whats more complicated, a car or a rocket ship?

What has more money go into R&D?

What has more money go into manufacturing?

If you put a team of NASA engineers against a team of BMW engineers and told them to both make a car and both make a rocket ship, could it be done?

A very simple rocket is much simpler than a very simple car. Heck, a very simple rocket is simpler than a single cylinder of a car engine. On the other hand, of course, something like the Space Shuttle is not a very simple rocket.

So what is a “rocket ship”? Arguably the Space Shuttle is the only rocket ship that ever saw use. Buran never carried humans, and the other human carrying spacecraft are a mix of launch vehicles that are used for many other purposes (from delivering nuclear weapons to lofting satellites) with capsules that do little more than protect the occupants and do basic manoeuvring. The Apollo capsule being the most advanced, and most capable, as it carried a significant propulsive capability. A capsule like the Apollo makes a car look trivial in complexity. It cost billions to design.

The vast majority of the development costs of a car go into designing it for mass production. Tooling so you can make tens of thousands to millions of a copy the issue. The very high end cars cost much less to design. The design costs for a Lamborghini are a fraction of those for a VW golf. But they are very expensive to make, being largely hand built with bespoke low volume components.

A space vehicle is more like a Lamborghini, and made in even smaller volumes. But with a level of safety and quality engineering that makes car design look like a couple of guys hammering a car out of tin cans with a rock.

An interesting point of comparison would be SpaceX and the Falcon-9 plus its Dragon capsule. The development costs for these are probably not a great deal different to a brand new BMW model.

I guess it depends. A solid rocket motor is pretty darn simple; a casing lined with a fuel/oxidizer mixture. The casing only has to be strong enough to contain the pressure of the burning propellant.

a liquid-fueled rocket motor is way more complex, what with the turbopumps, plumbing, controls, gimbals, etc.

SpaceShipOne, which won the X Prize a few years back, reportedly had a development cost of about $25 million. That’s a friggin’ bargain.

It’s not like we’re talking about Car Science.

Considr the technologies that have to work right: a human-carying rocket (I assume, what we’re discussing) needs pressure vessel, sealing doors, life support (at least, air supply and waste gas elimination), proper aerodynamics and some sort of maneuverability (to accomplish re-entry and to stop any tumbling), seats that prevent injury during high-G take-off, heat shield that can absorb untold high-oxygen, high-temperature blasting during re-entry, etc. That’s just the capsule. The major issue with initial shuttle testing was a pump that would ot shatter (and blow up everything) while pumping liquid hydrogen at absolutely masive volumes. The shuttle was apparently the largest controlled release of energy in human endeavors - I saw one, from 3 miles away it turned night into day and the noise was unbelieveable!

Part of the problem is - everything on a BMW is refinement of decades-old tech. It just has to be as good as a Trabant, everything else is refinement. A lot of what was in each manned rocket is new tech, new research and development - and has to work flawlessly. If a car breaks down you can get out, lift the hood, and hammer on the stuck part. With a rocket failure, they fish what body parts they can find out of the Bermuda Triangle.

As you can see with Spaceship One (not an orbital craft) or similar “private enterprise” efforts, a lot of what NASA does may be overkill, and a lot of what they need may be almost at the “off the shelf” point of technology now. But… nobody gets kudos for saving a few million dollars if that part from Home Depot turns out be the part that kills a few people on a prestigious government effort.

And what is a “car”, for that matter? The rocket scientists need only put a small rocket motor on the back of something with four wheels to have a “car” of sorts.

A rocket car.

As usual, Heinlein said it best:

– from The Rolling Stones

Given the time when Heinlein wrote that, it has some element of truth. Of course he was trying to be funny. However he clearly didn’t quite understand Carnot. A modern car pretty much obviates most of his legitimate complaints.

The OP was asking to compare the design team for a new BMW to a “rocket ship”. In the sense that a rocket ship was more a SF term for a human carrying craft for spacefaring (as opposed to a box to carry humans to the edge of the atmosphere and then to plummet back) I stick with my characterisation of the space shuttle as the nearest we have got.

Reliability and safety is however one interesting point that underlines the wide differences in the engineering. A modern car contains a number of active safety systems. Traction and skid control are becoming close to mandatory. Millions of cars take to the road every day with software controlled braking systems that are designed to keep the occupants safe. It is not hard to come up with any number of failures that would result in fatal accidents. Yet they don’t happen. Huge amounts of money has been invested in testing and engineering these systems. Many many hundreds of millions. Indeed much more than was spent on the control systems for the space shuttle. Cars also carry pyrotechnics - in the cabin; something almost never done in spacecraft. Mass production techniques, involving very expensive equipment and development, yields very cheap, very reliable and very safe airbag systems. Think about it. Every time you drive a car there is an explosive device sitting in front of your face. Getting those reliable enough that millions of cars scuttle about the roads every day with them installed is seriously impressive.

Heinlein moans about the “a small percentage of an exothermic chemical reaction”. A modern car engine is very close to the maximum theoretical possible recovery of energy. It is possible to spend insane money in developing internal combustion engines. The Formula One circus used to spend nearly a billion a year on engine development, until the FIA froze development because it was just getting silly. F1 probably spent more money on engine design than NASA did on the shuttle engines. But the engines developed were astounding. Power to weight had improved beyond imagining. Fuel economy on the other hand was appalling. But they didn’t care. The designs met the requirements - which was to win races.

This is wandering off topic, but it underlines a basic truth. The engineers on both sides are not idiots. But they are meeting very different requirements. Spacecraft have to meet very complex requirements in a the face of extreme engineering challenges. So they are made as simple as possible. Even then they end up very complex. They are made in very small numbers, and almost every component is bespoke.

Cars are designed to be made in very large numbers cheaply, but are required to be both very safe, reliable, and provide ever increasing features and luxury. But they operate in a benign environment, and do not provide extreme engineering challenges. Their engineering focusses on meeting the requirements by amortising the very high development costs, and costs of tooling, through mass production. Complexity of design is often by choice. Complexity of the design process however remains.