Orion shielding from radiation.

[ka9q]

The hydrogen burn ponds at Pads 39A and B are some distance from the pad itself. They did show up sometimes in certain TV shots.

[bknight]

OK, never knew that.

[ka9q]

This probably isn't the best map of LC39A, but it's the best one I could find in a few minutes of searching:

http://www.wpusa.dynip.com/space/LC39A.html

J8-1611 is the hydrogen burn stack. It's northeast of the pad, about halfway to the perimeter.

[bknight]

It pays to be cautious with the highly flammable H₂ as those around the Hindenburg found out!

[bknight]

Looks like NASA is still reviewing and refining the capsule in preparation for the first crewed launch.  I wonder what the CT's will have to say about that flight.
http://www.nasa.gov/feature/a-year-after-maiden-voyage-orion-progress-continues

[ka9q]

It pays to be cautious with the highly flammable H₂ as those around the Hindenburg found out!

Hydrogen safety is a timely topic for me, as I mentor a local high school ham radio club that builds and flies high altitude balloon payloads. Helium has become extremely expensive and scarce over the past few years, forcing many balloon enthusiasts to switch to hydrogen. I have yet to hear of an accident.

I've researched the safety issues extensively, and we've come to the conclusion that if you're willing to handle gasoline, then you should be willing to handle hydrogen. Both must be handled with respect, but I think hydrogen is actually less hazardous than gasoline. It's certainly less poisonous.

The main thing is to work in the open air so small leaks will quickly dissipate.

You also must avoid mixing it with air to form an explosive H₂/O₂ mixture, but that actually takes a deliberate effort; tiny amounts of air in a balloon will not be a problem because the hydrogen will be outside its flammability range.

We take the extra step of grounding the tank with a ground stake and working on a damp tarp to dissipate any static electricity charges. And it should go without saying that only the adults handle the gas and flames are kept far away. Fortunately, nobody smokes.

[Abaddon]

The hydrogen burn ponds at Pads 39A and B are some distance from the pad itself. They did show up sometimes in certain TV shots.

Somebody posted video of those in the not too distant past. Permit me to rummage in the memory bank, they were spectacular.

[bknight]

It pays to be cautious with the highly flammable H₂ as those around the Hindenburg found out!

Hydrogen safety is a timely topic for me, as I mentor a local high school ham radio club that builds and flies high altitude balloon payloads. Helium has become extremely expensive and scarce over the past few years, forcing many balloon enthusiasts to switch to hydrogen. I have yet to hear of an accident.

I've researched the safety issues extensively, and we've come to the conclusion that if you're willing to handle gasoline, then you should be willing to handle hydrogen. Both must be handled with respect, but I think hydrogen is actually less hazardous than gasoline. It's certainly less poisonous.

The main thing is to work in the open air so small leaks will quickly dissipate.

You also must avoid mixing it with air to form an explosive H₂/O₂ mixture, but that actually takes a deliberate effort; tiny amounts of air in a balloon will not be a problem because the hydrogen will be outside its flammability range.

We take the extra step of grounding the tank with a ground stake and working on a damp tarp to dissipate any static electricity charges. And it should go without saying that only the adults handle the gas and flames are kept far away. Fortunately, nobody smokes.

I never worked around it except in chemistry labs.  In those controlled environs it was interesting to burn, but not too dangerous.  I wonder why helium has become so expensive?  Perhaps the fields producing it have decline in production/reserves.

[JayUtah]

I never noticed any in the Shuttle launches, where were they/it?

I do remember watching challenger replays and there was a small igniter at the base of the vehicle

You may be thinking of the hydrogen burn-off igniters.  Hydrogen is a powerfully small molecule, and it's very difficult to design large gas-tight valves for it.  So some leakage is expected.  You really don't want hydrogen collecting in the nozzles after propellant pressurization and suddenly going off with a bang at SSME ignition.

But yes, the burn ponds are to dispose of boiled hydrogen from the LH2 tanks, prior to close-off and pressurization.  It's normally collected via vent hoods.

[JayUtah]

Hydrogen safety is a timely topic for me...

Several branches of engineering take hydrogen very, very seriously.  Nuclear physics experiments, for example, can suddenly liberate vast amounts of hydrogen.  At one place I worked, we had routine releases and subsequently routine evacuations and visits from HazMat guys to inspect and clear the spaces.  Got to know them by their first names.

The main thing is to work in the open air so small leaks will quickly dissipate.

This is actually a plus for hydrogen-fueled vehicles, should any be built.  In a wreck, gasoline and other liquid hydrocarbons spill out of their tanks and generally stay at the premises, ready to fuel horrible and difficult-to-extinguish fires.  In a similar wreck, should the hydrogen tank burst, its contents would disperse rapidly.

[Luke Pemberton]

Many of Apollo's critical control systems (e.g., Earth Landing System) were relay logic.  This is due in part to its being impervious to radiation and a host of other hostile influences, but also in part to the long experience in designing such systems.  Solid-state logic was still in relative infancy and not fully trusted.  Relay logic at that point had a 60-year design pedigree and had all the bugs (literal, in fact) worked out.

The Apollo shielding factor was almost entirely accidental.  Which is to say, no part of the Apollo spacecraft was designated as radiation shielding.  All the shielding effects came from things that were already there for other reasons.  They added up to a robust 7 g cm^-2, which turns out to be sufficient for an Apollo-type mission barring catastrophic solar activity.  Orion is intended for more extensive missions.

...and now that I have moved (reason for my abscence over the last few weeks) and have finally dusted off my old desktop, I can now access a small library of research that I downloaded when I had access to Oxford University's Library facilities. I'm trying to dig out the paper that discusses the August 1972 flare. I recall that had the astronauts been on the moon then they would have been rendered ill (or dead), but inside the CM the shielding was enough to reduce their dose to less harmful levels. The CM did offer some protection against SPEs. I'll try and find the article.

[bknight]

Many of Apollo's critical control systems (e.g., Earth Landing System) were relay logic.  This is due in part to its being impervious to radiation and a host of other hostile influences, but also in part to the long experience in designing such systems.  Solid-state logic was still in relative infancy and not fully trusted.  Relay logic at that point had a 60-year design pedigree and had all the bugs (literal, in fact) worked out.

The Apollo shielding factor was almost entirely accidental.  Which is to say, no part of the Apollo spacecraft was designated as radiation shielding.  All the shielding effects came from things that were already there for other reasons.  They added up to a robust 7 g cm^-2, which turns out to be sufficient for an Apollo-type mission barring catastrophic solar activity.  Orion is intended for more extensive missions.

Luke's reposting of your post gave me another thought.  In the event of a catastrophic solar burst, I have read somewhere that the contingency plan was to turn the CSM around and face the oncoming burst to allow the liquids in the SM to shield much of the event.  Is this correct?

[Luke Pemberton]

Luke's reposting of your post gave me another thought.  In the event of a catastrophic solar burst, I have read somewhere that the contingency plan was to turn the CSM around and face the oncoming burst to allow the liquids in the SM to shield much of the event.  Is this correct?

That's my understanding, and contrary to popular CT ideas the proton flux does not all arrive in one devastating front. There would be a lead edge of high energy protons which are detected, thus allowing the crew to turn the ship around as the flux rises to its maximum.

[bknight]

Luke's reposting of your post gave me another thought.  In the event of a catastrophic solar burst, I have read somewhere that the contingency plan was to turn the CSM around and face the oncoming burst to allow the liquids in the SM to shield much of the event.  Is this correct?

That's my understanding, and contrary to popular CT ideas the proton flux does not all arrive in one devastating front. There would be a lead edge of high energy protons which are detected, thus allowing the crew to turn the ship around as the flux rises to its maximum.

Have you had time to find the data on the Aug 72 flare?  If so, please post.

[Bryanpoprobson]

1972 SOLRAD (8-20A) DAILY BACKGROUND LEVELS (WATTS/METER*2)
=======================================================================
Day   Jan    Feb    Mar    Apr    May    Jun    Jul    Aug    Sep    Oct    Nov    Dec
--------------------------------------------------------------------------------------
 1 7.4E-6 4.2E-6 1.2E-5 2.9E-6 2.9E-6 7.0E-6 6.8E-6 4.6E-5 2.9E-5 1.4E-5 1.3E-5 4.5E-6   
 2 4.2E-6 4.4E-6 1.2E-5 3.2E-6 2.8E-6 6.4E-6 7.3E-6 1.0E-4 2.6E-5 1.0E-5 1.2E-5 4.3E-6
 3 3.5E-6 5.0E-6 9.5E-6 3.9E-6 3.4E-6 8.5E-6 1.0E-5 3.5E-5 2.1E-5 9.3E-6 1.0E-5 3.9E-6
 4 2.4E-6 4.3E-6 1.1E-5 4.4E-6 3.7E-6 8.6E-6 1.3E-5 4.3E-5 1.6E-5 7.0E-6 9.4E-6 3.2E-6
 5 2.8E-6 5.2E-6 1.3E-5 5.1E-6 4.3E-6 1.4E-5 1.1E-5 2.8E-5 1.7E-5 6.2E-6 9.5E-6 3.4E-6
   
 6 3.6E-6 4.6E-6 1.6E-5 6.0E-6 6.1E-6 1.1E-5 1.4E-5 2.7E-5 1.9E-5 7.0E-6 7.7E-6 3.2E-6
 7 3.3E-6 4.7E-6 1.3E-5 6.7E-6 6.0E-6 9.6E-6 1.1E-5 3.9E-5 1.1E-5 5.8E-6 4.6E-6 6.6E-6
 8 2.8E-6 6.9E-6 1.1E-5 6.3E-6 6.5E-6 1.3E-5 9.6E-6 3.0E-5 1.6E-5 7.1E-6 2.8E-6 8.5E-6
 9 3.3E-6 7.8E-6 1.0E-5 8.6E-6 7.9E-6 1.5E-5 8.6E-6 2.8E-5 1.4E-5 8.9E-6 3.3E-6 7.0E-6
10 2.3E-6 8.9E-6 8.2E-6 6.5E-6 9.6E-6 1.1E-5 7.0E-6 3.1E-5 1.2E-5 8.8E-6 4.7E-6 8.7E-6
   
11 4.4E-6 8.9E-6 8.7E-6 6.1E-6 1.4E-5 1.0E-5 7.9E-6 3.3E-5 8.6E-6 8.3E-6 5.6E-6 9.6E-6
12 5.2E-6 8.0E-6 8.0E-6 5.3E-6 1.4E-5 2.2E-5 7.8E-6 3.0E-5 6.8E-6 6.9E-6 5.4E-6 1.9E-5
13 6.1E-6 1.1E-5 9.5E-6 5.5E-6 1.7E-5 1.7E-5 7.9E-6 1.7E-5 5.9E-6 7.3E-6 4.8E-6 1.6E-5
14 7.0E-6 9.9E-6 8.6E-6 6.6E-6 1.8E-5 1.2E-5 1.1E-5 1.1E-5 6.4E-6 1.2E-5 4.3E-6 1.3E-5
15 5.2E-6 1.8E-5 1.0E-5 6.8E-6 1.7E-5 1.3E-5 9.3E-6 9.0E-6 7.9E-6 1.0E-5 3.5E-6 1.2E-5
   
16 8.8E-6 1.5E-5 8.9E-6 6.6E-6 1.3E-5 1.5E-5 6.6E-6 7.8E-6 8.1E-6 1.2E-5 4.3E-6 1.0E-5
17 4.7E-6 2.1E-5 8.1E-6 7.4E-6 1.1E-5 1.6E-5 6.5E-6 8.8E-6 7.3E-6 1.3E-5 5.5E-6 1.3E-5
18 4.5E-6 2.5E-5 8.4E-6 8.6E-6 1.2E-5 1.1E-5 4.3E-6 1.0E-5 1.2E-5 1.1E-5 8.2E-6 1.5E-5
19 8.4E-6 1.9E-5 9.0E-6 6.3E-6 8.3E-6 1.0E-5 4.6E-6 1.5E-5 1.2E-5 1.0E-5 8.9E-6 1.2E-5
20 6.7E-6 2.1E-5 9.5E-6 4.3E-6 8.5E-6 1.0E-5 4.9E-6 2.1E-5 1.6E-5 1.5E-5 1.0E-5 9.2E-6
   
21 6.5E-6 1.9E-5 9.5E-6 4.1E-6 7.6E-6 9.8E-6 7.3E-6 1.7E-5 1.8E-5 2.6E-5 1.0E-5 1.0E-5
22 9.6E-6 2.1E-5 8.5E-6 4.4E-6 8.3E-6 7.8E-6 6.1E-6 1.7E-5 2.6E-5 3.5E-5 9.9E-6 1.3E-5
23 1.3E-5 1.5E-5 9.1E-6 4.4E-6 1.3E-5 7.0E-6 7.6E-6 1.9E-5 1.8E-5 5.7E-5 1.3E-5 8.7E-6
24 1.3E-5 1.3E-5 8.7E-6 4.4E-6 3.1E-5 7.9E-6 5.6E-6 1.9E-5 1.5E-5 5.7E-5 1.4E-5 7.3E-6
25 1.1E-5 1.1E-5 5.8E-6 4.4E-6 1.5E-5 7.0E-6 4.9E-6 2.1E-5 1.2E-5 6.6E-5 1.3E-5 9.0E-6
   
26 1.0E-5 1.2E-5 6.3E-6 4.6E-6 1.0E-5 6.1E-6 5.1E-6 3.2E-5 1.2E-5 4.9E-5 1.3E-5 7.3E-6
27 8.5E-6 1.1E-5 5.4E-6 8.0E-6 1.2E-5 6.4E-6 6.8E-6 3.1E-5 1.0E-5 4.7E-5 9.2E-6 8.1E-6
28 7.7E-6 1.0E-5 5.8E-6 5.3E-6 2.2E-5 7.2E-6 8.8E-6 3.5E-5 1.1E-5 5.3E-5 6.3E-6 7.8E-6
29 8.1E-6 1.2E-5 4.0E-6 4.2E-6 1.0E-5 9.6E-6 8.1E-6 3.8E-5 1.1E-5 3.4E-5 4.6E-6 1.0E-5
30 8.1E-6        2.9E-6 3.9E-6 7.3E-6 8.1E-6 7.2E-6 4.5E-5 1.2E-5 5.4E-5 5.8E-6 1.3E-5
31 7.7E-6        2.8E-6        8.1E-6        9.5E-6 2.9E-5        2.3E-5        9.6E-6
--------------------------------------------------------------------------------------