Reusable Single Stage to Orbit Concept

[Hempsell]

John – Payload thingy? I am not sure why they did this. Where I have seen external cannisters before, they are to save weight – a somewhat desperate measure, the idea being you junk them in orbit so the return vehicle is smaller and lighter. The problem being that you lose both payload return from orbit capability and payload recovery during all aborts. But the picture seems to indicate the canister is covered with TPS so presumably is expected to return - I am left puzzled.

Warren -  Lunar resources: I like the idea of the Moon extending down over the Earth extending up. But I return to my point that this is not first generation solutions as you need to establish a major presence using earth centred systems and I cannot see how this could be managed with existing (or indeed even Saturn 5’s) but SKYLON can definitely hack it. Once you have a working Lunar infrastructure then second generation system using Lunar propellants can be deployed and then, I agree, magic happens.

NASA $$$ - sorry no US involvement with ITAR as currently enforced. At the moment SKYLON is an ITAR free product.

[JohnFornaro]

That payload thingy would certainly alter the launch characteristics, including, uhhhh... trimmability.   I do like SKYLON, tho.  Appreciate your comments.

[JohnFornaro]

OK, some questions:

Why does the Sabre engine have that gentle curve to it?  I usually visualize a jet engine being absolutely linear.

What are "shock-on-lip conditions", and why are they worthy of special mention?

I understand the necessity for the heat exchanger to cool the inlet air, but not liquify it.  Could you just discuss the heat exchanger further, since it has special mention on your website?

If ya don't mind.

[Warren Platts]

Warren -  Lunar resources: I like the idea of the Moon extending down over the Earth extending up. But I return to my point that this is not first generation solutions as you need to establish a major presence using earth centred systems and I cannot see how this could be managed with existing (or indeed even Saturn 5’s) but SKYLON can definitely hack it.

More power to you sir! An aggressive lunar presence could be done within anticipated budget levels if launch costs for propellant can be kept down to $5,000 USD per kg. If Skylon can do much better than that, that would be awesome! What are your current projections these days for bulk cargo launch prices, and when is the earliest do you think that Skylon can fly?

Once you have a working Lunar infrastructure then second generation system using Lunar propellants can be deployed and then, I agree, magic happens.

Getting to the point where the Moon could supply surplus propellant is definately a second generation project; but it could happen within about 10 years after first landing with the proper support and focus.

NASA $$$ - sorry no US involvement with ITAR as currently enforced. At the moment SKYLON is an ITAR free product.

I thought the US and the UK were allies! Whatever happened to the special relationship? I could understand it if Reaction Engines was a Chinese operation, but it's not. Have you considered relocating your headquarters to the USA? Maybe sell some stock on the NASDAQ--that might help.

[Jorge]

NASA $$$ - sorry no US involvement with ITAR as currently enforced. At the moment SKYLON is an ITAR free product.

I thought the US and the UK were allies! Whatever happened to the special relationship?

ITAR doesn't adequately distinguish. That's one of many reasons it needs to be reformed.

[Hempsell]

OK, some questions:

Why does the Sabre engine have that gentle curve to it?  I usually visualize a jet engine being absolutely linear.

What are "shock-on-lip conditions", and why are they worthy of special mention?

I understand the necessity for the heat exchanger to cool the inlet air, but not liquify it.  Could you just discuss the heat exchanger further, since it has special mention on your website?

If ya don't mind.

Why a Curved nacelle? – the most frequently asked technical question. The answer is: the air intake on the front of the nacelle needs to point directly into the incoming airflow whereas SKYLON’s wings and body need to fly with an angle of incidence to create lift, so the intake points down by 7 degrees to account for this. The rocket thrust chambers in the back of nacelle need to point through the centre of mass of the vehicle so are angled down; again by 7 degrees but it is a coincidence the angle is the same.

The Intake is “shock-on-lip”, it means the intake swallows the shockwave from the intake cone (and the cone moves to ensure this happens) so all the air passing through the shock enters the engine nacelle, which in turn means we have more air than the engine needs for most of the supersonic flight regime. This is why we have a spill duct to dump the excess air thorough the burners, where we also dump the excess hydrogen used for cooling but not needed by the engine, and thus get a bit more thrust

Most supersonic aircraft intakes spill the air round the outside of the engine but this adds drag and means we cannot to the ramjet trick.

The Pre-cooler heat exchangers are the main technology under development at Reaction Engines and will be our hardware contribution to the vehicle. They are arrays of very fine thin walled Inconel tubes with cryogenic cooled helium gas through them, while the air flows outside the tube through the tube matrix. At Mach 5 goes from around 950 degrees C to around -140 degrees C with a total heat transfer of around 400 MW. The SABRE heat exchanger of made up of spiralling modules nested within each other like a Swiss roll helium entering from the inside and flowing outwards while the air counter flows inwards. It means the temperature difference between the air and the tube is never more than 10 degrees.

[Hempsell]

A reply to Warren

QUESTION: What are your current projections these days for bulk cargo launch prices?

From the objectives laid out in the Requirement Specification

On entry into service cost per kg = $8000 (2004)
About 80% current prices but this is a true unsubsidised cost and is less than half the true cost of current expendables.

In Mature Service (the most meaningful number) cost per kg = $1000 (2004)

Not in the Req. Spec. but has been looked at is the cost if major activity like Solar Power Satellites cost per kg below $500 (2004).

QUESTION; When is the earliest do you think that Skylon can fly?

The programme we are working to has the production prototypes doing the qualification test flight programme from 2018 and into service in 2020

[mlorrey]

{snip}
And what's the point of an SSTO that cannot return to Earth without refueling?

Such an SSTO could be used to carry cargo and propellant into space.  Like current rockets it would be thrown away after its single flight.

Expendable SSTO is automatically cheaper to build and operate than a TSTO, allowing for more frequent launches and lower launch prices.

[mlorrey]

A reply to Warren

QUESTION: What are your current projections these days for bulk cargo launch prices?

From the objectives laid out in the Requirement Specification

On entry into service cost per kg = $8000 (2004)
About 80% current prices but this is a true unsubsidised cost and is less than half the true cost of current expendables.

In Mature Service (the most meaningful number) cost per kg = $1000 (2004)

Falcon 9 at current prices is $4667 per kg using latest pricing ($49 million per launch) and max payload estimates (10,500 kg). This is a true unsubsidized cost and is the true cost of a current expendable.

F9 Heavy single payload to LEO current price is $95 million, with a max payload of 32,000 kg = $2969 per kg.

Extrapolating this into future models by SpaceX (and yes, some SWAG is involved), the Falcon X price per kg I estimate will be around $1990/kg, the Falcon X Heavy will be $1330/kg, and the Falcon XX will be around $900/kg. I am not aware if SpaceX has a Falcon XX Heavy planned, if they did, it should price at about $600/kg.

[mlorrey]

NASA $$$ - sorry no US involvement with ITAR as currently enforced. At the moment SKYLON is an ITAR free product.

I thought the US and the UK were allies! Whatever happened to the special relationship?

ITAR doesn't adequately distinguish. That's one of many reasons it needs to be reformed.

Britain uses our Trident missiles in its subs. While Canada holds an exemption to ITAR, Rep Henry Hyde stymied an exemption for Britain for years (he is dead now). The US Government signed bilateral Defense Trade Cooperation Treaties with the UK and Australian Governments in June[103] and September 2007[104] respectively. The treaties are designed to allow the exchange of technical data, defense articles and defense services (including USML items) without the need for export authorizations such as TAAs and MLAs, subject to restrictions on the type and classification of the technology in question and its intended end-use.[105] In return, the UK and Australian Governments will be required to take steps to improve their export control laws (such as the Australian Customs Act).[106] As of September 2008, the US Senate Foreign Relations Committee had deferred consideration of the Treaties on the grounds that it had not had time to properly evaluate proposed amendments to ITAR required in order to implement the Treaties.[107] (from wikipedia)

[Hempsell]

A reply to Warren

QUESTION: What are your current projections these days for bulk cargo launch prices?

From the objectives laid out in the Requirement Specification

On entry into service cost per kg = $8000 (2004)
About 80% current prices but this is a true unsubsidised cost and is less than half the true cost of current expendables.

In Mature Service (the most meaningful number) cost per kg = $1000 (2004)

Falcon 9 at current prices is $4667 per kg using latest pricing ($49 million per launch) and max payload estimates (10,500 kg). This is a true unsubsidized cost and is the true cost of a current expendable.

F9 Heavy single payload to LEO current price is $95 million, with a max payload of 32,000 kg = $2969 per kg.

Extrapolating this into future models by SpaceX (and yes, some SWAG is involved), the Falcon X price per kg I estimate will be around $1990/kg, the Falcon X Heavy will be $1330/kg, and the Falcon XX will be around $900/kg. I am not aware if SpaceX has a Falcon XX Heavy planned, if they did, it should price at about $600/kg.

If Space-ex can really meet these numbers, wonderful, more power to there proverbial elbow, they will provide good competition and I am sure we will keep each other on our proverbial toes. My fear for them is I cannot see where the “magic” is that makes them so much better than everyone else, but that will be become clear as their programme progresses.

But it will not be un-subsidised they have had very substantial funding from NASA which will not be paid back.

[93143]

Expendable SSTO is automatically cheaper to build and operate than a TSTO, allowing for more frequent launches and lower launch prices.

An expendable SSTO has to be a lot bigger than an expendable TSTO with the same payload.  It's perfectly feasible with 1960s rocket technology; most likely no one's tried it because it's not worth it.

[JohnFornaro]

Mark, Thanks up there.

[mlorrey]

Expendable SSTO is automatically cheaper to build and operate than a TSTO, allowing for more frequent launches and lower launch prices.

An expendable SSTO has to be a lot bigger than an expendable TSTO with the same payload.  It's perfectly feasible with 1960s rocket technology; most likely no one's tried it because it's not worth it.

Actually, I think the major road bump is to do with ballistic rocket folks being somewhat separate from the hypersonic air breathing folks. I am 99% sure that if SpaceX were to experiment with a Falcon 1e first stage with an air ram ejector around the Merlin engine, running a bit more fuel rich than usual (it normally runs fuel rich), that this would be a feasible SSTO expendable with nearly identical payload as the Falcon 1 TSTO. Without the expense of a second stage, this would make the cost to orbit drop at least 25-30%, and enable a huge improvement in responsiveness in rapid launch.

[DLR]

A reply to Warren

QUESTION: What are your current projections these days for bulk cargo launch prices?

From the objectives laid out in the Requirement Specification

On entry into service cost per kg = $8000 (2004)
About 80% current prices but this is a true unsubsidised cost and is less than half the true cost of current expendables.

In Mature Service (the most meaningful number) cost per kg = $1000 (2004)

Falcon 9 at current prices is $4667 per kg using latest pricing ($49 million per launch) and max payload estimates (10,500 kg). This is a true unsubsidized cost and is the true cost of a current expendable.

F9 Heavy single payload to LEO current price is $95 million, with a max payload of 32,000 kg = $2969 per kg.

Extrapolating this into future models by SpaceX (and yes, some SWAG is involved), the Falcon X price per kg I estimate will be around $1990/kg, the Falcon X Heavy will be $1330/kg, and the Falcon XX will be around $900/kg. I am not aware if SpaceX has a Falcon XX Heavy planned, if they did, it should price at about $600/kg.

Zenit is even better than Falcon 9. On Zenit, it's about 3000 to 4000 $ per kg.

[Jim Davis]

I am 99% sure that if SpaceX were to experiment with a Falcon 1e first stage with an air ram ejector around the Merlin engine, running a bit more fuel rich than usual (it normally runs fuel rich), that this would be a feasible SSTO expendable with nearly identical payload as the Falcon 1 TSTO.

Do you have any numbers to share with us? What do you base your confidence on?

[mlorrey]

I am 99% sure that if SpaceX were to experiment with a Falcon 1e first stage with an air ram ejector around the Merlin engine, running a bit more fuel rich than usual (it normally runs fuel rich), that this would be a feasible SSTO expendable with nearly identical payload as the Falcon 1 TSTO.

Do you have any numbers to share with us? What do you base your confidence on?

Falcon 1e first stage:
Dry mass 5680 kg
Fuel mass 87000kg
payload mass 500 kg
Base Merlin Isp: 304 sec
Ram ejector average Isp: 1200 sec (mach 0.5-mach 8.5)
The degree the ram ejector boosts total average isp is related to the thrust of the ejector vs the thrust of the Merlin itself.
For any combined average flight Isp of 375 seconds or greater:
delta-v 9938 m/s

You should be able to reduce the dry mass a bit since you don't need the same amount of structural support that the TSTO needs to support the mass of the second stage.

[gospacex]

{snip}
And what's the point of an SSTO that cannot return to Earth without refueling?

Such an SSTO could be used to carry cargo and propellant into space.  Like current rockets it would be thrown away after its single flight.

Expendable SSTO is automatically cheaper to build and operate than a TSTO, allowing for more frequent launches and lower launch prices.

Why? SSTO is *simpler* that TSTO, but with the same GLOW it also puts less mass into the orbit.

Therefore "$ *per kg*" metric need not automatically be better.

IIRC there are 1st stages (Titan II?) which can be theoretically used as SSTOs, but they would have near-zero payload fractions.

[mlorrey]

{snip}
And what's the point of an SSTO that cannot return to Earth without refueling?

Such an SSTO could be used to carry cargo and propellant into space.  Like current rockets it would be thrown away after its single flight.

Expendable SSTO is automatically cheaper to build and operate than a TSTO, allowing for more frequent launches and lower launch prices.

Why? SSTO is *simpler* that TSTO, but with the same GLOW it also puts less mass into the orbit.

Therefore "$ *per kg*" metric need not automatically be better.

IIRC there are 1st stages (Titan II?) which can be theoretically used as SSTOs, but they would have near-zero payload fractions.

Actually, Titan II was a valid 1.5STO with a substantial payload fraction. It dropped two of its three 1st stage motors after 50% of fuel was consumed.

The cost of launching a TSTO is not simply 1+2=3. It is 1 plus 2 plus the time and expense of combining 1 and 2, plus the risk that 2 won't ignite and 3 will be lost. So it comes out to something like 1+2=4.3.... whereas 1 = 1....

Since you can produce and launch 1's all day long with a much higher chance each 1 will get to orbit, then even if your payload to orbit is less than half that of a TSTO, two or more SSTO's will still put the same amount of gross payload in orbit for less cost per kg.

[gospacex]

Actually, Titan II was a valid 1.5STO with a substantial payload fraction. It dropped two of its three 1st stage motors after 50% of fuel was consumed.

Titan-II had two engines on its 1st stage and it did not drop them. Did you mean "Atlas"?