
SpaceX's plan to fly you across the globe in 30 minutes [video] - mpweiher
https://www.youtube.com/watch?v=Dar8P3r7GYA
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arijun
I'm surprised they're talking bout having the landing pad 10km off shore--it
seems like that wouldn't be far enough for noise reduction, both outgoing
(rocket engines) and incoming (sonic booms).

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Retric
Doubling the distance only gives you a 6db drop. So, the best approach is
probably to have structures in the way to redirect sounds. Which should make a
dramatic difference.

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greedo
Unless the structure was miles high, wouldn't the sound just bypass it as it
climbed above?

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Retric
This mostly deals with ignition and static firing where the rocket is not
moving. Rockets have ridiculous acceleration, but create a lot of noise on the
ground. I assume being kind of noisy for 5-10 seconds a few times a day is not
that big a deal.

Assuming ~20 stories aka 200 feet is reasonable at 100 feet per second
acceleration aka just over 3 g's in 2 seconds the base of your rocket is just
over the 20 story building and your doing 130 MPH. Even still that building is
still going to be blocking a lot of sound as the fire is below that level.

7 seconds after launch your (5 after clearing the building) your doing 477 mph
and have traveled 1/2 a mile. At 12 seconds your doing 820 mph and have
traveled 2 kilometers up.

PS: Falcon Heavy is apparently ~160db vs 120db for thunder, which you can
barely hear at 10km. So, it's going to be noticeable at 10km, but not that
noticeable.

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api
There is definitely a market for this. When you hit really high levels of the
corporate or governmental world, time becomes enormously more valuable than
money. The market might bear a cost many times that of a private jet flight if
the time were this short.

This is an incredible idea for subsidizing the Mars rocket program via rapid
transit for executives, heads of state, etc.

Of course it would also have to be demonstrated to be at least as safe as air
travel first before it would hit the mainstream in that market.

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gldalmaso
I have yet to see any mention of how the passenger experience is going to be.
I assume it is much worse than some ear pain on take off and landing. Can the
average person handle this trip comfortably? Or do they have to pass some
astronaut-like conditioning test?

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mieseratte
> Or do they have to pass some astronaut-like conditioning test?

I wonder about military applications. One would imagine that special forces
groups would meet requirements. Being able to move SEALs around the world in a
matter of minutes would be a boon for force projection.

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DmenshunlAnlsis
Rocket launches take a certain amount of planning and favorable weather. Plus,
they are impossible to hide. All in all, not desirable.

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mieseratte
Ah, I forget that rockets are no where close to planes...

At best one could _maybe_ speed up pre-planned movements, as opposed to
allowing a QRF to more rapidly react.

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ben_w
This, combined with all the tech needed for a Mars colony, would make it
trivial to build a permanent settlement in Antarctica.

A domed, self-sufficient, city in Antarctica would also be a cheap way to test
most (not all) of the tech needed for Martian self-sufficiency, along with the
psychological impact of living in a desolate wasteland where rockets are the
only way in or out, and it would be a good insurance policy against many
possible global catastrophes.

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zeusk
Landing on ice, with a rocket firing down.

You sure?

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ben_w
Question (I don’t know if the answer is known to anyone, nor where to look
online): does Mars have significant CO2 permafrost that can be disturbed by
landing a rocket on it?

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zeusk
> This, combined with all the tech needed for a Mars colony, would make it
> trivial to build a permanent settlement in Antarctica.

> A domed, self-sufficient, city in Antarctica would also be a cheap way to
> test most (not all) of the tech needed for Martian self-sufficiency

GP is talking about testing the rockets in Antarctica.

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ben_w
I am GP. I’m talking about testing colony tech somewhere where failure isn’t
fatal. Rockets are only part of that, but it’s not really testing by the time
you have the rocket capacity to make a colony in Antarctica.

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godelski
> and the longest part of the trip is the boat trip

In other words, how to make human pancakes in 30 minutes.

But really, these are ballistic trajectories. Are we going to put everyone in
G suits? And you're going to really restrict who can/will go on. They will
likely go slower, so everyone doesn't have to go through endurance training.

Plus, being 5k-10k out from land, the total trip is definitely going to take
much longer than 30 mins (yeah shorter than the airline flight), to get people
on to the boat, onto the rocket, baggage loading, etc. It takes about 30
minutes between when they start loading people onto a plane and when they take
off (and baggage is already on!).

Let's be real, if they get it working, it will be 2-3hrs trip. Which is still
great, but not 30 minutes.

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schiffern
>But really, these are ballistic trajectories. Are we going to put everyone in
G suits?

I assume you mean because minimum-energy ballistic trajectories[1] come into
the atmosphere very steeply, so the G-forces are much higher.

But by using flatter trajectories (closer to an orbit than a parabolic "hop"),
you reduce the angle of entry considerably, at the expense of using more fuel.

The result is that for Earth-to-Earth rockets, essentially all trip distances
require the same amount of fuel.

>It takes about 30 minutes between when they start loading people onto a plane
and when they take off (and baggage is already on!).

I wonder if they can pack baggage into a lightweight "carriage" during the
boat ride, the simply load that single carriage onto the rocket. Or even a few
carriages.

It will incur a mass penalty ("box within a box"), which means fewer
passengers. But if it speeds up total trip time it could improve
competitiveness with long-distance plane trips.

Either that, or just force everyone to buy SpaceX-brand standardized luggage
that's ultra mass-efficient and supports automated handling/loading. :)

[1] [http://hopsblog-hop.blogspot.com/2014/06/travel-on-
airless-w...](http://hopsblog-hop.blogspot.com/2014/06/travel-on-airless-
worlds.html)

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greglindahl
You mean pack baggage in containers like the ones already used for cargo on
large passenger aircraft?

[https://en.wikipedia.org/wiki/Unit_load_device](https://en.wikipedia.org/wiki/Unit_load_device)

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schiffern
Yes, that's exactly why I thought of it! Thanks for the link.

If it makes sense for airlines, it stands to reason that it probably makes
sense for rocket-based passenger travel too. Though I expect the containers
will be even more heavily mass-optimized than those used on airplanes.

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stuaxo
Ah, the HOTOL from the 80s.

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JulianMorrison
Completely dissimilar except for being a cylinder with stubby wings. It's not
single stage to orbit, it's vertical launch, it only has rockets not an air
breathing engine, It's not a space-place, and it's interplanetary. Much
simpler and builds on established technologies.

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akavel
Can somebody tl;dr what is new in there? I tried jumping through the video,
but there seems to be a lot of fluff and background exposition for the assumed
"not in the loop audience" of TED. So I'm not sure where some new stuff
starts, if at all, for someone moderately aware that Falcon Heavy did succeed,
and BFR is planned?

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icc97
Nothing new, all from old footage.

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computerex
This has been addressed and debunked by:
[https://en.wikipedia.org/wiki/Phil_Mason](https://en.wikipedia.org/wiki/Phil_Mason)

My apologies for not including the link:

[https://www.youtube.com/watch?v=j4KR4-TN-
Yo](https://www.youtube.com/watch?v=j4KR4-TN-Yo)

He raises excellent points imo.

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Tade0
For a guy working as a "scientist" he's pretty ignorant when it comes to basic
chemistry.

His "debunking" of Goodenough's battery shows that he doesn't understand the
difference in the way energy is stored in carbohydrates vs batteries.

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computerex
He has a PhD in chemistry. I don't know about the Goodenough's battery
debunking, but imo his analysis on BFR Earth-Earth flights is spot on.

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Tade0
> He has a PhD in chemistry.

If that's so then I find his videos intentionally misleading and remain
skeptical.

Edit: added newline.

