Author Topic: SpaceX Starship (BFS) Engineering General Thread 2  (Read 252913 times)

Online lamontagne

  • Full Member
  • ****
  • Posts: 1576
  • Liked: 2035
  • Likes Given: 330
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1300 on: 04/14/2019 06:49 pm »
After seeing the telescope in the Starship, and thinking about the self manoeuvering capacities of the Falcon 9 fairing when they returned to land after the Falcon Heavy launch, I wonder if the Starship gator will not rather have a free flying hatch, that flies away then returns after the cargo has been sent away?
The space shuttle bay doors could be entirely removed, after all.
Great way to lose a Stargator when the redocking fails.
Why should it fail?  What could go wrong?
Why it this different from docking to the ISS?
Is there a hinge showing in the telescope picture?

Offline spacenut

  • Senior Member
  • *****
  • Posts: 2692
  • East Alabama
  • Liked: 529
  • Likes Given: 287
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1301 on: 04/14/2019 06:51 pm »
Liquid hydrogen is much colder than liquid methane or oxygen.  On earth we stored liquid natural (95%+ methane) gas in a double wall steel tank pulling a vacuum in between.   It was a giant thermos bottle.  It kept us from having boil off.  The looked like giant water towers on the ground.   Shouldn't be a problem if the fill it like F9/FH quickly before launch.  Space is cold stainless steel will reflect sunlight and Starship will also have solar panels deploy.  The solar panels could be designed to shade the Starship in space or they could fly with engines pointed toward the sun.   
« Last Edit: 04/14/2019 06:52 pm by spacenut »

Offline Keldor

  • Member
  • Posts: 65
  • Colorado
  • Liked: 59
  • Likes Given: 8
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1302 on: 04/14/2019 06:55 pm »
After seeing the telescope in the Starship, and thinking about the self manoeuvering capacities of the Falcon 9 fairing when they returned to land after the Falcon Heavy launch, I wonder if the Starship gator will not rather have a free flying hatch, that flies away then returns after the cargo has been sent away?
The space shuttle bay doors could be entirely removed, after all.
Great way to lose a Stargator when the redocking fails.
Why should it fail?  What could go wrong?
Why it this different from docking to the ISS?
Is there a hinge showing in the telescope picture?
All technical engineering concerns aside, what benefit would such a system have over just using a hinge?
« Last Edit: 04/14/2019 06:56 pm by Keldor »

Online lamontagne

  • Full Member
  • ****
  • Posts: 1576
  • Liked: 2035
  • Likes Given: 330
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1303 on: 04/14/2019 09:52 pm »
After seeing the telescope in the Starship, and thinking about the self manoeuvering capacities of the Falcon 9 fairing when they returned to land after the Falcon Heavy launch, I wonder if the Starship gator will not rather have a free flying hatch, that flies away then returns after the cargo has been sent away?
The space shuttle bay doors could be entirely removed, after all.
Great way to lose a Stargator when the redocking fails.
Why should it fail?  What could go wrong?
Why it this different from docking to the ISS?
Is there a hinge showing in the telescope picture?
All technical engineering concerns aside, what benefit would such a system have over just using a hinge?
It should be easier to remove stuff from inside the Starship.  Elements can be removed by motion on a single 'horizontal' axis, that will be the same as the loading axis.  While otherwise we need a support base than can be angled so the payload can be removed at an angle.  This seems doable in zero G though. 
I guess the hinge could open at 90 degrees or more, then the reasoning here would not be valid.

A hinge probably needs to be removable on the ground (perhaps not that difficult) for easy vertical loading of the Starship. 

The hatch will need to have a large number of attachment points if the inside of the Spaceship can be pressurized (Shotwell mentioned this as a probable feature).  A hatch with many attachment points also increases the rigidity of the ship at re-entry time.  So the hinge, in a way, is just another attachment point, that needs some kind of torquing mechanism.

All in all, a hinge seems simpler.  Guess this one can go into the bad idea file  :-)

Online OxCartMark

  • Full Member
  • ****
  • Posts: 1541
  • Former barge watcher now into water towers
  • Michigan
  • Liked: 1638
  • Likes Given: 1187
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1304 on: 04/15/2019 01:30 am »
Terrifyingly, it does not appear to be a joke.

https://twitter.com/elonmusk/status/1117581094415503360

Quote
With steel membrane wings like a Dragon, we may be able to lower Starship’s orbital reentry temp to ~1000 degrees C, which would allow the whole surface to be uncooled bare metal.

The picture that pops into my head is that of a large Chinese fan on either side that folds out to increase surface area and to allow roll control by varying the area of the wing on each side.  Substitute stainless sheet in for paper in this case.  Not well thought out but that's the picture that pops into my head in reaction to these words.

An alternative somewhat similar thought would be to go back to Frances Rogalo's semi-rigid hang glider style of wing that he proposed for recovering 1960s space capsules but to cover it with stainless sheet or stainless cloth instead of polyester or nylon.  That would be deployed before re-entry in this case and would be flown down to ~5km then dropped to disposal (!) and the rest of the landing completed on Raptor retro.

It seems from his tweet that the design still has a lot of fluidity to it, even though its being built now they're still at the whiteboard phase with parts of it and throwing things onto the twitter wall to see what sticks.

Offline Twark_Main

  • Member
  • Posts: 65
  • Technically we ALL live in space...
  • Liked: 28
  • Likes Given: 5
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1305 on: 04/15/2019 03:01 am »
Quote
lower Starship’s orbital reentry temp to ~1000 degrees C

How does ballistic coefficient vs. heating scale? Can this temperature delta be used to roughly estimate how big the "giant" wings must be?

The steel membrane seems to maximize drag area per kg, while maintaining full and rapid reuse (which disqualifies inflatables). I like the Chinese fan but propose an alternative: parallel tapered steel spars that curl up against the vehicle during launch (mechanism TBD) and remain slightly curved even when deployed. This layout increases the front-shell curvature radius too, further reducing hypersonic heating.

A hybrid body+wing hot structure has fundamental physics advantages over a body-only hot structure. Steel membranes radiate from both sides (doubling power density) while giving extra radiator area .
« Last Edit: 04/15/2019 03:02 am by Twark_Main »

Offline kkattula

  • Member
  • Senior Member
  • *****
  • Posts: 2524
  • Melbourne, Australia
  • Liked: 30
  • Likes Given: 8
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1306 on: 04/15/2019 03:29 am »
In-transit to/from Mars, all of the propellant should be in the header tanks, hidden from direct sunlight. The main tanks could be evacuated for extra insulation.

How they deal with CO2 ice build up on the tanks while ISRU refueling on Mars is another question. Rather than build insulation into the tanks, they could just carry insulating blankets on the StarShip carrying the ISRU equipment, and rig them on the outside in situ. 

Or just not worry about ice build up. It seems reasonable one of the uncrewed pre-cursor missions will be to land an ISRU propellant plant, to start making return propellant. If it's going to stay there and act a s storage facility, does it matter if the tanks are covered in dry ice?  Assuming the weight isn't too great.

Offline RobLynn

  • Full Member
  • ****
  • Posts: 487
  • Per Molestias Eruditio
  • NZ
  • Liked: 249
  • Likes Given: 145
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1307 on: 04/15/2019 03:53 am »
Problem with dragon-wings is the additional heavy structure required to support them and high heat loadings of sharp leading edges.  But if starship was fundamentally changed into a cluster of 2 or 3 long tank-bodies that were linked together at nose and pivoted with respect to each other then a huge roll-up sheet membrane surface could be slung between them utilising the tanks as the kite/rogallo wing structure without taking a large weight penalty, and large diameter tanks at leading edges of wing would limit the high localised heating of those edges.
The glass is neither half full nor half empty, it's just twice as big as it needs to be.

Offline geza

  • Full Member
  • ***
  • Posts: 302
  • Budapest
    • Géza Meszéna's web page
  • Liked: 130
  • Likes Given: 38
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1308 on: 04/15/2019 05:27 am »
There are no sharp leading edges. As Elon explained in his DearMoon lecture, SS will enter perpendicular to the air flow. No lift is needed, only deceleration. If the Dragon Wing is completely flat, it can be launched without curling up, or anything. It is just a large plane parallel to the main axis of the spacecraft. Nevertheless, some complications will be needed for aerodynamic stability. Some kind of actuated wing-tips?

 

Online meekGee

  • Senior Member
  • *****
  • Posts: 9359
  • N. California
  • Liked: 5687
  • Likes Given: 959
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1309 on: 04/15/2019 05:45 am »
not about wings:

Just watched this:


Gorgeous footage of rocket assembly, dirt-simple launch ops, portable flame deflectors...

25:00 is a good place to visit.
« Last Edit: 04/15/2019 05:45 am by meekGee »
ABCD - Always Be Counting Down

Offline rsdavis9

Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1310 on: 04/15/2019 12:41 pm »
The space shuttle bay doors could be entirely removed, after all.

The Space Shuttle doors weren't removed in flight, just hinged outward. You're idea while nerdy cool would require lots of over engineering, needing thrusters, guidance, it's own computer... Space X follow KISS (keep it simple stupid). A hinged comper and a hinged payload mount is what we will see.

However I agree with guckyfan on the ground loading payloads that door is going to be a problem if it's not removed. But we'll see, leave it to Space X to push the envelope and surprise us.

Hinge it a the nose. Still plenty big enough to eject big payloads in orbit. Opens upwards so it doesn't get in the way on ground loading/unloading.
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Online rakaydos

  • Full Member
  • ****
  • Posts: 890
  • Liked: 363
  • Likes Given: 9
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1311 on: 04/15/2019 12:58 pm »
Dragonwings really arnt the right model for steel brakerons. In order to fold, they need to be segmented. Like Falcon Feathers.

Offline jak Kennedy

  • Full Member
  • *
  • Posts: 164
  • Liked: 50
  • Likes Given: 46
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1312 on: 04/15/2019 01:18 pm »
re Dragonwings. Perhaps first we need to know the additional area needed to get the surface temp below 1,000C. And there may be small areas allowed to go above 1,000C but with shielding or cooling.

Offline jak Kennedy

  • Full Member
  • *
  • Posts: 164
  • Liked: 50
  • Likes Given: 46
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1313 on: 04/15/2019 01:25 pm »
re the doors. There could be an extra longitudinal hinge in the center of each door. (more folds)

edit: like the space shuttle doors but with an extra fold/hinge running longitudinally so each door does not fold out as much.
« Last Edit: 04/15/2019 02:38 pm by jak Kennedy »

Offline joncz

  • Veteran
  • Full Member
  • ****
  • Posts: 404
  • Atlanta, Georgia
  • Liked: 116
  • Likes Given: 181
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1314 on: 04/15/2019 01:48 pm »
Terrifyingly, it does not appear to be a joke.

https://twitter.com/elonmusk/status/1117581094415503360

Quote
With steel membrane wings like a Dragon, we may be able to lower Starship’s orbital reentry temp to ~1000 degrees C, which would allow the whole surface to be uncooled bare metal.

The picture that pops into my head is that of a large Chinese fan on either side that folds out to increase surface area and to allow roll control by varying the area of the wing on each side.  Substitute stainless sheet in for paper in this case.  Not well thought out but that's the picture that pops into my head in reaction to these words.

Somebody say frilled dragon?

« Last Edit: 04/15/2019 01:49 pm by joncz »

Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1315 on: 04/15/2019 01:51 pm »
Hinge it a the nose. Still plenty big enough to eject big payloads in orbit. Opens upwards so it doesn't get in the way on ground loading/unloading.

However that is not how it's being depicted by SpaceX. Hinge is toward the tail.

I honestly think the space shuttle door design is the best, spit and fold outward to the sides. Easiest way in a gravity well to do it, especially if loaded vertically. The chomper is a cool design but I don't see it as practical for loading a payload, they are going to have to remove it every time.

But what do I know, not an engineer just a fan boy.

Offline Keldor

  • Member
  • Posts: 65
  • Colorado
  • Liked: 59
  • Likes Given: 8
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1316 on: 04/15/2019 02:09 pm »
The space shuttle bay doors could be entirely removed, after all.

The Space Shuttle doors weren't removed in flight, just hinged outward. You're idea while nerdy cool would require lots of over engineering, needing thrusters, guidance, it's own computer... Space X follow KISS (keep it simple stupid). A hinged comper and a hinged payload mount is what we will see.

However I agree with guckyfan on the ground loading payloads that door is going to be a problem if it's not removed. But we'll see, leave it to Space X to push the envelope and surprise us.

Hinge it a the nose. Still plenty big enough to eject big payloads in orbit. Opens upwards so it doesn't get in the way on ground loading/unloading.

The thing's literally the size of a house.  Even the Falcon 9 fairing is big enough to hold a school bus inside.  I would be very uncomfortable working with something like that suspended above my head.

If the hinge were on the bottom of the fairing, and it opened 90 degrees or more, then for loading you could just have your access bridge go above the open fairing, keeping it nicely out of the way, and giving you options for tying it off to the underside of the bridge and the access tower so it doesn't blow around in the wind, which I suspect could be quite destructive otherwise.

Though it all also depends on if they go for horizontal or vertical integration.  There are pros and cons to each one.

Horizontal integration, the bottom of the fairing is the exact worst place for the hinges.  Here you'd want them either on the top or on the sides, depending on floor space and ceiling height constraints.  Vertical integration you'd probably want hinges on the sides or the bottom so it can open beneath the work area, or at least off to the side.  This means that side hinges are the most versatile, allowing for both.

Since the only time it would be opened under the spacecraft's own power and without a support line from above happens in zero gravity during deployment, engineering the mechanism attaching the door to the actuating motor no matter where it's attached is less of a problem since if you just open and close it slowly, torque is minimized.  It also makes lining up the edges and latches when closing it easier since it won't be flopping about like it will on the ground.

Closing it again might still be a real headache due to its length.  It will need to precisely line up.

Another option is to have the nose tip open, with the payload bay a cylinder like a gun barrel.  Payload just goes straight out the top.  This minimizes edge length, which makes closing the thing again simpler.  The downside is that the door seam will cross over the heatshield, which is its own problem, especially since the nose tip is very likely to be a hot spot that will need plumbing for transpirational cooling.  You might be able to get away with a flexible pipe to bridge the hinge area, though.  Corrugated silicone pipes?

Online docmordrid

  • Senior Member
  • *****
  • Posts: 5450
  • Michigan
  • Liked: 2839
  • Likes Given: 1
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1317 on: 04/15/2019 03:16 pm »
WRT the header tanks; are we sure they'd be metal?

There are cryo-polymers,

Link...

and a few hours ago Musk  "liked" a World of Engineering tweet about large blow-molded tanks

https://twitter.com/engineers_feed/status/1117646518121578497
« Last Edit: 04/15/2019 03:19 pm by docmordrid »
DM

Offline Keldor

  • Member
  • Posts: 65
  • Colorado
  • Liked: 59
  • Likes Given: 8
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1318 on: 04/15/2019 04:11 pm »
WRT the header tanks; are we sure they'd be metal?

There are cryo-polymers,

Link...

and a few hours ago Musk  "liked" a World of Engineering tweet about large blow-molded tanks

<snip>

It's hard to say.  We'd need to see some material data sheets.  There's a big difference between "stronger than regular plastics in cyrogenic conditions" and "comparable to steel in cyrogenic conditions".

Online lamontagne

  • Full Member
  • ****
  • Posts: 1576
  • Liked: 2035
  • Likes Given: 330
Re: SpaceX Starship (BFS) Engineering General Thread 2
« Reply #1319 on: 04/15/2019 04:19 pm »
The space shuttle bay doors could be entirely removed, after all.

The Space Shuttle doors weren't removed in flight, just hinged outward. You're idea while nerdy cool would require lots of over engineering, needing thrusters, guidance, it's own computer... Space X follow KISS (keep it simple stupid). A hinged comper and a hinged payload mount is what we will see.

However I agree with guckyfan on the ground loading payloads that door is going to be a problem if it's not removed. But we'll see, leave it to Space X to push the envelope and surprise us.

Hinge it a the nose. Still plenty big enough to eject big payloads in orbit. Opens upwards so it doesn't get in the way on ground loading/unloading.

The thing's literally the size of a house.  Even the Falcon 9 fairing is big enough to hold a school bus inside.  I would be very uncomfortable working with something like that suspended above my head.

If the hinge were on the bottom of the fairing, and it opened 90 degrees or more, then for loading you could just have your access bridge go above the open fairing, keeping it nicely out of the way, and giving you options for tying it off to the underside of the bridge and the access tower so it doesn't blow around in the wind, which I suspect could be quite destructive otherwise.

Though it all also depends on if they go for horizontal or vertical integration.  There are pros and cons to each one.

Horizontal integration, the bottom of the fairing is the exact worst place for the hinges.  Here you'd want them either on the top or on the sides, depending on floor space and ceiling height constraints.  Vertical integration you'd probably want hinges on the sides or the bottom so it can open beneath the work area, or at least off to the side.  This means that side hinges are the most versatile, allowing for both.

Since the only time it would be opened under the spacecraft's own power and without a support line from above happens in zero gravity during deployment, engineering the mechanism attaching the door to the actuating motor no matter where it's attached is less of a problem since if you just open and close it slowly, torque is minimized.  It also makes lining up the edges and latches when closing it easier since it won't be flopping about like it will on the ground.

Closing it again might still be a real headache due to its length.  It will need to precisely line up.

Another option is to have the nose tip open, with the payload bay a cylinder like a gun barrel.  Payload just goes straight out the top.  This minimizes edge length, which makes closing the thing again simpler.  The downside is that the door seam will cross over the heatshield, which is its own problem, especially since the nose tip is very likely to be a hot spot that will need plumbing for transpirational cooling.  You might be able to get away with a flexible pipe to bridge the hinge area, though.  Corrugated silicone pipes?
I think that whatever hinge is used, bottom, side or top it should be designed for easy removal.  Like a door hinge rod but most sophisticated than a nail and a hammer system :-).  So for vertical integration the door(s) can quickly come right off, using a properly designed spreader and crane arrangement.

The Spacex payload fairing elements look quite robust.  I guess some of that will be leveraged towards making the cargo bay door(s) sufficiently rigid and self adjusting.
How long does it take to add the existing fairing to Falcon 9? Or do they just add the entire nose assembly?

The opening of the space shuttle door was linked to cooling as they also held the radiators.  I still wonder how they plan to cool the Starship for anything but the shortest stays in space.  That seems to be another bit that is on the SpaceX to do list.

Tags: