Spaceflight – Page 2 – Journeys of Heart and Mind

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.

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.

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.

Blast from the past… 8

We are often in situations where we’re amongst people we recognise, but know almost nothing about.

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Notes from bygone years – Julys duly remembered
Hint: Click on the thumbnails for larger images.

A year ago

On 7th July 2022 I noted that ‘the Conservative party is in a state of confusion right now’. Not a lot has changed in the last twelve months; it seems the Conservative ship is still foundering. I included a picture of a sinking ship in my article, here it is again. I also argued for a general election as soon as possible and we’re still waiting on that one! So the big question now is, ‘Will the Conservatives still be in power in July 2024?’ Hard to say, isn’t it! In my judgement it’s very unlikely, but we’ll have to wait and see. The last possible date for the next general election is 28th February 2025. (See the original post.)

Two years ago

Starship’s first launch, 20th April 2023 – Image from Wikimedia

In July 2021, SpaceX‘s Superheavy Booster 3 was being tested at Boca Chica in Texas. They continue to develop and build boosters (and Starships too) at a prodigious rate, and have already launched the full stack on it’s first test flight. That flight failed to reach orbit, and caused serious damage to the launch mount but, following repairs, they are very nearly ready for a second attempt and have made a lot of changes following lessons learned from flight 1.

Five years ago

In July 2018 I shared an extract from my short guide, JDMC. I emphasised the work of the Holy Spirit in church life and looked at ways we can recognise and value his activity.

I didn’t want JDMC to be only about what we do, but more significantly about what Jesus does. (Read the original article)

Ten years ago

Research shows we are often in situations where we’re amongst people we recognise, but know almost nothing about. In July 2013 I was thinking about this and how I might notice and engage with such people. (Read the original article)

Fifteen years ago

In July 2008 I wrote about the famous Welsh hymn, ‘Dyma gariad fel y moroedd’ or in English ‘Here is love vast as the ocean’. Read about the hymn’s origins and listen to it in the original article.

Twenty years ago

July 2003 saw us meeting at home to listen to what the Spirit would say and watch what he would do. And of course, we were not disappointed. Afterwards I posted ‘Fallen and lifted up‘ to capture something of that evening.

Twenty-five years ago

In July 1998 we visited Kimbolton, just a short distance from our home in Tilbrook. Although it’s a village, Kimbolton always seemed much more like a small town with a market place and Kimbolton Castle, now a private school.

Thirty years ago

In July 1993 Judy, Debbie and Beth went to see a Sealed-Knot re-enactment of a Civil War battle. I didn’t go to this as I was probably at work at the time.

Thirty-five years ago

In July 1988 My Mum was sixty and we had a party at The Catherine Wheel pub in Bibury. Here she is unwrapping a present – a Mickey Mouse landline telephone. She had always wanted one of these!

Forty years ago

In July 1983 my mathematician friend, Phil, and I had a scientific paper published. Phil built a mathematical model for the effect of temperature on apple pollen tubes. This was based on experimental measurements I’d made in spring 1982.

<Jun 1983 – Aug 1983

Forty-five years ago

In July 1978 Beth was just two months old (whoops, I think I just gave her age away). We were living in a terraced house in Yatton and I was working on plum and apple pollination.

Fifty years ago

In July 1973 I inspected the base for a greenhouse with my father-in-law, Ron Hill. Here we are, having a good look. As you can see, Ron’s garden in Charlton Kings was beautifully maintained.

Fifty-five years ago

In July 1968 I celebrated my 20th birthday. I don’t remember the occasion, but it would have involved a bit of a party with my Mum and Dad, my three sisters, Judy, and possibly her parents and brother too. From my current perspective it seems a very long time ago!

Sixty years ago

In July 1963 I was 14 years old and we might have been on holiday, but more likely it would have been August. In any case, here’s my Dad taking a photo of the family on the beach on the coast of Ceredigion, Wales.

Sixty-five years ago

In July 1958 I turned ten-years-old, and I’d finished my fifth year of junior education. It was the summer holiday, hooray!

Seventy years ago

In July 1953 I was four, turning five and hadn’t yet started school. Mum, Dad, my little sister, Cindy, and I lived in Queen Anne’s Road on the Beeches estate in Cirencester.

Seventy-five years ago

July 1948 was the month I was born. I was one of the first two children to be delivered at Cirencester’s new maternity hospital. It’s now the main building of today’s Cirencester Hospital.

Eighty years ago

On 29th July 1943 my Dad cycled home from school at the end of term. It was his last day of full-time education.

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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).

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).