Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 421993 times)

Offline lkm

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1000 on: 12/06/2015 12:34 PM »
I thought it might be a good idea to repost some of the relevant papers given the current topics of conversation.

Offline Ric Capucho

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The Reaction Engines Skylon Master Thread (5)
« Reply #1001 on: 12/06/2015 12:42 PM »
If 400 test flights are planned then it would be a crying shame to haul 6,000 mt of dummy payloads to orbit.  After say a dozen successes you might as well start using all that capacity and stimulating the market with a low cost to orbit so that your potential vehicle customers actually SEE the huge demand bubbling up that would be necessary to justify purchasing a vehicle.


Good point.

I'd expect dummy payloads for the first couple of Skylon test flights, and then deeply discounted commercial payloads for each subsequent flight, with the price discount ever reducing as the vehicle is proven and risk of loss is reduced. Then once the 200+ flight testing period draws to a close, the final operator of the now fully tested vehicles will look in vain for anything remaining on the ground still left to be launched.

What then? Launch what exactly into LEO? Rocks?

That's the achilles heel of both the Skylon commercial proposition and also SpaceX: without a Mars or Lunar program or some other pressing *need* to launch lots and lots of stuff into orbit, then both systems are going to be spending most of their time on the ground. Granted SpaceX has a Mars program on the drawing board (but I'm sceptical that even Elon and his friends have deep enough pockets to pay for it) so they're at least on paper providing their own pressing need for a reusable launch system. But Skylon's first operator? What's the pressing need for them? And can they cover the huge opportunity costs whilst a Skylon or two sit on the ground with nothing to launch?

This is where the infamous airliner comparison quickly falls apart: any airliner spends a large proportion of its time in the air... it'd better at those capital costs. And if not, it's soon returned to the leasing company after the airline goes bankrupt.

I personally would *love* Skylon to fly, but I greatly fear for the first commercial operator. "Build it, and they will come" is a fallacy that engineering-first companies fall for time and again. The Brits have a rich history of that, but I deleted the long list of examples that spring to my mind because I don't want to distract anyone from my point. But there is one sector with deep pockets where Skylon has a hope: first they'll need to paint it olive green; and then they'll have to weaponise it.

Cue the rush of SpaceX fanboys, Skylon fanboys and anti-military establishment types. (Yawn) Sticks and stones...

Ric
« Last Edit: 12/06/2015 12:45 PM by Ric Capucho »

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1002 on: 12/06/2015 02:19 PM »

1.  I expect launch control to be much smaller given the higher structural margins and the underlying assumption that Skylon will work, rather than something that's a hairs breadth away from falling apart.

2.  I would expect Range Safety to be autonomous on the vehicle. with engine shut down and propellant dumping ( no self destruct charges) to be SOP.

3.  Mission Control? Isn't that what happens in an airport Control Tower? Shared across all vehicles using the runway.

So look at Spacex pad but without the erector.
4.  The word you're looking for is "runway."  :)

1.  No, LCC manning has nothing to with structural or operational margins.   Personnel are assigned by systems to manage.

2.  Still need to manage the range regardless of range safety methods.

3.  No.  That is the range control center.  The closest thing analogous wise would be the airline operations center, which are not typically at airports.  Mission control takes over after launch

4.  No, it would be the ramp at the terminal, which would be like the Spacex pad (hangar, prop storage, fueling area, payload facility, etc)

Offline banjo

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1003 on: 12/06/2015 03:34 PM »
Quote from: Spaceflight vol 58, p26
[reporting on IAC 2015]... the new head of Arianspace, Stephane Israel, said he had not heard of Reaction Engines or the Skylon concept.

a strange marketing ploy to pretend have poor knowledge of one's industry.   

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1004 on: 12/06/2015 05:43 PM »
I thought the 400 flights info comes from before they planned the boilerplate prototype?

The idea of boilerplate Y-plane testing feeding into production prototype testing appears in the earliest image of REL's website on archive.org, from December 2003.  Mark Hempsell referenced the 400-flight test programme last June (specifically, he confirmed that it's part of the development budget, and always has been).  So no.

Best recent description of the test programme I can find is here.

Quote
The qualification flight test programme has two production prototypes (there are also two earlier full scale development vehicles which are probably not orbital).

...

Back in 2012, Hempsell also stated that they hoped to fly as many as 16 ISS missions during the test programme.  So apparently they didn't want to just launch a bunch of dummy payloads either...

Offline Archibald

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1005 on: 12/06/2015 06:36 PM »
There was a paper back then analyzing possible relationships between Skylon and ISS. I have it somewhere on my HD - it is certainly available on REL website.
I think their conclusion was that 16 Skylon flight would probably be totally overkill for the ISS. The logistic need is just not there.
The ISS uses to be on a "diet" regime of Progress, ATV, HTV, MPLM and the likes. Skylon logistic-rich regime would make it "obese".

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1006 on: 12/06/2015 10:14 PM »

1.  Would that be covered by ATC?

2.  Do you think the prop storage and fueling area are likely to be a spaceport facility? does the decoupling of fueling from launch give any benefits in terms of reducing the complexity of the launch process. Any benefits in terms of the size of the range control staff?


1.  No, just as ATC doesn't cover the area around an airport

2.  Range control staff is independent of the vehicle type and the ground support equipment.  That is launch control staff

Offline Robotbeat

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1007 on: 12/06/2015 11:52 PM »
If 400 test flights are planned then it would be a crying shame to haul 6,000 mt of dummy payloads to orbit.  After say a dozen successes you might as well start using all that capacity and stimulating the market with a low cost to orbit so that your potential vehicle customers actually SEE the huge demand bubbling up that would be necessary to justify purchasing a vehicle.


Good point.

I'd expect dummy payloads for the first couple of Skylon test flights, and then deeply discounted commercial payloads for each subsequent flight, with the price discount ever reducing as the vehicle is proven and risk of loss is reduced. Then once the 200+ flight testing period draws to a close, the final operator of the now fully tested vehicles will look in vain for anything remaining on the ground still left to be launched.

What then? Launch what exactly into LEO? Rocks?

That's the achilles heel of both the Skylon commercial proposition and also SpaceX: without a Mars or Lunar program or some other pressing *need* to launch lots and lots of stuff into orbit, then both systems are going to be spending most of their time on the ground. Granted SpaceX has a Mars program on the drawing board (but I'm sceptical that even Elon and his friends have deep enough pockets to pay for it) so they're at least on paper providing their own pressing need for a reusable launch system. But Skylon's first operator? What's the pressing need for them? And can they cover the huge opportunity costs whilst a Skylon or two sit on the ground with nothing to launch?

This is where the infamous airliner comparison quickly falls apart: any airliner spends a large proportion of its time in the air... it'd better at those capital costs. And if not, it's soon returned to the leasing company after the airline goes bankrupt.

I personally would *love* Skylon to fly, but I greatly fear for the first commercial operator. "Build it, and they will come" is a fallacy that engineering-first companies fall for time and again. The Brits have a rich history of that, but I deleted the long list of examples that spring to my mind because I don't want to distract anyone from my point. But there is one sector with deep pockets where Skylon has a hope: first they'll need to paint it olive green; and then they'll have to weaponise it.

Cue the rush of SpaceX fanboys, Skylon fanboys and anti-military establishment types. (Yawn) Sticks and stones...

Ric
Agreed. This is also why SpaceX is branching out to building and operating a comm satellite constellation. It gives their RLV (partial or full) something to justify its existence.

Skylon really needs something like that, too. I'm hopeful they'll find something other than just using Skylon as a bomber.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1008 on: 12/07/2015 12:00 AM »

By decoupling the choreography of disconnections and releases, and by slowing the actual launch do you think the horizontal take-off concept have the potential to drastically simplify the launch sequence, or would it be only marginal, or make no significance difference? In addition by being dynamically stable and having a variety of intact abort options, does the Skylon concept have the potential to allow the launch control centre be scaled down? by how much?


not by much

https://blogs.nasa.gov/spacex/2014/09/21/mission-and-launch-control-centers-across-the-country/

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1009 on: 12/07/2015 04:32 AM »
Changing up the angle a bit, why don't airliners require the same level of ground control attention as rockets, and how can (or why can't) Skylon move in that direction?

Offline Hanelyp

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1010 on: 12/07/2015 06:43 AM »
Changing up the angle a bit, why don't airliners require the same level of ground control attention as rockets, and how can (or why can't) Skylon move in that direction?
A lot of that has to do with system failure rate and ability to survive failures.  And airliners got there by flying a lot, building a knowledge base of how the systems can break down, and how the breakdowns can be prevented, predicted, or worked around.  A vehicle that is flown once and thrown away will never have that same reliability.

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1011 on: 12/07/2015 01:21 PM »

I don't understand how your reference to a VTOL would help me to understand your answer -

It has nothing to do with orientation of takeoff or landing, it is the systems in the vehicle.  Skylon is going to have systems and operations that are similar to other launch vehicles that need monitoring prelaunch, like the loading of the propellants.  The example shown is a launch control center for a vehicle that both uses some of the latest technology.
« Last Edit: 12/07/2015 01:32 PM by Jim »

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1012 on: 12/07/2015 01:30 PM »
Changing up the angle a bit, why don't airliners require the same level of ground control attention as rockets, and how can (or why can't) Skylon move in that direction?

Because:
A.  Airliners have multiple back systems and also have the ability to have multiple abort modes.  Also, they have the ability to operate in a degraded mode.

b.  Jet engines are not working at the edge and they can contain a destructive failure or even fall off.

c.  An airliner fully fueled and ready to fly can sit on the ramp almost indefinitely.  A vehicle that uses cryogenics and hygols has to be monitored. 

Offline Ravenger

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1013 on: 12/07/2015 02:05 PM »

Because:
A.  Airliners have multiple back systems and also have the ability to have multiple abort modes.  Also, they have the ability to operate in a degraded mode.


I imagine Skylon will have some level of redundant systems. Skylon is also intended to have multiple abort modes. The runway length is designed for take-off aborts, the brakes are water cooled for aborts (with water dumped after take-off) and the tail fin has been sized to support steering with one engine out.

I believe Alan Bond has also said Skylon could generate enough thrust to continue flying using the bypass burners alone in the event of an engine failure.

Quote
b.  Jet engines are not working at the edge and they can contain a destructive failure or even fall off.

Skylon's test flight schedule is designed to test the limits of the engines so they can be operated within safe limits. I doubt they'll be operating at the edge without any safety margin. The engines only operate for a few minutes, not continuous hours of operation like Airliners, so that will mitigate some issues.

Quote
c.  An airliner fully fueled and ready to fly can sit on the ramp almost indefinitely.  A vehicle that uses cryogenics and hygols has to be monitored.

Agreed, cryogenic fuels require much more careful handling than AV fuels. There shouldn't be any major issues with Skylon having to wait on the runway while problems are resolved - after all standard rockets have to do this fairly frequently, even ones using cryogenics.

However Skylon is won't be using hygols - the OMS and RCS systems will use LH2/LO2.

The thing is that REL are trying for airport-like operations, but that doesn't mean it'll operate exactly like modern airliners, as there are and will be significant differences.

However it is intended to operate in a way which is much closer to normal airport operations than any other launch vehicle.

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1014 on: 12/07/2015 02:13 PM »

1.  Agreed, cryogenic fuels require much more careful handling than AV fuels. There shouldn't be any major issues with Skylon having to wait on the runway while problems are resolved - after all standard rockets have to do this fairly frequently, even ones using cryogenics.

2.  However Skylon is won't be using hygols - the OMS and RCS systems will use LH2/LO2.

3.However it is intended to operate in a way which is much closer to normal airport operations than any other launch vehicle.


1.  Hence the need for personnel in a launch control center.  I doubt that Skylon will wait on the runway.  It would wait on the fueling ramp/pad while getting topped off.    Or there will be a topping off station at the end of the runway.

2.  Its payloads will.

3.  It will be closer to other launch vehicle operations than airport operations.  Take away to the tow to the runway and the rest is like other vehicles.
« Last Edit: 12/07/2015 02:17 PM by Jim »

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1015 on: 12/07/2015 02:22 PM »

Skylon's test flight schedule is designed to test the limits of the engines so they can be operated within safe limits. I doubt they'll be operating at the edge without any safety margin.

No different than any other rocket engine.   All rocket engines are operated within safe limits with margin.  It still doesn't change the fact that is a large amount of power in a small package and a lot of rotational energy.  That is what is meant by "working on the edge".   As far as rocket engines go, ground tests vs flight tests, there is no difference.  It is just operation time and hence Skylon has no advantage.

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1016 on: 12/07/2015 04:03 PM »

That's useful insight, thank you. I've never dealt with anything scarier than LPG, what are the problems with cryogenic fuel handling that make you think the design has missed?

It uses LH2, which boils off quickly.   They have only talked about the flight vehicle and not the ground support equipment.
« Last Edit: 12/07/2015 04:05 PM by Jim »

Offline Hanelyp

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1017 on: 12/07/2015 04:25 PM »
LH2 has a known boil off rate for a given tank and ambient conditions.  A factor to be engineered into the design, not a show stopper.  Consider that the tanks and heat shields will need to deal with a period of supersonic flight, with a hot skin.  This implies to me some insulation.  A limited amount of boil off should be part of the design.  For a moderately extended hold I don't expect too much trouble driving out a truck to top off the tanks.  Longer holds (hopefully very rare) imply return to the hanger.

The one factor that comes to my mind where airliner style operations may come short for Skylon needs is on schedule liftoff when heading to a specific orbit.  The spaceplane may need to schedule a launch window.

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1018 on: 12/07/2015 05:02 PM »

I thought a fair amount of consideration had been put into the ground support equipment
Pages 26-28 of the concept manual outlines the Ground Operations Sequence and Timing  (pages34-36 of the PDF)


Not really.  This is the first time I have seen it and it has some holes.  The first thing I saw that is wrong is the payload integration facility.  Totally unrealistic.

And the timeline is just as funny as the two week shuttle turnaround. 
« Last Edit: 12/07/2015 05:06 PM by Jim »

Offline Jim

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #1019 on: 12/07/2015 05:04 PM »
Regardless of how long of a hold, LH2 is boiling off, especially at the beginning of tanking.  This will necessitate a vent line and a flare stack.  The vehicle is not going to sit on the runway venting H2 to the atmosphere.

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