SpaceX Starship/Super Heavy Engineering General Thread 4

[Chris Bergin]

New thread (Thread 4)

Thread 1:
Starship (BFS) Engineering Thread (#dearMoon edition + Musk Stainless Update)
https://forum.nasaspaceflight.com/index.php?topic=46395.0

Thread 2:
https://forum.nasaspaceflight.com/index.php?topic=47052.0

Thread 3:
https://forum.nasaspaceflight.com/index.php?topic=48757.0

L2 Section - intense level:
https://forum.nasaspaceflight.com/index.php?board=60.0

Be on topic. Don't wander into areas already covered on other threads and make sure your post is useful.

[aameise9]

Here is question that has, to the best of my knowledge, not yet been discussed on this thread.

Is it self-evident that a stainless steel skin -- without internal stringers, internal rings, or similar reinforcing structures -- will be sufficient to carry the various loads experienced by Spaceship and Super Heavy?

If reinforcements should be needed, how could they be attached without weakening the cold rolled skin and without large and costly equipment?

Apologies if this question (by a biologist) is overly naive! 

[Eka]

If reinforcements should be needed, how could they be attached without weakening the cold rolled skin and without large and costly equipment?

Any weld will do some weakening. The amount of weld spots needed shouldn't be that high so it easily should be able to be kept under 10%.

I'd use staggered spot welds. A relatively large ground pressure plate could be clamped to the outside of the general area where the spot weld will be, then the source electrode pushed against the interior and triggered. Do that once each at the bottom and top of a brace. They will provide alignment for the rest of the welds along the brace which can be done using the normal blunt point probes.

Another possibility would be to use plug welds. One cuts small holes into the brace. Then the inside of the hole is lap welded to the skin. Again each weld does some weakening, but overall there aren't enough of them to weaken the skin too much. Google "plug weld" to find out more.

[su27k]

This new job opening for FLIGHT OPERATIONS ENGINEER (STARSHIP) at Brownsville, TX mentioned the following design goal for Starship:

Drive development towards power on to launch in less than one hour with zero operators on console

Not quite sure what this entails though.

[testguy]

This new job opening for FLIGHT OPERATIONS ENGINEER (STARSHIP) at Brownsville, TX mentioned the following design goal for Starship:

Drive development towards power on to launch in less than one hour with zero operators on console

Not quite sure what this entails though.

I took it to mean just like an airliner but without air traffic control.

[AC in NC]

This new job opening for FLIGHT OPERATIONS ENGINEER (STARSHIP) at Brownsville, TX mentioned the following design goal for Starship:

Drive development towards power on to launch in less than one hour with zero operators on console

Not quite sure what this entails though.

Remote, and perhaps fully automated vs. just site-automated, power-up, systems validations, fueling and launch within 60 mins.

[Eka]

This new job opening for FLIGHT OPERATIONS ENGINEER (STARSHIP) at Brownsville, TX mentioned the following design goal for Starship:

Drive development towards power on to launch in less than one hour with zero operators on console

Not quite sure what this entails though.

Remote, and perhaps fully automated vs. just site-automated, power-up, systems validations, fueling and launch within 60 mins.

Yes, full automation of the entire fueling and launch process with no need for human intervention or monitoring. This is what is needed to have a streamlined facility that can launch a number of craft in short succession. With multiple launch pads one can drastically reduce time from first launch to TLI or TMI. The ground crews stack SH+SS on each pad, and then the SS+SH wait. Once all are stacked, the ground crews clear out. At the right time they all start fueling and launch very close together. Because they launched so close they can quickly get together and transfer fuel once in orbit. They don't have to spend much time or fuel chasing each other down. Once the SH have all returned, the ground crews can move in and start stacking the next set. Ground crews will also need to clear out when the SS return.

I don't think this will initially include stacking of SH on launch pad and SS on SH, but who knows. Automated stacking allows stacking to happen when launch operations are happening. That gets people away from the launch pads and landing pads. I can see automated tugs picking up a SS just after it landed and moving it to a terminal for passenger unloading, and reloading, or moving it to the cargo depot. The tugs will then bring the SS back to the launch tower for automated stacking on a readied SH. This means operations can go on at all times at the terminals and cargo depot because they are away from the launch and landing facilities. Also the launch facilities don't need crews that would need to be evacuated during launches and landings.

[Eka]

This new job opening for FLIGHT OPERATIONS ENGINEER (STARSHIP) at Brownsville, TX mentioned the following design goal for Starship:

Drive development towards power on to launch in less than one hour with zero operators on console

Not quite sure what this entails though.

Remote, and perhaps fully automated vs. just site-automated, power-up, systems validations, fueling and launch within 60 mins.

Yes, full automation of the entire fueling and launch process with no need for human intervention or monitoring. This is what is needed to have a streamlined facility that can launch a number of craft in short succession. With multiple launch pads one can drastically reduce time from first launch to TLI or TMI. The ground crews stack SH+SS on each pad, and then the SS+SH wait. Once all are stacked, the ground crews clear out. At the right time they all start fueling and launch very close together. Because they launched so close they can quickly get together and transfer fuel once in orbit. They don't have to spend much time or fuel chasing each other down. Once the SH have all returned, the ground crews can move in and start stacking the next set. Ground crews will also need to clear out when the SS return.

I don't think this will initially include stacking of SH on launch pad and SS on SH, but who knows. Automated stacking allows stacking to happen when launch operations are happening. That gets people away from the launch pads and landing pads. I can see automated tugs picking up a SS just after it landed and moving it to a terminal for passenger unloading, and reloading, or moving it to the cargo depot. The tugs will then bring the SS back to the launch tower for automated stacking on a readied SH. This means operations can go on at all times at the terminals and cargo depot because they are away from the launch and landing facilities. Also the launch facilities don't need crews that would need to be evacuated during launches and landings.

[Nomadd]

I wonder if that last pressure test on MK1 was fully automated.

[meekGee]

I wonder if that last pressure test on MK1 was fully automated.

I believe the pressure relief system was.

[Jcc]

Somewhat random question:

Starship design shows deployable and retractable solar arrays near the aft. Great idea, but yet to be proven. What is the likelihood in the near term of using surface mounted solar arrays on the leeward side, similar to (same as) the arrays on Dragon-2 trunk?

That way, for cislunar ops they have a viable power source without needing to deploy anything, and even landing on the moon or Mars, if they land with that side facing the sun, they have some power prior to deployment of arrays on the surface.

[OneSpeed]

Somewhat random question:

Starship design shows deployable and retractable solar arrays near the aft. Great idea, but yet to be proven. What is the likelihood in the near term of using surface mounted solar arrays on the leeward side, similar to (same as) the arrays on Dragon-2 trunk?

That way, for cislunar ops they have a viable power source without needing to deploy anything, and even landing on the moon or Mars, if they land with that side facing the sun, they have some power prior to deployment of arrays on the surface.

The Dragon2 trunk is designed to survive ascent to LEO, but not Earth re-entry (or Mars entry). The stainless steel leeward side of Starship would survive in that (~500°C) environment, but existing solar panel designs would be destroyed.

However, for a one-way (cargo?) trip to the moon, the ceramic thermal tiles would be unnecessary. Perhaps photo-voltaic devices could be mounted in their place, or even around the full circumference of the fuselage?

[su27k]

I just noticed from @Avron_p's hopper tweet that they removed the TPS tiles from the hopper and left the support structure for the tiles exposed. The following is cropped from bocachicagal's photos, seems that each tile is supported by 3 bolts, corresponding to the 3 holes on the tile.

[codav]

The following is cropped from bocachicagal's photos, seems that each tile is supported by 3 bolts, corresponding to the 3 holes on the tile.

I'm quite sure this way of mounting the heat shield tiles won't be the final method. While it works and allows for quickly attaching and detaching the tiles, the holes actually create weak spots in the tile, will probably add tension due to different thermal expansion coefficients of the tiles and the underlying steel structure and also trap some of the super heated plasma inside the cavity, probably melting the bolt.

[geza]

The following is cropped from bocachicagal's photos, seems that each tile is supported by 3 bolts, corresponding to the 3 holes on the tile.

I'm quite sure this way of mounting the heat shield tiles won't be the final method. While it works and allows for quickly attaching and detaching the tiles, the holes actually create weak spots in the tile, will probably add tension due to different thermal expansion coefficients of the tiles and the underlying steel structure and also trap some of the super heated plasma inside the cavity, probably melting the bolt.

You may want to plug the holes with the tile material.

[Proesterchen]

Somewhat random question:

Starship design shows deployable and retractable solar arrays near the aft. Great idea, but yet to be proven. What is the likelihood in the near term of using surface mounted solar arrays on the leeward side, similar to (same as) the arrays on Dragon-2 trunk?

That way, for cislunar ops they have a viable power source without needing to deploy anything, and even landing on the moon or Mars, if they land with that side facing the sun, they have some power prior to deployment of arrays on the surface.

It would appear to me that solar arrays mounted to the hull would be of limited use, as they would force the vessel into an undesirable attitude during travel, with either the TPS or the crew more exposed than necessary and constant insolation of the windowed crew compartment less than ideal from a crew safety, thermal management and I suppose tourism standpoint.

[livingjw]

The following is cropped from bocachicagal's photos, seems that each tile is supported by 3 bolts, corresponding to the 3 holes on the tile.

I'm quite sure this way of mounting the heat shield tiles won't be the final method. While it works and allows for quickly attaching and detaching the tiles, the holes actually create weak spots in the tile, will probably add tension due to different thermal expansion coefficients of the tiles and the underlying steel structure and also trap some of the super heated plasma inside the cavity, probably melting the bolt.

I disagree. To me this seems a good approach.

- The tiles have an outer covering for strength and toughness. Inside is insulation.

- Without knowing how the tile shell is designed, you can't say the holes will cause weak spots. They didn't just drill holes in the tile shell. I am sure they are designed to handle the loads.

- Thermal expansion was surely taken into consideration when engineering the fasteners and attachment. Why would they not?

- Attachment points are recessed and can be easily plugged with insulating material.

John

[Wolfram66]

The following is cropped from bocachicagal's photos, seems that each tile is supported by 3 bolts, corresponding to the 3 holes on the tile.

I'm quite sure this way of mounting the heat shield tiles won't be the final method. While it works and allows for quickly attaching and detaching the tiles, the holes actually create weak spots in the tile, will probably add tension due to different thermal expansion coefficients of the tiles and the underlying steel structure and also trap some of the super heated plasma inside the cavity, probably melting the bolt.

I disagree. To me this seems a good approach.

- The tiles have an outer covering for strength and toughness. Inside is insulation.

- Without knowing how the tile shell is designed, you can't say the holes will cause weak spots. They didn't just drill holes in the tile shell. I am sure they are designed to handle the loads.

- Thermal expansion was surely taken into consideration when engineering the fasteners and attachment. Why would they not?

- Attachment points are recessed and can be easily plugged with insulating material.

John

John,
If you inspect the left most tile from image above, you can see that it has fractured between the 3 bolt holes used to affix the tile.

[livingjw]

The following is cropped from bocachicagal's photos, seems that each tile is supported by 3 bolts, corresponding to the 3 holes on the tile.

I'm quite sure this way of mounting the heat shield tiles won't be the final method. While it works and allows for quickly attaching and detaching the tiles, the holes actually create weak spots in the tile, will probably add tension due to different thermal expansion coefficients of the tiles and the underlying steel structure and also trap some of the super heated plasma inside the cavity, probably melting the bolt.

I disagree. To me this seems a good approach.

- The tiles have an outer covering for strength and toughness. Inside is insulation.

- Without knowing how the tile shell is designed, you can't say the holes will cause weak spots. They didn't just drill holes in the tile shell. I am sure they are designed to handle the loads.

- Thermal expansion was surely taken into consideration when engineering the fasteners and attachment. Why would they not?

- Attachment points are recessed and can be easily plugged with insulating material.

John

John,
If you inspect the left most tile from image above, you can see that it has fractured between the 3 bolt holes used to affix the tile.

Hard to tell. Perhaps.

John

[Zpoxy]

The following is cropped from bocachicagal's photos, seems that each tile is supported by 3 bolts, corresponding to the 3 holes on the tile.

I'm quite sure this way of mounting the heat shield tiles won't be the final method. While it works and allows for quickly attaching and detaching the tiles, the holes actually create weak spots in the tile, will probably add tension due to different thermal expansion coefficients of the tiles and the underlying steel structure and also trap some of the super heated plasma inside the cavity, probably melting the bolt.

I disagree. To me this seems a good approach.

- The tiles have an outer covering for strength and toughness. Inside is insulation.

- Without knowing how the tile shell is designed, you can't say the holes will cause weak spots. They didn't just drill holes in the tile shell. I am sure they are designed to handle the loads.

- Thermal expansion was surely taken into consideration when engineering the fasteners and attachment. Why would they not?

- Attachment points are recessed and can be easily plugged with insulating material.

John

John,
If you inspect the left most tile from image above, you can see that it has fractured between the 3 bolt holes used to affix the tile.

That feature looks too uniform to have just "fractured", it looks intentional.