Poll

2 votes (66.66%)
No votes (0%)
No votes (0%)
No votes (0%)
1 vote (33.33%)

3 members have voted

Ayecarumba
Ayecarumba
Joined: Nov 17, 2009
  • Threads: 236
  • Posts: 6763
February 7th, 2020 at 12:46:57 PM permalink
Virgin Galactic plans to put paying tourists into space sometime this year. Using the X-15 program as a base, analysts think the probability of one Virgin Galactic crash among the 131 planned commercial flights in the next two years is about 48%:
Quote: MIchael Bruno article in Aviation Week quoting Vertical Research Partners analyst Darryl Genovesi


“If we assume that the probability of a fatal crash is [about] 0.5% per commercial flight, which is what X-15 actually realized during the late 1950s and early 1960s flying the same mission (one fatal crash over 199 flights), then the probability of Virgin Galactic crashing once over its next 131 commercial flights over the next two years, is [about] 48%,” the Vertical team says.

By the end of 2020, the company will have completed 16 of the 131 flights. Keeping with a 0.5% per flight likelihood, the probability of Virgin Galactic crashing during 2021 would then drop to around 44%. “We don’t estimate a probability of it crashing in a subsequent flight (beyond 131), but we do assume a crash out there doesn’t result in a program pause or meaningful loss of revenue subsequently,” they say.



So it's a little better than a coin flip you will experience a crash if you take all 131 flights What's the probability of a crash on any single trip?
Simplicity is the ultimate sophistication - Leonardo da Vinci
ChesterDog
ChesterDog
Joined: Jul 26, 2010
  • Threads: 6
  • Posts: 860
Thanks for this post from:
Ayecarumba
February 7th, 2020 at 1:44:08 PM permalink
Quote: Ayecarumba

...What's the probability of a crash on any single trip?




0.48 = 1-(1-p)^131
p = 1 - e^[ln(0.52) / 131] = 0.00498 = 0.5%
They did their math right because they got the 48% figure by assuming 0.5% of a single-trip crash.
SOOPOO
SOOPOO
Joined: Aug 8, 2010
  • Threads: 108
  • Posts: 6847
Thanks for this post from:
Ayecarumbabeachbumbabs
February 7th, 2020 at 2:21:35 PM permalink
Quote: Ayecarumba

Virgin Galactic plans to put paying tourists into space sometime this year. Using the X-15 program as a base, analysts think the probability of one Virgin Galactic crash among the 131 planned commercial flights in the next two years is about 48%:

Quote: MIchael Bruno article in Aviation Week quoting Vertical Research Partners analyst Darryl Genovesi


“If we assume that the probability of a fatal crash is [about] 0.5% per commercial flight, which is what X-15 actually realized during the late 1950s and early 1960s flying the same mission (one fatal crash over 199 flights), then the probability of Virgin Galactic crashing once over its next 131 commercial flights over the next two years, is [about] 48%,” the Vertical team says.

By the end of 2020, the company will have completed 16 of the 131 flights. Keeping with a 0.5% per flight likelihood, the probability of Virgin Galactic crashing during 2021 would then drop to around 44%. “We don’t estimate a probability of it crashing in a subsequent flight (beyond 131), but we do assume a crash out there doesn’t result in a program pause or meaningful loss of revenue subsequently,” they say.



So it's a little better than a coin flip you will experience a crash if you take all 131 flights What's the probability of a crash on any single trip?



I would think the crash rate in 2021 will be less than it was a half century ago. I’d bet ‘no’ on a crash if I have to lay 200-1 on any given journey.
Ayecarumba
Ayecarumba
Joined: Nov 17, 2009
  • Threads: 236
  • Posts: 6763
February 7th, 2020 at 2:53:14 PM permalink
If I take 130 rides without an incident, does that mean I should hedge with extra life insurance before #131 because a crash is "due"? I suppose in this instance, since they are using the same three craft over and over, the previous results do have an influence on future trials, but how much? One would think it would be safer as the number of trips goes up and bugs get worked out, but it may be the opposite due to operator complacency/error, structural fatigue... but also a mishap coming "due"?.

Unforeseen problems are expected to happen, but under these circumstances, the consequence of a small thing going wrong will be several fatalities. Do you think more safe rides = the bad one coming due?
Simplicity is the ultimate sophistication - Leonardo da Vinci
Joeman
Joeman
Joined: Feb 21, 2014
  • Threads: 34
  • Posts: 1772
Thanks for this post from:
Ayecarumba
February 7th, 2020 at 3:53:42 PM permalink
Quote: Ayecarumba

Do you think more safe rides = the bad one coming due?

Isn't that the very definition of Space Traveler's Fallacy? ;-)
"Dealer has 'rock'... Pay 'paper!'"
Ace2
Ace2
Joined: Oct 2, 2017
  • Threads: 20
  • Posts: 602
Thanks for this post from:
Ayecarumba
February 7th, 2020 at 4:55:29 PM permalink
Quote: Ayecarumba

If I take 130 rides without an incident, does that mean I should hedge with extra life insurance before #131 because a crash is "due"?

No, that’s a textbook case of Flyer’s Fallacy
It’s all about making that GTA
Gialmere
Gialmere
Joined: Nov 26, 2018
  • Threads: 37
  • Posts: 1496
Thanks for this post from:
Ayecarumba
February 7th, 2020 at 5:09:47 PM permalink
Wow. Over 600 tourists in the queue at $250,000 a ticket. That's actually a pretty reasonable price when you consider what some rich people are willing to pay for an automobile. I thought the trip would be little more than looking out a window at an (obviously) spectacular view. It turns out that, although the 2 1/2 hour flight is suborbital, travelers will spend 5 minutes at the top of the parabolic arc in weightlessness and will be allowed to leave their seats to float around the cabin. Photo Op!



Okay so Star Trek it ain't, but give Virgin credit; they're delivering a genuine outer space experience for the money. Yes, I suppose that part of that $250k is the ability for riders to boast that they've been to space, and that's fine. For ventures like this you need rich people to get the money flowing and then a "Model T" version can be provided with the profits. (Flying in jet airplanes was once only for the rich "jet set" crowd.) Eventually flights will get longer and prices will get lower and then Star Trek it will be.

As to the thread topic I see that a year ago some analysts were recommending investment in Virgin Galactic since space tourism was safer than many thought.

Quote: CNBC 11/5/19

Genovesi noted the safety risk as a particular weight on Virgin Galactic’s stock price, saying “the market appears to imply a high probability of failure, higher than we believe is appropriate.” His firm believes investors are using “a Space Shuttle like crash rate” to estimate Virgin Galactic’s potential failure rate. The Space Shuttle had two fatal accidents in 135 flights, or a crash rate of 1.5%. But that isn’t an accurate comparison, Genovesi says.

“Shuttle’s mission profile was much more demanding than SPCE’s space tourism mission profile is,” Genovesi said.

Vertical Research partners sees Virgin Galactic’s spacecraft as more comparable to the X-15 rocket-powered aircraft flown by NASA and the U.S. Air Force in the 1960s. The X-15 crashed once in 199 flights, a crash rate of 0.5%.

“And that was 50 YEARS AGO, meaning SPCE can likely to better,” Genovesi said.

Have you tried 22 tonight? I said 22.
beachbumbabs
Administrator
beachbumbabs
Joined: May 21, 2013
  • Threads: 99
  • Posts: 14227
Thanks for this post from:
Ayecarumba
February 8th, 2020 at 11:28:13 AM permalink
I think the .5% assumption is way overblown. Jmho. The math is fine, but proceeding from an initial assumption that predates most of manned flight, decades of improvement in fuels, craft construction, environmental factor evaluation, and crew safety procedures, makes it meaningless. If VG expects to lose one in 200, they're not going to fly until they can improve those odds tenfold.

We didn't accept killing airliners at a much much lower rate in the 70s thru 90s. We spent many billions of dollars and millions of man-hours improving all of the disparate reasons flights failed. And have come to an unprecedented low death rate for any type of transportation since the late 90s, even including 9-11.

Quote: wiki: aviation safely



...Since 1997, the number of fatal air accidents has been no more than 1 for every 2,000,000,000 person-miles flown (e.g., 100 people flying a plane for 1,000 miles (1,600 km) counts as 100,000 person-miles, making it comparable with methods of transportation with different numbers of passengers...

If the House lost every hand, they wouldn't deal the game.
TumblingBones
TumblingBones
Joined: Dec 25, 2016
  • Threads: 24
  • Posts: 383
February 8th, 2020 at 1:31:10 PM permalink
Quote: beachbumbabs

I think the .5% assumption is way overblown. Jmho. The math is fine, but proceeding from an initial assumption that predates most of manned flight, decades of improvement in fuels, craft construction, environmental factor evaluation, and crew safety procedures, makes it meaningless. If VG expects to lose one in 200, they're not going to fly until they can improve those odds tenfold.


I agree basing failure rates on the X-15 is mistake but for a different reason. The X-15 flights were all intended to push the flight profile to the edge (or what they thought was the edge). That's definitely not the case with VG and commercial flights.
My goal of being well informed conflicts with my goal of remaining sane.

  • Jump to: