Shotwell supposedly said first BFR flight will be an "earth hop"

[e-FTW]

I guess my backup plan to flee to Canada isn't a very good one then

I was specifically talking about FAA and flight certifications.
Worry not my friend, your plan is still good, especially if you like maple syrup and poutine.

 

[ecarfan]

Not leaves for mars, leaves FROM mars. As in you already landed there, spent some amount of time, refueled and are taking off again.

You are committed because Mars doesn't have a variety of fall back options if you abort a take off. You can't just walk to the next nearest NASA or SpaceX launch facility since there isn't one there.

You are correct, I misread the post I was replying to.

So no escape system for Mars launches. It's a risk. It won't stop people from making the Mars to Earth trip, however.

 

[jkn]

Escape systems are for the launch pad and early flight. Both the Dragon module and the BFS ship will be able to do emergency escape maneuvers using their thrusters (main engines).

The entire Crew module is the escape system for Dragon and the Entire 2nd stage aka Ship is the escape system for BFR.

Just know that if the BFS or Dragon has to abort it won't make it to orbit or any other city, it will abort very short range compared to the original destination. It will however be able to do so at a speed fast enough to escape an exploding first stage and get you away alive.

Now if you are leaving Mars with BFS there is no escape system for a mars launch. The escape system functionality only applies to Earth.

BFS has only two sea level engines. Those are not enough for escape. Vacuum engines cannot be started at low altitude. I don't know what would happen exactly. (Pressure of exhaust at end of the nozzle is much below 1 bar.)

Only possibility is to have 40 Dragon like capsules for passengers. Those could be made to work on Mars.

 

[AnxietyRanger]

I'm a little concerned about how they're going to deal with all of the puking customers. That will happen a lot.

I'm pretty sure this concern was expressed when first trains and later cars came into service... and indeed, it was a valid concern, some people do get travel sick. But for most it is just about getting used to it (both individually as well as culturally), rest can probably be solved with vomit bags of some sort...

Not saying things don't get increasingly tricky comparing a slow-by-modern-standards early steam train and a ballistic passenger rocket, but people, cultures and technologies do tend to adapt...

 

[mongo]

BFS has only two sea level engines. Those are not enough for escape. Vacuum engines cannot be started at low altitude. I don't know what would happen exactly. (Pressure of exhaust at end of the nozzle is much below 1 bar.)

Only possibility is to have 40 Dragon like capsules for passengers. Those could be made to work on Mars.

Depends on fuel in second stage at launch.
BFR (rocket) - Wikipedia

Lists max thrust as less than max mass for the 2nd stage. However, since it gets refueled, you could launch under weight with just enough fuel at transfer orbit for an abort re-entry and landing. Or with a mass that allows abort based on the altitude/ velocity curve. (Potential for fuel dump also)

Rocket engine nozzle - Wikipedia

Nothing I've seen precludes engine start at low level. The Space Shuttle's 3 main engines were all set up with vacuum based nozzles. While ideal size produces gas at ambient, rockets can't justify the mass. As long as the gas is not less than 40% of ambient, there is only a loss of efficiency.

Raptor (rocket engine family) - Wikipedia
Original design:
Sea level expansion ratio:150
Vacuum expansion ratio:200
Ratio of 1.33 to 1
However, nozzles diameters of 4'3" (<1.3m) and 7'10"(2.4m) from latest presentation yield an area ratio of 4:1.

Actual end pressure is dependent on fuel flow/ chamber pressure (300 bar projected for Raptor), but the vacuum engines look like they could be usable at sea level. If McGregor can test the vacuum engine, that means it is >40% ambient (or at least usable at sea level), since that threshold is based on flow separation which can cause damage.

Edit: rephrased last sentence, twice

 

[Nikxice]

As Grendal pointed out, parachutes are probably not an option. I'm optimistic that the BFR/BFS design will eventually get high marks for safety and reliability. There's no other choice, a failure with revenue passengers is not an option. The Air France Concorde crash certainly hastened the demise of that fleet of aircraft. Looking ahead, SpaceX will likely surprise us with redundant systems that for now, leave us only to guess. It seems paramount for the BFS to have at least a one or two engine out capability, presumably a requirement for certifying Earth to Earth returns. One lousy scenario would a BFR experiencing a full RUD event prior to MECO. There's typically some fuel penalty for a RTLS, so a BFS boost back burn might not be in the cards. Such a situation would probably benefit from additional ground/sea hardware. If we assume that the scheduled launch cities have regular pax routes, it might be practical to place semi-permanent drone ships (Supersized) strategically under each flight path.

Fortunately we probably won't have to wait too long to find out some answers. If BFR was a government project it would probably take a decade just to review contractor bids or even more likely, just get totally axed.

 

[Grendal]

Here's a fun one. These folks were inspired to create a poster for E2E:
Art Prints by Solarexploration | Society6

 

[sandpiper]

I'm pretty sure this concern was expressed when first trains and later cars came into service... and indeed, it was a valid concern, some people do get travel sick. But for most it is just about getting used to it (both individually as well as culturally), rest can probably be solved with vomit bags of some sort...

Not saying things don't get increasingly tricky comparing a slow-by-modern-standards early steam train and a ballistic passenger rocket, but people, cultures and technologies do tend to adapt...

Physiology doesn’t adapt. I suspect that will be a big messy issue.

 

[AnxietyRanger]

Physiology doesn’t adapt. I suspect that will be a big messy issue.

Perhaps. I guess my point was that expectations may be worse than reality - and, also, of course technology can and will improve.

I have no expertise on this topic. Just wanted to put this idea out there.

 

[sandpiper]

Perhaps. I guess my point was that expectations may be worse than reality - and, also, of course technology can and will improve.

I have no expertise on this topic. Just wanted to put this idea out there.

I have a LOT of experience with motion sickness. Much more than I wish I did. . The are 3 types of people... the living , the dead, and seasick - who just wish they were dead.

 

[dhanson865]

BFS has only two sea level engines. Those are not enough for escape. Vacuum engines cannot be started at low altitude. I don't know what would happen exactly. (Pressure of exhaust at end of the nozzle is much below 1 bar.)

Only possibility is to have 40 Dragon like capsules for passengers. Those could be made to work on Mars.

In an escape scenario you fire all 6 engines (2 sea level and 4 vacuum) the vacuum engines will have worse isp at sea level so they won't add as much thrust but they'll light and the more the better.

xkcd: Six Words

 

[Nikxice]

xkcd: Six Words

Funny. Working at NASA those six words might get you canned, while at SpaceX maybe lead to a promotion. Such is their culture of thinking and doing things differently.

 

[RDoc]

Escape systems are for the launch pad and early flight. Both the Dragon module and the BFS ship will be able to do emergency escape maneuvers using their thrusters (main engines).

The entire Crew module is the escape system for Dragon and the Entire 2nd stage aka Ship is the escape system for BFR.

Just know that if the BFS or Dragon has to abort it won't make it to orbit or any other city, it will abort very short range compared to the original destination. It will however be able to do so at a speed fast enough to escape an exploding first stage and get you away alive.

Now if you are leaving Mars with BFS there is no escape system for a mars launch. The escape system functionality only applies to Earth.

Actually, my understanding is that NASA requires an escape system to work from pre-launch all the way to orbit, so I don't think they would accept the second stage as an escape system. Incidentally, the last two catastrophic failures of SpaceX vehicles have been due to problems with the second stage, one just after launch, the other on the ground.

Back to the topic of this thread for a moment: I'm pretty doubtful that Canada would accept an aircraft that didn't meet FAA certification, much less European countries, Australia, Japan or S. Korea. That would narrow the market quite a bit. Short flight times between N. Korea and Venezuela wouldn't attract a lot of passengers I wouldn't think.

 

[dhanson865]

Actually, my understanding is that NASA requires an escape system to work from pre-launch all the way to orbit, so I don't think they would accept the second stage as an escape system. Incidentally, the last two catastrophic failures of SpaceX vehicles have been due to problems with the second stage, one just after launch, the other on the ground.

You are correct that they require abort options to what airplanes would consider high altitude. But in Space flight terms I'd still call that early flight. Once you get near a transfer orbit they disable the escape system and it stays disabled for the rest of the flight.

The ship in BFR/BFS is a hybrid of the 2nd stage from the Falcon 9 style and the dragon crew module from that style. Essentially the Dragon is the escape system for a stage 1 or stage 2 failure and BFS is an escape system for only stage 1 failure because there is no stage 2 between the crew and stage 1.

NASA - Launch Aborts Challenge Rocket Engineers discusses that variations on the escape system design are allowed and encouraged. It even specifically mentions SpaceX.

Incidentally the one on the ground could have been escaped successfully by the Dragon module save for the fact that the software wasn't set to enable that mode on the fateful day. All launches since have that feature enabled in software and the hardware supported it before that happened.

 

[adiggs]

I suppose it's worth adding - if this idea becomes real and the ticket price becomes reasonable (for today, I define that as $10k), then it really doesn't matter to me where it starts and ends - I won't be the first by a long shot, but I'll be in line and making the trip. Wherever my options are for starting and ending; it'll definitely be a case of it being about the journey, and not the destination

 

[ilovemycoffee]

How will they mitigate the sonic boom as the rocket leaves and returns? The video made it seem like it was awfully close to downtown Manhattan and Shanghi. Looking at current rocket launches and landing, I noticed there is a loud “kaboom” just before landing. This may piss off a lot of people!

 

[AZ Desert Driver]

How will they mitigate the sonic boom as the rocket leaves and returns? The video made it seem like it was awfully close to downtown Manhattan and Shanghi. Looking at current rocket launches and landing, I noticed there is a loud “kaboom” just before landing. This may piss off a lot of people!

As a teenager, I watched Apollo launches using the massive Titan rocket at the Cape from a small boat. The rocket exaust was diverted out to sea and one could watch the water ripple as the sonic boom moved across the bay. It was so loud that it crushed bird eggs close to the launch pad. As a kid, I thought that was exciting.
With the ability to launch and retrieve from a barge, perhaps "ground zero" can be put "near" metropolitain areas but not too near. Say 5 miles out to sea. Close enough for convienent customer use and far enough away to be minimaly intrusive.

 

[RDoc]

As a teenager, I watched Apollo launches using the massive Titan rocket at the Cape from a small boat. The rocket exaust was diverted out to sea and one could watch the water ripple as the sonic boom moved across the bay. It was so loud that it crushed bird eggs close to the launch pad. As a kid, I thought that was exciting.
With the ability to launch and retrieve from a barge, perhaps "ground zero" can be put "near" metropolitain areas but not too near. Say 5 miles out to sea. Close enough for convienent customer use and far enough away to be minimaly intrusive.

5 miles is about 25000 ft. The Concord flew at 60000 ft and was too loud, so I think we're talking more like 20 miles, which puts the launch/landing sites in pretty deep water for most places. Moving the people too and from shore, and from there to the final destination is going to significantly add to the end to end travel time, although for some cities it might be possible to depart and arrive very close to downtown.

Another option for the sonic boom issue may be to eliminate it by having the terminal velocity subsonic. That might already be the case if it fell belly first rather than tail first. Then the flare to vertical for final landing would be done at low altitude just before the landing burn, around 15000 ft. There would still be the issue of the noise from the engines firing of course.

If nothing else, it would be quite a sight, although the passengers might find the maneuver a bit disconcerting.

I still think though that getting FAA certification would be hard enough so as to be pretty indistinguishable from impossible.

 

[ilovemycoffee]

As a teenager, I watched Apollo launches using the massive Titan rocket at the Cape from a small boat. The rocket exaust was diverted out to sea and one could watch the water ripple as the sonic boom moved across the bay. It was so loud that it crushed bird eggs close to the launch pad. As a kid, I thought that was exciting.
With the ability to launch and retrieve from a barge, perhaps "ground zero" can be put "near" metropolitain areas but not too near. Say 5 miles out to sea. Close enough for convienent customer use and far enough away to be minimaly intrusive.

That's really cool! My father says he had me watch the moon landing, but I don't have any memories of it since I was only 3 years old.

(by the way, I thought the Apollo missions were launched by Saturn rockets?)

 

[dhanson865]

5 miles is about 25000 ft. The Concord flew at 60000 ft and was too loud, so I think we're talking more like 20 miles, which puts the launch/landing sites in pretty deep water for most places.

"The altitude at which the Concorde can go supersonic was limited by the regulations. For example, the aircraft was only allowed to go at 400 knots during the climb phase between 6,000 and 32,000 ft; also, the aircraft was allowed to go supersonic only after it has crossed the coastline.

As the air gets thinner during climb, the Mach number increases for same IAS, reaching around 0.93 at 25,000 ft and 0.95 at 28,000 ft. After this, the afterburners are engaged and autopilot is set to the cruising altitude (~ 60,000 ft). During this climb phase to the cruising altitude, the aircraft goes supersonic, settling at around Mach 2 at over 50,000 ft."

The problem with the Concorde was it was noisy as all get out at ground level going no faster than a Boeing or Airbus would at takeoff. It wasn't the sonic boom people complained about it was the god awfully loud engines. at barely missing the cars and buildings heights.

as you can see in this video you could stand or drive directly under the path of the concorde at takeoff, no way you'll ever do that for SpaceX.

SpaceX goes practically straight up. They don't cross parking lots, they don't cross highways, they don't cross apartment buildings. It's just not the same issue. They don't have to be further away because of how loud the concorde was, they are already further away at launch.

Guaranteed, you'll never see a spaceX rocket launching in between normal air traffic at JFK or Heathrow. It'll launch from somewhere less populated with less traffic and it won't set off car alarms for miles around.