Author Topic: SpaceX Dragon 2 Updates and Discussion - Thread 3 (Read 815108 times)

jpo234 · « **Reply #1540 on:** 09/02/2021 10:26 am »

Cupola question: Do they bring it back (closing the nose cone) or do they dump it before reentry (like the trunk)?

EspenU · « **Reply #1541 on:** 09/02/2021 11:06 am »

Quote from: jpo234 on 09/02/2021 10:26 am

Cupola question: Do they bring it back (closing the nose cone) or do they dump it before reentry (like the trunk)?

They close it to protect from reentry.

thebraylonwilliams · « **Reply #1542 on:** 09/02/2021 07:46 pm »

What Dragon serial number is this? Is there plans to use the cupola again for another tourism mission?

pospa · « **Reply #1543 on:** 09/03/2021 07:06 am »

Do we know what transparent material Copola's is made of?
Could it be the same material as the visors of spacesuits?

docmordrid · « **Reply #1544 on:** 09/03/2021 07:18 am »

Quote from: thebraylonwilliams on 09/02/2021 07:46 pm

What Dragon serial number is this? Is there plans to use the cupola again for another tourism mission?

Resilience is C207.

Nothing firm, but I'd be shocked if they didn't use it for the Space Adventures mission to exceed Gemini 11's LEO altitude record.

cube · « **Reply #1545 on:** 09/12/2021 02:13 am »

Hello I believe the crew dragon capsule has an offset center of mass to generate lift during atmospheric reentry but what I was wondering is how they maintain the center of thrust through the capsule's center of mass during maneuvers in space (to prevent the capsule from turning during the thrust) for example maneuvers to allow re-entry?

matthewkantar · « **Reply #1546 on:** 09/12/2021 02:47 am »

I believe the vehicles batteries are on a moveable ballast sled.

cube · « **Reply #1547 on:** 09/12/2021 01:31 pm »

Is this system used on other spacecraft? For example on the future orion ship which system will be used?

gongora · « **Reply #1548 on:** 09/12/2021 02:57 pm »

Quote from: matthewkantar on 09/12/2021 02:47 am

I believe the vehicles batteries are on a moveable ballast sled.

I don't think that's true any more. It was an early concept for Dragon 2.

Jorge · « **Reply #1549 on:** 09/12/2021 05:07 pm »

Quote from: cube on 09/12/2021 02:13 am

Hello I believe the crew dragon capsule has an offset center of mass to generate lift during atmospheric reentry but what I was wondering is how they maintain the center of thrust through the capsule's center of mass during maneuvers in space (to prevent the capsule from turning during the thrust) for example maneuvers to allow re-entry?

Offset mass center for lifting entry is nothing new and goes all the way back to Gemini and Apollo. And includes Cargo Dragon, so it's nothing new to SpaceX either.

The *general* solution to this control problem is also nothing new. For vehicles with separable crew modules and service modules, the service module systems can be arranged to offset the mass center in the opposite direction as the crew module to move the composite mass center closer to the centerline. Thruster-selection algorithms are designed to counteract the effects of an offset mass center, within limits, at the cost of additional prop usage. Likewise, vehicles with gimballed engines can adjust for an offset mass center within limits. These limits are usually expressed as a "box" during the design phase and then during the verification phase the vehicle is certified to be stable and controllable with acceptable prop usage as long as the mass center is maintained within that box. Mission planners must arrange crew/cargo appropriately and account for all plausible contingency scenarios of "no deploy/no return" of cargo to ensure the mass center remains within the certified box.

I don't know the *specific* solution SpaceX chose for Dragon. I'd be surprised if it didn't contain most, if not all (except the gimballing, of course), aspects of the general solution.

su27k · « **Reply #1550 on:** 09/13/2021 03:46 am »

Quote from: matthewkantar on 09/12/2021 02:47 am

I believe the vehicles batteries are on a moveable ballast sled.

The sled seems to be removed along with propulsive landing capability, see discussion starting from here: https://forum.nasaspaceflight.com/index.php?topic=41016.msg1765085#msg1765085

Jim's response: https://forum.nasaspaceflight.com/index.php?topic=41016.msg1765116#msg1765116

Robotbeat's response: https://forum.nasaspaceflight.com/index.php?topic=41016.msg1765892#msg1765892, https://forum.nasaspaceflight.com/index.php?topic=41016.msg1777353#msg1777353

snotis · « **Reply #1551 on:** 09/13/2021 11:13 pm »

Instead of a moveable sled - they rotate the capsule during re-entry to change the lift vector which enables you to steer it. Elon explains in this video at 41:38:

cohberg · « **Reply #1552 on:** 09/17/2021 01:41 am »

It looks like the external camera for the cupola is simply a repositioned Peripheral Target Camera with a wider lens (~220°)

The peripheral target camera is unneeded for I4 as there are no docking events. The current perspective of the camera (with the forward bulkhead draco shields as reference points for where the dracos are) matches the former location of the peripheral target camera exactly.

This is such a simple change rather than adding a new camera (with all its associated needs / changes).

woods170 · « **Reply #1553 on:** 09/17/2021 06:30 am »

Quote from: cohberg on 09/17/2021 01:41 am

It looks like the external camera for the cupola is simply a repositioned Peripheral Target Camera with a wider lens.

The peripheral target camera is unneeded for I4 as there are no docking events. The current perspective of the camera (with the forward bulkhead draco shields as reference points for where the dracos are) matches the former location of the peripheral target camera exactly.

This is such a simple change rather than adding a new camera (with all its associated needs / changes).

I think you nailed it. Good sleuthing.

nacnud · « **Reply #1554 on:** 09/17/2021 07:27 am »

Quote from: snotis on 09/13/2021 11:13 pm

Instead of a moveable sled - they rotate the capsule during re-entry to change the lift vector which enables you to steer it. Elon explains in this video at 41:38

Rotating a spacecraft with an offset centre of mass is not the same as changing the location of the centre of mass with a movable sled.

I think the latter was to be used for fine control while under thrust from the super dracos, especially when at low altitudes.

Dragon would need both to be able to make a controlled, precise targeted landing on a pad with super dracos.

snotis · « **Reply #1555 on:** 09/17/2021 08:40 am »

I agree they are not the same (I did not claim they were). SpaceX descoped / removed / never fully developed the ability to land with the SuperDracos - so they no longer needed the finer control that comes with using a movable sled so that got removed as well.

Quote from: nacnud on 09/17/2021 07:27 am

Quote from: snotis on 09/13/2021 11:13 pm
Instead of a moveable sled - they rotate the capsule during re-entry to change the lift vector which enables you to steer it. Elon explains in this video at 41:38

Rotating a spacecraft with an offset centre of mass is not the same as changing the location of the centre of mass with a movable sled.

I think the latter was to be used for fine control while under thrust from the super dracos, especially when at low altitudes.

Dragon would need both to be able to make a controlled, precise targeted landing on a pad with super dracos.

abaddon · « **Reply #1556 on:** 09/18/2021 06:04 pm »

Previously, the only reason for the forward hatch to open was to ingress the station. So reducing internal volume wasn’t much of a consideration, I’d assume.

Star One · « **Reply #1557 on:** 09/18/2021 07:38 pm »

A poster on the Inspiration4 discussion thread mentioned in passing that a private customer was looking to fly a flight that exceeded the altitude of the highest Gemini flight. I am guessing this would be with Dragon 2. The only thing is I thought the Inspiration4 mission was already at the maximum safe altitude for Drsgon 2?

cohberg · « **Reply #1558 on:** 09/18/2021 08:18 pm »

So many little details for this flight...

Looks like SpaceX added an extension plate to the footrest to decrease Hayley's knee bend angle when seated.

I'm assuming that its to help lower the stress on the prosthetic during launch and landing.

Jarnis · « **Reply #1559 on:** 09/18/2021 10:19 pm »

Quote from: cohberg on 09/18/2021 04:53 pm

It looks like the crew were understandably choosing to stow the fwd hatch in the closed position to maximise space in the cabin. The hatch really intrudes into the usable space in the cabin.

Also, it blocks the toilet.