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Author Topic: Skylon Spaceplane  (Read 72019 times)

Offline Zootycoon

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Re: Skylon Spaceplane
« Reply #180 on: December 17, 2016, 12:11:37 am »
The space shuttle orbiter empty weight is 68 ton, which is the weight it would have been on the back of 747. I believe, while in flight  the combination was significant limited in both airspeed and max altitude as well;- this would further reduce the orbital energy input. 110 Ton is an orbiter with an integrated payload and is well beyond the payload of a 747;- any claim that the structural modification to mount it on its back could extend to that level basic wing root bending enhancement is unsupported by physics or realty.

As for your assertion relating to air density this only effects nozzle expansion ratio optimisation which is a second order effect on payload mass fraction. I would welcome you to publish the physics which shows that kinetic energy is not the sole dominant factor in getting a payload into orbit. 

Sure a two stage to orbit concept gives the ability for launch point selection but that wasn't the point, a single stage such as Skylon can offer the same flexibility.

Pegasus's Tristar was the last one flying in the world because they deliberately chose to control costs by using obsolete equipment. Nothing wrong with that but is show how marginal the business case is.


Offline steelpillow

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Re: Skylon Spaceplane
« Reply #181 on: December 17, 2016, 02:51:29 am »
I would welcome you to publish the physics which shows that kinetic energy is not the sole dominant factor in getting a payload into orbit. 
Of course this has always been the prime rationale for multi-stage launch, as was first realised in the mid-twentieth century and ever since then multi-stage has been the only possible way to attain orbit. That Zootycon is using the same rationale to try and justify SSO technology over multi-stage is - what, ironic perhaps? SABRE makes it technically possible but it doesn't change the proven economic advantage of multi-stage.

Second-best is a subsonic COTS (commercial-off-the-shelf) mothership with SABRE upper stage. As British Aerospace found donkeys years ago (and contrary to Zootycon's dreams), this is the cheapest and lowest-risk orbiter to develop.  And as Pegasus has amply demonstrated, a conventional mothership brings operational flexibilities which have high value in themselves.

Better is a suborbital SABRE-powered mothership. It might even borrow a trick from the Shuttle, with the orbiter's conventional rocket engine providing boost for takeoff. But that's two specialist craft, with twice the development cost and the risk squared. Let's do it the easy way first.

You don't even need SABRE. An atmospheric mothership, suborbital rocket second stage and rocket orbiter would have been viable fifty years ago - think B52 plus X-15 with disposable orbiter hung beneath, then refine. But that refining triples the development cost, so nobody ever dared go there.

Exercise for the student: Taking the Virgin Galactic two-stage suborbital launch system as a starting point, how is it best developed to give orbital capability? SABRE for the mothership? SABRE for the second stage? A new rocket third stage? Richard Branson would love to know!

But if you are willing to set aside orbital flight for now then, whether or not you believe that SSO will ultimately triumph, a sub-orbital Skylon is an obvious next step.
« Last Edit: December 19, 2016, 10:50:47 am by steelpillow »
Cheers.

Offline SteveO

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Re: Skylon Spaceplane
« Reply #182 on: December 18, 2016, 09:21:26 am »
Hmmm... not much to look at anymore on the new website https://www.reactionengines.co.uk

Hopefully the lack of documents, images and videos indicates real world progress is being made!

Offline mz

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Re: Skylon Spaceplane
« Reply #183 on: December 18, 2016, 01:28:40 pm »
The space shuttle orbiter empty weight is 68 ton, which is the weight it would have been on the back of 747. I believe, while in flight  the combination was significant limited in both airspeed and max altitude as well;- this would further reduce the orbital energy input. 110 Ton is an orbiter with an integrated payload and is well beyond the payload of a 747;- any claim that the structural modification to mount it on its back could extend to that level basic wing root bending enhancement is unsupported by physics or realty.

As for your assertion relating to air density this only effects nozzle expansion ratio optimisation which is a second order effect on payload mass fraction. I would welcome you to publish the physics which shows that kinetic energy is not the sole dominant factor in getting a payload into orbit. 

Sure a two stage to orbit concept gives the ability for launch point selection but that wasn't the point, a single stage such as Skylon can offer the same flexibility.

Pegasus's Tristar was the last one flying in the world because they deliberately chose to control costs by using obsolete equipment. Nothing wrong with that but is show how marginal the business case is.

initial mass / final mass = exp ( delta vee / effective exhaust velocity)

The effective exhaust velocity can be made significantly higher for lower ambient pressures. Don't have info on 20% sea level air pressure, or whatever Pegasus is launched at, but here's some back of the envelope:

For example the SpaceX Merlin engine has a nozzle extension on the vacuum version.

Merlin 1C with sea level nozzle
Sea level: 350 kN, 275 s
Vacuum: 400 kN, 304 s

Merlin 1C with vacuum nozzle extension
Vacuum: 411 kN, 342 s

For example if you need 6 km/s of stage delta vee, with a normal ISP of 3 km/s you need e^(6/3) = e^2 = 7.4 mass ratio.
While with the air launch ISP 3.4 km/s you only need a 5.8 mass ratio.

You could downsize the first stage and leave out some engines, to save on cost per launch etc...

Offline Byeman

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Re: Skylon Spaceplane
« Reply #184 on: December 19, 2016, 08:52:17 am »
The space shuttle orbiter empty weight is 68 ton, which is the weight it would have been on the back of 747. I believe, while in flight  the combination was significant limited in both airspeed and max altitude as well;- this would further reduce the orbital energy input. 110 Ton is an orbiter with an integrated payload and is well beyond the payload of a 747;- any claim that the structural modification to mount it on its back could extend to that level basic wing root bending enhancement is unsupported by physics or realty.

2.  As for your assertion relating to air density this only effects nozzle expansion ratio optimisation which is a second order effect on payload mass fraction.

3.   I would welcome you to publish the physics which shows that kinetic energy is not the sole dominant factor in getting a payload into orbit. 



The fact that you are using wrong data just shows that the rest of your posts are suspect and you don't know what you are talking about. I make no "claims", I am only stating facts.

1.  When the shuttle orbiter landed at Edwards AFB and was ferried back to KSC, it was not empty, it still had some fluids onboard and payload.  And if the payload was a Spacelab, it was a full up payload. 
Here is a document covering the first 91 missions and it lists the ferry weights.  One was almost 230k pounds (i.e. 115 tons)

2.  Just as your assertion about  "combination was significant limited in both airspeed and max altitude as well;- this would further reduce the orbital energy input.".  Air launch is not about energy input.  Airspeed and altitude at launch figure little into the deltaV required. 
And as for my point on air density,  it is not an assertion on  nozzle expansion.  The benefit from air launch due to lower air density is less drag and dynamic pressure. 

3.  Never made any post that does not say otherwise.  However, there are other considerations and trades that affect what it costs to provide the kinetic energy.   
« Last Edit: December 24, 2016, 12:26:49 pm by Byeman »

Offline steelpillow

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Re: Skylon Spaceplane
« Reply #185 on: December 19, 2016, 10:57:49 am »
Hmmm... not much to look at anymore on the new website https://www.reactionengines.co.uk

Hopefully the lack of documents, images and videos indicates real world progress is being made!

Hedging their bets now:
"SABRE class engines are applicable in both multi-stage and single-stage architectures."
https://www.reactionengines.co.uk/vehicles/
Cheers.

Offline Ian33

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Re: Skylon Spaceplane
« Reply #186 on: December 19, 2016, 12:46:52 pm »
Hmmm... not much to look at anymore on the new website https://www.reactionengines.co.uk

Hopefully the lack of documents, images and videos indicates real world progress is being made!

Hedging their bets now:
"SABRE class engines are applicable in both multi-stage and single-stage architectures."
https://www.reactionengines.co.uk/vehicles/

No, not hedging their bets, fully realising the potential for small, bomber sized version as well as they big boys full sized monster to take payload to orbit.  I fully expect to see a little clip mid to late 2017 of such power plants demonstrated.
Resident know nothing and Dale Brown reader... Feel free to help me graduate from crayons!

Offline steelpillow

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Re: Skylon Spaceplane
« Reply #187 on: December 20, 2016, 02:58:21 pm »
...fully realising the potential for small, bomber sized version as well as they big boys full sized monster to take payload to orbit.
That's what I said, hedging their bets. :)
Cheers.

Offline bobbymike

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"The real man smiles in trouble, gathers strength from distress, and grows brave by reflection." - Thomas Paine

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Offline bobbymike

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"The real man smiles in trouble, gathers strength from distress, and grows brave by reflection." - Thomas Paine

"On what principle is it that with nothing but improvement behind us, we are to expect nothing but deterioration before us?" - Lord Macaulay

Offline Archibald

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Re: Skylon Spaceplane
« Reply #190 on: February 23, 2017, 11:33:20 pm »
Skylon on backburner until the 2030s. Et merde !!  :-\
Conservatoire de l'Air et de l'Espace d'Aquitaine - Bordeaux - Mérignac / Dassault aviation museum
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