On a lighter note there's a Simpons line when Homer has to land a plane and is talking to someone on the ground
Colby: Okay Homer, I don't know anything about planes, but I know about you. You have what made America great: no understanding of the limits of your power and a complete lack of concern for what anyone thinks of you. So you'll land that plane. And do you know why? Because I heard some guy say you couldn't.
Homer: What! I'll show him. I'll show that guy!
The best way to get something great done is to tell someone it's impossible for them to achieve.
Before the sky crane we had the bouncy ball, and both had supersonic parachutes which is also a mind bender.
1. When a distinguished but elderly scientist states that something is possible, they are almost certainly right. When they state that something is impossible, they are very probably wrong.
2. The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
3. Any sufficiently advanced technology is indistinguishable from magic.
SpaceX also had that same opinion originally. I believe their first concept was to use parachutes for the first stage (and maybe splash down in the ocean for recovery).
They interviewed an engineer from Masten Space Systems (who have really cool test platforms). He was talking to them about VTVL (vertical takeoff, vertical landing) systems, and SpaceX basically just laughed at him.
Please share why you thought it was not possible. Just curious.
Since realizing that I became more wary of unconscious biases picked up from environment, and how they affect what I think is technologically possible.
The ascent into space looks like a massive show of raw power, and in contrast these vertical landings look so graceful and controlled.
Personally, I think both are a "massive show of raw power" - both literally and figuratively.
Literally goes without explanation. But what I mean of the word "figuratively" is that it shows our capability as a species to fully harness our intellect, knowledge, and emotions to do this kind of engineering, despite knowing it can all go horribly wrong (especially in the case of manned space flight).
Certainly there are many other drivers to why we do this (profit in the case of SpaceX certainly is a great one), but part of it is also to show ourselves we can push beyond what seemed or seems impossible at times, and make it routine, and eventually both practical and relatively "safe" (always knowing it might never be perfect).
If you think about it that's not really the case. Post launch the boosters are empty and must sustain their own weight and that of the payload sitting upright on the launch pad prior to fueling.
During the launch the full force of the engine is exerted on everything and it must withstand that force even as the tanks empty. If the boosters were not able to withstand these forces then as the rocket climbed into the sky you'd see it start to compress like a tin can the higher into the atmosphere it climbed.
- The wafer thin margin of actual payload that the booster put up now being shared with landing fuel
- Engine restart after launch
- Re-entry forces on the engines
- The fact (perhaps since addressed) that a single Merlin puts out more thrust at near minimum throttle than the dry mass of the booster itself.
Think about that last one. If you start the burn too early you'll miss the ground .. for a while. The lesson here is trust calculus!
It's addressed in the sense that they live with it. The rocket still does a suicide burn.
I mean, take a yardstick or short rod or something, and try to balance it upright on the tip of your finger. That's basically what they're doing, but with a -rocket-. It's amazing.
The magic is in a) ensuring the whole construct survives reentry, and b) timing the landing burn - even a single Merlin engine is too powerful for the almost empty rocket to hover, so they need to zero out their velocity at precisely the moment they're hitting the ground. There's no second attempt.
While you drop your hand toward the ground at mach 5.
Indeed. For their last launch, they decided to try landing the booster with three engines rather than one, which brings the whole 'hoverslam' concept to the next level.
This was considered so risky that they didn't try landing it on the barge, for fear of damaging it. Instead, they soft landed on the ocean.
But much to everyone's surprise, it actually worked! There's a picture of the Falcon 9 booster floating awkwardly. Musk said they'll try to tow it to shore.
And all that is really the core of why I love SpaceX: continuous improvement. It's a grand thing!