A Space & astronomy forum. SpaceBanter.com

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » SpaceBanter.com forum » Space Science » Policy
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Easy Ride to Sub Orbital Altitudes



 
 
Thread Tools Display Modes
  #11  
Old July 2nd 20, 12:51 PM posted to sci.space.policy
David Spain
external usenet poster
 
Posts: 2,783
Default Easy Ride to Sub Orbital Altitudes

On 2020-07-02 3:25 AM, wrote:
The acetate resin doped with alumiunum powder had already destroyed one and maybe two other airships. Zeppelin (the company) was working day and night to find an alternative. The company's lab where the new materials were tested actually survived WWII and the samples were later put in storage. Zeppelin knew there was a problem (a big one) but couldn't afford to shut down its chief source of revenue, or risk losing lucrative potential defense contracts with the Third Reich over a 'petty' safety concern.

Analysis of the very famous Hindenburg plunging to the ground in flames movie revealed a few things to the aforementioned scientist.

(1) The spectacular fireball was in fact the doping catching fire and then setting fire to one of the elements in the aluminium (magnesium I think) that the Hindenburg was made of. Significant but less spectacular fireballs occur when the heat from the burning doping ignites the fuel tanks ( I can't remember if its petrol or diesel).


But in order to get to those temperatures wouldn't you need an
accelerant? Like plentiful and abundant hydrogen? If there is no
accelerant like gas/diesel/hydrogen how aggressive is the fire?


(2) hydrogen + O2 flames are typically all but invisible and would have been completely invisible on the film of the time, given how it was processed. Analysis of the film through modern filters did turn up a signature of H2+O2 flames in the UV Spectrum. But the flames are gone after the first second of the film clip, most of the hydrogen is either consumed or has already escaped.


My bad. I'll grant the fireball was the resins going up, nearly all at
once. Thanks to an accelerant. There would have been momentary enormous
heat from the hydrogen burn in infra-red. It depends how close you were
to the airship to how significant that exposure would have been.
Clothing would have protected you from that to some extent.

(3) the film actually shows a number of people jumping to their deaths while people (at the rear of the Zeppelin) wait until the tail hits the ground before trying to bail.


Granted that.


(4) No source of ignition external to the Hindenburg could be identified. This doesn't rule out all of the exotic weather related possible causes, it just points out that (then) 60 year old film technology can not be trust to capture every detail.


you? Why does everyone on USENET split hairs?


USENET, such as still exists (note I read and post through Google.Groups because I can't get a local ISP to accept NNTP traffic), exists to SPLIT HAIRS. It is the nature of the beast.


lol. true.

Good stuff that followed this snipped because I have no comment other
than to say: Thanks for the response. Your Internet connection is
certainly working well for text.

Dave

Ads
  #12  
Old July 2nd 20, 12:54 PM posted to sci.space.policy
David Spain
external usenet poster
 
Posts: 2,783
Default Easy Ride to Sub Orbital Altitudes

On 2020-07-02 3:51 AM, Niels Jørgen Kruse wrote:
wrote:

USENET, such as still exists (note I read and post through Google.Groups
because I can't get a local ISP to accept NNTP traffic), exists to SPLIT
HAIRS. It is the nature of the beast.


Try a free NNTP server like nntp.aioe.org' no user name / password, no
registration, just plug the server name into your USENET client.


I'll put a plug in for Eternal September as a news server. They are also
free (as in liberty and beer).

https://www.eternal-september.org/in...showpage=terms

Dave
  #13  
Old July 3rd 20, 12:43 PM posted to sci.space.policy
David Spain
external usenet poster
 
Posts: 2,783
Default Easy Ride to Sub Orbital Altitudes

On 2020-07-03 1:57 AM, JF Mezei wrote:
Generic question:


For the sake of discussion, lets sya that the culplrit was a Terminator
coming from the future and materialized inside one of these H2 bags,
creating lots of sparks.

Would sparks in a bag of pure H2 cause ignition since there is no O2 inside?

No. See this reference on Wikipedia:

https://en.wikipedia.org/wiki/Hydrogen_safety

"Ignition
Main article: Minimum Ignition Energy

"Hydrogen-air mixtures can ignite with very low energy input, 1/10
that required igniting a gasoline-air mixture. For reference, an
invisible spark or a static spark from a person can cause ignition."
"Although the autoignition temperature of hydrogen is higher than
those for most hydrocarbons, hydrogen's lower ignition energy makes the
ignition of hydrogen–air mixtures more likely. The minimum energy for
spark ignition at atmospheric pressure is about 0.02 millijoules."

Mixtures
"The flammability limits based on the volume percent of hydrogen in
air at 14.7 psia (1 atm, 101 kPa) are 4.0 and 75.0. The flammability
limits based on the volume percent of hydrogen in oxygen at 14.7 psia (1
atm, 101 kPa) are 4.0 and 94.0."
"The limits of detonability of hydrogen in air are 18.3 to 59
percent by volume"[6][7]
"Flames in and around a collection of pipes or structures can
create turbulence that causes a deflagration to evolve into a
detonation, even in the absence of gross confinement."

So in pure O2 if the concentration of H2 is below 4% or above 94% it
won't burn at 1atm (surface pressure). 100% H2 in the absence of O2 or
any other oxidizing gas will not ignite. Those ratios vary with
pressure. Concentrations between 18.3% and 59% in air are explosive. I
suspect it was fortunate for all involved that the Hindenburg burned
quickly as opposed to suffering a hydrogen leak in a hanger.

The hazards of H2 for this high altitude balloon ride are more on the
ground side, filling the balloon and the ground equipment used to store
H2 and pressurize the balloon in the first place.

Now, lets assume the Terminator materialized on a gangway outside the H2
bags, (so ship intact after he materialized). Then rips one of the H2
bags to let H2 flow into human compartment, and lights a match.

That would not happen for either of these scenarios since in both cases
of the Hindenburg and this high altitude balloon scheme the hydrogen is
ABOVE the gondola (human compartment) as since it is lighter than air
would drift away or flame away ABOVE or away from the compartment.

Forgetting densities for a moment, burning 1 cubic metre of H2 would
require 2.5 cubic metres of air containing 20% O2, leaving steam and
Nitrogen in its wake.

Since the inside volume of the ship was vastly H2 with limited volume
filled with breathable air, wouldh't that limit how much H2 can burn,
leaving the remaining H2 unburned?

If your scenario was plausable, once either oxidizer or fuel is totally
consumed combustion would stop yes. The Hindenburg was burning in the
open atmosphere with essentially an unlimited supply of oxidizer
compared to the hydrogen it contained.

There isn't footage of the initial signs of problem. Apparently there
was a rip that was fluttering in blue light before the big fire.

Of course, once the outside fabric caught fire, all bets were off as it
allowed air to come in.

What is interesting to me is that there was no big flash, and the front
of the ship remained bouyant for quite a bit longer. And more puzzling,
while the back had lost all its skin, the front was still intact, but
first flames started to come out from the nose and then the remaining
skin burned from both ends.


It is posisble that its angle, the H2 that was still keeping the font up
started to escape from the nose and as soon as it hit air, it ignited,
at which point, it ignited the fabric at the nose?

Seems plausible. Hydrogen is mixing with air until it becomes flammable.
The flame front appeared to run from back to front of the airship.


When H2 gas at 1atm converts to steam, does it result in huge expansion
of volume? When the Challenger blew up, the H2 was liquid and under
pressure, so conversion to steam would result in massive volume expansion.

I ask because Hindenburg didn't seem to explode. And visually, you see
the skin burn rapidly, and no hint it is filled with hydrogen.

Convert to steam? Or you mean gaseous H2? Steam happens only after
combustion has occurred. That rapid burning was aided and abetted by the
escaping and burning hydrogen. That's why I called it an accelerant.

BTW, on my bike trip to Delaware, (likely not this year since bornder
likely to remain closed), I bike in front of the Lakehurst/McGuire joint
air force base, and can see the massive hangar built to house the
Hindenburg.

Cool. I did not know it was still standing. It is used for blimps?



The memorial for where the Hindenburg fell:


(zoom out to see area, And you can see the 3d hangars for size when you pan.

To see the site relative to hangar:


In doing research for this, found out that parts of the tail did NOT
burn, and when NASA started to design the Shuttle, the decision to go
with H2 involved some scientist studying the Hindenburg and had access
to some of the fabric.


Was that the same NASA scientist mentioned by Frank Scrooby already in
this thread?

Dave

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Choosing moon orbit altitudes Matthew Ota[_1_] History 10 June 29th 07 04:13 PM
Choosing moon orbit altitudes Matthew Ota[_1_] Amateur Astronomy 9 June 29th 07 04:13 PM
IEEE SPECTRUM On-Line: Breathing Easy in Space Is Never Easy Jim Oberg Space Station 3 November 2nd 06 06:09 PM
How does the ISS maintain orbit across a range of altitudes? Rueffy Space Station 3 June 15th 06 03:10 PM
Drag at Orbital Altitudes Mike Miller Science 5 November 22nd 03 10:55 PM


All times are GMT +1. The time now is 06:41 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Copyright 2004-2020 SpaceBanter.com.
The comments are property of their posters.