Author Topic: BFR ASDS  (Read 16987 times)

Offline Dave G

  • Senior Member
  • *****
  • Posts: 2002
  • Liked: 742
  • Likes Given: 1016
Re: BFR ASDS
« Reply #80 on: 01/13/2018 01:45 PM »
One thing that bothers me about launching from off shore is the impact on marine life in the area of the launch pad. All of that  thrust blasting directly into shallow water is going to cook anything close by. Not good if they start finding dolphins and endangered sea turtles washing up on the beach cooked......

Er what? They won't be directing the exhaust straight in to the water, surely?

I'm also assuming some sort of underwater flame ducts, but unlike flame trenches for land-based pads, liquid cooling is free, so the flame duct material wouldn't need to be very thick.

« Last Edit: 01/13/2018 05:37 PM by Dave G »

Offline Dave G

  • Senior Member
  • *****
  • Posts: 2002
  • Liked: 742
  • Likes Given: 1016
Re: BFR ASDS
« Reply #81 on: 01/13/2018 01:46 PM »
What’s shown is like an ASDS but larger and set up for BFR launches as well as landings.

What Elon presented at IAC 2017, I believe this is a fixed launch platform with legs that physically connect it to the ocean floor.  More like a man-made island than a ship.  Most coastal areas are relatively shallow for miles offshore, often less than 100 feet deep.  A fixed platform would probably have underwater cables for power and data, plus underwater pipelines that connect it with on-shore propellant depots.  All of this is commonly used in the oil and gas business, so it shouldn't be expensive.

If it were a floating platform, it would probably need to be an order of magnitude larger.  Remember, we're talking about 5,400 tons of thrust at takeoff.  To counteract that on a floating platform, it would need to be really, really huge.  For this reason, I believe a floating launch site for BFR is extremely unlikely.

Offline darkenfast

  • Member
  • Full Member
  • ****
  • Posts: 746
  • Liked: 395
  • Likes Given: 804
Re: BFR ASDS
« Reply #82 on: 01/14/2018 03:35 AM »
If that barge/platform/whatever is 900' long by 300' wide at the waterline (just an example, eyeballed from the screen-grab), it would take an increase of over 17 million pounds to sink it one foot deeper in the water. 

Edit to add: I'm not arguing one way or another, as I personally don't think SpaceX plans to seriously look at this for some years.  Just wanted to remind everyone why big barges can carry so much!
« Last Edit: 01/14/2018 03:40 AM by darkenfast »

Offline Dave G

  • Senior Member
  • *****
  • Posts: 2002
  • Liked: 742
  • Likes Given: 1016
Re: BFR ASDS
« Reply #83 on: 01/14/2018 04:16 AM »
If that barge/platform/whatever is 900' long by 300' wide at the waterline (just an example, eyeballed from the screen-grab), it would take an increase of over 17 million pounds to sink it one foot deeper in the water. 
Wouldn't that require it to be perfectly centered?

I'm not arguing one way or another, as I personally don't think SpaceX plans to seriously look at this for some years.
You're guess is as good as mine, but I'm leaning toward sooner.  BFR is a huge rocket, so there may be issues launching it from land.

Offline CameronD

  • Full Member
  • ****
  • Posts: 1256
  • Melbourne, Australia
    • Norton Consultants
  • Liked: 401
  • Likes Given: 301
Re: BFR ASDS
« Reply #84 on: 01/14/2018 11:04 PM »
I'm not arguing one way or another, as I personally don't think SpaceX plans to seriously look at this for some years.
You're guess is as good as mine, but I'm leaning toward sooner.  BFR is a huge rocket, so there may be issues launching it from land.

However difficult launching this thing from land may be, there will be more issues launching it from water:  The ocean is never still.. and, unlike on land where you can retreat into a nice cozy hangar, there is no place to hide if the mother-of-all-storms happens by.

IMHO, they'd be better advised to takeover a small island.. they've done that before!
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline Dave G

  • Senior Member
  • *****
  • Posts: 2002
  • Liked: 742
  • Likes Given: 1016
Re: BFR ASDS
« Reply #85 on: 01/15/2018 01:58 AM »
IMHO, they'd be better advised to takeover a small island.. they've done that before!
How about a man-made island 5-10 miles offshore?  More specifically, a fixed launch site with legs attaching it to the ocean floor.  I believe this is what Elon showed at IAC 2017.

However difficult launching this thing from land may be, there will be more issues launching it from water...
Assuming they can get permission to launch it from land.  BFR has 1.6x the thrust of a Saturn 5.  The thing is huge.

unlike on land where you can retreat into a nice cozy hangar, there is no place to hide if the mother-of-all-storms happens by.
I see it just the opposite.  When a hurricane storm surge hits, I'd guess a land-based launch pad near the shore would sustain more damage than a fixed launch site 5-10 miles offshore.

Also, for a fixed launch site 5-10 miles offshore, what prevents them from bringing the rocket back to the hangar?  There's always advance warning for severe weather.

Offline CameronD

  • Full Member
  • ****
  • Posts: 1256
  • Melbourne, Australia
    • Norton Consultants
  • Liked: 401
  • Likes Given: 301
Re: BFR ASDS
« Reply #86 on: 01/15/2018 02:33 AM »
unlike on land where you can retreat into a nice cozy hangar, there is no place to hide if the mother-of-all-storms happens by.
I see it just the opposite.  When a hurricane storm surge hits, I'd guess a land-based launch pad near the shore would sustain more damage than a fixed launch site 5-10 miles offshore.

Also, for a fixed launch site 5-10 miles offshore, what prevents them from bringing the rocket back to the hangar?  There's always advance warning for severe weather.

Heh.  I guess you've not experienced what hurricane-force winds can do 5-10 miles offshore.  :)  So let's just say that, assuming a 'fixed launch site' in shallow water of the style shown in the presentation actually remains floating during a hurricane (which is unlikely), there wouldn't be anything remaining above deck level worth consideration once the storm passes.

The advantage of small islands, especially ones with rocks and established trees, is that rocks are generally immovable and trees act as wind breaks (to some extent) limiting ground-level damage to some extent.  And an island is more likely to stay where you left it.

What prevents them from bringing the rocket back to the hangar?  The waves kicked up before the storm warning is broadcast.  The calm seas shown in the presentation is no accident.
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline Dave G

  • Senior Member
  • *****
  • Posts: 2002
  • Liked: 742
  • Likes Given: 1016
Re: BFR ASDS
« Reply #87 on: 01/15/2018 11:56 AM »
So let's just say that, assuming a 'fixed launch site' in shallow water of the style shown in the presentation actually remains floating..
remains floating ?  I'm not talking about a floating launch site.

As I said before, I believe the launch site Elon presented at IAC 2017 is more like a man-made island than a barge, with a rigid structure connecting it to the ocean floor.

I'm also not talking about a direct hit from a hurricane, which would likely damage any launch site.

I'm talking about the surge.  When a storm surge comes inland, it picks up cars and other large objects and slams them into buildings and other fixed structures.

Offline CameronD

  • Full Member
  • ****
  • Posts: 1256
  • Melbourne, Australia
    • Norton Consultants
  • Liked: 401
  • Likes Given: 301
Re: BFR ASDS
« Reply #88 on: 01/15/2018 09:14 PM »
I'm talking about the surge.  When a storm surge comes inland, it picks up cars and other large objects and slams them into buildings and other fixed structures.

So am I.  If you do your research on storm surge you'll discover it can be even more damaging to fixed structures at sea-level in shallow water not far off-shore.. before it's had an opportunity to expend some of it's energy on land.

IMO, a structure of the type shown in the presentation 'fixed' in some way to the sea floor can be expected to cop a real hiding.  That's a key reason oil rigs are generally anchored (not 'fixed').. they can ride this stuff out if necessary.
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Online vanoord

  • Full Member
  • ****
  • Posts: 520
  • Liked: 310
  • Likes Given: 53
Re: BFR ASDS
« Reply #89 on: Today at 02:29 PM »
So let's just say that, assuming a 'fixed launch site' in shallow water of the style shown in the presentation actually remains floating..
remains floating ?  I'm not talking about a floating launch site.

As I said before, I believe the launch site Elon presented at IAC 2017 is more like a man-made island than a barge, with a rigid structure connecting it to the ocean floor.

I'm also not talking about a direct hit from a hurricane, which would likely damage any launch site.

I'm talking about the surge.  When a storm surge comes inland, it picks up cars and other large objects and slams them into buildings and other fixed structures.

The surge is the rise in water level - the stuff being thrown around is thrown around by the wind (and the resultant waves).

For an offshore platform, a surge is only of concern if it brings water to a level where it will cause damage - ie a 5ft surge makes no difference to a platform that is usually 15ft clear of the water as there's still 10ft clear below; and if it's offshore there shouldn't be anything around to be slammed into it.

Tags: