Little Bits of History

July 3

Posted in History by patriciahysell on July 3, 2017

1969: The USSR launches 5L-Zond L1S-2. This was the second  N-1 launch and the booster rocket carried a modified L1 Zond spacecraft. There was a rumor the rocket also carried a mass model lunar module, but this is seriously doubted. The N1 (sometimes called H1) was a super heavy-lift launch vehicle, similar to the US Saturn V rockets. It was intended to carry payloads beyond low Earth orbit. There were plans for ten launches with nine of the rockets built. The first was a dynamic test model built at ¼ scale. The second was a test/training rocket. The third was launched but ended with an engine fire and explosion at 7.5 miles. The fourth one built developed cracks and was never launched.

On this day, more than four months after the disastrous 3L – Zond L1S-1 flight, at 11.18 PM Moscow time, L1S-2 launched. The rocket began to majestically lift into the night sky. As it cleared the launch tower, there was a flash of light and debris began falling from the bottom of the first stage. All the engines, except engine #18, immediately cut off. But with just one engine firing, the rocket angled to 45⁰ and then dropped back onto the launch pad at 110 East. There was almost 2,300 tons of propellant on board and a massive blast was triggered. The shock wave shattered windows across the launch complex and sent debris falling as far as 6 miles away. The blast was visible 22 miles away.

The launch crew was permitted to venture out of safe shelter half an hour after the explosion and they were met with droplets of unburned RP-1 still raining down from the sky. Luckily, the majority of the rocket’s propellant load had not been burnt in the accident and most of what had burned was in the first stage of the rocket. A worst case scenario was also avoided when the propellant did not mix with the LOX (liquid oxygen) to form an explosive gel. While investigating the cause of the catastrophe, it was found that up to 85% of the propellant on board the rocket did not detonate which greatly reduced the blast. Even so, this was the largest artificial non-nuclear explosion in human history.

The cause was never identified but some information was uncovered during investigation. The initial fire damaged the thrust section which led to gradual shutdown of the engines by T+10 and T+12 as they detected abnormal pressures. Why #18 did not shut off is unknown. The turbo pump explosion causing the accident may have been damaged by debris from other pieces of machinery or the blades may have rubbed against metal and caused a spark. The engine’s designer was adamant his engines were faultless and the investigation, with his help, determined debris was the root cause. The entire launch complex was destroyed in the blast and took 18 months to rebuild which delayed USSR Space Race launches.

I saw for the first time the earth’s shape. I could easily see the shores of continents, islands, great rivers, folds of the terrain, large bodies of water. The horizon is dark blue, smoothly turning to black… the feelings which filled me I can express with one word – joy. – Yuri A. Gagarin

The new socialist society turns even the most daring of man’s dreams into a reality. – TASS press statement regards Sputnik 1

There is no easy way to the stars from the earth. – Seneca

Anyone who has spent any time in space will love it for the rest of their lives. I achieved my childhood dream of the sky. – Valentina Tereshkova


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