[AR] Re: Reaction Engines' Sabre Rocket Engine Demo Core
- From: Keith Henson <hkeithhenson@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx, Power Satellite Economics <power-satellite-economics@xxxxxxxxxxxxxxxx>
- Date: Mon, 18 Mar 2019 11:35:21 -0700
On Sun, Mar 17, 2019 at 10:09 PM Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Sun, 17 Mar 2019, Keith Henson wrote:
...and second, figuring out if the rocket traffic for a significant
power satellite construction rate would wipe out the ozone. This has
been done for Skylon, but it's a hydrogen burner and (burning rich)
makes almost no NOx on the way up.
As far as I know, there's nothing magic about burning hydrogen that helps
with this -- in fact, hydrogen may actually be a bit worse for the ozone
layer than hydrocarbons, because there's more water vapor in the exhaust.
(The stratospheric chemistry in question happens mostly on the surface of
ice crystals, so more water injected into the stratosphere -- which is
normally very dry -- is not good news.)
The surface chemistry is correct for chlorine but not for NOx. I was
initially concerned about the air passing through the engines and
making NOx. But it turns out that the reducing presence of excess
hydrogen (throughout the flight envelope) suppresses the formation of
NOx almost entirely. See Figure 1 here:
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016EF000399
This is also an area where rockets win over airbreathers, because running
the air through the combustion system is rather more worrisome for NOx
formation than just having the exhaust jet emerging into air.
Perhaps. You have to pay close attention to the chemistry involved.
To get NOx requires oxidizing conditions--a situation which exists
where the rocket plume emerges into air. The details of the chemistry
involved need more investigation. For Skylon, the big NOx production
is reentry (see Figure 1 as above). I hope not, but I suspect that
this is not the case for hydrocarbon rockets.
It's a really important issue since (as I have mentioned before)
solving the energy problems at a cost of a billion cases of skin
cancer seems to be a poor tradeoff.
Keith
cc to PSE group.
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