The Reaction Engines Skylon Master Thread (1)

[lkm]

Do you know why the top speed in air breathing mode is mach 5.14? If you could boost the speed to mach 6, there would be a substantial payload gain.


 I remember reading somewhere that the temperature in the ramjet burners was a limiting factor, is that correct? If so could you use a higher temperature material or active cooling to allow higher speeds? The material specified for the burners is C/SiC I think, but there is a newer material which can withstand higher temperatures - up to 3000 F.  Its called tufroc and is used on the x-37 heat shield.

As I understand it the upper speed of Skylon airbreathing is pretty fixed as determined by this:

http://www.islandone.org/Propulsion/LACE.html

See Hempsell's response here:

http://forum.nasaspaceflight.com/index.php?topic=22434.msg632622#msg632622

Thanks for the link to that lace derivation, but as I understand that is a simplified derivation which assumes the hydrogen that is used to cool the air is dumped overboard rather than burnt in the ramjets. The top speed  then should be higher and the limiting factor is thermal considerations.

I didn't mean to suggest that the LACE equation gave exactly the right numbers only that the argument and derivation explained why there was a limit, as alluded to by Hempsell.

[lkm]

So there's no new info in this but it's a fantastically rousing opinion piece pleading for Skylon and the future. You can practically hear an orchestral swell.

http://www.bis-space.com/2012/05/04/4545/building-the-engines-of-tomorrow 

[simonbp]

So there's no new info in this but it's a fantastically rousing opinion piece pleading for Skylon and the future. You can practically hear an orchestral swell.

http://www.bis-space.com/2012/05/04/4545/building-the-engines-of-tomorrow 

Playing Land of Hope and Glory while a Spitfire flies over a beefeater and Big Ben chimes...

[93143]

An interesting question would be how much propellant would be needed to get Skylon to orbit and then de-orbit it with whatever down mass you are targeting.

I would expect downmass to be at least equal to upmass, based on abort considerations.  A Skylon experiencing a failure after takeoff can dump its propellant, but it has to land with a full payload bay.  A Skylon experiencing a failure on orbit (jammed payload deployment mechanism or bay doors?) likewise has to be capable of deorbit and landing with a full payload bay.

The emergency landing itself could be off-nominal, I suppose, but the deorbit either works or it doesn't, and it needs to work.

See Hempsell's response here:

http://forum.nasaspaceflight.com/index.php?topic=22434.msg632622#msg632622

Expansion/Defection nozzles

Considering the evident concerns about keeping critical IP under wraps for as long as possible, perhaps it would be wise to add an L...

[adrianwyard]

I wonder if Skylon is being considered as part of the next generation ESA booster discussions. According to the following article decisions start to narrow choices in June of this year, but the expectation is this could be a 15 year development program.

June 2012 seems a bit soon to hope for a commitment to Skylon (even though the precooler testing is encouraging). But if they are planning as far out as 2027 they really have to consider the possibility Skylon could be operational by then... It will either be a competitor to Ariane 6, or Skylon could be 'Ariane 6', or of course testing could have exposed an insurmountable problem by then and SSTO will once again return to the realm of Sci-Fi...

http://www.spacenews.com/launch/120504-affordability-not-geographic-return.html

[Robotbeat]

I wonder if Skylon is being considered as part of the next generation ESA booster discussions. According to the following article decisions start to narrow choices in June of this year, but the expectation is this could be a 15 year development program.

June 2012 seems a bit soon to hope for a commitment to Skylon (even though the precooler testing is encouraging). But if they are planning as far out as 2027 they really have to consider the possibility Skylon could be operational by then... It will either be a competitor to Ariane 6, or Skylon could be 'Ariane 6', or of course testing could have exposed an insurmountable problem by then and SSTO will once again return to the realm of Sci-Fi...

http://www.spacenews.com/launch/120504-affordability-not-geographic-return.html

If Skylon doesn't close, it'd still make a heck of a reusable first stage.

[adrianwyard]

If Skylon doesn't close, it'd still make a heck of a reusable first stage.

No doubt about that. You could hope that only a small upper stage would be needed to make up for any underperformance. But for now, the economic justification for Skylon is as an SSTO.

[Lampyridae]

So there's no new info in this but it's a fantastically rousing opinion piece pleading for Skylon and the future. You can practically hear an orchestral swell.

http://www.bis-space.com/2012/05/04/4545/building-the-engines-of-tomorrow 

Playing Land of Hope and Glory while a Spitfire flies over a beefeater and Big Ben chimes...

Can you help it? SKYLON comes screaming straight out of the pages of Eagle comic and Dan Dare...

[john smith 19]

So there's no new info in this but it's a fantastically rousing opinion piece pleading for Skylon and the future. You can practically hear an orchestral swell.

http://www.bis-space.com/2012/05/04/4545/building-the-engines-of-tomorrow 

Playing Land of Hope and Glory while a Spitfire flies over a beefeater and Big Ben chimes...

Well it is the *British* Interplanetary Society.

[flymetothemoon]

If Mr (or is it Professor?) Hempsell comes back I am particularly interested in further information about durability too.

1) Do we know much about working with pyrosic type materials? e.g. do you believe panels can be easily replaced if they become damaged?

2) As far as I am aware, the SSMEs were very difficult and expensive to maintain, required frequent maintenance and were a major contributor to the cost of the Shuttle programme. Are there aspects of Sabre's design that alleviate maintenance complexity? They also have a complex job to do in a tough regime, having to return from orbit. Are there aspects of the design that make them more resilient - that give you confidence they won't end up having to be stripped down every other flight - just in case?

I am also interested in the down mass capabilities. If you can abort any time up to orbit we might conclude the down mass capability were 15 tons, but without fuel that could conceivably be more. Can you let us know any more about that?

Many thanks.

[Celebrimbor]

Time to write to my MP I think...

This is a bit out of date, but might be useful reference material if anyone else wants to nudge their elected representative...

http://www.publications.parliament.uk/pa/cm201012/cmselect/cmbis/writev/735/73522.htm

[Hempsell]

If Mr (or is it Professor?) Hempsell comes back I am particularly interested in further information about durability too.

1) Do we know much about working with pyrosic type materials? e.g. do you believe panels can be easily replaced if they become damaged?

2) As far as I am aware, the SSMEs were very difficult and expensive to maintain, required frequent maintenance and were a major contributor to the cost of the Shuttle programme. Are there aspects of Sabre's design that alleviate maintenance complexity? They also have a complex job to do in a tough regime, having to return from orbit. Are there aspects of the design that make them more resilient - that give you confidence they won't end up having to be stripped down every other flight - just in case?

I am also interested in the down mass capabilities. If you can abort any time up to orbit we might conclude the down mass capability were 15 tons, but without fuel that could conceivably be more. Can you let us know any more about that?

Many thanks.

It is Just Mr

The reinforced glass ceramic is very tough; it is also cheaper to produce so we do not foresee TPS maintenance as being a major issue.  Damage due to debris impact on orbit is the chief concern and inspecting for it is the main turn around driver.

We have not analysed re-entry beyond 15 tonnes but it may be OK to go to 30 tonnes if you stick to the Centre of Mass constraints in Figure 16 of the User’s Manual.  My concern is the increase in ballistic coefficient may push the re-entry temperatures above where we would be comfortable, but without analysis I could not be sure.  And before you ask - such analysis is very low down the “to do” list at the moment.
 

[john smith 19]

The reinforced glass ceramic is very tough; it is also cheaper to produce so we do not foresee TPS maintenance as being a major issue.  Damage due to debris impact on orbit is the chief concern and inspecting for it is the main turn around driver.

Would this also be a driver for insurance premiums on a launch? While proper procedures could eliminate or substantially reduce threats from bird strike or FOD on the runway the density of orbital debris is something no single company can do anything about, although Skylon might be a very good launch platform for "sweeper" vehicles to collect or de-orbit such debris.

I recall Carnegie Mellon proposing an automated inspection system for the Shuttle in the early 90's but I wonder if something as simple as a pressure test with the whole vehicle at slightly above 1atm absolute to measure rate of pressure fall (or if its internal pressure falls) as a quick simple test before detailed surface scanning.

[Space OurSoul]

Hi folks,

I had a really dumb idea, but I was wondering if somebody could explain why it is dumb.

if the fact that the undercarriage doors make the TPS engineering more difficult, would it be possible to avoid the issue by having skylon, or any winged reentry vehicle, re-enter upside down and then flip for low-speed flight and landing?

In skylon's case, the vertical stabilizer has to stay out of the reentry flow, so would end up being on top (along with the gear and the payload doors) during reentry, but then be underneath when the craft flips over for lower-speed aerodynamic flight and landing, perhaps doubling as a tail dragger gear strut.

Not that I think a half-Mach landing speed would be a good idea in a tail dragger... :-)

This doesn't make much sense in terms of skylon's current design, but might there be another configuration of aero surfaces etc wherein this makes any sense?

Thanks,
-Jeff

[docmordrid]

What so you do about the payload bay doors, run it up on a ramp and load/unload from below? Then you still have to deal with windows, the tail fin etc. Seems to violate KISS.

[douglas100]

if the fact that the undercarriage doors make the TPS engineering more difficult, would it be possible to avoid the issue by having skylon, or any winged reentry vehicle, re-enter upside down and then flip for low-speed flight and landing?

As well as violating the KISS principle, Skylon faces much greater engineering challenges than the undercarriage doors. It's challenging but doable. Remember the Shuttle doors worked without problem in over 100 flights.

[flymetothemoon]

I wonder if Skylon is being considered as part of the next generation ESA booster discussions. According to the following article decisions start to narrow choices in June of this year, but the expectation is this could be a 15 year development program.

June 2012 seems a bit soon to hope for a commitment to Skylon (even though the precooler testing is encouraging). But if they are planning as far out as 2027 they really have to consider the possibility Skylon could be operational by then... It will either be a competitor to Ariane 6, or Skylon could be 'Ariane 6', or of course testing could have exposed an insurmountable problem by then and SSTO will once again return to the realm of Sci-Fi...

http://www.spacenews.com/launch/120504-affordability-not-geographic-return.html

You'd certainly hope so. They seem to be looking at a 7 ton launcher for the same sort of projected development  costs as Skylon.

Probably not though.

[flymetothemoon]

It is Just Mr

I saw Professor on Google somewhere. Just trying to be polite 
 

The reinforced glass ceramic is very tough; it is also cheaper to produce so we do not foresee TPS maintenance as being a major issue.  Damage due to debris impact on orbit is the chief concern and inspecting for it is the main turn around driver.

I have read it is very tough. Just wondering about day-to-day maintenance. I guess that may be part of the learning curve though - as it has been for composites in the airline industry. Indeed. Every spacecraft has got to be concerned about debris impact.

Also, in hindsight, what my question about Sabre was overlooking I guess is that the hundreds of flights in the test flight programme will give us an idea how durable the engines are. Also, I believe a one engine out abort is part of the design which covers things pretty well.

We have not analysed re-entry beyond 15 tonnes but it may be OK to go to 30 tonnes if you stick to the Centre of Mass constraints in Figure 16 of the User’s Manual.  My concern is the increase in ballistic coefficient may push the re-entry temperatures above where we would be comfortable, but without analysis I could not be sure.  And before you ask - such analysis is very low down the “to do” list at the moment.

30 tonnes...? 15 is interesting enough given where we are with regard to any other current downmass capability. It would also seem interesting with regard to recent 'mining' announcements. I am sure you chaps haven't overlooked that 

[simonbp]

Every spacecraft has got to be concerned about debris impact.

Though, Skylon's shape would seem to reduce the fuselage area where impacts would hit face-on, so I'd guess the nose, leading edges (Columbia!), and inlets would be the main areas of concern.

Speaking of which, will there be any bird-ingestion tests? It's a bit morbid, but bound to come up on any vehicle taking off from a runway...

[flymetothemoon]

Every spacecraft has got to be concerned about debris impact.

Though, Skylon's shape would seem to reduce the fuselage area where impacts would hit face-on, so I'd guess the nose, leading edges (Columbia!), and inlets would be the main areas of concern.

Speaking of which, will there be any bird-ingestion tests? It's a bit morbid, but bound to come up on any vehicle taking off from a runway...

According to Mr Smith there has (as you would expect) been much consideration of bird strike.

http://forum.nasaspaceflight.com/index.php?topic=24621.msg880428#msg880428