Boing Boing call: send in your green initiatives!
Phil Marshall
Bernadette, John, James and I are featured in a Boing Boing feature today:
http://www.boingboing.net/2011/04/29/low-energy-astrophys.html
It's a good article, explaining what we in this little online
community are all about. Show it to your colleagues!
I've been thinking about how to get us all connected a little better -
and thought I'd start by putting you all on the map! If you are part
of, or run, any sort of green initiative at your institute or
observatory, I'd like to hear about it. I bet there are plenty of
cool schemes out there in US astroland, and we could all learn from
each other's ideas. And since the Boing Boing article is something of
a call to arms, well I figured now might be a good time to assess the
state of the profession again. Reply to the group or to me, and I'll
keep track and make a map of all your efforts!
Cheers
Phil
David W Hogg
the community's carbon footprint?
> --
> This message was sent to the "low-energy-astrophysics" Google group.
> To post to this group, send email to LEa...@googlegroups.com
> Visit the group at http://groups.google.com/group/LEastro?hl=tk
> Visit our wiki at http://low-energy-astro.physics.ucsb.edu
>
> To unsubscribe, send email to LEastro+u...@googlegroups.com
>
--
David W. Hogg ~ CCPP, NYU; MPIA ~ http://cosmo.nyu.edu/hogg/
Benjamin Weiner
I came up with a couple of different ways of calculating this,
both suggest that SOFIA's contribution to the astronomy energy
budget is very large, if not 2x. It will also depend on what you
consider the astronomy energy budget (travel? rockets? whatever
energy Ball Aerospace uses to construct satellites?)
The gory details follow, but the summary is that SOFIA's
planned operating schedule would work out to of order
30,000 extra jet miles/year or 90 kWh/day _per US astronomer_.
Some rough numbers found with Google, some of dubious origin,
but sound reasonable:
1. SOFIA's plan for full scale operation is 8 hours observing per flight,
3 flights a week. Probably have to assume about 10 hours airtime/flight
for takeoffs, landings etc.
2. A stock 747 has fuel consumption 12,800 liters/hour, carries
about 400 passengers, cruise speed 580 mph. Jet fuel energy
content is about 43 MJ/liter.
analysis a) flying SOFIA for one year is about 1500 flight hours,
1.9e7 liters/yr, equivalent of about 2.8e8 passenger miles/year. If
there are 7000 astronomers in the US it's the equivalent of us each
flying an extra 39,000 miles/year.
analysis b) SOFIA energy use is about 8.2e14 J/yr, averaging to
6.2e5 kWh/day or 89 kWh/day/US astronomer. Arguably we should be
counting German astronomers too since it is a joint project.
The low energy astrophysics white paper and wiki estimates
were that the average astronomer flies 23000 miles/yr and
thus averages 113 kWh/day. (Differences between analysis a
and b are probably due to the kWh/passenger mile assumptions.)
The white paper also estimated that flight miles dwarf energy
use due to observatories, computing etc.
I don't think we estimated energy use due to rocket launches,
which could be significant, but I think it winds up much less.
For a small satellite, like a SMEX, it could be launched on say
a Pegasus which weighs 18500 kg, probably no more than
17000 kg of solid rocket fuel - solid fuel is about 3 MJ/kg and
liquid fuel 10 MJ/kg (numbers from wikipedia). That works
out to ~5e10 Joules (plus flying a 747 to drop the Pegasus from).
A heavy Ariane 5 (eg XMM launch) has ~180 tons liquid fuel
capacity and 540 tons solid, which is of order 3.4e12 J. It seems
remarkable that launching an Ariane uses less energy than
one SOFIA flight, but the numbers appear to say that, unless
I messed up the fuel energy density somehow. A 747 has
fuel capacity around 2e5 liters, so I think the conclusion that
a 747 carries as much or more fuel energy than an Ariane
is legitimate.
Ben
p.s. Phil, the wiki sections on observatory and computing uses
have gotten lost, any chance you can restore those from the
white paper? Feel free to raid the above if you want to add
something about rockets.
--
Benjamin Weiner
Assistant Astronomer, Steward Observatory
b...@as.arizona.edu
http://mingus.as.arizona.edu/~bjw/
David W Hogg
answer: SOFIA's energy use is significant. I didn't check your
launch numbers; they are relevant because if you trace it down to
final margins and per-traveler costs they show that space tourism /
SpaceX have very limited markets (unless energy gets much, much
cheaper in the future)!