Author Topic: Titanium Falcon  (Read 10005 times)

Offline sevenperforce

  • Full Member
  • ****
  • Posts: 746
  • Liked: 175
  • Likes Given: 220
Titanium Falcon
« on: 08/24/2016 07:34 PM »
Obviously, when the Falcon 1, Falcon 5, and Falcon 9 were being designed, they chose aluminum for a lot of reasons. It was strong and lightweight and cheap, which is good when you're building rockets that will be expended for a while until you manage to nail down reuse.

Now that returning the stages seems to be a pretty regular thing and reuse appears to be just around the corner...what kind of margins would you get from replacing the aluminum-lithium alloy in the body of the Falcon 9 with titanium instead? Cost would be far higher, of course, but the specific strength of titanium is roughly 40% higher, meaning you could afford to reduce the weight of the stage body by more than 20% and still have a 10% higher safety margin.

Granted, the stage body is not all the dry mass of the stage. With 4.2 tonnes of engine on the bottom of the first stage, you're looking at less than 80% of the stage weight being aluminum-lithium body. So mass savings are not terrific...but it is still a reduction in dry weight of 10-15%, permitting pretty substantial increases in orbital throw weight.

Of course, they'd never do this now; everything they have is designed around their aluminum-lithium alloy.

But what about BFR? Since BFR will be designed for reuse from the very start, is it possible that SpaceX would go for a more expensive, higher-performing body material?

Offline spacenut

  • Senior Member
  • *****
  • Posts: 2150
  • East Alabama
  • Liked: 310
  • Likes Given: 195
Re: Titanium Falcon
« Reply #1 on: 08/24/2016 08:22 PM »
I think they are going to composites which are lighter than aluminum and also stronger pound for pound.  Titanium is heavier than aluminum and does have a higher melting point, but not necessary on the tanks which is 90% of the body of the booster. 

Offline sevenperforce

  • Full Member
  • ****
  • Posts: 746
  • Liked: 175
  • Likes Given: 220
Re: Titanium Falcon
« Reply #2 on: 08/24/2016 08:59 PM »
I think they are going to composites which are lighter than aluminum and also stronger pound for pound.  Titanium is heavier than aluminum and does have a higher melting point, but not necessary on the tanks which is 90% of the body of the booster.
Ah, I see.

How do composites compare to titanium? Titanium is 40% stronger than aluminium alloy, pound for pound, so you could use almost 30% less of it by weight and still have the same tank strength.

Offline acsawdey

  • Full Member
  • ***
  • Posts: 301
  • Minnesota
  • Liked: 175
  • Likes Given: 307
Re: Titanium Falcon
« Reply #3 on: 08/24/2016 09:43 PM »
I think they are going to composites which are lighter than aluminum and also stronger pound for pound.  Titanium is heavier than aluminum and does have a higher melting point, but not necessary on the tanks which is 90% of the body of the booster.
Ah, I see.

How do composites compare to titanium? Titanium is 40% stronger than aluminium alloy, pound for pound, so you could use almost 30% less of it by weight and still have the same tank strength.

How well understood are the properties of titanium alloys at cryogenic temperatures? Is it compatible with direct LOX contact?

Offline sevenperforce

  • Full Member
  • ****
  • Posts: 746
  • Liked: 175
  • Likes Given: 220
Re: Titanium Falcon
« Reply #4 on: 08/24/2016 10:28 PM »
How do composites compare to titanium? Titanium is 40% stronger than aluminium alloy, pound for pound, so you could use almost 30% less of it by weight and still have the same tank strength.

How well understood are the properties of titanium alloys at cryogenic temperatures? Is it compatible with direct LOX contact?
If I recall correctly, titanium alloys have comparable or superior cryogenic performance against aluminum alloy. I imagine the oxidization chemistry is also similar.

How about composites? Does carbon-fiber composite lose tensile strength at subcooled LOX temperatures?

All other things being equal, it is better to go with denser materials if equal or better specific strength can be attained, because a denser tank metal will have a larger internal volume for the same strength and external volume. Probably a negligible difference between aluminum and titanium despite the significant volume-specific strength difference, thanks to our old friend square-cube.

Offline Herb Schaltegger

Re: Titanium Falcon
« Reply #5 on: 08/24/2016 10:33 PM »
This reminds me of the all the post-STS 107 chit chat on Usenet. "What if Columbia's wing spar had been titanium instead of aluminum?!?!"

Titanium is not a miracle metal; it's generally more difficult to work for large structural members and actually, I doubt SpaceX could afford the material cost hit even if they could work through the manufacturing and assembly process changes. This isn't a Cold War project like the B-70 (which was ultimately too expensive to produce more than the 3 airframes anyway).
Ad astra per aspirin ...

Offline acsawdey

  • Full Member
  • ***
  • Posts: 301
  • Minnesota
  • Liked: 175
  • Likes Given: 307
Re: Titanium Falcon
« Reply #6 on: 08/24/2016 10:39 PM »
This is the link I was looking for:

http://www.dtic.mil/dtic/tr/fulltext/u2/273489.pdf

"Unalloyed titanium (Ti-75A) and Ti-6Al-4V alloy were consumed by violent reactions when ruptured in gaseous oxygen under suitable pressure from -190F to room temperature."


Offline CameronD

  • Full Member
  • ****
  • Posts: 1242
  • Melbourne, Australia
    • Norton Consultants
  • Liked: 394
  • Likes Given: 295
Re: Titanium Falcon
« Reply #7 on: 08/25/2016 12:02 AM »
Titanium is not a miracle metal; it's generally more difficult to work for large structural members and actually, I doubt SpaceX could afford the material cost hit even if they could work through the manufacturing and assembly process changes. This isn't a Cold War project like the B-70 (which was ultimately too expensive to produce more than the 3 airframes anyway).

Titanium's strength also requires using extremely dangerous chemicals (like HF/Nitric Acid mix using in the etching process) it which is at least part of the reason for the high cost of large structural components.

I remember the line manager of one component processing facility here telling me a rookie OH&S guy asked him why there was no ladder on the inside of the open HF/Nitric bath so if someone fell in they could climb out.  His response was "if anyone falls in there, they won't even hit the bottom!".  The fume scrubber hiccupped one day and a smallish cloud of vapour wafted across the car-park, but before it could dissipate it neatly stripped the paint off the top of five cars and turned the windows opaque.  Fortunately no-one was in the car-park at the time..

Although aerospace-grade aluminium etching still uses nasty chemicals (including some weak HF/Nitric for desmutting) it's not quite in the same league safety-wise.
 
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 dorkmo

  • Full Member
  • ****
  • Posts: 643
  • Liked: 292
  • Likes Given: 758
Re: Titanium Falcon
« Reply #8 on: 08/25/2016 03:11 AM »
heres a discussion that talks a bit about the pros and cons of ti

http://forum.nasaspaceflight.com/index.php?topic=39295.0

Offline octavo

  • Member
  • Posts: 60
  • Liked: 22
  • Likes Given: 44
Re: Titanium Falcon
« Reply #9 on: 08/25/2016 10:10 AM »
With regard to use on BFS, higher-density (afaik) actually hurts you as the secondary radiation from gamma rays striking the titanium would be far worse than if they strike a less dense material

Offline sevenperforce

  • Full Member
  • ****
  • Posts: 746
  • Liked: 175
  • Likes Given: 220
Re: Titanium Falcon
« Reply #10 on: 08/25/2016 07:21 PM »
With regard to use on BFS, higher-density (afaik) actually hurts you as the secondary radiation from gamma rays striking the titanium would be far worse than if they strike a less dense material
Wouldn't be an issue for the first-stage booster.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 31277
  • Cape Canaveral Spaceport
  • Liked: 9561
  • Likes Given: 299
Re: Titanium Falcon
« Reply #11 on: 08/25/2016 07:25 PM »
With regard to use on BFS, higher-density (afaik) actually hurts you as the secondary radiation from gamma rays striking the titanium would be far worse than if they strike a less dense material
Wouldn't be an issue for the first-stage booster.

But having booster and upper stage made of different materials eliminates any production synergism.  it would require separate tank production lines.

Offline sevenperforce

  • Full Member
  • ****
  • Posts: 746
  • Liked: 175
  • Likes Given: 220
Re: Titanium Falcon
« Reply #12 on: 08/25/2016 07:37 PM »
With regard to use on BFS, higher-density (afaik) actually hurts you as the secondary radiation from gamma rays striking the titanium would be far worse than if they strike a less dense material
Wouldn't be an issue for the first-stage booster.

But having booster and upper stage made of different materials eliminates any production synergism.  it would require separate tank production lines.
Well, the MCT is (purportedly) more than just a second stage, so comparing BFR to MCT is less like comparing Falcon 9's stage 1 to stage 2 and more like comparing Falcon 9's stage 1 to the Dragon 2.

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 31277
  • Cape Canaveral Spaceport
  • Liked: 9561
  • Likes Given: 299
Re: Titanium Falcon
« Reply #13 on: 08/25/2016 07:48 PM »

Well, the MCT is (purportedly) more than just a second stage, so comparing BFR to MCT is less like comparing Falcon 9's stage 1 to stage 2 and more like comparing Falcon 9's stage 1 to the Dragon 2.

No, it is still the same comparison.  The MCT will have a propulsion system with elements common to the booster.

Offline sevenperforce

  • Full Member
  • ****
  • Posts: 746
  • Liked: 175
  • Likes Given: 220
Re: Titanium Falcon
« Reply #14 on: 08/25/2016 07:57 PM »

Well, the MCT is (purportedly) more than just a second stage, so comparing BFR to MCT is less like comparing Falcon 9's stage 1 to stage 2 and more like comparing Falcon 9's stage 1 to the Dragon 2.

No, it is still the same comparison.  The MCT will have a propulsion system with elements common to the booster.
But it will also have a pressure vessel designed for human occupancy, so....

Offline Lee Jay

  • Elite Veteran
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 6639
  • Liked: 913
  • Likes Given: 137
Re: Titanium Falcon
« Reply #15 on: 08/25/2016 08:09 PM »
This isn't a Cold War project like the B-70 (which was ultimately too expensive to produce more than the 3 airframes anyway).

Only two XB-70s were built (the second crashed, the first is in the USAF museum in Dayton, OH), and they were almost entirely made of stainless steel, with titanium just in the most critical parts.

The SR-71, on the other hand...

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 31277
  • Cape Canaveral Spaceport
  • Liked: 9561
  • Likes Given: 299
Re: Titanium Falcon
« Reply #16 on: 08/25/2016 08:16 PM »

But it will also have a pressure vessel designed for human occupancy, so....

So that is the same as the Dragon on top of the second stage

Offline mvpel

  • Full Member
  • ****
  • Posts: 1116
  • New Hampshire
  • Liked: 1279
  • Likes Given: 1676
Re: Titanium Falcon
« Reply #17 on: 08/25/2016 08:17 PM »
Cryogenic composite fuel tanks have been the subject of very aggressive R&D work over the past few years.

NASA/Boeing composite launch vehicle fuel tank scores firsts - January 2016
Quote
For more than 50 years, heavy metal cryogenic tanks have carried the liquid hydrogen (LH2) and oxygen necessary to launch vehicles into space. But in a joint effort, NASA and The Boeing Co. (Chicago, IL, US) have designed, fabricated and tested a composite cryotank that, if scaled up to current space launch system dimensions, would weigh 30% less and cost 25% less than the best aluminum-lithium cryotanks used today, and could warrant transport of as much as 1,400 kg of additional payload to low-Earth orbit and beyond.

The US$25 million Composite Cryotank Technologies and Demonstration (CCTD)  project, part of the NASA Space Technology Mission Directorate’s Game Changing Development (GCD) program, involved a team of Boeing and NASA engineers.

“This is the first effort to successfully build and test a tank of this scale,” says Douglas McCarville, Technical Fellow at Boeing Research & Technology (BR&T) in Seattle, WA, US. “The tank would work for liquid oxygen or liquid hydrogen on a variety of next-generation launch systems.”
"Ugly programs are like ugly suspension bridges: they're much more liable to collapse than pretty ones, because the way humans (especially engineer-humans) perceive beauty is intimately related to our ability to process and understand complexity. A language that makes it hard to write elegant code makes it hard to write good code." - Eric S. Raymond

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 27018
  • Minnesota
  • Liked: 6910
  • Likes Given: 4872
Re: Titanium Falcon
« Reply #18 on: 08/26/2016 07:37 PM »
Might make sense to make /portions/ of Falcon out of Titanium. Like the grid fins or maybe parts of the thrust structure. To enhance durability and reduce the amount of TPS you need.

But I don't think they'll make the tanks (etc) out of it. Hard to work, not generally as good structure/mass (the lower density of aluminum helps for compressive structures in ways beyond pure strength/weight ratio because of reduced buckling).
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 27018
  • Minnesota
  • Liked: 6910
  • Likes Given: 4872
Re: Titanium Falcon
« Reply #19 on: 08/18/2017 04:09 AM »
Might make sense to make /portions/ of Falcon out of Titanium. Like the grid fins or maybe parts of the thrust structure. To enhance durability and reduce the amount of TPS you need.

But I don't think they'll make the tanks (etc) out of it. Hard to work, not generally as good structure/mass (the lower density of aluminum helps for compressive structures in ways beyond pure strength/weight ratio because of reduced buckling).
Called it.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline biosehnsucht

  • Full Member
  • *
  • Posts: 178
  • Liked: 43
  • Likes Given: 52
Re: Titanium Falcon
« Reply #20 on: 08/18/2017 07:41 AM »
At first I didn't notice the day of month or year and was like "well, duh, we already know they switched to titanium grid fins".

You totally called that.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6035
  • Everyplaceelse
  • Liked: 780
  • Likes Given: 4853
Re: Titanium Falcon
« Reply #21 on: 08/18/2017 07:46 AM »
But having booster and upper stage made of different materials eliminates any production synergism.  it would require separate tank production lines.
Indeed.

Conceptually it would duplicate the Saturn V architecture, trading performance for cost, but with structure changes rather than fuel changes.  :(

That would be a re-visiting of the design-for-minimum-cost paradigm, with a big simple booster and the higher performance reserved for the US.

While theoretically attractive in reducing the overall recurring costs of a govt programme (the really expensive tech gets used where its weight is 1:1 ) I think SX have found that commonality of structures, propellants and engines across both stages has been much more productive.

And SX have shown themselves quite sensitive to the costs of splitting an LV design by fuel, materials or engine design
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6035
  • Everyplaceelse
  • Liked: 780
  • Likes Given: 4853
Re: Titanium Falcon
« Reply #22 on: 08/18/2017 08:03 AM »
This isn't a Cold War project like the B-70 (which was ultimately too expensive to produce more than the 3 airframes anyway).

Only two XB-70s were built (the second crashed, the first is in the USAF museum in Dayton, OH), and they were almost entirely made of stainless steel, with titanium just in the most critical parts.

The SR-71, on the other hand...
AIUI Titanium was ruled out of the XB70 on cost and availability grounds. It's payload was about 10x that of the A12/SR71 and even then the CIA set up front companies to buy the raw Titanium  from Russia.

Books on the SR71 say that while Titanium was being used a bit in the US at the time,  Kelly Johnson's team had to set up quite a lot of the infrastructure themselves. [EDIT and learn things like you can't use felt tip pens on the alloy as they will eat through it (what ??? ) likewise IIRC Chrome in Chrome Vanadium steel tools embrittled it. It seems like real EE Smith territory (where the hero has to build the tools, that build the tools, to build the machinery that's actually needed  :(  )  ]

Either no one had experience of doing what they wanted or doing it on the scale they wanted to do it.

What was amazing about the XB70 (apart from its shockwave rider aerodynamics) was how NAA did it with a relatively pedestrian 17/7 steel alloy by using honeycomb panels, although QC on them seems to have been a nightmare.  :( [EDIT in principal, with pervasive use of shop floor CNC and real time monitoring of mfg processes  they would be much more consistently reproducible. Provided you could live with a vehicle with an enormous RCS  :( ]

People seem to forget that people have already built LV's with steel tanks and did so up to the Atlas III, while Centaur is still a steel tank design.

No one has AFAIK built a Titanium stage, although it's relatively easy to diffusion bond.
To play to its strengths you'd need to decompose a design into "primitives" you could use standard Ti sections for (which actually have quite tight dimensional tolerances)like the "slicing" software used to analyze CAD drawings to drive a 3D printer , then construct a layup of steel sections to support the structure before canning it, evacuating the can and sticking it in a large heated press. 

BTW IIRC the Atlas steel tanks were about 1-2mm thick ("no thicker than a Dime" was the phrase) in the SS301 FH temper. This is roughly 1/10 the maximum thickness that modern FSW systems can cope with in steel (not just Aluminum), so well within the current SoA for FSW but with near 100% weld efficiency.
« Last Edit: 08/18/2017 08:38 AM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Online LouScheffer

  • Full Member
  • ****
  • Posts: 1554
  • Liked: 1732
  • Likes Given: 197
Re: Titanium Falcon
« Reply #23 on: 08/18/2017 01:09 PM »
Might make sense to make /portions/ of Falcon out of Titanium. Like the grid fins or maybe parts of the thrust structure. To enhance durability and reduce the amount of TPS you need.

But I don't think they'll make the tanks (etc) out of it. Hard to work, not generally as good structure/mass (the lower density of aluminum helps for compressive structures in ways beyond pure strength/weight ratio because of reduced buckling).
Called it.
For historical interest only, mvpel may have called it first.  The idea was certainly rattling around:
Titanium grid fins for supersonic rocket manufactured

Quote from: LIN Industrial
3D printed plastic grid fins we currently use can't withstand the dynamic pressure and heating at supersonic. That's why we have started manufacturing titanium grid fins. They are cut from a single piece of titanium with a CNC machine:



Offline tdperk

  • Full Member
  • **
  • Posts: 225
  • Liked: 70
  • Likes Given: 21
Re: Titanium Falcon
« Reply #24 on: 08/18/2017 05:18 PM »

Well, the MCT is (purportedly) more than just a second stage, so comparing BFR to MCT is less like comparing Falcon 9's stage 1 to stage 2 and more like comparing Falcon 9's stage 1 to the Dragon 2.

No, it is still the same comparison.  The MCT will have a propulsion system with elements common to the booster.

Which in no way requires identical tankage, or even concept of how that tankage is to be made.

Offline dorkmo

  • Full Member
  • ****
  • Posts: 643
  • Liked: 292
  • Likes Given: 758
Re: Titanium Falcon
« Reply #25 on: 08/18/2017 09:33 PM »
Might make sense to make /portions/ of Falcon out of Titanium. Like the grid fins or maybe parts of the thrust structure. To enhance durability and reduce the amount of TPS you need.

But I don't think they'll make the tanks (etc) out of it. Hard to work, not generally as good structure/mass (the lower density of aluminum helps for compressive structures in ways beyond pure strength/weight ratio because of reduced buckling).
Called it.
For historical interest only, mvpel may have called it first.  The idea was certainly rattling around:
Titanium grid fins for supersonic rocket manufactured

Quote from: LIN Industrial
3D printed plastic grid fins we currently use can't withstand the dynamic pressure and heating at supersonic. That's why we have started manufacturing titanium grid fins. They are cut from a single piece of titanium with a CNC machine:




shout out to dorkmo for starting that clairvoyant thread :P
« Last Edit: 08/18/2017 09:34 PM by dorkmo »

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6035
  • Everyplaceelse
  • Liked: 780
  • Likes Given: 4853
Re: Titanium Falcon
« Reply #26 on: 08/21/2017 07:41 AM »
shout out to dorkmo for starting that clairvoyant thread :P

Consider yourself shouted out.

"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline darkenfast

  • Member
  • Full Member
  • ****
  • Posts: 735
  • Liked: 370
  • Likes Given: 718
Re: Titanium Falcon
« Reply #27 on: 08/21/2017 08:16 AM »
Every time Titanium comes up in this forum, I think of the line in the early part of "Destination Moon", where the rocket-building industrialist barks into his telephone: "Too heavy! Try Titanium!".

On a slightly more factual note, I was always impressed that the Soviet Union managed to build whole large submarine pressure hulls out of the stuff.   None of which is germane to Falcon 9, of course!

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6035
  • Everyplaceelse
  • Liked: 780
  • Likes Given: 4853
Re: Titanium Falcon
« Reply #28 on: 08/21/2017 09:44 AM »
On a slightly more factual note, I was always impressed that the Soviet Union managed to build whole large submarine pressure hulls out of the stuff.   None of which is germane to Falcon 9, of course!
Rocket propellant tanks are also pressure vessels and welding Titanium (which I think is how the Russians did it) is pretty tough, although they also seem to have worked on diffusion welding quite a bit, especially in devising clever ways to build and operate on site vacuum chambers.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Karloss12

  • Full Member
  • *
  • Posts: 198
  • Liked: 28
  • Likes Given: 0
Re: Titanium Falcon
« Reply #29 on: 08/22/2017 09:15 PM »
When comparing the running costs of a reusable Aluminium core vs Titanium core the only difference is the cost of fuel.
The 20% heavier Aluminium core will need to burn 20% more fuel.  If Elons statement that the cost of fuel per launch is $500k is correct then each launch will be a total of $100k less expensive.
If the fabrication of a titanium core costs $20mil more than an Aluminium core then the small $100k saving per flight will never pay off the $20mil sunk into the cores fabrication.

Offline Stan-1967

  • Full Member
  • ****
  • Posts: 465
  • Denver, Colorado
  • Liked: 247
  • Likes Given: 162
Re: Titanium Falcon
« Reply #30 on: 08/22/2017 09:25 PM »
It is not the cost of fuel that would drive any use of titanium.  I think of the following drivers.
1.  Does titaninum enables more re-uses to ammortize the full cost? ( this covers safety margins & more re-use margin)
2.  Does it enables less refurbishing effort that can be monetized?
3.  Does it increase safety margins that might affect insurance rates?

Titanium grid fins definately met #1 & #2.  Would a Ti core do the same?

Offline russianhalo117

  • Senior Member
  • *****
  • Posts: 3799
  • AR USA / Berlin, DE / Moscow, RF
  • Liked: 733
  • Likes Given: 448
Re: Titanium Falcon
« Reply #31 on: 08/22/2017 10:37 PM »
This isn't a Cold War project like the B-70 (which was ultimately too expensive to produce more than the 3 airframes anyway).

Only two XB-70s were built (the second crashed, the first is in the USAF museum in Dayton, OH), and they were almost entirely made of stainless steel, with titanium just in the most critical parts.

The SR-71, on the other hand...
Actually they are XB-70A's the original XB-70 programme ended when the B-70 programme was cancelled. XB-70A research programme replaced the XB-70 development programme: http://www.boeing.com/history/products/xb-70-valkyrie.page

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6035
  • Everyplaceelse
  • Liked: 780
  • Likes Given: 4853
Re: Titanium Falcon
« Reply #32 on: 08/23/2017 07:17 PM »
Actually they are XB-70A's the original XB-70 programme ended when the B-70 programme was cancelled. XB-70A research programme replaced the XB-70 development programme: http://www.boeing.com/history/products/xb-70-valkyrie.page
Interesting point from that webpage.

The landing gear for the XB70 weighed 5.4 tonnes for a GTOW of 542Klb (which comes to 246363 Kg, not 245,847 )
That means it's 2.197% of GTOW.

That's relevant because the SEI study for the SABRE based TSTO reckoned you needed at least 4% for a similar sized vehicle.

Which demonstrates the difference between (common) state of practice and state of the art (and IIRC the B58 was even lower).

Unfortunately this has limited relevance to a VTOL Titanium rocket, given that a)Most of the XB70A was steel honeycomb and b)the landing legs only deploy on landing, when it will be realistically <10% of stage takeoff weight (probably by quite a wide margin).   :(
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 27018
  • Minnesota
  • Liked: 6910
  • Likes Given: 4872
Re: Titanium Falcon
« Reply #33 on: 08/24/2017 12:27 PM »
Yeah, it's definitely possible to get lower than 4% weight for legs. This is a point HMXHMX often makes.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6035
  • Everyplaceelse
  • Liked: 780
  • Likes Given: 4853
Re: Titanium Falcon
« Reply #34 on: 08/24/2017 04:11 PM »
Yeah, it's definitely possible to get lower than 4% weight for legs. This is a point HMXHMX often makes.
True but that misses the point.

It's basically a time honored heuristic of aircraft design.

But AFAIK there is no equivalent heuristic for VTOL, although I think Armadillo and Masten have both done enough to have some number in mind depending on wheather you want it to stand on them fully fueled or only deploy when the tanks are nearly empty.

That's clearly going to make a big difference to what mass you need to assign given loads.

IDK, for a fully fueled VTO stage 4% might be too low, while for gear that's only going to be needed during it's near empty landing it's grossly high, but by how much?
"Vertical Landing" (as a thing) is not going to go away any time soon.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline envy887

  • Senior Member
  • *****
  • Posts: 2701
  • Liked: 1243
  • Likes Given: 776
Re: Titanium Falcon
« Reply #35 on: 08/24/2017 06:08 PM »
Yeah, it's definitely possible to get lower than 4% weight for legs. This is a point HMXHMX often makes.
True but that misses the point.

It's basically a time honored heuristic of aircraft design.

But AFAIK there is no equivalent heuristic for VTOL, although I think Armadillo and Masten have both done enough to have some number in mind depending on wheather you want it to stand on them fully fueled or only deploy when the tanks are nearly empty.

That's clearly going to make a big difference to what mass you need to assign given loads.

IDK, for a fully fueled VTO stage 4% might be too low, while for gear that's only going to be needed during it's near empty landing it's grossly high, but by how much?
"Vertical Landing" (as a thing) is not going to go away any time soon.

The F9 is about 27 tonnes (or tons?) at landing according Hans K. The legs are about as much as a Model S (about 2,000 kg) according to Elon. So that's between 7.4% and 8.1% of the landing mass, depending on whether Hans meant short or metric tons.

Either way, a lot more than 4%...

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6035
  • Everyplaceelse
  • Liked: 780
  • Likes Given: 4853
Re: Titanium Falcon
« Reply #36 on: 08/24/2017 07:17 PM »
Yeah, it's definitely possible to get lower than 4% weight for legs. This is a point HMXHMX often makes.
True but that misses the point.

It's basically a time honored heuristic of aircraft design.

But AFAIK there is no equivalent heuristic for VTOL, although I think Armadillo and Masten have both done enough to have some number in mind depending on wheather you want it to stand on them fully fueled or only deploy when the tanks are nearly empty.

That's clearly going to make a big difference to what mass you need to assign given loads.

IDK, for a fully fueled VTO stage 4% might be too low, while for gear that's only going to be needed during it's near empty landing it's grossly high, but by how much?
"Vertical Landing" (as a thing) is not going to go away any time soon.

The F9 is about 27 tonnes (or tons?) at landing according Hans K. The legs are about as much as a Model S (about 2,000 kg) according to Elon. So that's between 7.4% and 8.1% of the landing mass, depending on whether Hans meant short or metric tons.

Either way, a lot more than 4%...
Well that's intriguing. Definitely not my instinct would have been. So 7-8+% of gross landing weight.

I'm pretty sure one of the (theoretical) benefits of VL was expected to be it's very low landing gear penalty  compared to the wheeled landing gear on HTOL or VTOHL systems.

This suggests that has not really worked out IRL.  :(

Perhaps the new on deck grabber robot will help?
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Online guckyfan

  • Senior Member
  • *****
  • Posts: 6373
  • Germany
  • Liked: 1605
  • Likes Given: 1408
Re: Titanium Falcon
« Reply #37 on: 08/24/2017 07:59 PM »
Well that's intriguing. Definitely not my instinct would have been. So 7-8+% of gross landing weight.

I'm pretty sure one of the (theoretical) benefits of VL was expected to be it's very low landing gear penalty  compared to the wheeled landing gear on HTOL or VTOHL systems.

This suggests that has not really worked out IRL.  :(

Perhaps the new on deck grabber robot will help?

The dry mass penalty for horizontal landing is the added structural mass needed for different load paths and the wings. In total much more mass, even if the landing gear itself would be lighter.

Offline livingjw

  • Full Member
  • **
  • Posts: 292
  • Liked: 284
  • Likes Given: 126
Re: Titanium Falcon
« Reply #38 on: 08/24/2017 11:49 PM »
That much weight for the landing gear just seems way to high. Just my opinion.

John

Offline Apollo100

  • Member
  • Posts: 25
  • Liked: 0
  • Likes Given: 0
Re: Titanium Falcon
« Reply #39 on: 08/25/2017 01:28 AM »
No comments yet about the ability/complexities to FSW Ti?

Offline envy887

  • Senior Member
  • *****
  • Posts: 2701
  • Liked: 1243
  • Likes Given: 776
Re: Titanium Falcon
« Reply #40 on: 08/25/2017 01:54 AM »
That much weight for the landing gear just seems way to high. Just my opinion.

John

He did say "less than a Model S", but that has to be the right ballpark for a comparison. The legs are quite large.

https://twitter.com/elonmusk/status/330054002148515841

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 27018
  • Minnesota
  • Liked: 6910
  • Likes Given: 4872
Re: Titanium Falcon
« Reply #41 on: 08/25/2017 03:42 AM »
The legs are really long. That's why they weigh a lot. A squatter stage could use shorter and more efficient legs.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6035
  • Everyplaceelse
  • Liked: 780
  • Likes Given: 4853
Re: Titanium Falcon
« Reply #42 on: 08/25/2017 01:58 PM »
The legs are really long. That's why they weigh a lot. A squatter stage could use shorter and more efficient legs.
Good point.

That's what happens when you try to turn something that's not designed to carry out a task into something that can do it, rather than go with a clean sheet approach.

Good thing the "exchange rate" between stage dry mass and payload mass lost is so high for first stages, otherwise SX could have been in real trouble.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 6035
  • Everyplaceelse
  • Liked: 780
  • Likes Given: 4853
Re: Titanium Falcon
« Reply #43 on: 08/25/2017 02:07 PM »
No comments yet about the ability/complexities to FSW Ti?
Not a showstopper Researched since at least 1995

http://www.twi-global.com/technical-knowledge/published-papers/friction-stir-welding-of-titanium-alloys-a-progress-update/

Titanium is also extremely amenable to diffusion Bonding as the protective oxide can be dissolved by the metal.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Tags: