Reusability, and the Future of Rockets

It’s been a while, but my exams are done and it’s time to get this blog rolling again!

SpaceX successfully executed a “double header”, that is, two launches in a very short period of time.

 

BulgariaSat 1:

The first Falcon 9 that recently launched was for BulgariaSat-1. They opted to use an already-flown Falcon 9 first stage booster, which was used in January this year. The rocket launched successfully on June 23 and landed on one of SpaceX’s Of Course I Still Love You ocean barge.

The launch costs are thus presumably a lot cheaper than if the customer has wanted to use a brand-new Falcon 9, since SpaceX doesn’t need to make a completely new first stage for the rocket.

BulgariaSat-1. Photo Credits: Space Systems/Loral
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Photo Credits: Flickr/SpaceX

This is a great example of how the “ultimate dream” of SpaceX is sort of coming together – SpaceX has proven that they can launch a rocket, and reuse part of it.

However, right now, the current generation of Falcon 9 rockets are only designed to be reused 2 or 3 times before being thrown away. Elon Musk tweeted after the launch that the “Rocket is extra toasty and hit the deck hard (used almost all of the emergency crush core), but otherwise good”.

The “emergency crush core” that was mentioned is a special honeycomb-like structure within the landing legs that is used to absorb a huge impact in case the rocket lands hard. It is designed to be easily replaced so the fact that the crush core was almost used up is not a huge problem.

(Source: @SpaceX)

The bigger problem is that rocket was well scorched and the structural integrity may not be up to par with SpaceX’s standards. It is also possible (not confirmed) that the engines hit the deck of the landing barge.

SpaceX is constantly trying to optimize the design of the Falcon 9, and this has been made obvious by their most recent mission.

Iridium NEXT-2:

After launching 10 satellites for Iridium earlier this year (in January; the exact rocket whose first stage was used for BulgariaSat-1), SpaceX has continued to work with Iridium. On June 25, an upgraded Falcon 9 rocket successfully launched from Cape Canaveral and landed on the ocean barge Just Read the Instructions. A key difference this time was the grid fins.

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Photo Credits: Flickr/SpaceX

This time around, the grid fins were made of titanium, rather than aluminum. Shown below are the grid fins that were previously used.

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The old grid fins, as seen around 2 years ago. Photo Credits: Flickr/SpaceX

Aside from being bigger, the new titanium fins aren’t covered in the white paint that is seen on the older fins. Why is this?

The white paint is actually ablative, which means that it’s designed to char (become darker in colour) during flight. Due to the fact that the booster reenters the atmosphere at very high speeds, the ablative paint is required to absorb the heat produced by re-entry. Otherwise, the rocket would become severely damaged.

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An after mission view of the Iridium NEXT-2 Falcon 9. Notice how the rocket is well charred at some spots. Photo Credits: Flickr/SpaceX

The new titanium fins are resilient enough to heat that they no longer need the layer of ablative paint.

A huge advantage of the lack of ablative paint is for the cameras on the rocket. A big problem in the past during re-entry would be that the paint flakes off and sticks onto the camera, which blocks the view of the outside. The new titanium fins mean that people watching the livestream won’t have to deal with the camera becoming blurry or blocked.

SpaceX is doing a lot of cool things with their rockets, and they’re on the way to launching rockets even more often. Soon, we might be able to see Falcon 9 launches every week!

I’ll be back soon with some more content. Thanks for reading!

Stay tuned and stay sciency,

Mingde

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