Tag: Super Heavy

The biggest Mach diamonds ever!

Together, all these engines produce 75.9 MN of thrust, much more than Saturn 5’s 34.5 MN.

The first question you might want answered as you read this title will be, ‘What on Earth is a ‘Mach diamond’?’ I’m glad you asked.

If you’re interested in rockets and spaceflight you may already know. Where there are rocket engines, there will be Mach diamonds (also known as ‘shock diamonds’). They are formed by the high velocity of the gases leaving a powerful jet or rocket engine. The shock waves created by this process interact with the ambient air around the nozzle, sculpting the exhaust into angled zones. When seen from the side, these appear as a repeated diamond pattern.

Mach diamonds from an F-16 on afterburner – Image from Wikimedia

The largest rocket ever built is SpaceX’s Super Heavy booster designed to lift Starship to a high altitude on the first part of its journey to orbital velocity. This booster is powered by 33 Raptor engines clustered closely together; they behave rather like a single engine with a 9 m diameter nozzle. When the rocket flew for the second time in 2023, giant Mach diamonds appeared, 9 m across and 6 m in length. These truly are the world’s biggest Mach diamonds ever – by a very considerable margin.

Super Heavy’s engines – SpaceX

This view shows all 33 Raptors firing shortly after liftoff on the 2nd flight test (IFT-2). Each engine bell has a diameter of 1.3 m and the rocket itself has a diameter of 9 m. Together, all these engines produce 75.9 MN of thrust, much more than Saturn 5’s 34.5 MN.

IFT-2 – BocaChicaGal

Here’s an image of the IFT-2 vehicle shortly after launch. The first Mach diamond is very sharply defined, subsequent diamonds less so as the exhaust plume slows, cools and becomes more ragged. Four can be clearly identified with some hints of a fifth and sixth.

So what is happening here? How are the diamonds generated?

Because a rocket engine is all about producing thrust, the velocity of the exhaust is paramount. Rocket engines are designed to maximise velocity and in doing so they minimise pressure. Inside the combustion chamber, pressures are extremely high; but the bell shape of a rocket nozzle expands the gases and directs them downwards. The pressure inside the exiting plume is much lower than the ambient air pressure. This pressure difference ‘squeezes’ the plume and prevents it spreading out sideways.

Higher in the atmosphere, air pressure is lower and the mach diamonds vanish; as atmospheric pressure drops away towards the vacuum of space, the exhaust plume spreads out sideways more and more because the exhaust gas is now at a higher pressure than the diminishing, surrounding air. Notice how the spacing of the diamonds decreases with distance from the rocket. This is because the exhaust velocity is falling off as the plume interacts and mixes with the air around it.

That’s the essence of the process in everyday language. Check the links below if you want more technical detail.

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Starship launch attempt postponed

** LATEST ** – The next launch attempt is now scheduled for Thursday 20th April. Check the latest news at Spaceflight Now.

Monday’s planned test flight of the Super Heavy booster carrying Starship was called off due to a pressurisation issue caused by a failed valve. The booster’s ability to carry a significant load (like a fully fuelled Starship) depends on the fuel tanks being pressurised at all times. It’s the same process that makes drinks cans so strong despite being very thin walls. An empty can crumples whereas an unopened can is pressurised and is significantly stronger.

If the valve issue can be fixed on Tuesday, there might be a new launch attempt on Wednesday. Watch this space (no pun intended).

See also:

Starship’s first launch

Just a short post this time, to alert anyone who may not know… SpaceX is planning the first ever launch of Starship on an orbital flight tomorrow, Monday 17th April.

There are several places you can watch this attempt live on YouTube. I recommend three of them in particular. If you’re new to all this, try the SpaceX stream. If you’re more knowledgeable you might prefer one of the others.

  • Felix Schlang, a German who moved to Florida to be closer to the action
  • Marcus House, an Australian spaceflight enthusiast in Tasmania
  • SpaceX, the company’s official stream

I just wanted to get this alert out today. I’ll be back after the launch attempt with more thoughts. (More details about Super Heavy and Starship).

SpaceX’s Starship launch

For this first flight both parts of the vehicle will be lost after landing on the sea (but hopefully not before)

Elon Musk’s company, SpaceX, is close to the first launch of their new spacecraft – Starship. This is an exciting step forward in space flight technology as fully reusable Starship versions are planned to return NASA astronauts to the moon, act as orbital fuel tankers, take people and materials to destinations throughout the solar system, and colonise Mars.

The world’s most powerful rocket is likely to make its first orbital flight attempt during March. Whatever happens, the attempt will be spectacular in the extreme! With twice the thrust of NASA’s SLS rocket, SpaceX’s Super Heavy booster will attempt a launch from Starbase on the Texas coast, heading east. The Starship will separate and pass between Florida and Cuba.

Starship on the pad – Image from Wikimedia

The Super Heavy booster will attempt a landing on the surface of the sea, offshore of its launch point. When fully operational, SpaceX intends that Super Heavy boosters will return to the launch site to be caught in mid-air by arms on the launch tower. Starship will attempt a landing, also on the sea surface, north of Hawaii, but again, the intention is to eventually catch Starship at the launch site as well.

For this first flight both parts of the vehicle will be lost after landing on the sea (but hopefully not before). It’s likely they will attempt to hover above the sea surface to practice the manoeuvre they will need to perform for a catch. Once landing precision is good enough, SpaceX will attempt the first catches. But that’s something for future flights and will depend on data returned from this first attempt. You can’t put a note in your diary to watch the launch as we don’t yet know exactly when it will happen. But I’ll keep you posted here on JHM.

The previous step forward for Starship was a static fire by the Super Heavy booster on 9th February. This is worth watching in this video clip from NASA. Thirty-one of the booster’s thirty-three engines fired for the duration of the test, one was not ignited at all, and one shut down early. The engines fired at half thrust during the test, but for the first launch they’ll be run at 90% thrust.

See also:

The SpaceX website carries an introduction to the concept of the Starship system.

The launch is listed on Spaceflight Now’s Launch Schedule page and on Next Spaceflight’s SpaceX Launch Manifest page. You can check those sources for schedule updates as they become available.

Wikipedia has a good article about the Starship vehicle covering details of size, thrust, the development process, purpose, capabilities and so on.

For YouTube channels tracking Starship developments I highly recommend Everyday Astronaut, Marcus House, and What about it!?