[ExI] [Server-sky] [Beowulf] Server Sky - Internet and computation in orbit

Fri Jun 21 20:40:14 UTC 2013

----- Forwarded message from "Lux, Jim (337C)" <james.p.lux at jpl.nasa.gov> -----

Date: Fri, 21 Jun 2013 20:32:14 +0000
From: "Lux, Jim (337C)" <james.p.lux at jpl.nasa.gov>
To: "keithl at keithl.com" <keithl at keithl.com>, Eugen Leitl <eugen at leitl.org>
CC: "server-sky at server-sky.com" <server-sky at server-sky.com>
Subject: Re: [Server-sky] [Beowulf] Server Sky - Internet and computation in orbit
user-agent: Microsoft-MacOutlook/14.3.5.130515

James Lux, P.E.
Task Manager, FINDER – Finding Individuals for Disaster and Emergency
Response
Co-Principal Investigator, SCaN Testbed (née CoNNeCT) Project
Jet Propulsion Laboratory
4800 Oak Grove Drive, MS 161-213
Pasadena CA 91109
+(818)354-2075

On 6/21/13 1:01 PM, "Keith Lofstrom" <keithl at gate.kl-ic.com> wrote:

>Most questions are answered on the wiki, http://server-sky.com
>There's a search function that will help sift through the hundreds of
>pages.
>Plenty of unanswered questions, but that is why I am sharing the idea,
>so others can contribute and claim some of the credit.
>
>
>Forwarded message from "Lux, Jim (337C)" <james.p.lux at jpl.nasa.gov>
> 
>> 1) orbital debris - fling those thousands of widgets out there.  Are
>>they high enough to stay in orbit for a while? Are they going to damage
>>things that hit them?
>
>6411km altitude / 12789km radius, about one Re out.  Thinsats might
>damage some objects in crossing orbits if we let collisions happen,
>but arrays are capable of both continuous maneuvering and high
>luminance lookdown radar.  There aren't many objects in crossing
>orbits, and all are derelicts, according to the NORAD database.
>
>Thinsats are much thinner than the Whipple shields enclosing
>most critical spacecraft systems.  They will remove some paint
>and some material underneath, but they are unlikely to do
>anything more than micrometeoroids do.
>
>And your next question will be about radiation - we are aiming
>for the lower van Allen belt.  I'm a chip designer.  Recent
>rad-hard developments in semiconductors and integrated circuits
>are what led me to server-sky.  Look at the website for more.

Actually, radiation probably isn't much of an issue. It's much
overthought.. I am unaware of any actual loss of satellite using
commercial non rad-hard parts, and there's been a lot flown.  Yes, there's
a latchup problem with some parts, but that's design-around-able.

>
>> 2) orbital mechanics - the "array" pretty much has to be flat, that is,
>>they're all at the same orbit height, otherwise they'll drift apart,
>>since the period is different.
>
>All thinsats in an array have identical orbital periods (and
>the same semimajor axis, to first order), though all have
>slightly different orbital elements.  The arrays rotate,
>though their shape is skewed by the velocity changes associated
>with radius variations.  Rule of thumb - a 1 meter radial
>"apogee" turns into a 2 meter retrograde displacement relatve
>to array center 1/4 orbit later.  To see how an array of thinsats
>evolves over an orbit, look at http://server-sky.com/IEEESustech2013
>
>There are small second order distortions (J₂ and light pressure,
>for example), factored into array shape and central orbit choice,
>and third order distortions ( lunar/solar/jupiter tides for example )
>that will be dealt with by orbit shape again.  The small residual
>errors ( < 1E-9 of orbit velocity ) can be dealt with by light sail
>maneuvering.
>
>> 3) does it really save anything to put the computation in orbit?
>
>Server Sky doesn't save much for developed nations.  Google and Amazon
>will still build 100 megawatt data centers and pump CO₂ into the
>atmosphere while pretending to be "green".  Much of the CO₂ generated
>while making the concrete and metal and plastic constituting 99.99%
>by weight of those data centers.  Part of the pretense is building
>solar arrays as if replacing plants with solar panels and destabilizing
>the electrical grid with intermittent and unpredictable power demand
>somehow helps the environment.

But it's not like making silicon is particularly green either.. But that's
a complex issue and one others will have to thrash away on. It's the whole
externalities thing and where do you draw the boundary line.  That's
essentially political, not technological.

>
>It is quite different for poor nations with large rural populations
>that haven't deployed much communication infrastructure.  India has
>400,000 cell towers, connected by microwave and powered by diesel,
>with the "backbone" being a mix of fiber and microwave that follows
>their rail network.

Like Sprint and the SP railroad<grin>

> No way they can afford to deploy much fiber
>beyond that.   Even their microwave grid is way oversubscribed with
>the rapid uptake of cell phones.  Bringing broadband to half a
>billion rural Indians can create trillions of dollars a year of
>economic value.  The cheapest way to do that is with computation,
>and large-aperture/millimeter-wave communication in orbit.

OK.. I can buy that.

>
>> I'd like to see more justification of the 100x cost differential
>> between ground and space 25 years from now.
>
>My career as a chip designer has spanned a 1 billion times decrease
>in the cost of a transistor, and a 1 million times increase in the
>speed-power capability of transistors.  By 2015, we will have deployed
>a zettatransistor, 1e21 devices.  Much of that growth came from
>invading and transforming seemingly unrelated fields, like biology
>and publishing and transportation.  We point the transistor hose at
>problems and wash them away.

Yes, for the logic part.  But I don't see similar improvements in, say, 30
Ghz RF devices, although I will readily concede that the amount of money
being thrown at the problem is a lot less, and it's true that fT for the
transistors is steadily climbing.

There is, though, a challenge of coupling the RF energy to space in some
way.  I've seen on-die and in-package antennas for, say, 60 Ghz (Hittite),
so I can envision that one could make a large array of them.  And as you
know, once it's just a matter of lithography, it gets very cheap in large
scales.

However, you're probably still talking exotic materials (e.g. It's not
regular old CMOS, just smaller).

There are some challenges with poor power added efficiency, too.  Even if
you have an array of thousands of little 100mW or 10mW transmitters it
takes a lot more juice to make them work and there's still the not
inconsiderable effort of phasing, etc., although that's clearly solvable
in a distributed sense.. I've done a fair amount of research on
distributed antennas that self calibrate for deformation and while it
might not be practical today, it's not a "breaking the laws of physics"
thing, more an economics.

Same sort of applies on the receive side.

I'll have to take a look at your telecom link design to see what you're
thinking of on the ground terminal side.  Cheap hydroformed dishes (1.5
meter dishes can be stamped out for a few bucks) or printed phased arrays?
Or active arrays? 

If you're looking at megabits/sec for 6000-10000 km range that's not all
that big a deal. If you're looking at Gbit/sec, It's somewhat more
challenging..

>
>Meanwhile, space development has stagnated - we've built a bunch
>of plausible-but-wrong systems like shuttle, but our workhorse
>launchers (Atlas and Proton) are incremental improvements of
>1960 designs.  The major advances in space technology have
>been electronic systems like Opportunity, using semiconductors
>10 years behind the stuff you can buy at Walmart, and system
>construction techniques resembling 1950s aircraft.

I would agree with you, except we use parts that are more like 20-30 years
behind state of the art. But that *is* starting to change.  It partly
comes from conservatism.. You spend a billion dollars on a Mars probe and
you want your perceived risk to be in the science, not in the
infrastructure, so you make do with what performance you get with your
20-30 year old parts.  It is what I call the penguin approach to
technology infusion.. All the penguins stand at the edge of the ice,
hungry, but unwilling to jump in because there might be a leopard seal
waiting. They jostle around, and one falls in, and doesn't get eaten, so
all the rest cascade in.

The system construction is a bit more modern than 50s aircraft (not many
composites in the 50s, for instance).  But to a certain extent, this comes
from the one-off nature and conservatism.  It's easier to partition the
job with old style system engineering.  Again, this is slowly changing,
but nobody is seriously proposing mass production of anything at NASA.

A not so subtle aspect is also that if Jim Lux's college class puts up a
small satellite built with commercial parts and it has issues, it's "look
at those plucky students trying to do space on a budget".  If JPL puts up
exactly the same satellite and it has issues, it's "JPL satellite fails,
wasting money"

>
>Craig Venter used modern semiconductor technology to sequence the
>human genome, turning a planned two decade multibillion dollar
>government effort into a 2 year 300 million dollar transformation
>of biology.  As a direct result of his work, you can get a 1M-SNP
>genotyping for $99, and can expect a whole genome sequence for
>less than $1K in a year or two.
>
>I've spent my whole life waiting for the "cheap-rocket-first"
>community to deliver.  I'm not waiting any more.  I'm not nearly
>as smart as Craig Venter, but shifting attention from rockets to
>electronics and market needs doesn't require the same brainpower,
>just assembling off-the-shelf processes into new systems serving
>ignored markets, and doing so at Moore's law rates.   There's a
>cornucopia of new technology and new opportunities out there,
>and those who cling to the old ideas will be left in the dust.

Rockets are hard to do cheap.  SpaceX is making excellent progress and I
think they will set the new bar.
But ultimately, there's regulatory stuff that makes it hard to do grass
roots innovation.  The second you put any kind of guidance system on a
rocket, no matter how small, you're building a "guided missile" and that
attracts a LOT of attention from the authorities. So that tends to make it
hard for clever folks at small scales. Not exactly regulatory capture, but
still, in the same sort of vein.

That's really where the cleverness needs to come.. It's not about better
technology: that exists, and you don't need 100% performance engines, and
such.. You can throw more fuel at it, to a certain point.

We need to find a cheaper way to get launch sites, etc.

>
>25 years?  I've organized chip products in 25 weeks (design/fab/
>test/sell).  Server sky's long lead times involve team building at
>the front end, and negotiating with the ITU at the back end.  There
>are plenty of revenue opportunities along the path to deployed
>arrays, and a team whose combined cleverness far exceeds mine will
>be rich before we put the first thinsat in space.  The job now is
>to define viable long term goals, discover people who share them,
>and develop a search process that finds the easiest and most
>lucrative stepping stones on the shortest path from here to there.
>
>There are certainly trillions of plausible-but-wrong ways to do
>this, and with bad planning my team will pick one of those.
>But the opportunity is far too large to be ignored, and even a
>magnificent failure will inspire thousands of others who think
>they can do better.  Some of them will be right.

Certainly interesting.. And I'll be sure to look at the web stuff this
weekend..

BTW, this is all my own and shouldn't be construed to be representing what
JPL or NASA think..

>

----- End forwarded message -----
-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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