Author Topic: The Reaction Engines Skylon/SABRE Master Thread (6)  (Read 173122 times)

Offline Star One

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The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #620 on: 06/15/2017 08:42 AM »
Yeah, governments could potentially want to own their own means of getting to orbit.  I was just addressing the commercial part of the argument.

I think it's questionable whether governments would rather spend money buying a launch vehicle built in another country rather than plowing money into domestic capability, but there is at least the potential some governments might.

Boeing has made money selling aircraft to foreign airlines.

Foreign airlines are businesses.  The whole point of this conversation you're replying to is that governments might put money into space programs for non-business reasons.  The point is that Skylon might be bought by governments for non-business reasons.  So Boeing selling to airlines is not very relevant.


Foreign airlines are frequently owned by their government making them little more than government departments. They exist to be flying adverts for the government - a non-business reason. So selling is very relevant.

This is not going to be like a 737 anytime soon so I don't think it's a useful comparison at the moment.
« Last Edit: 06/15/2017 08:43 AM by Star One »

Offline hkultala

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #621 on: 06/15/2017 09:17 AM »

Is there any fundamental reason the Blue Origin and SpaceX approaches would take any longer to turn around than Skylon would?  I don't believe so.  Bezos and Musk don't seem to believe so either.

BO plans to land on barge. It takes many hours for that barge to sail back to port. Then aditional time to unload the rocket and transport it back to launch site.

Same with SpaceX for barge landings.

And even when landing to a landing pad near the launch site, transporting the rocket from the landing pad back to the launch pad easily takes many hours, as special cranes need to be used etc.

Towing Skylon at the runway can be done in minutes.



So, until SpaceX/BO land directly into the launch pad, they have a fundamental disadvantage in this.

Offline Star One

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #622 on: 06/15/2017 09:19 AM »

Is there any fundamental reason the Blue Origin and SpaceX approaches would take any longer to turn around than Skylon would?  I don't believe so.  Bezos and Musk don't seem to believe so either.

BO plans to land on barge. It takes many hours for that barge to sail back to port. Then aditional time to unload the rocket and transport it back to launch site.

Same with SpaceX for barge landings.

And even when landing to a landing pad near the launch site, transporting the rocket from the landing pad back to the launch pad easily takes many hours, as special cranes need to be used etc.

Towing Skylon at the runway can be done in minutes.



So, until SpaceX/BO land directly into the launch pad, they have a fundamental disadvantage in this.

I'd though eventually Skylon would be able to land at any sufficiently long runaway providing the relevant facilities had been added. Comparing it with things like Falcon 9 & NG is like comparing apples with oranges.

Offline IRobot

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #623 on: 06/15/2017 09:26 AM »
Probably this was already discussed, but what about a Stratolaunch-like concept with Skylon?
Simplify the airplane, it "only" goes up to Mach 5 and then launch a rocket at higher altitude and speed than Stratolaunch.

It could probably launch a larger payload than Skylon itself, without the need of all the other SSTO hassles.

The major problem I see is launching a rocket from Mach 5. Unsure how it would work out.

But even if it works, I see it only as a cheaper and faster way to use SABRE engines. Still I think it would not be as good as a standard rocket, especially regarding volume and lack of hold down test.

Offline t43562

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #624 on: 06/15/2017 11:17 AM »
Probably this was already discussed, but what about a Stratolaunch-like concept with Skylon?
Simplify the airplane, it "only" goes up to Mach 5 and then launch a rocket at higher altitude and speed than Stratolaunch.

It could probably launch a larger payload than Skylon itself, without the need of all the other SSTO hassles.

The major problem I see is launching a rocket from Mach 5. Unsure how it would work out.

But even if it works, I see it only as a cheaper and faster way to use SABRE engines. Still I think it would not be as good as a standard rocket, especially regarding volume and lack of hold down test.

That's what the current crop of TSTO ideas for SABRE are.

Offline JCRM

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #625 on: 06/15/2017 06:05 PM »

Worst, Skylon is LEO-only, meaning you need to add the cost of an upper stage for GTO.

IMO, Skylon won't be able to compete with SpaceX/BE. Cost per Kg will be similar, but with smaller volume, smaller payload weight, limited to LEO and a huge upfront investment.
The ESA had the development cost of the SUS (reusable Skylon Upoer Stage) included in the development budget.


I think it's questionable whether governments would rather spend money buying a launch vehicle built in another country rather than plowing money into domestic capability, but there is at least the potential some governments might.


The British canned Black Arrow to buy launches from NASA.


Skylon hasn't seemed to be on the agenda for a while now,
No, not since the D1 and its business case was signed off - that's about as far as it could go/was worth taking it, and getting hard figures on SABRE became the next hurdle of development.

Quote
and especially since BAE took a share in the company. They've looked far more interested in the monetisation of the elements of the technology than a grand project like Skylon.
I would put the interest in monetisation at the newer REL management's feet. Perhaps they believe they want investment they have to show a potential for return well before the 20 billion research is complete, even if that isn't the most efficient way of getting there.
Quote
Also they only seem interested in TSTO in as far as they can sell the concept to someone like the USAF to pick up and give them funding to develop it further.
in the same was as they were interested in a Mach 5 antipodean plane when LAPCAT was paying for research.




The researchers now at REL got burned by that with HOTOL.  I'm pretty sure they are well aware of what they can and cannot do to retain rights over their inventions.
The original engineers at REL got burned. They've handed over to new faces. Hopefully they will remember the lessons.
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The new direction is finally creating opportunities to grow, and this moaning about BAE or TSTO is getting boring.

Unless some multi-billionaire or foreign government was willing to swoop in and pay the costs upfront Skylon was never going to happen. 
Absolutely.

Offline ChrisWilson68

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #626 on: 06/16/2017 01:12 AM »
I think it's questionable whether governments would rather spend money buying a launch vehicle built in another country rather than plowing money into domestic capability, but there is at least the potential some governments might.

The British canned Black Arrow to buy launches from NASA.

Yeah, exactly, they cancelled owning their own launch vehicle to buy launch services from NASA.

The argument for Skylon having an advantage because they're selling the vehicle doesn't hold if government either (a) are fine having someone else do the launch or (b) want to own the launch capability but want to develop it locally.  Killing black arrow is an example of (a).

Where's the example of a government not wanting to have their payloads launched by another country but being willing to buy the launch vehicles from another country?

Of course, my asking for examples of that is a little unfair because historically launch vehicles have not been reusable, so buying them from another country makes you dependent on a continuing supply from that country.  But still it means there's no evidence to support the thesis that governments would be willing to buy launch vehicles.

In the long term, I do expect launch vehicles to become commoditized, just like airliners are today, and at that point, I do expect governments that want their own launch capability to buy them.  But I don't think those commoditized launch vehicles will look like Skylon.  I think they're more likely to look like ITS.

I also think that as soon as launch vehicles are commoditized, all manufacturers of them will switch over to selling them to anyone who wants to buy (subject to ITAR-style rules that will leave out North Korea and friends).  If somehow, it turns out a business can be made selling Skylons, at that point SpaceX, Blue Origin, and any other launch vehicle manufacturers are likely to go after that market too.  So even if and when selling launch vehicles becomes a compelling business, I don't think Skylon will have an advantage.

Offline ChrisWilson68

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #627 on: 06/16/2017 01:12 AM »

Is there any fundamental reason the Blue Origin and SpaceX approaches would take any longer to turn around than Skylon would?  I don't believe so.  Bezos and Musk don't seem to believe so either.

BO plans to land on barge. It takes many hours for that barge to sail back to port. Then aditional time to unload the rocket and transport it back to launch site.

Same with SpaceX for barge landings.

And even when landing to a landing pad near the launch site, transporting the rocket from the landing pad back to the launch pad easily takes many hours, as special cranes need to be used etc.

Towing Skylon at the runway can be done in minutes.

So, until SpaceX/BO land directly into the launch pad, they have a fundamental disadvantage in this.

Have you really not seen the video of Falcon 9 first stages flying back and landing at the launch site?

Offline t43562

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #628 on: 06/16/2017 04:49 AM »
I think it's questionable whether governments would rather spend money buying a launch vehicle built in another country rather than plowing money into domestic capability, but there is at least the potential some governments might.

The British canned Black Arrow to buy launches from NASA.

Yeah, exactly, they cancelled owning their own launch vehicle to buy launch services from NASA.

The argument for Skylon having an advantage because they're selling the vehicle doesn't hold if government either (a) are fine having someone else do the launch or (b) want to own the launch capability but want to develop it locally.  Killing black arrow is an example of (a).

Where's the example of a government not wanting to have their payloads launched by another country but being willing to buy the launch vehicles from another country?

Of course, my asking for examples of that is a little unfair because historically launch vehicles have not been reusable, so buying them from another country makes you dependent on a continuing supply from that country.  But still it means there's no evidence to support the thesis that governments would be willing to buy launch vehicles.

In the long term, I do expect launch vehicles to become commoditized, just like airliners are today, and at that point, I do expect governments that want their own launch capability to buy them.  But I don't think those commoditized launch vehicles will look like Skylon.  I think they're more likely to look like ITS.

I also think that as soon as launch vehicles are commoditized, all manufacturers of them will switch over to selling them to anyone who wants to buy (subject to ITAR-style rules that will leave out North Korea and friends).  If somehow, it turns out a business can be made selling Skylons, at that point SpaceX, Blue Origin, and any other launch vehicle manufacturers are likely to go after that market too.  So even if and when selling launch vehicles becomes a compelling business, I don't think Skylon will have an advantage.

The UK is a trick question because it's the *only* country to give up its launch capability.  You would get a country to adopt your tech in exactly the way BAE is doing with the Turkish TFX or Leonardo did with the T129 helicopter.  They get to develop a customised vehicle using your engines and your consultancy to build up their skills.

Offline Star One

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #629 on: 06/16/2017 06:28 AM »
I think it's questionable whether governments would rather spend money buying a launch vehicle built in another country rather than plowing money into domestic capability, but there is at least the potential some governments might.

The British canned Black Arrow to buy launches from NASA.

Yeah, exactly, they cancelled owning their own launch vehicle to buy launch services from NASA.

The argument for Skylon having an advantage because they're selling the vehicle doesn't hold if government either (a) are fine having someone else do the launch or (b) want to own the launch capability but want to develop it locally.  Killing black arrow is an example of (a).

Where's the example of a government not wanting to have their payloads launched by another country but being willing to buy the launch vehicles from another country?

Of course, my asking for examples of that is a little unfair because historically launch vehicles have not been reusable, so buying them from another country makes you dependent on a continuing supply from that country.  But still it means there's no evidence to support the thesis that governments would be willing to buy launch vehicles.

In the long term, I do expect launch vehicles to become commoditized, just like airliners are today, and at that point, I do expect governments that want their own launch capability to buy them.  But I don't think those commoditized launch vehicles will look like Skylon.  I think they're more likely to look like ITS.

I also think that as soon as launch vehicles are commoditized, all manufacturers of them will switch over to selling them to anyone who wants to buy (subject to ITAR-style rules that will leave out North Korea and friends).  If somehow, it turns out a business can be made selling Skylons, at that point SpaceX, Blue Origin, and any other launch vehicle manufacturers are likely to go after that market too.  So even if and when selling launch vehicles becomes a compelling business, I don't think Skylon will have an advantage.

The UK is a trick question because it's the *only* country to give up its launch capability.  You would get a country to adopt your tech in exactly the way BAE is doing with the Turkish TFX or Leonardo did with the T129 helicopter.  They get to develop a customised vehicle using your engines and your consultancy to build up their skills.
Being from the UK and knowing something of what our politicians are like I would say trying to extrapolate anything from a political decision made 50 odd years ago as being indicative of any decisions that might be made in the future is a mugs game. I would argue that the politicians then and the politicians we have now are not that alike.

Offline JCRM

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #630 on: 06/16/2017 07:54 AM »
I think it's questionable whether governments would rather spend money buying a launch vehicle built in another country rather than plowing money into domestic capability, but there is at least the potential some governments might.

The British canned Black Arrow to buy launches from NASA.

Yeah, exactly, they cancelled owning their own launch vehicle to buy launch services from NASA.

The argument for Skylon having an advantage because they're selling the vehicle doesn't hold if government either (a) are fine having someone else do the launch or (b) want to own the launch capability but want to develop it locally.  Killing black arrow is an example of (a).

Where's the example of a government not wanting to have their payloads launched by another country but being willing to buy the launch vehicles from another country?
I'd say it was option (c) a country that wanted it's own launch capability, but wasn't able to afford the development (most particularly not being able to weather the failures) and so had to make do with the commoditised launch offered by another country.
As a different half-answer, I give you ESA, who through Arianespace buy Soyuz as a medium lift launcher.


Quote
I also think that as soon as launch vehicles are commoditized, all manufacturers of them will switch over to selling them to anyone who wants to buy (subject to ITAR-style rules that will leave out North Korea and friends).  If somehow, it turns out a business can be made selling Skylons, at that point SpaceX, Blue Origin, and any other launch vehicle manufacturers are likely to go after that market too.  So even if and when selling launch vehicles becomes a compelling business, I don't think Skylon will have an advantage.
The advantage Skylon would have is that it was designed to be commoditised, with simplified integrataion and infrastructure, rather than it being retrofitted. Whether that design would work is a different matter. 

Offline ChrisWilson68

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #631 on: 06/18/2017 11:50 PM »
Quote
I also think that as soon as launch vehicles are commoditized, all manufacturers of them will switch over to selling them to anyone who wants to buy (subject to ITAR-style rules that will leave out North Korea and friends).  If somehow, it turns out a business can be made selling Skylons, at that point SpaceX, Blue Origin, and any other launch vehicle manufacturers are likely to go after that market too.  So even if and when selling launch vehicles becomes a compelling business, I don't think Skylon will have an advantage.
The advantage Skylon would have is that it was designed to be commoditised, with simplified integrataion and infrastructure, rather than it being retrofitted. Whether that design would work is a different matter.

It doesn't look that way to me.  To me, Skylon's operations and maintenance would be likely to be much more difficult and expensive than those of two-stage vertical take-off and landing rockets like those of SpaceX and Blue Origin.  Most of that is because single-stage to orbit requires more exotic technologies, and they tend to be more finicky.

SpaceX/Blue Origin rockets only need kerosene or methane and LOX.  Skylon needs liquid hydrogen.  Liquid hydrogen is far more difficult to handle.  The ground-side equipment for it has many more problems.  Just look at how often the Space Shuttle was scrubbed because of liquid hydrogen issues.  The greater temperature difference between liquid hydrogen and ambient temperature causes more thermal issues.  The small size of hydrogen molecules means it tends to work its way into materials and make them brittle over time, or just leak out.

Since Skylon is SSTO, it also needs special heat shielding technology that is very lightweight, and not used in the past.  That is exactly what led to huge operational costs for the shuttle.  The Skylon heat shield plans are very different from shuttle's, but the operational issues are a big unknown.

More generally, with SSTO, it's harder to add mass to make parts more resilliant compared with a two-stage system, so it's harder to find ways to fix operational issues.

Offline Star One

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #632 on: 06/19/2017 10:47 AM »
Quote
I also think that as soon as launch vehicles are commoditized, all manufacturers of them will switch over to selling them to anyone who wants to buy (subject to ITAR-style rules that will leave out North Korea and friends).  If somehow, it turns out a business can be made selling Skylons, at that point SpaceX, Blue Origin, and any other launch vehicle manufacturers are likely to go after that market too.  So even if and when selling launch vehicles becomes a compelling business, I don't think Skylon will have an advantage.
The advantage Skylon would have is that it was designed to be commoditised, with simplified integrataion and infrastructure, rather than it being retrofitted. Whether that design would work is a different matter.

It doesn't look that way to me.  To me, Skylon's operations and maintenance would be likely to be much more difficult and expensive than those of two-stage vertical take-off and landing rockets like those of SpaceX and Blue Origin.  Most of that is because single-stage to orbit requires more exotic technologies, and they tend to be more finicky.

SpaceX/Blue Origin rockets only need kerosene or methane and LOX.  Skylon needs liquid hydrogen.  Liquid hydrogen is far more difficult to handle.  The ground-side equipment for it has many more problems.  Just look at how often the Space Shuttle was scrubbed because of liquid hydrogen issues.  The greater temperature difference between liquid hydrogen and ambient temperature causes more thermal issues.  The small size of hydrogen molecules means it tends to work its way into materials and make them brittle over time, or just leak out.

Since Skylon is SSTO, it also needs special heat shielding technology that is very lightweight, and not used in the past.  That is exactly what led to huge operational costs for the shuttle.  The Skylon heat shield plans are very different from shuttle's, but the operational issues are a big unknown.

More generally, with SSTO, it's harder to add mass to make parts more resilliant compared with a two-stage system, so it's harder to find ways to fix operational issues.

Being as a lot of this technology like in heat shielding falls under proprietorial information and therefore what we can know about it is limited I am not sure other than talking in fairly unhelpful very great generalities that there is much useful that can be discussed about it at this stage.

Offline IRobot

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #633 on: 06/19/2017 11:33 AM »

Worst, Skylon is LEO-only, meaning you need to add the cost of an upper stage for GTO.

IMO, Skylon won't be able to compete with SpaceX/BE. Cost per Kg will be similar, but with smaller volume, smaller payload weight, limited to LEO and a huge upfront investment.
The ESA had the development cost of the SUS (reusable Skylon Upoer Stage) included in the development budget.

Yeah, but that cost is not on cost per kg for LEO... so for GTO, cost is much more expensive because of the extra upper stage.

Offline knowles2

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #634 on: 06/20/2017 01:14 AM »
I think it's questionable whether governments would rather spend money buying a launch vehicle built in another country rather than plowing money into domestic capability, but there is at least the potential some governments might.

The British canned Black Arrow to buy launches from NASA.



Where's the example of a government not wanting to have their payloads launched by another country but being willing to buy the launch vehicles from another country?

The US relies on Russian made engines for it vehicles.

Offline knowles2

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #635 on: 06/20/2017 01:16 AM »

Worst, Skylon is LEO-only, meaning you need to add the cost of an upper stage for GTO.

IMO, Skylon won't be able to compete with SpaceX/BE. Cost per Kg will be similar, but with smaller volume, smaller payload weight, limited to LEO and a huge upfront investment.
The ESA had the development cost of the SUS (reusable Skylon Upoer Stage) included in the development budget.

Yeah, but that cost is not on cost per kg for LEO... so for GTO, cost is much more expensive because of the extra upper stage.
depends on what type of upper stage you use, I thought Reaction engine was planning on using a fully reusable upper stage.

Online docmordrid

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #636 on: 06/20/2017 10:49 AM »
>
The US relies on Russian made engines for it vehicles.

Falcon 9, soon Falcon Heavy, and Delta IV do not use Russian engines.  Only Atlas V and the non-EELV Antares use Russian engines.
« Last Edit: 06/20/2017 10:51 AM by docmordrid »
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Offline john smith 19

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #637 on: 06/21/2017 11:52 AM »
Being as a lot of this technology like in heat shielding falls under proprietorial information and therefore what we can know about it is limited I am not sure other than talking in fairly unhelpful very great generalities that there is much useful that can be discussed about it at this stage.
And that's the easy stuff.  :)

There are 2 other big jokers in the SX story.

1) SX can't do 2nd stage return from orbit.  In 2011 they thought they could. Then in 2014 they said it was off the table for all F9 derived hardware. Now they are saying it may be possible after all.

This is not engineering. This is science. The truth is they don't know if it will work, or if it will ever work with Kerolox, although they seem more confident that it will work with Methalox. Probably. we will find out when FH launches (when is that now?)

OTOH we know large vehicles with Isps of 3000 can be built that can take off from the ground and reach at least M3+. The XB70 proved that. We also know large winged vehicles can land from orbital speed. It's been done 135 times. SABRE gives the "virtual staging" benefits of high Isp that allows you build a winged airframe without the minuscule mass fraction that a rocket imposes on you.

SX was betting that when they'd got their rocket flying "something" would turn up.  For 1st stage recovery it has. 

But we don't know if "something will turn up for 2nd stage recovery.

Skylon requires a lot of money and good engineering.

A full reusable VTO TSTO needs several breakthroughs in physics which may (or may not) happen.

2) The repeated shock loads of slamming the airframe of the first stage into the ground, or if you're really unlucky into a pitching deck that's coming up as it's going down. I'm unaware of any similar industrial situation, or of any design standards that exist for it. What happens when you decellerate a large, high aspect ratio structure from X m/s to 0 m/s in << 1 sec? How good are the landing legs at smoothing this out? Will they have to be replaced every time as the price for protecting the rest of the structure? If that's ineffective what parts may be cracked off by those loads?

IOW SX are looking at more science.  Maybe the damage will be trivial. Maybe it will set a very hard limit on viable reuse.

The difference between HTOL and VTO TSTO reusability ideas is this.

We know that if you can build a vehicle with the necessary Isp and mass fractions a complete vehicle capable of HTOL SSTO is possible because SABRE/Skylon duplicates enough of known flight paths (the powered takeoff of large jets to the no engine glide of the Shuttle) to expect there will be no major "unknown unknowns" to find. That's because aircraft are designed to fly by aerodynamic lift and the human race has built a lot of them.

In contrast we are not even sure all the problems are actually known to do the same for a complete (IE not a capsule) upper stage. IOW you are trying to make something (a VTO ELV) do something that it was never, ever designed to do (land again). It has taken SX 14 years to get to get to the point where they can recover and recover a first stage.

Yeah, but that cost is not on cost per kg for LEO... so for GTO, cost is much more expensive because of the extra upper stage.
What exactly is the point you're trying to make?

In fact REL looked at putting Skylon to (IIRC) an 8000Km orbit for comm sats with ion thrusters to get to GEO without repeated passed through the Van Allan belt.

The Skylon Upper Stage was targeted at 10 reuses.  A few $m increase on launch price.  or you could shop around and ask other Skylon operators what price they'd give you.

BTW SX's stated price for GTO only applies to comm sats below a certain mass. Above that limit things will get a lot more expensive.
« Last Edit: 06/21/2017 11:53 AM by john smith 19 »
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Online Lars-J

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #638 on: 06/22/2017 12:35 AM »
...
Skylon requires a lot of money and good engineering.

A full reusable VTO TSTO needs several breakthroughs in physics which may (or may not) happen.
...

Wha..? I don't even know where to start. The rest of your rant makes little sense, but I think you here you have got something twisted around quite a bit. VTO TSTS is well within known physics and current engineering capabilities. SpaceX didn't abandon it because of physics  ;D :o, it was because of the excessive payload hit. The added performance of Methane and further improved mass fractions is what will make it more doable with the next generation vehicle.

In your world (tenuously connected to ours), you seem to think that Skylon is just expensive but doable. Whereas VTOL TSTO is ... what ...cheap but impossible?? Let me let you in on something... Skylon is projected to cost so much because of how difficult is to pull off, because of how much of the technology does not exist.

And don't start with your odd ideas about physics vs engineering. You do not appear to understand the difference.

2) The repeated shock loads of slamming the airframe of the first stage into the ground, or if you're really unlucky into a pitching deck that's coming up as it's going down. I'm unaware of any similar industrial situation, or of any design standards that exist for it. What happens when you decellerate a large, high aspect ratio structure from X m/s to 0 m/s in << 1 sec? How good are the landing legs at smoothing this out? Will they have to be replaced every time as the price for protecting the rest of the structure? If that's ineffective what parts may be cracked off by those loads?

You write this as if it is some unique issue with vertical landing. Have you never heard of hard aircraft landings?


« Last Edit: 06/27/2017 06:06 PM by Lars-J »

Offline Robotbeat

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Re: The Reaction Engines Skylon/SABRE Master Thread (6)
« Reply #639 on: 06/22/2017 02:01 AM »
"Breakthrough in physics"... for real??
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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