
385 Feet of Crazy: The Most Audacious Flying Machine - xhrpost
https://www.wired.com/story/stratolaunch-airplane-burt-rutan-paul-allen/
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xoa
The best economic argument I've seen for this is not based on cost so much as
positioning it as a "premium product" that can offer a lot of flexibility and
(potentially) specific temporal launch reliability (ie,. mission not being
scrubbed and hitting one exact date vs simply making it to orbit with a high
reliability, though the latter of course is key too). As a flying jet powered
mobile launch platform it can take off far away from bad weather, fly above
many weather formations, fly directly to an optimal point over the ocean for
any desired launch angle, and then launch. Any bonuses that come from not
needing to punch through the heaviest parts of the atmosphere and being able
to optimize accordingly both in terms of fuel and when it comes to nozzle
geometry and such certainly help them but it may well never be enough to hit a
lower absolute price/kg at all. However, some possible customers (in
particular military/intel) may offer a high premium if a company can offer
them a very high assurance that they can hit a specific launch day to any
orbit at all from a more flexible origin.

I don't know if ultimately there is a big enough market but I can at least see
theoretical potential there, and just in general it often works better to try
to carve out a specialized niche with higher margins then take the 400kg
gorillas head-on at their greatest strengths. And if the medium/medium-heavy
launchers work then this doesn't have a total joke payload either, 3.4 to 6
tons to LEO isn't just cubesats.

It'll be interesting to see how it goes at any rate whether it pans out or
not. It's ambitious and it could offer a niche but new additional mission
capability.

~~~
mikeash
I wonder if there might be unique military applications. I’m thinking recon
satellites launched on short notice to be able to observe a target that’s
trying to hide. Launch site flexibility also means you can launch from a
location that would let you recover the payload after only one orbit, like the
Shuttle could do.

~~~
xoa
Yeah, that's exactly the sort of thing that comes to mind and what might make
the scheme work: not merely trying to serve an existing market but create an
entirely new capability that can then command sufficient margins. Could the
military have reusable birds on standby and then just be able to launch them
for some specific conflict aiming for a quick lifetime at much lower altitude
and with a path and period that wouldn't be known to adversaries? I haven't
crunched the math, but in principle it seems like they could launch something
stratospheric even, not high enough for a long term stable orbit but in turn
could have higher mass and useful new intel gathering potential.

Of course economics still matters here even for the military, it still will be
weighed against conventional satellites and spy planes and so on. But a sales
pitch of:

> _" We can pick up your bird from anywhere with enough runway, fly it to
> somewhere it can be launched at any time with minimal to zero worries about
> weather, other air traffic, or bothering (or even being visible to)
> populated areas, and hit any azimuth (no population overflight concerns
> either)"_

seems like it might be worth _something_ at least. It's certainly somewhat
different beyond cost at least, even if it doesn't matter to most. The AF has
their own robotic spaceplane project after all, seems like there is at least
some interest in this kind of area?

~~~
mikeash
From a quick google, a 200km orbit lasts roughly a day and it drops to zero
very quickly after that, so I don’t think you could save _too_ much by
launching lower, but it might be worthwhile.

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finnh
Related: The New Yorker just a few weeks ago published a great profile[0] of
the Virgin Galactic pilots, including a lot of detail about Burt Rutan, Scaled
Composites, and WhiteKnightTwo.

[0] [https://www.newyorker.com/magazine/2018/08/20/virgin-
galacti...](https://www.newyorker.com/magazine/2018/08/20/virgin-galactics-
rocket-man)

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hwc
I don't understand the math of this sort of launch vehicle. Any rocket
launched at a high altitude still needs to accelerate up to orbital velocity,
which is orders of magnitude more energy than is saved by starting out moving
at a sub-sonic speed and a high altitude.

The layers of complexity here can't be worth it economically. Is this a
solution in search of a problem?

~~~
proaralyst
I thought the argument was that rockets spend a lot of fuel just getting
through the thick low part of the atmosphere, which is the same point at which
they're heaviest. Skip the start & you need less fuel.

~~~
Quequau
But it's not just altitude, right? Acceleration and Speed are important
factors to getting to orbit (not that I'm a rocket surgeon).

~~~
throwanem
Right. The closer to sea level you are, the denser the atmosphere you're
pushing out of the way as you accelerate - thus, the more force you need to
use in doing so, and the lower the acceleration you obtain from the propellant
you expend.

So if you can get above the thickest part of the atmosphere, say attached to a
giant goofy-looking airplane, before you light off your engine - rather than
having to push your way through that same thick air on your own - you need
less propellant, overall, to reach orbit, which means you can devote a larger
fraction of your launch vehicle's mass to payload.

~~~
Retric
Rockets are not moving very quickly in the lower atmosphere, which makes a
real difference.

Space shuttle was 3 g - 1 from gravity = 2g net acceleration, but that's kept
low for passengers. Even then 2 g net ~= + 44 MPH every second.

So, first 15 seconds your going under 660 MPH which is not that fast, but you
get ~1.4 miles up. Because drag increases with speed very quickly the next bit
is harder, but you very quickly get above what an aircraft could take you with
~5.6 miles at 30 seconds. Note: Higher g's mean more drag in denser
atmosphere, but less gravity drag it's a meaningful trade-off.

However, aircraft's velocity is very useful essentially saving those first 15
seconds of full burn, but comes at the price of needing more structural
elements to support the hanging rocket.

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nradov
Could someone explain why Burt Rutan designed _Stratolaunch_ with two separate
tail structures instead of joining them with a center section like the wing?
It seems like the center wing could be subject to a lot of stress, especially
in turbulence or with an engine out.

~~~
throwanem
Control surfaces behind the payload would be aerodynamically shadowed, and,
depending on payload shape, either unable to develop significant control
moments or subject to chaotic airflow that'd make them more of a liability
than an asset.

~~~
nradov
But wouldn't a center tail section still help with overall structural strength
even if it didn't have control surfaces?

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nsm
I just saw the Spruce Goose in the Evergreen Aviation Museum near Portland.
That has a wing span of 320’ and is already impressive in its own right. This
must be better! Bit of trivia: the Goose is made largely of wood, one of the
older “composites” :)

~~~
throwanem
She is a gorgeous aircraft, isn't she? I'm glad she found a good home; we'd be
the poorer for her loss.

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walrus01
What exactly is the back of the napkin calculation for Delta v saved by
dropping a rocket from 40,000 ft and 400 knot airspeed vs launching from
ground level?

If we assume that 7800-8000 m/s is required for low earth orbit, how much does
stratolaunch plan to shave off? How much Delta v is saved in the current small
rocket setup with the pegasus dropped from an ex commercial airliner at
approximately the same altitude?

~~~
walrus01
Replying to myself, these seem to be the rough numbers:

[https://news.ycombinator.com/item?id=14456602](https://news.ycombinator.com/item?id=14456602)

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techbio
In comparison the Airbus A380's wingspan is about 260 feet, and the Boeing
747-8's is about 230'.

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dgritsko
Some pictures of this thing on the runway available here:
[https://www.space.com/39155-stratolaunch-wprlds-largest-
plan...](https://www.space.com/39155-stratolaunch-wprlds-largest-plane-test-
photos.html)

Can't wait to see videos of it in action.

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ChuckMcM
My wife and I saw this plane outside the hangar when we were driving through
Mojave I seriously thought it was two planes parked next to each other. The
scale is really impressive. I'm hoping there are some hints as to when it will
be flying so that we can drive out and watch.

~~~
throwanem
> I seriously thought it was two planes parked next to each other

It is. Just that it's the first such pair of aircraft that _stay_ parked next
to each other in all regimes, not just the one.

~~~
scottlamb
> It is. Just that it's the first such pair of aircraft that stay parked next
> to each other in all regimes, not just the one.

Apparently not! I learned from the video embedded in the article (just before
the paragraph starting with "The Next Steps") that Scaled Composites has
already built one:
[https://en.wikipedia.org/wiki/Scaled_Composites_White_Knight...](https://en.wikipedia.org/wiki/Scaled_Composites_White_Knight_Two)

and from there I found a wikipedia category about them:
[https://en.wikipedia.org/wiki/Category:Twin-
fuselage_aircraf...](https://en.wikipedia.org/wiki/Category:Twin-
fuselage_aircraft) including another Burt Rutan design:
[https://en.wikipedia.org/wiki/Rutan_Boomerang](https://en.wikipedia.org/wiki/Rutan_Boomerang)

The Stratolaunch is just so much bigger.

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wsgreen
Why would they seemingly manually create the panorama instead of using
photoshop to create a smoother image? Seems like the vignette and color
mismatch would be worth removing?

~~~
roywiggins
I think it's a stylistic choice to emphasize that it's so wide, they needed to
make a panorama.

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Markoff
article is not readable, why anyone still links this site?

[https://imgur.com/a/OKPeK8C](https://imgur.com/a/OKPeK8C)

thank you wired for warning, i will make sure not to open any link anymore

