Author Topic: BFR ASDS  (Read 11337 times)

Offline edkyle99

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Re: BFR ASDS
« Reply #40 on: 10/06/2017 01:48 PM »
Hmmm.. I just had a whole bunch of ideas of creating an area of calm water where the docking part is.. then I realised, we must do this all the time. Eg nice quiet bays. Has anyone ever done this for floating platforms before?
Cruise ships use stabilizing systems designed to minimize seasickness of passengers.  Also, the deeper the below-surface draft of a ship, the more stable it can be, as I understand things.  Still, none of these ships have passengers sitting within the nose of a 350 foot tall rocket atop them!

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Online envy887

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Re: BFR ASDS
« Reply #41 on: 10/06/2017 01:57 PM »
Hmmm.. I just had a whole bunch of ideas of creating an area of calm water where the docking part is.. then I realised, we must do this all the time. Eg nice quiet bays. Has anyone ever done this for floating platforms before?
Cruise ships use stabilizing systems designed to minimize seasickness of passengers.  Also, the deeper the below-surface draft of a ship, the more stable it can be, as I understand things.  Still, none of these ships have passengers sitting within the nose of a 350 foot tall rocket atop them!

 - Ed Kyle

The oil and gas industry has taken 6 DOF stabilization in the open ocean down to an exact science. These are mostly solved problems; not cheap, but solved.

Offline speedevil

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Re: BFR ASDS
« Reply #42 on: 10/06/2017 02:10 PM »
Cruise ships use stabilizing systems designed to minimize seasickness of passengers.  Also, the deeper the below-surface draft of a ship, the more stable it can be, as I understand things.  Still, none of these ships have passengers sitting within the nose of a 350 foot tall rocket atop them!

The BFR for ASDS will be significantly larger than the one for F9.
Cruise ships use stabilisation to minimise motion, but most cruise ships are under 40m wide. The good cabins are often around half as high as the top of the BFS.

ASDS-BFR is around twice as wide as most cruise ships, will not operate close-in to shore, does not have to point in a specific direction, and the passengers have already experienced a much rougher high-speed ship.

In addition, they are all packed to the gills with seasickness medication, and are going to be launched into space immediately after boarding, at 3G, before a period of weightlessness and then 3G again. I suggest swaying may not be a huge concern.

In principle, if you're deploying passenger systems like this in numbers, a stabilised launch cradle would not be the hardest part of this system.


Offline intrepidpursuit

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Re: BFR ASDS
« Reply #43 on: 10/06/2017 05:09 PM »
http://dynamic-positioning.com/proceedings/dp2003/design_berkeley.pdf

Quote
The Mobile Offshore Base (MOB) is a large, self-propelled, floating, pre-positioned ocean structure formed
of three to five modules and reaching up to 1,500 meters in length.
It must accommodate the landing and take-off  of  C-17  conventional  aircraft,  host  3000  troops,  carry  10  million  gallons  of  fuel  and  provide  3   million  square  feet  of  internal  configurable  storage.  The  alignment  of  the  modules  is  maintained  through   the use of slew-able thrusters and/or connectors.

Plenty of room for passengers, methane, LOX, and commuter aircrafts to carry the passengers. A C-17 is as big as an A350 or 787.
add some shopping malls, hotels, and other goodies.

I think even in a high reliability world the ship will probably be evacuated during launch and landings. I also think that large scale (more than 1 or 2 launches) fuel storage would not be attached the launch platform. In the real world there may be a small flotilla of ships, including a launch and landing ship, a transportation/logistics/security ship, and a fuel tanker or two. Purpose built ships could turn this into a well oiled machine with ships converging and diverging in a tightly choreographed schedule to allow a point to point launch every 2 hours or so.

I doubt the same ship(s) could be used for space launch though. Much more careful packing of sensitive equipment for interplanetary travel, quick volleys of multiple tankers, and satellite encapsulation would all go counter to the requirements of an airliner-like workflow. A mars caravan launch campaign would interrupt point-to-point travel for at least a few days at a time if they tried to use the same platform and LEO/BEO ships would likely need more processing than would make sense to be done on a ship.

Offline R.Simko

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Re: BFR ASDS
« Reply #44 on: 10/06/2017 08:09 PM »
If Mr. Musk did choose to build an island for launching BFR, any thoughts of where the best location would be to build an island?

Offline RobLynn

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Re: BFR ASDS
« Reply #45 on: 10/07/2017 12:25 AM »
With two ASDS ships they could launch from one and land on the other, then swap location for next launch etc, even if launch ASDA is tied up to end of a pier for easy access. Ships are incredibly cheap, typically only about $2000/tonne so being able to build majority of launch towers, cranes, fuel tanks etc in a shipyard might reduce their costs considerably.

I wonder about the possibility of using a variable buoyancy design - big catamaran with ballast tanks to sink almost entirely below sea surface for launch and landing so that little more than the landing cradle is exposed to rocket exhaust.  Catamarans are fast and very stable, and if submerged so that they have minimal water-line area they are very insensitive to waves.

I'm a "glass is twice as big as it needs to be" kinda guy

Offline Zed_Noir

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Re: BFR ASDS
« Reply #46 on: 10/07/2017 07:51 AM »
What does folks think of the idea to put vertical BFS protective hangars abreast of the crane on the BFR ASDS for storing 2 or 4 BFS?

For a simple dual hangar design. Two vertical cylindrical structures with one to the starboard and one to port side of the BFR ASDS crane with a hatch on top. You already got the crane aboard the ASDS to move the BFS. Internal service platforms could be fitted in the hangars.

Should speed up the tempo of launch. Especially with BFS tankers on a BFR ASDS with quad BFS hangars.

Also useful to shelter the BFS in bad weather.

Offline DOCinCT

Re: BFR ASDS
« Reply #47 on: 10/07/2017 04:45 PM »
...
* doesn't the BFS suffer the same problem that the Space Shuttle suffered, which was that you are essentially launching a mini space station into orbit on every launch?  Why not separate people and cargo?
I know, I know, Elon's idea is that the people are the cargo, but that's barely true for commercial aviation today, in a context where ships carry everything heavy.  In a context where his ride is the only ride, I have to believe there will be a huge amount more cargo than people.
Why not do both?  Modern container ships have comfortable accommodations for up to 12 passengers, there are also conventional cargo freighters that have passenger accommodations.  If the spaceship was taking cargo or crew to the ISS (or equivalent), lot's of room for space tourists, who get to see the ISS before heading out on their orbital excursion (or cis-lunar excursion).

Offline CameronD

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Re: BFR ASDS
« Reply #48 on: 10/09/2017 12:21 AM »
...
* doesn't the BFS suffer the same problem that the Space Shuttle suffered, which was that you are essentially launching a mini space station into orbit on every launch?  Why not separate people and cargo?
I know, I know, Elon's idea is that the people are the cargo, but that's barely true for commercial aviation today, in a context where ships carry everything heavy.  In a context where his ride is the only ride, I have to believe there will be a huge amount more cargo than people.
Why not do both?  Modern container ships have comfortable accommodations for up to 12 passengers, there are also conventional cargo freighters that have passenger accommodations.  If the spaceship was taking cargo or crew to the ISS (or equivalent), lot's of room for space tourists, who get to see the ISS before heading out on their orbital excursion (or cis-lunar excursion).

It would certainly put a new slant on travelling "Freight" (a.k.a. Baggage Class).  ;D

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 RobLynn

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Re: BFR ASDS
« Reply #49 on: 10/21/2017 12:52 AM »
With a big and relatively lightweight catamaran as a launch platform and ASDS they could utilise the ships thrusters to move the launch tower away from the launch vehicle immediately after takeoff, saving some launch tower complexity.  Could also use a big keel mass held up by a line to bow and stern of ship and at lift-off cut one of those lines so that keel mass swings pulling the ship fore or aft as it does so.
I'm a "glass is twice as big as it needs to be" kinda guy

Online docmordrid

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Re: BFR ASDS
« Reply #50 on: 10/21/2017 08:45 PM »
Or, water depth permitting, use one or several adjacent jack-up rigs.  Their legs would sit on the sea floor providing a very solid, yet still mobile if needed, platform.
« Last Edit: 10/21/2017 08:53 PM by docmordrid »
DM

Offline RobLynn

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Re: BFR ASDS
« Reply #51 on: 10/25/2017 01:03 AM »
if you suspend a large mass on 3 long cables 100's of meters below a floating mass it acts as a 100's m long rigid keel preventing almost all pitching and rocking.  The keel cables can be wound in for ease of transport.

alternatively if you additionally use small water-line area - essentially submersed buoyant chambers with small struts extending through water surface to support an elevated platform then waves have almost no effect on the platform and high stability is maintained.
I'm a "glass is twice as big as it needs to be" kinda guy

Offline CameronD

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Re: BFR ASDS
« Reply #52 on: 11/02/2017 09:26 PM »
Or, water depth permitting, use one or several adjacent jack-up rigs.  Their legs would sit on the sea floor providing a very solid, yet still mobile if needed, platform.

if you suspend a large mass on 3 long cables 100's of meters below a floating mass it acts as a 100's m long rigid keel preventing almost all pitching and rocking.  The keel cables can be wound in for ease of transport.

You guys might be forgetting that, whilst it indeed needs to be a stable platform for landing, this ASDS must also be able to move quickly in an emergency - out of the way of an incoming rock(et).

The current design achieves this in spades; the above suggestions possibly not so much..
« Last Edit: 11/02/2017 09:31 PM by CameronD »
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 biosehnsucht

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Re: BFR ASDS
« Reply #53 on: 11/02/2017 09:35 PM »
The current design can barely maintain it's position in rough seas. It can't get out of  the way of an incoming rocket without at least a few minutes of warning, and that's assuming they can remotely retarget the ASDS (no reason they couldn't if they wanted to, just might not be a current feature).

Offline CameronD

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Re: BFR ASDS
« Reply #54 on: 11/02/2017 09:49 PM »
The current design can barely maintain it's position in rough seas. It can't get out of  the way of an incoming rocket without at least a few minutes of warning, and that's assuming they can remotely retarget the ASDS (no reason they couldn't if they wanted to, just might not be a current feature).

We've known about the requirement to splash a stage by moving out of the way ever since the first landing attempt - so it's not only a current feature, it's a primary one - and we've all seen what can happen after a bad  (non-emergency) landing.

Truth is (a) they may have less than a few minutes warning and (b) they certainly can re-target the ASDS from the support ship - that's how they set the position now, once the tow is released.
« Last Edit: 11/02/2017 09:51 PM by CameronD »
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 speedevil

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Re: BFR ASDS
« Reply #55 on: 11/02/2017 10:17 PM »

You guys might be forgetting that, whilst it indeed needs to be a stable platform for landing, this ASDS must also be able to move quickly in an emergency - out of the way of an incoming rock(et).

The current design achieves this in spades; the above suggestions possibly not so much..

The existing platform can't move significantly in time to matter.
A BFR landing platform could not move significantly unless you actually put many raptors on it.

Moving the barge  when it's more than 10-30s or so up is basically pointless, as the size of the probable landing ellipse if the rocket becomes uncontrolled exceeds the size of the barge.

While I am for a flying barge, it seems unlikely.


Offline AC in NC

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Re: BFR ASDS
« Reply #56 on: 11/03/2017 03:18 AM »
We've known about the requirement to splash a stage by moving out of the way ever since the first landing attempt - so it's not only a current feature, it's a primary one - and we've all seen what can happen after a bad  (non-emergency) landing.

The IIP is off the Landing Target until they are committed to the attempt.  The booster decides to try to hit the ASDS if things look good.  The ASDS doesn't decide to try to dodge the booster if things look bad.

« Last Edit: 11/03/2017 03:20 AM by AC in NC »

Offline CameronD

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Re: BFR ASDS
« Reply #57 on: 11/03/2017 05:00 AM »
We've known about the requirement to splash a stage by moving out of the way ever since the first landing attempt - so it's not only a current feature, it's a primary one - and we've all seen what can happen after a bad  (non-emergency) landing.

The IIP is off the Landing Target until they are committed to the attempt.  The booster decides to try to hit the ASDS if things look good.  The ASDS doesn't decide to try to dodge the booster if things look bad.

Are you implying by that that they start off with the ASDS off-target and move it in if all is good??  ???

Better go read https://forum.nasaspaceflight.com/index.php?topic=39766.0 and especially http://forum.nasaspaceflight.com/index.php?topic=36326.0 again..
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 octavo

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Re: BFR ASDS
« Reply #58 on: 11/03/2017 05:25 AM »
We've known about the requirement to splash a stage by moving out of the way ever since the first landing attempt - so it's not only a current feature, it's a primary one - and we've all seen what can happen after a bad  (non-emergency) landing.

The IIP is off the Landing Target until they are committed to the attempt.  The booster decides to try to hit the ASDS if things look good.  The ASDS doesn't decide to try to dodge the booster if things look bad.

Are you implying by that that they start off with the ASDS off-target and move it in if all is good??  ???

Better go read https://forum.nasaspaceflight.com/index.php?topic=39766.0 and especially http://forum.nasaspaceflight.com/index.php?topic=36326.0 again..
No, the barge doesn't move at all. The booster changes its landing target to the preset asds coords once it is happy that a safe landing can be attempted.

Offline Lars-J

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Re: BFR ASDS
« Reply #59 on: 11/03/2017 08:46 PM »
The current design can barely maintain it's position in rough seas. It can't get out of  the way of an incoming rocket without at least a few minutes of warning, and that's assuming they can remotely retarget the ASDS (no reason they couldn't if they wanted to, just might not be a current feature).

We've known about the requirement to splash a stage by moving out of the way ever since the first landing attempt - so it's not only a current feature, it's a primary one - and we've all seen what can happen after a bad  (non-emergency) landing.

Truth is (a) they may have less than a few minutes warning and (b) they certainly can re-target the ASDS from the support ship - that's how they set the position now, once the tow is released.

You are mistaken.

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