EPA: perchlorates

[Dr Mordrid]

This is a big hit to the use of perchlorates in solid fuel rockets such as the shuttle SRB's, and the companies that make them - in the case of SRB's ATK - Alliant Technsystems.

Even though the shuttle program is winding down ATK had hoped NASA's proposed heavy lift rocket would be "shuttle derived" and use upgraded SRB's for years to come, but now their impact on the KSC wetlands and around the plants that produce & install their fuel will ave to be taken onto account. EPA says there are 400 problem locales.

NY Times....

[Brian Ellis]

As far as perchlorates are concerned, this appears to be much ado about nothing. Any schoolboy taking high school chemistry can tell you that these are oxidants whose anion is -ClO4. By definition, they are therefore unstable in aqueous solutions. Their folded-e lifetime in solution depends on the temperature and the amount of organic matter in the water, but is typically counted in days or less. After decomposition, the resultant anion is -Cl (chloride), which is considered as non-toxic.

A 50% chance of a lethal dose with rats is 2100 mg/kg NaClO4. By extrapolation, an 80 kg man would have to absorb more than 160 g in one dose to have a 50% chance of popping the clogs. At a very unlikely concentration of 1 g/l, he would have to drink twice his own body weight. Little is known about chronic effects because it would decompose at low concentrations even before it reached the stomach:

Potential Chronic Health Effects:
CARCINOGENIC EFFECTS: Not available. MUTAGENIC EFFECTS: Mutagenic for bacteria and/or yeast. TERATOGENIC EFFECTS: Not available. DEVELOPMENTAL TOXICITY: Not available. The substance may be toxic to blood, kidneys, liver, thyroid. Repeated or prolonged exposure to the substance can produce target organs damage.

Certainly, when I was working at the KSC, the alligators round the launch area seemed very healthy, also hundreds of bird species on Merritt Island.

OTOH, the last paragraph re tri- and tetra-chloroethylene (TCE and PCE resp.) is much more apposite. It is probable that the toxicity of these and similar substances in drinking water does cause a problem with the CNS and liver as targeted organs. They are relatively persistent compounds and it is possible that sub-ppm concentrations may be harmful in drinking water.

[Dr Mordrid]

For the record;

each shuttle launch requires the production, transportation and use of at least 821,280kg of ammonium perchlorate, 69.6% of the fuel/oxidizer mass, and any shuttle-derived heavy lift rocket proposed would use either that or up to 1,129,260kg (4 vs. 5 or 5.5 segments).

[Brian Ellis]

Whereas I agree that the mass of NH4ClO4 is enormous, I believe your figures are wrong. When I was at the Thiokol (then) plant in Utah, where the shuttle SRBs are made, our information was that the total propellant mass per booster was 500 000 kg. At 69.6%, this gives 696 000 kg/launch.

The loading of the propellant mixture into the segments is a highly hazardous manual operation, done in a large hangar with safety chutes. We were told that, if propellant did ignite there, the chances of a worker reaching a chute were almost nil but, if he did, he would have two broken legs on landing!

[Dr Mordrid]

You're right - I posted numbers for Ares V by mistake. Still - thats a s***load of AP and the new regs are going to make continued use problematic. Better if they go with a kerosene/lox first stage & hydrogen/lox second stage: Atlas V Block 2/3, Falcon X/X Heavy/XX etc.

[degrub]

and the shock wave would knock you down before you got there, or maybe push you through the wall.

[Dr Mordrid]

For Falcon XX thst's certainly the case - it'll be the beast heard & felt 2 states away.

To that end I hear SpaceX is being courted by the Stennis test center, NASA's engine test facility in Mississippi, for vacuum testing the Raptor hydrogen 2nd stage and for testing Merlin 2 - which will be significantly more powerful than the Saturn V's F-1 engine at 1.7 to 2.0 million lb-f each.

Using Stennis would benefit both: Stennis stays open and SpaceX doesn't have to build $$ new stands in Texas, plus the folks there might object to Merlin 2's artificial earthquakes. As is Falcon 9 rattles everything for nearly 40 miles

[degrub]

nah, we're used to em. We lit off a large cloud of LPGs a while back. Richter 3 in the nearest large city. As long as the cattle don't mind too much, the oil wells won't care.

[Dr Mordrid]

You live near Waco, or are you talking Texas generically?

[degrub]

Houston.

[Brian Ellis]

I witnessed 2 test firings of the Blue Streak first stage at Spadeadam c.1960. This was a kerosene/LOX affair. My Rolls-Royce interlocutor used to say it was only a giant blow torch. The first time was from the underground control bunker, about 1 km away, through periscopes. The second time was serendipitous in that traffic was stopped from going on site about 10 km from the firing platform, but in sight of it, and that was even more impressive than the first. Apart from the ground trembling, we got the full benefit of the noise. I wonder, in retrospect, whether the Spadeadam complex was well thought out because it was built largely on peat bog.

My involvement was instrumentation to measure the volume of remaining LOX under weightless conditions. We did it, but how?

[Dr Mordrid]

Other than guesstimating by burn time & flow rate, one way used in satellites is to use a heater of known output and temp sensors around the tank to determine how much time it takes to raise the fuel/oxidizer x degrees then calculate the volume from that. Other systems using optics, EM fields etc. hit the patent office every year.

[Brian Ellis]

The way we did it was to put two titanium interlocking honeycomb arrays in the LOX tank at 90° to each other so that they were electrically insulated from each other and the tank. If the capacitance between the honeycombs in an empty tank were, say, 1 nF, it would rise to about 2.4 nF in a full tank and linearly in between, no matter where the LOX was situated in the tank. It was simple to hsve a capacitance meter calibrated directly in 100s kg of LOX. Accuracy was about ±1%

[Dr Mordrid]

1% is all you need, and that much sticks to the tankage & baffles, stays in the lines etc. anyhow.

Another thing SpaceX is looking at is a methane/lox version of the Merlin. XCOR is also working on one with ATK.

Methane's big advantage is that fuel could be obtained in space through ISRU (in situ resource utilization). One example is using tanked hydrogen and solar power to convert the atmosphere of Mars into fuel for the return leg - methane being a more powerful fuel than the hydrogen, but the hydrogen needed being lighter on the way there.

XCOR's methane rocket engine firing