Hang on...
Isn't there a Thunderbirds episode about this very plane? I got the weirdest feeling of deja vue looking at the pictures. Any bald headed men with glowing eyes seen in the vicinity???
Microsoft founder Paul Allen reveals world's biggest-ever plane
Microsoft co-founder Paul Allen has shown off the “Stratolaunch”, a colossal aircraft he hopes can soon help to hoist satellites into low earth orbit. Allen's company of the same name has been working on the craft since 2011, with the help of Scaled Composites. The result of their efforts is 238 feet long, 50 feet tall and …
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Thursday 1st June 2017 16:46 GMT Anonymous Coward
Re: Elon Musk has five sons...
Obviously he's not going to tell anyone when he buys a remote volcanic island in the South Pacific Ocean. A secret base isn't secret if you tweet out "just bought a remote volcanic island in the South Pacific Ocean that will be perfect for my secret base".
So I think we can assume he owns at least one such island, based on the fact he hasn't tweeted about it.
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Thursday 1st June 2017 16:57 GMT TRT
Re: Elon Musk has five sons...
http://blog.solarcity.com/island-in-the-sun/
He has form of course...
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Saturday 3rd June 2017 13:38 GMT Steve Crook
Re: Hang on...
> make a jumbo jet from the VC10 - by having three fuselages flying
Had to look because it was so hard to believe. In the event, utterly awesome and very definitely Thunderbirds material if the outer fuselages detached shortly after launch. I can hear the music now...
Thanks for the link.
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Thursday 1st June 2017 09:19 GMT Arthur the cat
Re: Hang on... Nuclear
Or why bother with "spaceplanes" at all? Project Orion.
Orion has the bijou problemette that the resulting EMP would fry virtually all the electronics in the same hemisphere. Apart from that though, it's basically early 20th C (battle)ship building technology - loads of thick steel plate and bloody big springs.
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Friday 2nd June 2017 22:19 GMT HelpfulJohn
Re: Thunderbirds
Set in the early 1980's yet here we are, over 30 years later, still wearing shirts with buttons and neckties as "smart" "professional" business attire in spite of the hazards.
And we still don't have a Moonbase with pretty girls in purple wigs and very short skirts.
Those skirts would be quite interesting on the Moon. Other things, too.
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Thursday 1st June 2017 10:33 GMT MyffyW
Re: Hang on... Nuclear
I think Orion's bijou problemette was the radiation that would rain down on mother earth with each launch. The Project calculated statistically that each launch would kill 2 people. Now that sounds bad but look how many folks (usually construction workers) die in major civil engineering projects. Still, a tough call to make and the atmospheric test ban treaty finally sealed the fate.
Put a Project Orion craft outside the magnetosphere and said radiation wouldn't be a problem. So we're back to needing a more benign method of getting into orbit. One-and-a-half 747's strapped together suddenly doesn't look that crazy.
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Saturday 3rd June 2017 11:10 GMT MacroRodent
Re: Hang on... Nuclear
>Put a Project Orion craft outside the magnetosphere and said radiation wouldn't be a problem
Trouble is, you would need dozens of ordinary rocket launches to deliver the little nuclear bombs to your bomb-powered interplanetary ship. They would probably cause a of concern and protest, to put it mildly. I fear this idea will not fly, until you can manufacture the bomblets off-Earth.
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Friday 2nd June 2017 13:23 GMT dmacleo
Re: Hang on... Nuclear
convair nb-36h
https://en.wikipedia.org/wiki/Convair_NB-36H
The Convair NB-36H was a bomber that carried a nuclear reactor. It was also known as the "Crusader".[1] It was created for the Aircraft Nuclear Propulsion program, or the ANP, to show the feasibility of a nuclear-powered bomber. Its development ended with the cancellation of the ANP program.
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Friday 2nd June 2017 22:30 GMT HelpfulJohn
Re: Hang on... Nuclear
I have sometimes wondered why they didn't go for an RTG style power plant driving propellers. That way they could have had something like a SHIELD helicarrier.
Refuels would be as simple as plug-and-play, hot-swappable units being replaced as each was used up.
Or is that a totally absurd, physically impossible non-starter?
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Monday 5th June 2017 12:45 GMT Alan J. Wylie
Re: Hang on... Nuclear
Charlie Stross:A Colder War
"The Convair B-39 Peacemaker is the most formidable weapon in our Strategic Air Command's arsenal for peace. Powered by eight nuclear-heated Pratt and Whitney NP-4051 turbojets, it circles endlessly above the Arctic ice cap, waiting for the call.
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Thursday 1st June 2017 07:37 GMT Mage
Interesting
I wonder why the tails are separate rather than sharing a wing,
See
It would maybe reduce drag (if no outer wing) and also make the structure more stable?
( I nearly typed Theresa May).
This is weird: Airbus patent
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Thursday 1st June 2017 07:58 GMT jake
Re: Interesting
I wondered that too. All I can think of is they actually want it to have a little more flexibility. The thing is big, even a hundredth of a degree of difference between fuselages would add up to disaster if the tails were fused, especially under the kinds of load that this thing will be subject to.
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Thursday 1st June 2017 08:21 GMT Anonymous Coward
Re: Interesting
> I wonder why the tails are separate rather than sharing a wing,
Yes, it seems odd, but I would imagine the tail, rather like the good old Vampire, would be fried by the launching rocket, which would either leave the solution as raising the tails or leaving a blast gap. But it would be interesting to understand the engineering that allows this plane to cope with the torsional stresses it must surely experience, and it is somehow surprising that the mid-wing section is so thin. Or to put it another way, I wonder how much the two tails will move in relation to each other, especially when banking.
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Thursday 1st June 2017 09:50 GMT Phil O'Sophical
Re: Interesting
the tail, rather like the good old Vampire, would be fried by the launching rocket,
Not sure I'd want to be flying that if the rocket were ignited while still attached, though. I'd been assuming more of a 'light the blue touch paper & retire" operation where they'd start a delayed ignition sequence and then drop the rocket, so they were well clear when it lit up (or blew up).
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Thursday 1st June 2017 10:57 GMT SkippyBing
Re: Interesting
'I'd been assuming more of a 'light the blue touch paper & retire" operation where they'd start a delayed ignition sequence and then drop the rocket'
Probably correct, although I guess it depends how far you plan for it to drop whether there's a risk of the tailplane being damaged. Of course they may have left the gap there to reduce the chance for rocket/aircraft interference in the event of some sort of emergency requiring jettisoning the rocket.
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Thursday 1st June 2017 11:38 GMT Brangdon
Re: Interesting
Although if it then failed to ignite, you'd probably lose rocket and payload. For comparison, during a SpaceX launch the rocket is held down by clamps for a few moments after ignition, while the computer checks the telemetry and decides whether it is healthy. Launches have been aborted after ignition, with no harm done; just fix the problem and try again. I don't know if this is standard for rockets that are not reusable.
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Thursday 1st June 2017 12:10 GMT Anonymous Custard
Re: Interesting
And for reference, they can just look at the XS-1 space plane and its launch system plus its predecessors and parallel projects like the X-43.
Those were usually slung under the wing of a standard aircraft and released before ignition, but it's a similar concept. Of course the release before ignition was rather crucial unless you wanted to send aforementioned aircraft into a rather interesting if short-lived spin before it hit the dirt hard.
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Thursday 1st June 2017 13:14 GMT lglethal
Re: Interesting
@ Brangdon - just for reference, if the Rocket uses liquid propellants the Engine can be switched on and off. If the Rocket uses Solid Fuels, the Motor (solids always have Motors, whilst liquids always have Engines) once ignited cannot be stopped.
So with something which carries both liquid engine stages and solid boosters, like Ariane 5, once you've lit the solid motors, you are going to space today...
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Thursday 1st June 2017 15:29 GMT Eddy Ito
Re: Interesting
I wonder why the tails are separate rather than sharing a wing
It may actually make it too stiff and have adverse effects on the rudder given the two fuselages look to be more or less 100' apart. Just spitballing but one might imagine a rigid beam across the back may require something akin to Ackermann geometry for the rudder deflection but if they are independent each side is free to move a bit without undue stress. It also seems to be a trend of modern design as looking at your twin fuselage link many of the newer designs have independent tails from the Pipistrel and twin C-5 Galaxy to other Scaled Composite designs like White Knight One and Two.
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Friday 2nd June 2017 09:23 GMT imanidiot
Re: Interesting
This is most likely simply about weight. A full tailplane joining the two tailbooms would be quite hefty. The only task of the tailplane is to provide a certain amount of force to keep the plane balanced and an added amount of variable force to provide pitch control. If that can be done by 2 smaller tailplanes you have less weight far aft of the CG that then needs to be compensated ahead of the CG with even more weight to keep the CG within limits.
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Thursday 1st June 2017 07:47 GMT Mage
Advantages?
" The twin fuselage configuration offers the advantage of a clean payload area underneath the wing centre section."
I count about 30+ aircraft (most military) that have been twin fuselage.
"During World War II a need sometimes also arose for a heavy fighter, which could not be met by a new design in the time needed. Joining two examples of an existing lighter aircraft was one way to achieve this."
See also what are the advantages of twin-fuselage aircraft?
The first seems to have been around 1915. Most didn't meet expectations of performance. There would probably be no advantage in having more than two fuselages.
I think the single fuselage approach might end up like this family:
Still looks like SF 60 years later. Came in different sizes.
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Thursday 1st June 2017 18:58 GMT Swarthy
Re: Advantages?
Also, by locating the large hunk of temporary mass (satellite + rocket) at the Center of Mass for the plane, the CoM doesn't change (and with it flight characteristics, like not flying in circles) when the payload gets launched.
If one were launching 2 satellites at a time, a single fuselage would be preferred, as the gobs o' mass could be balanced on either side of the CoM. Bu that would take a much larger plane.
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Thursday 1st June 2017 11:00 GMT PNGuinn
Re: It's that big...
"can launch from different runways"
At the same time?
No, not quite.
You launch each fuselage from a different airfield and join 'em up in flight. A bit like in flight refuelling.
Then they meet up with a third plane carrying the little bits they want to launch, stick 'em onto the hooks underneath the middle bit and proceed to launch.
Simples, shirly.
It's all about cost reduction and versatility in runway use. So I'm told.
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Thursday 1st June 2017 08:23 GMT allthecoolshortnamesweretaken
The 'avoiding bad weather' bit makes sense to me. And you can launch at the equator for maximum efficiency.
Also, you could pick up the launcher and payload directly at the assembly site (if they have the runway to do it).
But we'll have to wait and see whether it will fly more than once like one of its predecessors...
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Thursday 1st June 2017 08:42 GMT lglethal
Two aircraft in disguise?
Why do I have a mental Image that its really two aircraft in disguise? Very 70's Bondesque style. Fly the two aircraft to the location, join them up, strap a rocket underneath, fly up, launch it and then break apart and fly as two seperate aircraft back to separate bases....
No-one will suspect a thing... mwhahahahahahahaha...
*cough* sorry... *cough*
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Thursday 1st June 2017 12:07 GMT Anonymous Coward
"look at the distance those roof trusses are supporting over a single span. Amazing!"
Well, its designed for the 385ft wingspan and looks form the picture to have not a great deal of extra spave which puts the span at around 400ft. Meanwhile, here in Bristol at Filton we have the Brabazon hangar which (from quite search) has 3 bays with a total length of 352m which means around 350 feet per bay ... and that's been around for ~60 years.I remember when the Concorde exhiit (shortly to re-opem a new museum) was just outside the hanger and on a tour there the guide explained that one of the bays was being used by a company the painted aircraft as they could fit anything current inside ... at the time they had a 747 which seemed a little dwarfed by the hangar
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Thursday 1st June 2017 10:54 GMT Anonymous Coward
Re: "can launch from different runways"
My first thought on seeing it outside its hanger, where you've some sense of scale, was that there won't be very many "different runways" from which this could operate at all, let alone safely, because its landing gear tracking is too wide. Whilst it may just fit on a typical runway, there won't be much 'wiggle' room between the main gears and the edges of said runway. This issue will be exacerbated by the off-center piloting position - one can imagine a conversation between the flight crew in each of the two cockpits as they try to line up with the runway for landing:
Starboard Pilot: "Come to port a bit, come to port a bit"
Port Pilot: "No!, come to starboard a bit, come to starboard a bit"
In addition to the risks resulting from the closeness of the main gear to the edges of the runway, the camber of the runway is also likely to cause problems with such a wide-tracked landing gear, not just because each of the main gear sets will be running along the side of a gradient but also because dirt and other crud will tend to end up along the edges of the runway, due to both the passage of other conventional aircraft using the runway and rainfall, which will 'wash' wind-blown dirt and grit off the crown of the camber down towards the edges. It will be a bit like driving along the hard-shoulder at full motorway speed - not good.
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Thursday 1st June 2017 12:31 GMT Anonymous Coward
Re: "can launch from different runways"
"It will be a bit like driving along the hard-shoulder at full motorway speed - not good."
In Africa there are "strip" roads. Basically a single lane of tarmac with wide gravel verges. When vehicles approach each other then they each move sideways to put one set of wheels on the gravel. The sudden drag on one side is very disconcerting if you don't anticipate to counter it.
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Thursday 1st June 2017 09:56 GMT steelpillow
Half way there
Twin fuselages make for a clean payload space without massive undercarriage. The split tail removes any risk of interference or contact if the payload gets mardy, either before or during launch. It's becoming a classic configuration for space launchers. ISTR Rutan has retired from Scaled Composites, nevertheless I find the most surprising thing about this ship to be how conventional it is in other respects.
Main problem is that nobody has yet built a sensible orbiter on this scale that can launch horizontally: the structural, and hence weight, penalties of turning a coke can on its side are surprisingly large. If this beast finds a customer to do it justice, that will be the real breakthrough.
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Thursday 1st June 2017 10:33 GMT S4qFBxkFFg
Re: What happens if the pilots in each cockpit decide to bank in opposite directions?
"SNAP"
In a way, you aren't joking, in certain aircraft the pilot/co-pilot controls, while linked, will connect to different control surfaces (e.g. the left seat controls might be connected to the upper rudder and left elevator while the right seat's has the right elevator and lower rudder). Normally, when everything's fine, moving one set of controls moves the relevant control surfaces, and the other set of controls. If things are not fine (e.g. pilots trying to perform different manoeuvres or a dropped meal tray preventing one control column moving) the linkage is designed to break at a certain level of force, so at least some sort of control is maintained.
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Thursday 1st June 2017 14:36 GMT Tikimon
Re: What happens if the pilots in each cockpit decide to bank in opposite directions?
I assume you're thinking of both pilots moving their wing down (or up) at the same time. It's definitely amusing to imagine the airplane flexing up or down in a U shape! Reality is less interesting, since that would lift or lower both wings at once and the plane would simply rise or sink.
Nevertheless, I'm having fun imagining the plane flexing around into interesting shapes as two pilots struggle for control. If they got into an oscillation loop fighting each other, you might see the wings actually flapping up and down as it flew, wouldn't that be a sight to tell your grandkids about?
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Thursday 1st June 2017 10:43 GMT cray74
Why air launch?
This is an incredible feat of aerospace engineering. I'm glad to see that, as a species, we're really experimenting and dreaming again. The lulls after the Apollo program, Challenger disaster, and 1990s launch market collapse were disappointing.
But isn't this air launch approach inherently limited? Even the gigantic Stratolaunch airplane has a payload limit of 230,000kg for an entire rocket. As I understand it - corrections and clarifications welcome - this is only offering a ~250m/s boost to the rocket, a reduction in launch drag penalties, and more flexible launch inclinations than a fixed launch pad.
That's nice, but you can get those advantages in other ways. Like, a bigger rocket. For example, a fixed launch pad easily adopted to the growth of the 330-ton Falcon 9 v1.0 (which already had a larger capacity than anything the Stratolaunch could launch) to the 550-ton Falcon 9 Full Thrust, which saw a large jump in performance: more payload, new recovery options, new orbit options. Fixed launch pads also could handle the US shuttle's 5-segment SRBs, which gave the shuttle most of the flexibility of an air launch (like "dog leg" flight paths into polar orbits) and increases in cargo capacity. Aerial approaches couldn't handle the original launchers, never mind the enlarged ones.
But the Stratolaunch approach is not the first aerial launch system (hello, Pegasus) so there's got to be something behind them. What are the advantages of these aerial launches over a bigger rocket?
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Thursday 1st June 2017 12:07 GMT Paul Smith
Re: Why air launch?
For a once off launch, ground launch is clearly cheaper, but at least 98% of the take off mass is lost. (Saturn V took off weighing 3,000 tons to get 40 tons on the moon and 10 tons back to earth). For repeated launches, once the cost of the bits lost getting to the air launched altitude match the cost of air launching, you are at break even, but after that is all profit. Potentially 20 or 30% lower costs per launch add up to a lot of money when you consider the current costs per kilo are (roughly) $5k to LEO and $30k to GEO.
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Thursday 1st June 2017 15:44 GMT Yet Another Anonymous coward
Re: Why air launch?
It's all about the size of your nozzles (ooh-err missus)
In vacuum you want great big wide open nozzles, at sea level you need narrower ones. The result is a rocket that is less efficient at all stages of flight and least efficent at the start when you need the most thrust. The nearer you can be to vacuum when you light the blue touch paper, the more vacuum designed nozzles you can use.
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Thursday 1st June 2017 17:38 GMT cray74
Re: Why air launch?
Launch when you want without worrying about rain and wind at the launch site.
Yep, definitely a plus. Flexible launch sites are also part of the attraction of sea launching.
It's all about the size of your nozzles
Avoiding sea level-optimized nozzles helps a bit, but it's not everything. For example, the shuttle's SSME nozzles were a compromise to operate from sea level to vacuum but only gave up a bit of vacuum specific impulse. They eventually having achieved 453 seconds in vacuum (where they spent about 6 of their 8 minutes operating), while a purely vacuum-optimized nozzle would've delivered 455 seconds.
For multi-stage, non-parallel rockets, the rocket nozzle advantages of air launch are even smaller. The Pegasus gives a good data point...
For a once off launch, ground launch is clearly cheaper, but at least 98% of the take off mass is lost. (Saturn V took off weighing 3,000 tons to get 40 tons on the moon and 10 tons back to earth)
...Understood, but subsonic air launch isn't giving you much in launch mass savings. The 18,500kg Pegasus has a 443kg LEO payload (40:1), which is a worse payload ratio than the ground launched Atlas V (18:1), Delta IV (26:1), and Falcon 9 FT (24:1).
The point of that comparison is that air launch mass savings are small enough to be wiped out by differences in propellant selections. Despite being carried to 12,000 meters and 270m/s by an L-1011 carrier aircraft, the solid-fueled Pegasus has lower mass-normalized performance than liquid-fueled ground launched vehicles.
The all-solid, 4-stage Pegasus II slated for the Stratolauncher will also fall short of liquid fueled, ground launched rockets in performance.
For repeated launches, once the cost of the bits lost getting to the air launched altitude match the cost of air launching
You don't save much with an air launch except fuel, and rocket fuel is one of the lower costs in rocket operation. The purchase price of a $100 million used carrier aircraft like an L-1011 would fuel a lot of Falcon 9s.
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Thursday 1st June 2017 11:13 GMT eldakka
Re: Not Maetric not interested
A wingspan of:
838.2 Linguine, or
12.7 Double-decker buses, or
5.3 Brontosaurus.
And a MTOW of:
140403931310.0767 MicroJubs,
140403931.3101 MilliJubs,
140403.9313 Jubs,
140.4039 KiloJubs.
67782.1431 Adult Badgers;
662.2827 Great White Sharks;
393.131 Skateboarding Rhinoceri;
13.1044 Austrailian Trams;
1.1043 LINQ Hotel Recycling.
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Thursday 1st June 2017 12:45 GMT Anonymous Coward
Re: Not Maetric not interested
"[...] a pound seems the wrong unit to be using when you get to the point of needing 6-digit numbers of them."
An avoirdupois pound is a consistent weight in both the UK and USA - as long as you ignore the lighter troy or apothecaries’ weight. However hundredweights and the three variants of ton(ne)s can be significantly different measures.
https://www.britannica.com/science/ton
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Friday 2nd June 2017 04:58 GMT graeme leggett
Re: Not Maetric not interested
Pound may be consistent weight in UK and USA. But even for that population element of the UK that is not comfortable with kg and tonne, any large number of lbs is expressed in stones, hundredweight and (long) tons. (so 8lb of potatoes, 6-stone woman, 1/2 ton of gravel* )
*though actually bought by the cubic yard as I remember from when I was younger.
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Thursday 1st June 2017 13:27 GMT chivo243
Re: Not Maetric not interested
I have a US 1970's education, and I had to learn the metric system. I am comfortable in metric or imperial. We were told that we "had to learn the metric system, the whole world uses it" 40 or so years later the only thing the US got out of that exercise was a 2 liter bottle of Coke. Why?
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Friday 2nd June 2017 04:23 GMT Rattus Rattus
Re: Not Maetric not interested
Re: "the only thing the US got out of that exercise was a 2 liter bottle of Coke. Why?"
Because the US is filled with reactionary conservatives who are terrified at any sort of advancement and fight any kind of change. This is why the US is slowly surrendering its global superpower status to China.
Also, "litre" goddamnit. Like in every other English speaking country, including Canada.
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Friday 2nd June 2017 03:41 GMT david 12
Re: Not Maetric not interested
It's not "Imperial measurements". Those are "International measurements", from the international yard, adopted by the USA in 1933 / 1959. And the United Kingdom went off the "Imperial Standard Yard" in 1930 / 1963, so you aren't using Imperial measurements either.
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Thursday 1st June 2017 11:26 GMT John Brown (no body)
Re: Look at that hanger ...
I was more concerned about the non-visible folding joints in those tail booms. That aircraft looks a lot longer than the depth of the hanger behind it. The hanger does appear to have a lower extension at the back, but that doesn't look high enough to accommodate the tail fins.
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Thursday 1st June 2017 13:21 GMT lglethal
Re: No Way
Yes, because I'm sure they never thought to have someone look over the design, do some hand calculations, do some FEM Analysis, some small scale testing and then ramp up to full scale testing.
What? They did do all that. Oh well I'm sure that you, AC, having looked at a picture on the Internet, know more then all of those Aerospace Engineers on this topic.
Muppet...
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Thursday 1st June 2017 12:29 GMT graeme leggett
I like to imagine
That somewhere in the UK, a boffin has looked up from their calculations to watch on a tv in the corner of their office news coverage of this plane.
After a moment's consideration they grunt, shift the (unlit) pipe to the other side of their mouth and go back to their work.
[camera pulls back to show wall covered by enormous blueprint outline of Skylon spaceplane]
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Thursday 1st June 2017 12:40 GMT Fenton
Another idea
Rather than design a large aircraft to carry the payload up to a certain height. Why not design a smaller aircraft that attaches to the payload (with it's own fuel), that uses the engines on the payload.
The Payload then drops the aircraft bit, which flys itself home.
No need for large fusalages, automate the whole thing with no need for people on board.
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Thursday 1st June 2017 17:56 GMT John Smith 19
It's a monster.
Although not a Caspian Sea Monster.
The problem with these concepts (apart from hanging a 250 tonne rocket off a large wing) is that the you can't just tip a rocket on its side.
Rockets are tremendously strong in 1 axis while the rocket this carries has to be very strong top-to-bottom (while it's hanging from the wing) and equally strong when the engines fire up.
Also the aircraft does not give you anywhere near the velocity of a stage. So having spent a metric shedload of a cash to build your humougous aircraft you still need to build a 2 stage rocket anyway.
If you could build a rocket that was SSTO (if launched from this aircraft) that would be a major breakthrough in the SoA.
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Saturday 3rd June 2017 08:34 GMT John Smith 19
"They start on their sides and are raised into the vertical for launch."
At which point they and there boosters are loaded with the propellants that the engines run on.Multiplying their weight about 9x.
Which is also how SX does it.
NASA did move the Saturn V full loaded to the pad, but only vertically. SRB's are either moved vertically (like Ariane 5) or built up on the pad like Shuttle (an astonishingly dangerous process, demanding the precision location of pieces of high explosive weighing 10s of tonnes).
IRL you can't take a rocket designed to be fully loaded only when vertical and hang it from a single point on its side. TBH if you want to be avant garde in your rocket design go the whole hog. Optimize the shape as more of a flying wing (or lifting body) . High altitude flight at < M1 is pretty cold so let it cool the propellants and then top them up from tanks in the fuselage. Go LOX Methane if you're trying to be low price and so on.
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Friday 2nd June 2017 06:34 GMT John Smith 19
"the world's biggest ever plane is An-224 "Mriya","
The question however is
a) How big a payload can it carry on its back (which it was designed to do)?
b)What's the maximum speed the plane can go while still allowing safe separation of the payload?
c)How available is it?
In cost terms the An224 is the OTS shelf solution if you wanted to go to orbit this way but the devils in the details.
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Thursday 1st June 2017 23:14 GMT Duncan Macdonald
Big advantage - no need for launchpad
Existing large rockets need big expensive launch facilities - with a lot of unoccupied land around to handle the occasional large bang.Doing an air launch over an ocean removes the need for the ground based launch facility. There is also the advantage that the rocket can start in the desired orbital plane rather than having to expend fuel to allow for the difference between the desired orbital plane and the launch site (eg an equatorial orbit when launched from Cape Canaveral wastes quite a lot of fuel due to the launch point being over 28 degrees north of the equator.) For an equatorial orbit there is an additional 200 km/h advantage from launching from the equator rather than Cape Canaveral from the earth's rotational speed.
The speed benefits
1) Starting at 30000 feet instead of sea level - equivalent to over 400 m/s
2) Equatorial launch (instead of Cape Canaveral) - equivalent to 200 km/h
3) Plane velocity - around 200 m/s
4) Orbital plane correction - ??? km/h
There is an additional benefit from an air launch - the maximum dynamic pressure will be reduced as the spacecraft will be in thinner air than for a ground launch for any given supersonic speed.
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Friday 2nd June 2017 06:42 GMT John Smith 19
"1) Starting at 30000 feet instead of sea level - equivalent to over 400 m/s"
I'm not sure where you get this from.
Equatorial launch is normally reckoned to give about 400m/s impetus. IE about 1400Kmh.
You've also missed one of the bigger benefits. Roughly speaking atmospheric pressure halves every 18000 ft. Flow separation on a rocket nozzle starts at about 36-40% of ambient atmospheric pressure (depends how good your design software is). That means you can put a bigger nozzle on the back as it can exhaust to a lower outside pressure to begin with. Bigger nozzle --> Higher Isp. Alternatively you can run with a lower chamber pressure, which usually makes engine design simpler.
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Friday 2nd June 2017 10:31 GMT Duncan Macdonald
Re: "1) Starting at 30000 feet instead of sea level - equivalent to over 400 m/s"
Simple - gravitational energy - a body falling from 30000 feet in earths gravity would attain a speed of over 400 m/s in a vacuum. This energy will be provided to the rocket by the plane rather than by burning its own fuel.
The 400 m/s extra from equatorial launch probably includes the gain from not needing the orbital plane correction - the rotational velocity change between the equator and Cape Canaveral is about 200 m/s. I was not sure of the amount of energy consumed by the correction which is why I showed it as ??? .
I am not a rocket design engineer so I did not know how much advantage the reduced atmospheric pressure would give to the performance of the engine so I left this out of the list of advantages.
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Friday 2nd June 2017 12:41 GMT Yet Another Anonymous coward
Re: "1) Starting at 30000 feet instead of sea level - equivalent to over 400 m/s"
It's not clear that equatorial launch helps so much for this.
It has the biggest boost for GSO orbits but anything going to GSO is going to be too big for this thing (see todays other reg satelite story). Smaller payloads are going into LEO at a whole bunch of orbital inclinations that don't need equatorial boost as much, ones in a polar orbit don't benefit at all.
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Friday 2nd June 2017 15:22 GMT CatW
Thats such a crap design, they would have been so better of with a large slim delta wing with nose plane. Not only would it have been stronger and been able to 'flick' the vehicle up harder but there is no way in the even of a false launch that the vehicle could fall back on the tail damaging the launch aircraft.
Typical Americans - one design, just make the wings longer, more engines. We built Concorde.
Biting the hand that feeds IT
