
Paul Allen's new rocket-launching plane - MBCook
https://arstechnica.com/science/2017/05/paul-allen-showed-off-his-new-rocket-launching-plane-today-it-is-big/
======
mLuby
IANARS but this plane should give the remaining stage(s) four advantages:

1\. +230m/s orbital velocity [1]

2\. +9km launch altitude [1]

3\. can launch in more weather conditions

4\. 1st stage can abort mid-launch without loss of payload.

Of these, the most important is the increase in launch altitude, because that
means stage 2 launches in air of greatly decreased density, leading to the
following efficiencies:

A. a vacuum-optimized nozzle can be used, increasing engine performance

B. less aerodynamic/drag energy losses

C. max Q should be lower, allowing full throttle usage, reducing mass needed
for structural elements, and reducing vibration stresses on payload

[1] [http://dailym.ai/2soH6FD](http://dailym.ai/2soH6FD)

P.S. Thank you KSP for teaching me this stuff! :D

Bonus: video of pegasus air launched rocket:
[https://www.youtube.com/watch?v=jz_5hnIw2jc](https://www.youtube.com/watch?v=jz_5hnIw2jc)

~~~
iijj
The primary advantage of airplane launch is that you can fly to into a launch
window for an orbital rendezvous. Otherwise you'd have to wait for the
target's orbit to be just right w/respect to the launch site, or do a long
orbit matching process.

This is very useful if say you want to very quickly and quietly launch
something towards another satellite.

People are making comparisons with the Spruce Goose, but the Glomar Explorer
may be a better analogy.

~~~
Retric
The largest downside is the rocket needs to be strong in more than one
direction which adds a lot of weight. Sub Mach 1 first stage will save a
little net weight but significantly less than you might diets assume.

~~~
CydeWeys
Sure, but the strength it needs to have in the additional "hanging horizontal"
orientation is only 1g -- much less than the many-g strength that all rockets
need to have along their thrust axis. It adds some weight, but not enough to
ruin the other benefits.

------
Animats
Scaled Composites built it. It should work. Although Rutan has retired, the
company goes on. It's interesting that they didn't connect the tails, like the
old Lockheed P-38, but there's probably some good reason for that.

Launching a Pegasus XL has to be just a demo. That's normally launched by
dropping it from an old Lockheed L-1011; it doesn't need this monster. They
need something bigger to launch. There was a contract with Pegasus for a
"Pegasus II", but that didn't work out. The "Dream Chaser" mini-shuttle is a
possibility, if that ever gets built.

The 747 engines are probably used. There are lots of retired 747s around, many
at the Mojave boneyard. Great aircraft, but a fuel hog by current standards.

~~~
schiffern
>The 747 engines are probably used. There are lots of retired 747s around,
many at the Mojave boneyard. Great aircraft, but a fuel hog by current
standards.

Correct. They just flew in two used 747s and cannibalized them for parts.
[http://www.seattletimes.com/business/boeing-
aerospace/paul-a...](http://www.seattletimes.com/business/boeing-
aerospace/paul-allens-giant-plane-takes-shape-in-the-desert-but-its-market-is-
unclear/)

> _The crew’s flight deck is literally that of a 747._

> _Allen bought two used jumbo jets formerly flown by United Airlines and
> cannibalized them for parts that account for about half the empty weight of
> the Roc._

> _So although the shell of the cockpit and all the rest of the plane’s body
> is new — hand-built by Scaled Composites from carbon fiber composites —
> various key pieces and systems, including avionics, hydraulics and fuel
> subsystems, are salvaged 747 parts. BAE Systems was subcontracted to
> disassemble the 747 and install its systems on the Roc._

> _The cockpit seats look old and used because they are. The seats as well as
> the controls the crew will manipulate and the windows they’ll look out of
> all came from the 747s._

> _So did the plane’s six Pratt & Whitney engines, which are already
> refurbished, cleaned, wrapped and set aside in a corner, ready to hang on
> the airframe when it’s finished._

~~~
CydeWeys
That's absolutely how I would've done it. Way cheaper to make a monster hybrid
of two used 747s than to try to make a one-off custom airplane from scratch.
Sure, it won't be as efficient at its job as if it were purpose-built, but
you'd never get all of that R&D money back.

~~~
rbanffy
Once the concept is proven, once there is a real market for that, other, more
efficient planes designed for bigger rockets will be built.

~~~
CydeWeys
The market would have to be really large (like way larger than the current
global launch market) to justify it though. The conjoined twin 747s are gonna
be good enough for any payload that they can carry.

~~~
rbanffy
If the cost goes down enough, new previously impractical products become
practical, driving new demand.

~~~
sbierwagen
Big _if_ there.

The Seattle Times article says that the Vulcan rocket will have a mass of 375
tons. (Probably US tons?) Assume it's got the same payload fraction as a
Soyuz, about 2.5%, which means it can put 9.4 tons into orbit. (A Falcon 9 can
put 22 metric tons into orbit)

According to some comment on stack exchange, the world collectively orbited
255 tons of stuff in 2007. Assuming every payload can be launched on a Vulcan
rocket, (Which they can't) and assuming a generous turnaround time of one
week, (Allen says it should be faster than that) then it would take only a
single plane 27 weeks to satisfy the launch needs of the _entire world._ You
could double the amount of stuff launched, and still only need one plane.

There's probably not going to be a lot of airframes to spread development
costs across.

~~~
rbanffy
Either that, or we will launch a lot more stuff, 9 tons at a time.

The biggest thing going against it is it's not clear this scheme can drive the
costs down enough to double or triple the launched mass per year. There is a
limited number of things we can do in space. A significant part of the cost of
any single probe is the launch.

If we can reduce launch costs enough (maybe making the booster reusable) and
through building a standard probe with pluggable sensors, drive down the
building costs, we could have dozens of probes going places we currently can't
afford to go. We spend enormous effort in shaving off every single gram from
anything that goes to space. If going to space gets cheaper, we can spend a
lot less time shaving probes and more time probing.

------
OperationHealth
This is being blown out of proportion. Vulcan's Stratolauncher is not the
future of launch; if this thing ever manages to leave the ground (with a
payload), I doubt it will host more than five-to-seven launches throughout its
lifetime, and that's a generous estimate.

This vehicle is going to be incredibly expensive, compared to both other air
launch options and dedicated smallsat options. Although this can change, the
current plan is for Stratolaunch to use OATK's Pegasus-XL payload, which
provides an indicator for cost. Pegasus-XL launches are incredibly expensive
($337.3K per kg). Now, this is due to a variety of reasons (the L-1011's
incredibly high maintenance costs, OATK's expensive labor structure, low
launch cadence). Vulcan will bear similar costs--the inefficient OATK overhead
tied to Pegasus-XL, Stratolauncher is a one-of-a-kind aircraft and increasing
maintenance costs (despite using 747 engines). Due to significant development
delays, the company has yet to develop or execute a customer strategy.
Depending on how much more PA pumps into it, the company will not be price
competitive in the market.

For comparison, other small launchers charge ~$25K/kg-$41K/kg (e.g., Rocket
Lab, Virgin, Arianespace), and most of these will be able to launch US
payloads. Virgin's comparable airlauncher delivers slightly less mass (15 kg
less), but is priced at ~$40K/kg. Virgin is already a leg up as it has engaged
commercial, civil govt., and mil-govt. customers.

Lastly, it's worth noting that this vehicle still has significant work to be
done--look at the wings in the picture.

~~~
victork2
Hi there,

you seem to know a lot, any chance we could talk about this topic, would love
to hear more of your thoughts on the topic? I don't see an address to contact
you.

Thanks!

------
SkyMarshal
This is awesome but a little bit scary. Interesting that they didn't
physically connect the tail wings at all, I wonder what stresses and torques
the main wing will endure under maneuvering or turbulence. I assume all the
control surfaces are computer controlled to synchronize and minimize that, but
from the perspective of an ignorant observer, looks a little fragile.

~~~
kashkhan
it's a proven design.

scaled composites, which built this also built the GlobalFlyer with similar
configuration.

[https://en.wikipedia.org/wiki/Virgin_Atlantic_GlobalFlyer](https://en.wikipedia.org/wiki/Virgin_Atlantic_GlobalFlyer)

~~~
endorphone
Clearly Allen and his team did the necessary engineering work, but I'm not
sure the GlobalFlyer is a good example. It had a single mid-mounted engine,
and had a gross, fully loaded weight of 22,000lbs. This thing has 70,000+ lbs
of engines alone. The torque has to be absolutely colossal.

Again, I know that much smarter people did the math, but from the eye check
this does not look like a tenable design.

~~~
blunte
I agree. There are so many forces at such incredible potential levels of
torque that the center wing must be almost entirely full of structural
elements... and those probably pass through to the outer wings.

Imagine differing oscillations of pitch or yaw from each fuselage happening at
the same time... and at just the right/wrong frequency for the connecting
structure.

I'm sure I'm just overly paranoid, but often we find out long after something
is built that some "little possibility" was overlooked.

~~~
SkyMarshal
_> Imagine differing oscillations of pitch or yaw from each fuselage happening
at the same time... and at just the right/wrong frequency for the connecting
structure._

Exactly. I expect they have real-time computer control of all control services
that quickly adapt the relative attitude of both fuselages to prevent over-
stressing the wing, but what about "rogue waves" of turbulence hitting each
fuselage differently. What's the safety factor on both the adaptive controls
and, as a backup, the structural integrity of the wing?

------
gambiting
385-foot wingspan

1.3 million pounds

65 feet

2,000 nautical mile

I'm sorry, I know it has been mentioned a billion times already, but can
someone make a browser plugin that converts everything on a website to normal
SI units? As a non-american I have no idea how big this aircaft is or how much
it can lift - sure I can look up conversions(I have) but it would be awesome
if there was an automatic website conversion option.

~~~
aj7
Just type the quantity and units into google.

~~~
gambiting
As I said in my comment - I have. I just said it would be awesome if there was
some automatic conversion option.

------
curtis
It seems like air launch doesn't buy you a whole lot, but it turns out that a
small win on delta-v can result in a fairly big win on payload. This might
seem counter-intuitive, but you have to remember that in orbital class
rockets, payload is only 5% or so of total mass at take-off.

~~~
InclinedPlane
It's a small win on delta V, a small win on gravity losses, and a small win on
Isp (due to atmospheric pressure). The delta V and Isp wins are exponentially
related to stage mass fraction so they actually become very big wins.

------
vadym909
Any more billionaires feeling left out of the space race?

~~~
mabbo
Should we worry that every billionaire seems highly intent on building ways to
get the heck off the planet?

... Do they know something we don't?

~~~
ORioN63
No. We already know that the planet will undergo drastic changes in the next
100 years.

------
Analemma_
I'm confused as to what this thing can accomplish. It can probably fly very
high, but I assume it can't fly very fast (relative to orbital speed), and I
thought the overwhelming majority of the delta-V to get something into orbit
was for forward momentum and that just launching from higher up wouldn't help
much.

Clearly there's something I'm missing here (or they wouldn't have built it),
can anyone fill me in?

~~~
ThrustVectoring
From wikipedia [1]:

>Atmospheric and gravity drag associated with launch typically adds 1.3–1.8
km/s to the launch vehicle delta-v required to reach normal LEO orbital
velocity of around 7.8 km/s (28,080 km/h).

So it'll help. Also significant is the ability to base out of an airport and
launch closer to the equator.

[1]
[https://en.wikipedia.org/wiki/Low_Earth_orbit](https://en.wikipedia.org/wiki/Low_Earth_orbit)

~~~
vlasev
Combine that with the tyranny of the rocket equation and it becomes sensible.

~~~
ThrustVectoring
Right. Reducing the delta-v by a constant amount reduces the fuel requirements
by a specific percentage. The correct thing to measure delta-v savings to
isn't the launch requirements, but rocket exhaust speed. That is, if your
rocket exhaust speed is 1 km/s, saving a km/s of delta-v will reduce your fuel
requirements by a factor of 2.718

------
InclinedPlane
This is pretty cool but to be honest I don't expect it to be very
advantageous.

The big advantage of airlaunch is the Isp improvement from launching at
altitude. Since the rocket equation is exponential with respect to the ratio
of delta V and Isp improving Isp even a little has big effects, and reducing
delta V even a little does too.

But the big advantage of ordinary vertical launch rockets is that it's fairly
straightforward to just make them bigger. The Saturn V was able to launch
Skylab with a 6.6 meter diameter. And rockets could easily be scaled up to
launch even larger diameter payloads. That's pretty difficult with something
like Stratolaunch. Even with basically the largest aircraft ever made it still
has a pretty small payload mass and fairing size.

One other cool thing about stratolaunch is that it has the ability to launch
out of a lot more locations since it doesn't depend on a launch pad and tower.
However, I suspect that's not going to be of huge importance.

I'd like to see what they can do with this technology but I suspect it'll be
underwhelming.

------
simonh
Since the Orbital ATK Pegasus already exists and already has a customised
plane it launches from, can we assume launching Pegasus is just phase 1 for
this plane? If that's all it's going to do there would be no point. So
presumably this has capabilities the current Pegasus launch plane doesn't
have, and eventually we'll see it launching something like a Pegasus XL Plus?
Do we have any indication how big a rocket this thing can carry?

Also, I wonder how this compares in capability to the XS-1 currently under
development, which will be a vertically launched first stage rocket that can
fly back for a runway landing.

Edit: just found the link below from last year on Space.com.

[http://www.space.com/32680-stratolaunch-rocket-vulcan-
aerosp...](http://www.space.com/32680-stratolaunch-rocket-vulcan-aerospace-
mystery.html)

~~~
HXFIVE
Originally it was going to use a Falcon 5 Air, and later a Pegasus II. Both
projects were cancelled.

------
Tomminn
This is a very good idea. In rocketry, air is your enemy. At the speeds
rockets move it causes enormous heat/mechanical stress on the rocket, drag
energy losses, and it messes with the flow of matter out the back of the
engine that provides your thrust.

With a jet engine, air is your friend, because it _is_ the matter you spit out
the back of the engine. And at the much smaller speeds of an airplane,
mechanical and thermal stresses are much smaller.

------
jeffdavis
Dumb question: why don't they launch rockets from the tops of mountains?

~~~
jcfrei
Related question: Couldn't we create some sort of rocket elevator with huge
and very high balloons?

~~~
adrianmacneil
[https://what-if.xkcd.com/58/](https://what-if.xkcd.com/58/)

~~~
Symmetry
The point isn't to get higher up, the point is to get out of the damn
atmosphere so you can use wider bells, lower chamber pressure, and lighter
weight tankage.

------
ndr
The article doesn't mention SpaceX, I wonder what's the difference in energy
and cost for launching (and landing) the relative stage 1s. Does anyone have
an idea on that?

~~~
wolf550e
At separation, Falcon 9 first stage is doing about 2500 meters/second and is
at about 70km altitude. The two connected 747s flying in formation don't get
that fast (or that high, but horizontal velocity is much more important).

------
rmason
Paul Allen isn't alone in this endeavour. The field is actually getting quite
crowded:

[https://en.wikipedia.org/wiki/Air_launch_to_orbit](https://en.wikipedia.org/wiki/Air_launch_to_orbit)

------
innergame
I feel overcome by the Dianne Kruger effect, to an extent I don't remember
feeling any time recently. I'm becoming more and more interested in news about
rocketry (due to SpaceX of course) but I'm still a full on space-pleb. I see
something like this and my intuition screams "Woah! Of course! Why don't other
rocket companies do this? What's wrong with them?!"

But the rational part of my brain kicks in and slaps me down for being so
arrogant. It feels humbling to be reminded how stupid one can be.

~~~
sidegrid
Dianne Kruger......?????

~~~
MBCook
The Dunning-Kruger effect: The idea that people of low skill or knowledge
about something don't know how much they don't know and thus think they're
much better at it then they actually are.

[https://en.m.wikipedia.org/wiki/Dunning–Kruger_effect](https://en.m.wikipedia.org/wiki/Dunning–Kruger_effect)

~~~
oculusthrift
was dianne his wife?

~~~
sidegrid
Thank you for getting it.

------
jacquesm
I'd really hate to see that thing land in a crosswind, I don't think I could
watch it.

~~~
nbanks
They could always use a chase car like they do with the U-2 Dragon Lady
because of its ridiculous wing span. This wouldn't help you avoid watching it,
though. youtu.be/W2tnCDBkIoI

~~~
jacquesm
That pilot is an artist. Such a narrow gear stance on such a huge wingspan and
he lands it perfectly. Wonder how many times it went wrong versus how many
times it worked.

------
bogomipz
Does anyone have any insight into how the dual flight decks are utilized?

~~~
jeffbarr
There's only one flight deck and it in the right-hand fuselage. I was at a
recent friends and family day at Scaled Composites and was able to see and
touch this amazing plane.

~~~
PhasmaFelis
Both fuselages seem to have identical windows. Is that just so they can use
the same tooling for both, or is there something else in the left fuselage?
Passenger/observer seating, maybe?

~~~
CydeWeys
The fuselages are used 747s that were repurposed. They have identical windows
because of the design of a typical 747, not anything purpose-specific to this
mission.

------
tomkat0789
Has anybody tried launching a rocket from an airship/dirigible?

------
sargun
This might be a dumb question, but it looks like there are two cockpits on
this plane. I imagine the plane is drive by wire, so it doesn't matter where
you are on the plane. Why do they have two?

Extending my question further, why does this plane have a cockpit at all?
Isn't this something you could remotely pilot, especially to mitigate the
potential risk of being at 30k feet with thousands of kilos of RP-1 or
similar?

~~~
CydeWeys
They just bought two used 747s and stuck them together. Way more work to
remove the cockpits than just leave them intact on their individual airframes.

Hell, for all we know, this could be remotely piloted.

------
ufmace
The really interesting question - does the modest increase in initial velocity
and altitude with a boost out of the lower atmosphere make it practical to
build a Single Stage To Orbit rocket? If they can, then it's an impressive
achievement. If not, then it doesn't really seem worth the trouble.

~~~
Symmetry
The altitude boost is certainly not worth the work. The velocity from the
plane is small but since fuel requirements go up exponentially with necessary
velocity every bit helps.

More important than that is that the rocket doesn't have to punch through as
dense of an atmosphere when getting up to speed. That means you don't have to
reinforce the rocket as much since it's maximum dynamic pressure (maxQ) is
lower giving you a better mass ratio and it means that you're not losing as
much delta-v to air resistance but that's only another 100 m/s or so for a
decently sized rocket like the one being launched here.

But more importantly you can design your engines so that they don't have to
work at higher atmospheric pressures.

[https://en.wikipedia.org/wiki/Rocket_engine_nozzle](https://en.wikipedia.org/wiki/Rocket_engine_nozzle)

A Merlin engine with a bell designed for taking off from sea level has a trust
at sea level of 845 kN but a thrust in Vacuum of 914 kN all while burning the
same amount of fuel. And a Merlin with a nozzle sized for vacuum use can go up
to 934 kN when firing in vacuum, again for the same fuel flow rate.

------
sigrlami9
The general idea like USSR's An-225 Buran tandem within MAKS program
[https://en.wikipedia.org/wiki/MAKS_(spacecraft)](https://en.wikipedia.org/wiki/MAKS_\(spacecraft\))
and it's 25 years old.

------
daveslash
The article claims that it hold's the record for largest wingspan, which is
385ft. It then goes on to say that this blows away the previous record of
65ft. I don't know what the largest wingspan is, but I thought B-52s had a
wingspan of 185ft? Error in the article?

~~~
sparky_z
Blows past the previous record _by_ 65 ft. The Spruce Goose[0] had a wingspan
of 320 ft.

(It's possible the article has been updated since you saw it to correct that.)

[0]
[https://en.wikipedia.org/wiki/Hughes_H-4_Hercules](https://en.wikipedia.org/wiki/Hughes_H-4_Hercules)

------
nether
Really interesting thing is the flat walls on the fuselages. They were done
that way for ease of construction, and are not pressurized containers
therefore don't suffer from stress singularities at the corners.

------
jlebrech
Why not the other way round?

Have a plane take off with a small load and have rockets connect with it at
it's highest altitude and push it into orbit.

expended stages could reconnect with another plane of the same model on the
way down.

------
kadavero
I wonder if they considered a half-loop launch, toss bombing style. That way
they could dump the wing, perhaps at a price of higher strength requirements.

------
synicalx
I can just imagine him up there in the plane, listening to Huey Lewis and the
News.

~~~
PhantomGremlin
I'm confused by this. I don't know if Paul Allen is a Huey Lewis fan. What I
do know is that he's a big Jimi Hendrix fan.

Allen basically built a museum to (mostly) Hendrix. It's since been re-
purposed somewhat, and Wikipedia doesn't have much of the history. But
originally the museum was mostly Hendrix. Here are links to a few early
articles that make it clearer:

[http://www.independent.co.uk/travel/americas/in-search-of-
ji...](http://www.independent.co.uk/travel/americas/in-search-of-jimi-hendrix-
in-seattle-9131310.html)

[http://www.voodoohendrix.com/jimi-hendrix-
museum/](http://www.voodoohendrix.com/jimi-hendrix-museum/)

~~~
yakshaving_jgt
It's a reference to American Psycho.

[https://www.youtube.com/watch?v=vzN3qO-
qc8U](https://www.youtube.com/watch?v=vzN3qO-qc8U)

[https://www.youtube.com/watch?v=cISYzA36-ZY](https://www.youtube.com/watch?v=cISYzA36-ZY)

------
wakeupworld
Nice to read how people are so out of touch when they reach to certain
threshold.. lol where mark suckerberg rackets ?

