to split them into "short stay" IE coming back on the same Skylon that took them to (notionally) the ISS and "long stays" who'd been on orbit for months (years) and would need to come down on basically a stretcher.

Now sub orbital is a short flight (a LEO orbit is 90 mins, 45 min puts you anywhere on the planet from your launch point) so consumables should be minimal but the fact remains even if you increase the seating density (45 in the bay?) that's just not going to cut it when you're looking at needing 250-300  :(

Wheather it's a M5 cruising aircraft or a sub orbital vehicle (I don't think there's even an agreed term for one of these. SOV?) it won't be a 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 tl6973

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #446 on: 07/23/2015 12:00 PM »
I find it hard to pin down what I find most exciting about REL.

It's a toss-up between the engineering wonderments of SABRE and Skylon, and the actual Business Culture/ operating model of REL themselves.

There's plenty on this thread about the science, engineering and economics, so I'd like to talk more about the business. They seem to occupy this very intriguing, contradictory spot between old and new space - like a start up but with 30 years' experience/ existence, with a visionary idea but that will clearly require significant collaboration with traditional aerospace and government/ political bodies. A bunch of very British Boffins in a shed, with the increasing possibility of changing the entire game.

Of course it is very hard to comment accurately on an organisation from outside, but I am very impressed with their calm determination, ability to stay completely focused on a very clearly defined technology development roadmap, and organisational unity/ rationality/ lack of internal politics and strife.

I would be very interested to know people's thoughts on how this has come about. Is it down to strong visionary leadership? is it that having a small team and constrained resources forces one to maintain focus? is it simply because the design concept is so compelling? Was the experience of working with the government on HOTOL a good lesson in how NOT to run a development programme? or is it something else entirely?

Offline flymetothemoon

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #447 on: 07/23/2015 02:04 PM »
It's an interesting idea but misses a few factors. Hempsell said a sub orbital Skylon flight could carry 30 tonnes, but passenger wise I think the payload bay is volume limited, not mass limited.

I accept everyone's points (although as usual perhaps not QuantumG's  ;) ), but I was trying to imagine a different study or future. One where a craft was specifically optimised for maximum passenger carrying purposes and sub-orbital - whatever the trajectory would be to minimise time in atmosphere, but maximise distance. So yes, not Skylon. A2 isn't Skylon either.

I am not at all saying that LAPCAT wasn't a useful study, I am merely suggesting that if the EU had given REL the money for a different study, to look into *that* sort of vehicle, they might have been able to propose a realistic design, different from both A2 and Skylon, but still using technology derived from SABRE engine technology, that would seat a significant number of passengers to make an economically viable vehicle and avoid the in-atmosphere heat problems.

Then we might get our 45 minute trip - and one hell of a ride ;)
« Last Edit: 07/23/2015 02:05 PM by flymetothemoon »

Offline RonM

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #448 on: 07/23/2015 02:24 PM »
It's an interesting idea but misses a few factors. Hempsell said a sub orbital Skylon flight could carry 30 tonnes, but passenger wise I think the payload bay is volume limited, not mass limited.

I accept everyone's points (although as usual perhaps not QuantumG's  ;) ), but I was trying to imagine a different study or future. One where a craft was specifically optimised for maximum passenger carrying purposes and sub-orbital - whatever the trajectory would be to minimise time in atmosphere, but maximise distance. So yes, not Skylon. A2 isn't Skylon either.

I am not at all saying that LAPCAT wasn't a useful study, I am merely suggesting that if the EU had given REL the money for a different study, to look into *that* sort of vehicle, they might have been able to propose a realistic design, different from both A2 and Skylon, but still using technology derived from SABRE engine technology, that would seat a significant number of passengers to make an economically viable vehicle and avoid the in-atmosphere heat problems.

Then we might get our 45 minute trip - and one hell of a ride ;)

That would be fun, but I don't see it happening. There are no operational SSTs today because of cost, so I doubt suborbitals would be economically viable. Even the military doesn't have supersonic transports, let alone suborbitals.

Teleconferencing takes care of rapidly attending business meetings and missiles takes care of rapidly needing to reach out and touch someone.

An issue with suborbital passenger transport is all the time on the ground. You go to the airport, wait in the security line, wait to board, wait for takeoff, ***high speed flight***, wait to land, wait to disembark, wait for your luggage, wait in line for customs, leave airport and arrive at hotel. I'd rather take a cheaper subsonic flight and take a nap while in the air.

Skylon could make an interesting SSTO spacecraft, but I doubt it or any other technology will succeed as a suborbital transport.

Offline flymetothemoon

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #449 on: 07/23/2015 02:37 PM »
That would be fun, but I don't see it happening.

Ah! "There's no market for it"  :)

Even if that's true, it would be an interesting study.

Offline t43562

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #450 on: 07/24/2015 07:23 AM »
An issue with suborbital passenger transport is all the time on the ground. You go to the airport, wait in the security line, wait to board, wait for takeoff, ***high speed flight***, wait to land, wait to disembark, wait for your luggage, wait in line for customs, leave airport and arrive at hotel. I'd rather take a cheaper subsonic flight and take a nap while in the air.

Skylon could make an interesting SSTO spacecraft, but I doubt it or any other technology will succeed as a suborbital transport.

To solve a problem you first have to "have it".  We haven't really fixed the issues of the time it takes to offload and process people because perhaps we are only just beginning to experience them.

I still wonder if a ticket that cost you e.g. 5000 wouldn't also pay for expedited customs processing - or even perhaps processing onboard the flight.

As for getting on and off - I'm not saying this is the answer but at least people are thinking about the problem:

http://clipair.epfl.ch/
[youtube]
NEJ3bAh7LUw[/youtube]

I love it because I had a similar idea not long ago and it's nice to know it wasn't so ridiculous as to not even be considered. :-)
« Last Edit: 07/24/2015 07:30 AM by t43562 »

Offline francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #451 on: 07/24/2015 10:09 AM »
50k more likely than 5k.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #452 on: 07/24/2015 10:32 AM »
To solve a problem you first have to "have it".  We haven't really fixed the issues of the time it takes to offload and process people because perhaps we are only just beginning to experience them.

I still wonder if a ticket that cost you e.g. 5000 wouldn't also pay for expedited customs processing - or even perhaps processing onboard the flight.

As for getting on and off - I'm not saying this is the answer but at least people are thinking about the problem:
I had a similar idea not long ago and it's nice to know it wasn't so ridiculous as to not even be considered. :-)
I understand that the trip through Reagan at Washington DC is very fast.

It can be done if law makers are feeling inconvenienced enough to do something about it.  :(

Likewise a service that preloaded all your address, hotel and credit card details on a data base that is used to upload to the DHS system to expedite trips to and from the US was offered some years ago.

Until someone stole the laptop on which a copy was sitting from a locked office in the secure area of a major airport (as happened a few years ago).

As for this cargo module idea, considered and built (in the 1940's or 50's) in prototype by (IIRC) the Fairchild aircraft company.

The problem has always been compatibility.  You end with using the lowest common denominator.

Which turns out to be a) A person walking or b) A standardized air cargo package.

[EDIT and here it is.

https://en.wikipedia.org/wiki/Fairchild_XC-120_Packplane ]
« Last Edit: 07/24/2015 10:37 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.

Online Hankelow8

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #453 on: 07/27/2015 09:32 AM »
Reaction Engines concept  of a full-scale Sabre ground demonstrator.
Clearly not a flight model engine yet, but massive progress if this proves successful in 2018/2019.
« Last Edit: 07/27/2015 09:40 AM by Hankelow8 »

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #454 on: 07/27/2015 10:43 AM »
Reaction Engines concept  of a full-scale Sabre ground demonstrator.
Clearly not a flight model engine yet, but massive progress if this proves successful in 2018/2019.
Where did this come from?
"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.

Online Hankelow8

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #455 on: 07/27/2015 11:17 AM »
From the Aviation Week digital magazine. Photo credit  Reaction Engines

Offline aga

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Offline pippin

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #457 on: 07/27/2015 01:50 PM »
So many things wrong with that picture....

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #458 on: 07/27/2015 03:19 PM »
So many things wrong with that picture....
I'd certainly say it look like it was made by a graphics artist, not an engineer.

What specifically did you have in mind?
"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 pippin

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The Reaction Engines Skylon Master Thread (5)
« Reply #459 on: 07/27/2015 04:39 PM »
Oh, it shows the engine running at power but just placed in some kind of better workshop table assembly. So it doesn't have any thrust?
Four radiation cooled nozzles that close to each other would immediately burn through.
With all that it's almost irrelevant that all the deep-cold cryo piping is uninsulated and that the air inlet would suck up all kind of stuff at that power and so on.

It's so: oh, we have this image of the raw engine assy, let's just display it at work....
And then let's add these glowing red-hot engine bells people know from the SpaceX videos, they look so cool...
« Last Edit: 07/27/2015 04:42 PM by pippin »

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