"SpaceShipTwo could be single stage to SUBorbit"
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From: Pat Flannery on 18 May 2010 06:40 On 5/17/2010 8:26 PM, Sylvia Else wrote: >> From the above I conclude that the Shuttle must go about 6 times >> faster than the Hindenburg :-) > > Can we calculate the relative safety? Actually, you could; although people seem to get the Hindenburg confused with the Titanic, and think it was destroyed at the end of its first flight, it had made several successful trips before it caught fire. In 1936 it carried a total of 2,798 passengers (I'm not sure if that includes the 61 man crew) on a total of 17 transatlantic flights. The fatal flight was the first of the 1937 season, with 36 passengers and 61 crew, so total was 2,895 people carried, minimum. 35 died in the fire (13 passengers and 22 crew), so total fatality rate of all who flew on it was 2,895/35=82.714 or 1.2%. Vehicle loss rate per fight was 1 in 18, or 5.5% (this doesn't include propaganda flights inside Germany, such as overflying the Olympics). The Shuttle in comparison has flown on 132 flights including the present one, with a loss of two vehicles, so that's 1 in 66 or 1.5%; If I've got my numbers right, a total of 389 people have flown on the Shuttle so far, including the crew members that were shuttled to or back from Mir or the ISS on different flights. We lost a total of 14 crew aboard the Challenger and Columbia, so that's 389/14=27.789 or 3.86%. So there's two ways of looking at it; by total fatal crashes per flights flown, the Shuttle easily wins; but conversely, if you measure fatality rate versus total number of people flown, then the Shuttle is over three times as dangerous as the Hindenburg to fly on. Pat
From: Scott Stevenson on 18 May 2010 04:06 On Mon, 17 May 2010 21:40:11 -0400, Alain Fournier <alain245(a)sympatico.ca> wrote: >Dr J R Stockton wrote: > >> In sci.space.history message <4befef29$0$13586$c3e8da3(a)news.astraweb.com >> >>>, Sun, 16 May 2010 23:12:07, Sylvia Else <sylvia(a)not.at.this.address> >> >> posted: >> >> >>>How long would an SSME run on the hydrogen in Hindenburg? >> >> >> http://en.wikipedia.org/wiki/Hindenburg_class_airship ; "200,000 cubic >> metres of gas" >> >> http://en.wikipedia.org/wiki/Space_Shuttle_external_tank : "LH2 tank >> 1,497,440 l" >> >> and http://www.kayelaby.npl.co.uk/toc/ should enable it to be worked >> out. > >I think the Hindenburg used gaseous hydrogen and that the Shuttle >uses liquid hydrogen but I didn't see the density of hydrogen, liquid or >gaseous in there. A cubic metre being 1000 litre, the Hindengurg has >a volume about 133 times that of the Shuttle LH2 tank. > >The density of hydrogen at 101 kPa and 0 �C is 0.0899 g/l. >The density of liquid hydrogen is 70 g/l, about 780 times that >of gaseous hydrogen. So the Shuttle uses about 6 times more >hydrogen that the Hindenburg. > > From the above I conclude that the Shuttle must go about 6 times >faster than the Hindenburg :-) And remember, kids--it's based on actual math! take care, Scott
From: Pat Flannery on 18 May 2010 08:59 On 5/18/2010 2:40 AM, Pat Flannery wrote: > If I've got my numbers right, a total of 389 people have flown on the > Shuttle so far, including the crew members that were shuttled to or back > from Mir or the ISS on different flights. Okay, now let's fix the Shuttle total passenger math I botched here, and should have seen right off the bat. Total shuttle passengers carried (the other number was apparently total number of _different_ people carried): 828 So 828/14=59.14 or 1.7% fatality risk per passenger. So even with the revised math, it's 1.2% for Hindenburg and 1.7% for Shuttle, so you were a bit safer on the Hindenburg. Pat
From: Sylvia Else on 18 May 2010 08:57 On 18/05/2010 10:59 PM, Pat Flannery wrote: > On 5/18/2010 2:40 AM, Pat Flannery wrote: > >> If I've got my numbers right, a total of 389 people have flown on the >> Shuttle so far, including the crew members that were shuttled to or back >> from Mir or the ISS on different flights. > > Okay, now let's fix the Shuttle total passenger math I botched here, and > should have seen right off the bat. > Total shuttle passengers carried (the other number was apparently total > number of _different_ people carried): 828 > So 828/14=59.14 or 1.7% fatality risk per passenger. > So even with the revised math, it's 1.2% for Hindenburg and 1.7% for > Shuttle, so you were a bit safer on the Hindenburg. > > Pat Probably ought to be comparing rates for hydrogen airships in general, rather than just Hindenberg. Alternatively, only consider those shuttles that were lost. Sylvia.
From: Rick Jones on 18 May 2010 12:45
In sci.space.history Pat Flannery <flanner(a)daktel.com> wrote: > As part of that project, I started looking up installed horsepower > on airships of various sizes required to move them at various > speeds, and made a most interesting finding...as the size of the > airship increases, it takes proportionally less horsepower to move > it at the same speed. I presume you mean its length and not its cross-section right? In broad terms, it sounds a bit like a boat and hull speed. rick jones -- the road to hell is paved with business decisions... these opinions are mine, all mine; HP might not want them anyway... :) feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH... |