SpaceX #5: Reusing Boosters

At one point in his book on SpaceX, Liftoff, Eric Berger quotes Elon Musk on the next challenge he set for the company:

“One of the hardest engineering problems… is making a reusable orbit rocket.”

Booster reuse was high on SpaceX’s priorities. To that end, they tried attaching parachutes to the top stage of the rocket to slow it down when it fell back. The idea was doomed because the speed of re-entry was too high and the stage burnt up long before the parachutes could deploy. As Musk said with hindsight:

“We were very naïve… We were huge idiots.”

 

Why was SpaceX so obsessed with reuse? Cost reduction was just one reason. Remember Musk’s intention to make human flight to Mars affordable?

“If an airline discarded a 747 jet after every transcontinental flight, passengers would have to pay $1 million for a ticket.”

 

If the rocket would burn up on re-entry, what was the way out? A heat shield was the first step, to protect the rocket. The second step was a never-done-before challenge: how do you slow it down enough for the parachutes to work? For that, they needed to re-light the engines high in the atmosphere when the booster was travelling at a speed of Mach 10. Engineers worried about turbulence at those speeds, and the stability of the booster if the engines “fire directly into an atmosphere rushing toward it”.

“It took a good bit of tinkering and failure… (but eventually, they got the) booster to a safe night time landing.”

 

This was an awesome achievement, but the economics of it was still a problem. Shortly after takeoff, a rocket will lean forward bit by bit so it becomes horizontal by the time it hits orbit. But this horizontal position meant the first stage was moving away from the launch site when it detached. How do you make it turn around if you wanted to save and re-use it? Adding fuel to it was too costly and made it too heavy. The solution is easy – in theory. Keep a drone ship miles away at sea which would catch the booster as it fell back to earth. In practice:

“It requires some damn good computer programming to make the rocket and autonomous drone ship line up just right, and no one had done it before. Until it happened.”

And then SpaceX did it again. And again:

“Suddenly, SpaceX had a hangar in Florida full of first stages.”

 

SpaceX soon mastered the art:

“Today it is normal for SpaceX to launch rockets, catch them on land and at sea, and fly them again a couple of months later. In fewer than three years, the paradigm has shifted entirely.”

It also cut down the cost for the customer, reducing the price of satellite launches.

 

And yet, Musk is not satisfied. 19 years after he started the venture, he rues:

“We’re still not on Mars. Not even close. It’s a goddamn outrage.”

This is the passion that continues to drive Elon Musk and SpaceX.