Thursday, May 28, 2009

Finally Solar Power Satellites?

Not a lot of details. This would be a pretty big satellite. The idea is to use "existing rockets" which does not narrow things down much. From an emissions perspective, the interesting factors are:

1. which launch vehicle
2. what launch rate
3. what period of time

But here is an interesting quote from the CEO: "These space launch vehicles primarily use natural fuels (H2, O2) and have an emissions profile similar to a fuel cell."

So he means Delta IV Heavy I guess. But this notion of "natural fuels" - the word natural is not defined and is usually a marketing ploy - leaves me wondering if this is serious at all.

Also I wonder what PG&E's exposure is. The risk is all Solaren's? I could not even find a website for Solaren. Anyway it looks very cool.

Wednesday, May 27, 2009

Disruptive Technology

This is an excellent overview of hypersonic propulsion. It is interesting that Director calls this "disruptive technology". He also touches briefly on scaling up X-51 by 100X and how hypersonic propulsion can be used for launch with "aircraft like" operations. The charts, while pretty cool, do not mention anything about the possible stratospheric effects of burning hydrocarbon fuel at 25 km altitude.

As you can see from the plot 25 km is right in the middle of the ozone layer. But ozone chemistry is tricky and sometimes adding one ozone destroying molecule just chemically ties up another and results in a decrease in ozone destruction. This is how subsonic aircraft cause an ozone increase.

Will hypersonic propulsion do that too? Or will they cause ozone loss? How much gain or loss?

Saturday, May 23, 2009

Space Shuttle Reentry "Emission"

Space Shuttle and trailing hot gas plume during entry

If you add molecules of nitric oxide (one oxygen and one nitrogen, chemical symbol = NO) in the stratosphere at altitudes greater than about 20 km, the result is ozone depletion. One way to generate NO molecules to air is to heat it to about 2500 deg centigrade at which point nitrogen and in the air react to form nitric oxide (that is, NO).
Air can be heated to this temperature by the friction around a Space Shuttle during entry (or reentry). (BTW it is not really "friction" heating, but that is another post.) That is why the Space Shuttle has those tiles, to protect it from the very hot air that surrounds the vehicle during reentry and forms the glowing plume behind it. So the Shuttle for practical purposes the Shuttle is an "NO emitter" during reentry.

Almost three decades ago two guys Park and Raish (1980) did a quick calculation and estimated that the Space Shuttle generates approximately 0.02 kilotons of NO in the upper stratosphere during each entry as air heats up in the hot tail (see picture above) behind the Shuttle.

This is interesting of course because this NO will react with and destroy some ozone. This is also bad because ozone destruction, in general, is bad. So it is interesting that simply by returning to earth, the Space Shuttle causes ozone depletion.

Very roughly this is equivalent to the mass of total NO emitted by the jet engines of a Concorde supersonic transport during half a dozen or so transatlantic flights. (The Concorde does not fly anymore by the way.) I point this out so that you can put the Space Shuttle reentry NO production during reentry into some context by comparing it to another source of NO molecules that scientists worry about, supersonic transports. Park and Raish did not calculate the ozone destruction caused by a Shuttle reentry. A different model would be needed to do that.

I wonder a few things here:

1. The Park and Raish work was done over a quarter of century ago. Would the result be different using up to date calculations and models?

2. How does the ozone depletion from Shuttle entry compare to the depletion from Shuttle launch? The emissions from the big solid rockets likely cause more ozone depletion but I wonder how much more?

Friday, May 22, 2009

Where Is the White House going on HFCs?

This is interesting.  EPA and State Department want to phase-out HFCs using the levers and buttons of the Montreal Protocol.  In the process, the Montreal Protocol would become the de facto international legal mechanism for greenhouse gas regulation.  But the President is not going that way despite hard lobbying by EPA and State..

What is the White House policy here?   The big plan is not obvious. 

Monday, May 18, 2009

Advecting and Mixing Space Shuttle Plume at Sunset

Note the inset detail showing where ice particles have grown large enough to fall from the cloud layer.  This phenomenon, called virga, indicates that ice particles in the plume are growing to a critical size.  This might be removing ozone destroying nitrogen compounds (called denitrifying) the tropopause region since we know that the solid rocket motor alumina particles carry HNO3.   

Sunday, May 3, 2009

Rocket Emissions and the Montreal Protocol

One of the most interesting comments in response to Ross et al. (2009) was from David Fahey of NOAA's Chemical Science Division.  David in a key figure involved with the many and varied scientific aspects of ozone layer protection.  See here for a nice review by David. 

Here his comment: "There's a number of exemptions to the protocol," he said. "Each one by itself is small, but if you go too far, it could be death by a thousand cuts."
Often it is difficult to make reccomendations without falling to the "Cassandra Complex" but the space industry should take an interest in not being one of the thousand cuts.  

A World that Might Come About

Here is an interesting paper that shows how large space systems might cause so much ozone loss that a few decades down the road rocket launches could be regulated.   That is to say - limited or capped.  That paper is not definitive in any sense but that is the point.  There are factors of 10 uncertainty in:

1. How much global ozone loss rockets actually cause - especially liquids
2. How much ozone loss would be "too much"?
As the Iridium - Kosmos collision showed it is most unwise to allow multiple factors of ten to run around your space policy and space ops spreadsheets and white boards.  Before that collision, certain "Cassandras" were hinting that such a collision was likely to happen in the next few years. 
Ross et al. (2009) play the same hand.  There are factors of ten running around the science and policy that will cause a collision at some point if ignored.