ApolloHoax.net

Off Topic => General Discussion => Topic started by: 12oh2alarm on December 23, 2020, 09:41:57 AM

Title: Reality Check: Elon's BFR for City Hopping. Snake Oil or a Vision of Transport?
Post by: 12oh2alarm on December 23, 2020, 09:41:57 AM
One thing is sure: Elon Musk dreams big. He has made billions with
PayPal and pioneered electric cars for the mass market with the Tesla
brand. His SpaceX rocket has made history several times, last but not
least with the first commercial manned mission to the ISS in 2020.
His supporters stand in awe whenever he announces another big dream he
intends to pursue. Making space flight affordable for people like you and
me, by pushing for 100% reusability is the aim of the BFR, the
Big Falcon Rocket, except the F is not for Falcon, says Musk with his
signature big smile.

The BFR is the vehicle for another big dream: going to Mars, building
colonies on the Red Planet. Concept art and high quality CGI can be
found with little effort. In one clip Elon contemplates another idea: If
I have a BFR that can go to Mars, why use it only for long haul? Why not
use it for city to city hopping? Think of it, at speeds up to
27,000km/h, you can get from anywhere to anywhere often in under 30
minutes. How would that work? Let's go to the source and find out. This
is the SpaceX promotional video:



The scene is set in Manhattan, New York City. 57 people are boarding a
ship destined to a swimming space port a few km south where the mighty
BFR stands erect, flanked by propellant tanks, next to a tower.
Passengers enter the rocket via a 30m long retractable arm. Then the
monster roars towards the sky. The spent first stage retrofires to be
reused. The shiny metal tube reenters over Shanghai and descends onto
another swimming space port with the skyline maybe a few km in the
background. Flight time: 39 minutes.

Wow! How impressive!

Or is it?

Sometimes ideas collide with reality and reality wins. Just because a
dream is big, doesn't make it feasible. Just because an idea is put
forward by Elon Musk doesn't make it come true in 2022. Just because someone is a
billionaire doesn't allow them to violate the laws of Physics. Or
engineering. Or economics (only for while). If the idea is put under scrutiny by
independent and down-to-earth, slide rule carrying boring physicists,
engineers, accountants and safety regulators, who ignore for a moment
whose idea they are looking at, will the idea survive a reality check?
Will it crumble? Is the verdict "Take my money!" or "Nope, not gonna
happen."? City hopping with the BFR, thumbs up or down, that is the
question I want to shed some light on. Why? Because talking rockets is
fun! And maybe to help people make sound investment decisions. We all
know the saying about fools and their money.

What are the arguments in the way of the proposed mode of transport? How
hard would obstacles be to overcome? Which problems could be solved by
throwing money at them? Which can't? Which problems just need more time?
Which are hopeless and why? Which problems in rocketry are intrinsically
hard to solve? Is it allowed to call a spade a spade or is criticizing
the visionary a case of Lèse-majesté that should be punished with a
tweet storm? The deck of persuasion is stacked heavily in favor of those
who can spend big bucks for a marketing department capable of ordering
snazzy CGI clips. So I find it fair game if critics don't beat around
the bush and use strong words to describe an idea. Here's one of them.



To paraphrase and occasionally expand a bit on what is to see:


The aforementioned issues could likely be ignored or accepted. People
might be ok with some discomfort for the trip of a lifetime. I certainly
would. Regulators might require space ports to be 50km away from cities
of more than N inhabitants. We accept getting to an airport may take 2 hours, plus
a 2 hour margin for international travel. At both ends (baggage claim?
customs?). When it comes to space ports, well, there's a fueled rocket
waiting for me, I'm fine if the actual travel time door to door is 20
times that of the snake oil droplets in a friggin promo CGI. We've heard
a lot of sales pitches before, haven't we? Who would trust them anyway?

But other issues are not so easy to accept, overcome, or ignore. They
are more fundamental. Earth's gravity well is devilishly deep and hard
to climb. No amount of money and engineering will change that fact.
Not even dreams of a 150 bn wunderkind.



Which is why BFR city hopping is an exercise in snake oil salesmanship
that would make Trump blush. A publicity stunt to throw a bone to the
cultists. NYC to Shanghai, thank you, I take the cheaper airplane flight
that gets me there alive. If it takes twice as long so what, I'm jet lagged
either way.

(*) Obviously a major malfunction https://www.americaspace.com/2016/01/30/obviously-a-major-malfunction-30-years-since-the-loss-of-challenger-part-1/
(**) The leaning tower of Bocachica https://www.teslarati.com/spacex-starship-prototype-sn9-damaged/
Title: Re: Reality Check: Elon's BFR for City Hopping. Snake Oil or a Vision of Transport?
Post by: Zakalwe on December 23, 2020, 10:17:15 AM
Quote
  A fueled BFR is comparable to a 10kT bomb, that's half a Little Boy,
  which is why it is usually done last after astronauts are
  strapped in with BFLB (Big Frigging Leather Belts), and takes hours.

No, it doesn't.

Quote
  An honest calculation of travel time should take this into account. Droplets of snake oil?
 
Clearly you've never flown on a commercial airline flight. I've never, ever seen an airline flight-time include check-in and security.

Quote
  Launch sites are far away from cities for a reason: safety and noise (see
  bomb above).
Best tell that to the people who live in, say Courtney. 10 miles from Cape Canaveral.


Quote
 
  People living near airports hate the noise. Would the mayor of New York City
  want a space port near the Statue of Liberty with noise levels exceeding
  Saturn V launches? Possibly several times a day? Sonic booms for incoming
  BFRs? I doubt any mayor (or voters) would welcome a busy space port.
 

Which is why the space ports are shown as being sea-based. Noise, however, is a big problem, so yes, location is important.


Quote
  Launch scrubs are not uncommon, either. Anybody got delay statistics for
  Mercury, Gemini, Apollo, Space Shuttle, SpaceX? Can we expect the BFR
  to be different?
For sure.

it's a good job that planes and trains never get delayed or hell no-one would ever use them, now would they?
Title: Re: Reality Check: Elon's BFR for City Hopping. Snake Oil or a Vision of Transport?
Post by: mako88sb on December 23, 2020, 03:03:15 PM
Well, with regards to launches from Cape Canaveral, aren’t they all equipped with the means to be self destructed in case they go off course enough to threaten a town/city? Is the same safety measures going to be required for the BFR’s?