Will Skylon Actually Fly?

[Kryten]

You don't need to bring in politics, there are more than enough technological and economic reasons for this to be stuffed.

[KerikBalm]

Yeah, this actually should be a problem. Skylon needs a huge market to work economically, and it won't be built until that is proven.

But once it is built, it won't be limited by external tank construction rates - and the infrastructure is supposed to be much less than what the shuttle required.

So you can have a higher launch rate, and you don't need a higher launch rate to offset the "per launch" costs due to lots of infrastructure.

It remains to see if the marginal launch cost will actually end up being cheaper... the marginal launch cost of the shuttle was terrible.

Even if they launched 100 missions per year, they'd still lose more money than if they did 100 disposable missions per year - they'd just lose less money per launch, offset by more launches.

This thing, if it works, and if its not even a few % overweight (turning a 5% payload fraction into a 2% payload fraction will absolutely wreck the cost per ton economics), should at least have the lower marginal cost + higher launch rate capability + less infrastructure cost.

This should be a big problem for Skylon. Such a big program is inherently political, and the UK hasn't got the bucks to go at this alone.

Well, it avoids the US mess. The UK is much smaller, so if work is spread around the UK, its still more consolidated than having stuff scattered throughout the US.

And... does it have to be political? could not some enterprising billionaire step in? What is SpaceX looks at the engine, and see's something they like?

What if Virgin Galactic wants to get into the orbital game?

There are no politicians with their claws into this thing, fighting to pack it with as much pork as possible... at least not yet.

So, for now, its not a problem.

[fredinno]

Skylon needs to be designed to allow for h2lox upper stages- otherwise, anything BLEO is basically screwed, unless ion drive tugs are used. This will be a pain to do- the shuttle designers literallly hated Centaur-G.

[Majorjim!]

The UK government are in the second phase of building a working spaceport. Supposedly by 2018. This is exciting news.

I also read that the European commission cleared £50 million towards development of the engine. Personally I believe they should be giving a lot more. This is what us Brits do very well indeed, aircraft design. We are a nation of tinkerers and I have firm belief that the engine at least will be built.

Edited October 12, 2015 by Majorjim

[Shania_L]

Skylon itself is a sound idea, many independent studies have verified it as "possible" the thing that will kill it is capitalism or politics.

Reaction Engines already has an agreement with the US Airforce (PDF) so expect them to suck all the secrets and then build their own "totally not a copy" Skylon off in the US somewhere.

The guys running Reaction Engines have fallen foul of Government cancelling tech projects before, Re Rolls Royce HOTOL, so they have stated they will not agree to become a government project.

Its something I really want to see happen, and something that the space industry really needs. Save the brute force rockets for the ungainly or super heavy payloads, and let spaceplanes take the regular cargo and crew delivery missions.

You cannot compare Skylon to the shuttle, they are entirely different beasts, the shuttle was essentially a disposable rocket with a massively oversized return capsule. Skylon doesnt have the same payload ability, but it is truly re-usable, to the point where there is nothing stopping you from launching the same ship twice a day.

Edited October 12, 2015 by Shania_L

[Kryten]

You cannot compare Skylon to the shuttle, they are entirely different beasts, the shuttle was essentially a disposable rocket with a massively oversized return capsule. Skylon doesnt have the same payload ability, but it is truly re-usable, to the point where there is nothing stopping you from launching the same ship twice a day.

Except the fact nobody needs anything launched twice a day, and especially not to low earth orbit. This is the biggest problem with Skylon, and it's one it shares with all the 80s and 90s SSTO proposals it should've dies with; the figures come out great, just as long as you assume there's much more demand than there actually is.

[Der Anfang]

Skylon itself is a sound idea, many independent studies have verified it as "possible" the thing that will kill it is capitalism or politics.

Reaction Engines already has an agreement with the US Airforce (PDF) so expect them to suck all the secrets and then build their own "totally not a copy" Skylon off in the US somewhere.

The guys running Reaction Engines have fallen foul of Government cancelling tech projects before, Re Rolls Royce HOTOL, so they have stated they will not agree to become a government project.

Its something I really want to see happen, and something that the space industry really needs. Save the brute force rockets for the ungainly or super heavy payloads, and let spaceplanes take the regular cargo and crew delivery missions.

You cannot compare Skylon to the shuttle, they are entirely different beasts, the shuttle was essentially a disposable rocket with a massively oversized return capsule. Skylon doesnt have the same payload ability, but it is truly re-usable, to the point where there is nothing stopping you from launching the same ship twice a day.

The weights between both the Skylon and the space shuttle are also interestingly different. Skylon weoghs nearly as much as a 747, I think somewhere at 250+ t, whereas the spaceshuttle itself (excluding the latter stages) weight about somewhere between 25-40 t? I don't remember exactly. Regardless, this is something I really hope to see happen.

[Shania_L]

Virgin Galactic got a contract recently for 300 LEO satellites, launch them a few at a time, put it up in a few months.

Also the frequency of launch allows you to get away with the reduced payload capacity. Launch an ISS supply on a dragon maybe once every 6 months, but Skylon could put fresh food on (or floating above) the table every week.

Who ever thought you would need to be able to get across the Atlantic faster than a cruise liner? Well, once planes could do it we certainly found many reasons why.

[Red Iron Crown]

Put me in the "cool idea, but it will never fly" camp, at least to orbit. I've been following spaceflight for long enough to view any project that promises lower operating costs through reusability with a healthy dose of skepticism, especially those that require revolutionary new propulsion. Sure, it looks good on paper, as all such projects do, but the devil truly is in the implementation details. I suspect the projected turnaround times are just as optimistic and unlikely as those of the STS and, as others have alluded to, the economies of scale only start to pay off with a launch schedule that is greater than total global demand.

I'd love to be wrong, but I'm really skeptical.

[Kryten]

Virgin Galactic got a contract recently for 300 LEO satellites, launch them a few at a time, put it up in a few months.

They only got a contract to send up replacement sats; the constellation construction is with Soyuz-Fregat, which worked out much cheaper. Even if we assume this ends up happening, there'll only be demand to send up a replacement say every few months, which is not remotely enough to sustain something the size of Skylon.

Also the frequency of launch allows you to get away with the reduced payload capacity. Launch an ISS supply on a dragon maybe once every 6 months, but Skylon could put fresh food on (or floating above) the table every week.

Can you put up a GTO comsat a tiny bit at a time? No. Can you put up an SSO imaging sat a bit at a time? No. Those are the real commercial markets, not food for the ISS.

Who ever thought you would need to be able to get across the Atlantic faster than a cruise liner? Well, once planes could do it we certainly found many reasons why.

Build it and they will come, that's all you've got? This has happened before, and 'they' didn't appear. We had all sorts of people running around with SSTO concepts in the 90s, which much better funding and backing than skylon, and the orders didn't appear to keep them alive.

[Guest]

Until they fire and prove that engine, and I'm not going to put any bets down in favor of it actually happening, the entire concept is just a pipe dream.

[jwenting]

Except the fact nobody needs anything launched twice a day, and especially not to low earth orbit. This is the biggest problem with Skylon, and it's one it shares with all the 80s and 90s SSTO proposals it should've dies with; the figures come out great, just as long as you assume there's much more demand than there actually is.

the payload capacity is so small, you'd need several launches just to come close to a single launch of a small model disposable rocket.

Which completely negates any cost benefits you may have per launch...

IF it flies, it's a nice technology demonstrator, but won't be a viable commercial transportation system unless someone manages to find a way to make major money selling cubesats...

[Shania_L]

Have you even looked at the technical specs of Skylon?

Reaction Engines state that it is a demonstration design, they are an engine company, even so the design is 4.6m x 12m and 15 tonnes (D1 variant) to 300km LEO. That is plenty for an imaging satellite, plenty for a smaller GSO sat+boost stage. There is a design on their website for an upper stage that can put 4 tonnes into GSO.

I said in my previous post, leave the massive payloads to brute force rockets, Skylon isnt trying to compete for the massive launches, 15 tonnes is more than enough for regular Low Orbit missions, crew and cargo delivery to ISS etc.

Even if noone picks up on the Skylon design itself, you can bet that the armed forces are salivating over the SABRE engine, that if nothing else will get built.

[Kryten]

So how exactly is it supposed to be launching frequently with those kind of payloads? You get that maybe once a month, and many of those are non-competed launches.

[Rakaydos]

So how exactly is it supposed to be launching frequently with those kind of payloads? You get that maybe once a month, and many of those are non-competed launches.

By being cheap and reliable enough to get the ENTIRE low mass market to itself?

If it can reenter with a payload, that another market that right now only Dragon fills.

[Bill Phil]

So how exactly is it supposed to be launching frequently with those kind of payloads? You get that maybe once a month, and many of those are non-competed launches.

Come to think of it, which payload mass range is the most demanded? For LEO, of course. I was thinking maybe launch a number of satellites with each Skylon flight.

Heh, maybe send up a few scores of cubesats?

[problemecium]

No, because it is a building.

https://en.wikipedia.org/wiki/Skylon_Tower

[kStrout]

Except the fact nobody needs anything launched twice a day, and especially not to low earth orbit. This is the biggest problem with Skylon, and it's one it shares with all the 80s and 90s SSTO proposals it should've dies with; the figures come out great, just as long as you assume there's much more demand than there actually is.

And the reason nobody tries to launch things twice a day is because nobody has the ability to launch stuff twice a day. When airplanes were first mass produced I bet you never had hundreds of people trying to get from point A to point B consistently every day, now look at the world. As supply increases, cost decreases to increase demand, and when you have enough demand cost will increase and whoever has supply gets rich.

[juanml82]

Reliable piggyback payload separation is suicidal at supersonic speeds, let alone hypersonic, read up on the M-21/D-21 project

Ok, I'm a layman, but how much different is that to a combat aircraft firing large (say, cruise) missiles?

Who ever thought you would need to be able to get across the Atlantic faster than a cruise liner? Well, once planes could do it we certainly found many reasons why.

The Concorde, however, was retired and no aircraft has appeared to compete with it. There is a lot of difference in the time it takes to cross the Atlantic by ship than by subsonic aircraft. But how many people would be willing to pay the price difference of a few hours in first class at match 0.9 and a super-fast, less than an hour, but vastly more expensive suborbital hop?

I don't think it will work for regular transportation. Where it can work, is for tourism.

And the reason nobody tries to launch things twice a day is because nobody has the ability to launch stuff twice a day. When airplanes were first mass produced I bet you never had hundreds of people trying to get from point A to point B consistently every day, now look at the world. As supply increases, cost decreases to increase demand, and when you have enough demand cost will increase and whoever has supply gets rich.

Keep in mind there is also the cost of making/buying the satellite itself and tracking it later. A cheaper launch vehicle doesn't help with that.

[Rakaydos]

Keep in mind there is also the cost of making/buying the satellite itself and tracking it later. A cheaper launch vehicle doesn't help with that.

Cheaper transportation makes top of the line satelite compnents unnesisary. If you can afford three times as many replacement flights, you can afford to pay a tenth the cost for something that breaks down twice as fast.

[Nothalogh]

Ok, I'm a layman, but how much different is that to a combat aircraft firing large (say, cruise) missiles?

Those are often launched at subsonic speeds, and even at supersonic speeds, a relatively small missile has considerably less aerodynamic loading

[KerikBalm]

There are very few aircraft that flew at hypersonic speed... and I'm only aware of one that tried to release another flying object... the SR-71.

The XB-70 would have dropped bombs... the Mig-25 didn't break mach 3 with weapons (and could not sustain mach 3 for long at all).

I don't think its much of a problem if you're not launch something that is also generating aerodynamic lift.

If it was just a hypersonic launcher for a rocket that just falls for a bit before igniting its rocket, then it should be fine?

If you want to reuse the rocket, perhaps it could have fold out wings?

I'm not sold on the idea of an SSTO at all.

Reusable yes, SSTO, no...

I really like the concepts from the early shuttle design process:

Seems to me if the first booster gets it high enough in the atmosphere, that the seperation shouldn't be a problem, because the air would be so thin, and the orbiter would be accelerating rapidly away due to its rocket thrust (the booster would decelerate due to drag) - the SR-71&D-21 system would have a much slower seperation compared to that... because their propulsion was very similar... they successfully seperated 3 times, the 4th was fatal. The 4th the SR-71 was not pitching down during release as before. I think that it wouldn't be too hard to get the seperation to proceed smoothly.

The D-21 was first launched from an M-21 on 5 March 1966.[8] The drone was released but stayed close to the M-21's back for a few seconds, which seemed like "two hours" to the M-21 crew.[9] A second launch took place on 27 April 1966, with the D-21 reaching its operational altitude of 90,000 feet (27,400 m) and speed of over Mach 3.3, though it was lost due to a hydraulic pump failure after a flight of over 1,200 nmi (1,400 mi; 2,200 km). The Air Force's interest in the program continued and more D-21s were ordered after the second launch.[8] A third flight took place on 16 June with the D-21 flying 1,550 nmi (1,780 mi; 2,870 km) through its complete flight profile, though its camera hatch was not released due to an electronics failure.[10]

The fourth and final launch from an M-21 on 30 July ended in disaster. Unlike the three previous launches this one was performed straight and level, not in an outside loop to assist in the separation of the drone from the aircraft. The D-21 suffered engine problems and struck the M-21's tail after separation, leading to the destruction of both aircraft.

* Seperation would occur in thinner atmosphere.

* Pitching down during release = standard proceedure.

* Start the orbiter rocket engine a fraction of a second before release... no release if the engine doesn't start. No flameouts to worry about with rocket engines.

I sounds trivial to solve to me.

Now you don't carry nearly as much dead weight to orbit -> higher payload fraction

And you don't have to design much of the craft at all to survive reentry temperatures... just mach 5... not mach 17...

You cannot compare Skylon to the shuttle, they are entirely different beasts, the shuttle was essentially a disposable rocket with a massively oversized return capsule. Skylon doesnt have the same payload ability, but it is truly re-usable, to the point where there is nothing stopping you from launching the same ship twice a day.

They re-used everything except the external tank.

The SRBs, the main engines, the life support, guidance... etc... no capsule was ever reused either.

The ET is much cheaper than a whole rocket... the problem is... those things needed a lot of work to use them again

So the question is... how much work will skylon need?

Initial rentry doesn't care about density, is about velocity, and those engine nacells are going to take the brunt of erosion. They will simply degrade before hitting breathable atmosphere.

Sure it does... who cares about hitting breathable atmosphere?

F=MA... aerodynamic force is related to area, which is related to density.

A very low density object will decelerate much faster, as it has a lot of surface area per unit mass.

A low density spaceplane would be able to decelerate more in the upper atmosphere. If lift isn't being used to keep it out of the thicker atmosphere where heating is more intense, it still experiences heating for a shorter duration.

More surface area per unit mass will do good things for you during reentry (generally speaking).

Edited October 13, 2015 by KerikBalm

[Kryten]

By being cheap and reliable enough to get the ENTIRE low mass market to itself?

It's only cheap if it has sufficient flight rate, and it needs more than the entire market to hit aircraft-like flight rates. The classic SSTO problem, or indeed the Pegasus problem, or the Delta IV problem. People keep making the same mistake.

And the reason nobody tries to launch things twice a day is because nobody has the ability to launch stuff twice a day.

Soyuz does have a demonstrated ability to launch once a day from the same pad, as was demonstrated multiple times in the 60s for various rendezvous and docking tests. As there is now an identical pad of the same design, it could very well be launched twice a day.

Edited October 13, 2015 by Kryten

[prophet_01]

KerikBalm, you seem to forget about the fact that skylon is a 'plane' and generates a lot of lift which will improve it's ability to slow down high up in the atmosphere. It won't drop on a balistic trajectory, but 'glide' and compared to a heavy capsule this makes a huge difference. The reentry speeds and heat levels of the space shuttle for example were significantly lower compared to a capsule and skylon's would be even lower since it has to have considerably more lift relative to it's weight in order to get off the ground fully fueled.

Still, reentry is a real challenge. The materials stretch out a lot when heating up like that. Especially non-ablating reusable shielding experiences loads of structural stress.

The shuttle's heat tiles were a good and leightweight answer to that problem on paper, but introduced lots of other issues as they were fragile and required expensive and time consuming maintenance.

The SR 71 on the other hand solved it's (not nearly as problematic) heat issues with a frame made of titanium and small empty spaces between many parts (as a result it actually leaked fuel when not heated up ). And even with this vastly less complicated concept, it was still a maintenace heavy and expensive beast which ultimately led to it being retired against the military's will which still had important tasks that could only be performed by the SR 71 (no, drones can't do everything. I work in a related branch ).

Also, the titanium frame was a super expensive thing to build and design which is why the shuttle wasn't build like that (and I highly doubt that skylon will be as it would skyrocket the costs).

If the skylon aims for full reusability and orbital flights, we are back to heat tiles as any other heat shielding I ever heard of would be way too heavy. This fragile and expensive detail is what will likely destroy the idea of launching it twice a day.

Woth suborbital reentries however they might get away without tiles, but I'm not sure about that.

edit: @softweir: very interesting. will check

Edited October 13, 2015 by prophet_01

[softweir]

Reaction engines claim to have solved the thermal expansion problem by mounting the aerodynamic skin on the airframe using sprung mounts which will allow the skin to expand as it heats. (There will be an insulating layer between the shell and airframe.) The skin itself is supposed to be thin enough and flexible enough to absorb differences of expansion between different areas of itself. Because of this they don't have to use those fragile silica fibres the shuttle used, and they propose Skylon will use a carbon/ceramic composite shell.

Whether any of this will work as intended is another matter!