Hacker News new | comments | show | ask | jobs | submit login
SpaceX's plan to fly you across the globe in 30 minutes [video] (youtube.com)
40 points by mpweiher 7 months ago | hide | past | web | favorite | 69 comments

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).

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.

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

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.

Guess we have to build a dome around the city.

I was thinking this was the use case for Hyperloop and the boring company... take an underground shuttle to the launch pad in 30 minutes or less...

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.

As I recall, that was the justification for Concorde. The market said otherwise, and that was before video conferencing had become too cheap to meter.

Concorde was run at a significant profit for years. R&D costs where not recuperated, but that that's just a question of scale.

Concorde is about 4x faster than an airliner with a fairly limited range. BFR is 10x faster with global range. The point being that you can do 10x the trips and make 10x the money compared to airlines. Plus there's no taxiing around an airport. It's purely refuel and go.

Even if my numbers are out Concorde was borderline viable and BFR should be more capable of bringing in money.

Plus you go into frigging space. Branson wants to sell just that, this gets you into space and down to China.

Another advantage I can think of over Concorde is that there should be more space and the trip is only ever 30-40 mins, so no cramping up in the seat.

Finally a Concorde ticket was about $12,000, BFR was mentioned to be $1-2k at the end of the video.

That ticket price is definitely relevant. For some reason I thought Concorde was “only” $2500.

However, your point about cramped space made me realise that although the BFR isn’t going to be volume limited, that’s because it’s mass limited. Every 10kg of luggage will add about $250 to the price.

It was in fact the justification for the first commercial airplane travel in general. Initially only well off people traveled by commercial passenger plane. It was extremely dangerous and very uncomfortable.

Fortunately we didn't stop our pursuit of progress due to such challenges. Now 3.5 billion or so passengers take extraordinarily safe, comfortable flights every year.

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?

There was some analysis on the SpaceX subreddit saying the G loads would peak out at 4 Gs. So a bit worse than those carnival rides where you stick to the pads on the periphery of a spinning room, which IIRC are only 3 Gs. With a well padded reclining seat it should only be mildly unpleasant for healthy adults but I worry that there are potential customers who won't be able to deal with it.

> 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.

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

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.

Some of the things Burt Rutan has said over the years imply that this niche is already filled.

Assuming 1) a trip is about 10,000 miles in distance, 2) acceleration is constant and speeding up for 15 minutes and slowing down for 15 minutes, they are looking at (very roughly) 0.4g of additional acceleration i.e. you would feel 1.4 times as heavy as you do standing still on takeoff and landing. As you angled horizontally, the effect of earth's gravity would be counteracted by your centripetal acceleration so that you would feel approximately 0.4g at the midpoint of the flight. So 1.4g at takeoff and landing, 0.4g at the midpoint (again assuming constant acceleration due to thrust)

That sounds not too bad. Two 15 minute burns sounds in the realm of possibility.

Edit: changed some numbers and my conclusion.

Forget about comfort. Rocket engines are dangerous and unreliable compared to planes and any other mode of transportation. People aren't going to tolerate the risk.

>Rocket engines are dangerous and unreliable compared to planes

To be fair, that's the problem they are trying to fix. This is like telling Microsoft that personal-computers will never work because they are big, expensive, difficult to use, and crash all the time.

> This is like telling Microsoft that personal-computers will never work because they are big, expensive, difficult to use, and crash all the time.

That's not a fair comparison. The energy difference between a rocket engine and an airplane combustion engine is huge. Rockets are all about raw energy output and are essentially a bomb. The fuel is volatile, and rockets use a lot more fuel than planes. If a failure happens with rockets, the whole thing usually ends up blowing up catastrophically.

Rockets are inherently more dangerous. But hey, more power to them. I would love it if we can make rocket flight safe enough for everyday use by everyone.

To be fair, only half of those statements have changed. Computers still crash all the time, just less frequently than they used to.

>Computers still crash all the time

My personal XP is 20 years my computer crashed 1-5 times a day, now days my computer crashes maybe once every 4-6 months. That is considerable.

But there's a magnitude difference there from "the early days".

Plane crashes still happen too, but with significantly less frequency.

In general if your PC crashes you don’t explode though.

But now we have computers running our planes, running our cars, running our pacemakers.

Your PC might not kill you, but the software running the drive-by-wire system in your car will.

Still, my point wasn't to get into a discussion about the differences between software and rockets, but more to point out that their goal is to change those things about rockets. To make them reliable, safe and cheap.

You can think they won't be able to pull it off, but saying that it will never work because it doesn't currently work that way seems a bit silly.

While I agree with you that there's a desire for this I'm not yet convinced there's a market for it.

As you say, this needs to be proven to be at least as safe as air travel.

Beyond that, for certain wealthy individuals, government dignitaries and the like commercial flight represents an unacceptable risk and cost in time eg Apple's board requires Tim Cook to fly private now.

Next, if the launch and landing pads are indeed offshore and otherwise remotely, this adds travel time at either end.

Also, rockets are subject to weather much more than planes are. If your landing pad is offshore then those weather effects are more pronounced as you have to deal with sea conditions too.

Lastly, current SpaceX landing is a "dead stop" approach (vertical velocity is designed to hit 0 when altitude is 0), which seems like it may not have the safety margins for mass transit. Future designs may of course improve on this.

So much as we'd like this, I'm not yet sure how we get there. Planes have to log many thousands of hours to be certified for passenger flight. Will we have enough launches to certify rockets this way? Even reusable rockets are, in comparison to planes, expendable because they're combusting huge amounts of fuel. Like I don't see you reusing the same rocket every day for 30 years like you can with a plane.

I don't understand your point about dead stop approach. What would be the alternative?

It's an issue of safety margins. Just consider the airplane.

- A two-engine plane can operate on just one engine

- In the event of losing power or losing both engines, a plane has a certain glide capability

- Runways are built allowing a certain amount of overshooting

- A bad approach allows you to circle back around and try again

- Planes can land and takeoff with significant winds and precipitation (including cross winds)

- A plane can actually land in a body of water (as happened on the Hudson).

Now compare the safety margins for a dead stop rocket reentering from space at Mach 30.

To address your first point - the rocket has 3 sea-level engines on the spaceship stage, each of which has enough thrust to land the ship on its own if the other two fail. (This is partly a byproduct of it being much lighter during landing than takeoff as most fuel has already been burned.)

I think the issue with the current hoverslam solution is that the timing of the rocket relight is critical to the rocket hoverslamming (and not just regular slamming). I don't have the answer to this but imagine that if an engine fails to relight at the correct time there's a much smaller (or maybe non-existent?) margin of error.

A plane on the other hand has two engines and can also generally just glide to the ground in the event that neither of them are working.

>time becomes enormously more valuable than money

In some sense this is true, but keep in mind you're not actually creating more time -- time spent on business jets can be quite productive, in-person encounters are not always necessary, and it is often possible to use scheduling to get two powerful people in a room together when they happen to be near each other anyway.

Also not sure if the video goes into this, but rocket launches are LOUD, and so tend to be away from densely populated areas -- plan on another 20-30 minutes on each side to get to/from the pad.

(Maybe tunnels will help with this? Load yourself into a tunnel pod, which then gets robotically loaded on the rocket, so door-to-door transport? Man, the future's gonna be sweet!)

20-30 minutes for checked luggage. 20-30 minutes for security groping. 20-30 minutes waiting for that idiot to find his seat. 20-30 minutes waiting for luggage or the carousel.

Flying a VIP (semi-private) airline avoids all of this, and surely anyone that would take a rocket is already flying a fully private airline.

Using this as an example because I make this trip often: I can fly Cincinnati, OH to Charlotte, NC on a VIP airline for $500 round trip. I drive my car right up to the plane, and there is a rental car waiting for me at the plane exit on the other side. The entire plane is first class only. There is no baggage check, no TSA, no nothing. I can walk on to the plane 5 minutes before takeoff.

Putting on a pressure suit, guaranteeing your body can handle 5-6 Gs sustained for a few minutes, having a death rate of 1.5 percent.

I am still awaiting a day when you can be projected anywhere and acceptance of it as a means of face to face. The old hologram style of science fiction interaction.

You're thinking like a technical person. The management caste needs face to face time, in person, where you can get social cues. Drinks, meals, walks together, golf games. Not Facetime or Skype.

Don't forget the girly bars. Never forget the girly bars.

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.

We already have domed cities in Antarctica that test the psychological impact of living in desolate wastelands. It is in fact so desolate there that we can't physically access those places for months at a time and rockets wont change that one bit. You literally can not move a person to or from the South Pole research station for months of the year. Rockets aren't the tech needed.

We have domed villages, not cities. Musk is aiming for a million, dynamics might be different. Or not, I’m not a psychologist.

We already are doing that there is no need to do it in Antarctica since there is an atmosphere there and the soil isn't toxic.

Deserts, volcanic landscape like those of Hawaii and even a large enough basement would be just as good of a simulation without needing to worry about the environmental impact in Antarctica.

And plus we already have a "city" there.

I often think about this Bruce Sterling quote on The WELL from 2004:

``I'll believe in people settling Mars at about the same time I see people settling the Gobi Desert. The Gobi Desert is about a thousand times as hospitable as Mars and five hundred times cheaper and easier to reach. Nobody ever writes "Gobi Desert Opera" because, well, it's just kind of plonkingly obvious that there's no good reason to go there and live. It's ugly, it's inhospitable and there's no way to make it pay. Mars is just the same, really. We just romanticize it because it's so hard to reach.``

Yep and while Mars can provide a possible plan b any disaster other than the planet disintegrating would likely leave a more hospitable environment than mars, and if we have the geo engineering needed to terraform Mars we can terraform the earth just as easily.

That said however settling the Gobi isn’t cool and as such it won’t drive innovation that could and would improve life on earth.

What is missing from life on Earth that is more improved by turning Mars green than by turning Earth’s deserts green?

Sure, Mars is cool and I intend to by a ticket, but making Earth deserts productive sounds like a great improvement down here.

Well turning the desert green may have an impact on the global ecosystem of the planet at least as far as local species go.

If that isn’t a problem for you then sure go a head.

Mars would require us to solves many more problems which can be then used to solve problems here on earth sometimes a bigger challenge is required to push for a breakthrough.

But if we go about geoegineering then I rather terraform mars which by all accounts is a dead planet than terraform the less livable places on earth as they are a host to their unique life forms.

Landing on ice, with a rocket firing down.

You sure?

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?

> 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.

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.

They don't land on ground, it's a landing pad .

How big of a pad will you have to build in Antarctica to deflect heat from any ice that might be structurally supporting the base?

Would that matter? When it melts, it turns to water. There are already landing pads that float on water.

This doesn’t mean it doesn’t matter, but my engineering skills are purely software — I really am asking if it would matter because I don’t know.

> 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.

>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...

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


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.

Ah, the HOTOL from the 80s.

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.

Except this isn't HOrizontal TakeOff and Landing, as I understand it?

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?

Nothing new, all from old footage.

This has been addressed and debunked by: https://en.wikipedia.org/wiki/Phil_Mason

My apologies for not including the link:


He raises excellent points imo.

His comparison of the Shuttle to SpaceX reusability is pretty bad considering how non-reusable the Shuttle actually was and how almost none of the reasons behind the Shuttle's problems apply to Falcon 9 or BFR.

I think noise/safety are the real show stoppers. You can get the noise down by moving it further away from civilization, but I think the distance required would simply be too far. I also don't think a rocket will ever approximate the safety of a plane with current tech. If it was 10x more dangerous than a heavy aircraft (which is highly optimistic) would anyone go?

I think SpaceX can make it work, can make it affordable to some degree, but making it a practical form of travel is ... yeah, no.

I have no problem with them trying though. Their money.

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.

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.

> He has a PhD in chemistry.

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

Edit: added newline.

What? Where?

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact