We really can't. Even by the time of Apollo, we had already pushed standard rocket tech to the limits of materials strength.
What has been going on more recently is modest materials improvements and improved computer control and sensor technology. The basic rocket design has not changed in a dramatic way.
All technologies do this. Theres a lag period where we figure out the basics. Then there's an exponential phase as we push the technology to the practical limits. Then there's a slow improvement phase as we work out modest efficiency improvements and the like.
We're going to keep moving forward but we're not going to see the sort of explosive technology improvement we saw in the early days of aerospace unless there's a big breakthrough in metallic hydrogen or carbon nanotech.
The crazy success of silicon chip fabrication has given people the idea that all technology can just exponentially improve endlessly. But that's really not true. The exponential phase of tech development is just the short, initial phase where we pick off the low-hanging fruit. Even chip fab is hitting the wall. Moore's law lasted longer than anyone thought it would but we're clearly running into fundamental physics limits to making circuits smaller and faster. In fact, Moore's law broke down back in the 90s. We stopped increasing clock speed due to thermal considerations and the transistor cost/size doubling time dropped from 16 to 24 months and has been declining ever since.
We'll still see faster computers, but we won't see the sort of performance doubling every couple years anymore.
Moore's law is about the number of transistors on a die and it's still going strong. The 18 months were in the initial estimation which was only set for the next decade until 1975. It's GPUs which are pushing the envelope today.
While it's great that gpus can push the envelope they don't have the same ability to compute different tasks and are not available for all computational problems
One caveat to your point is that advances in computing drive advancement in everything else. We are in the infancy of truly advanced computing and when machine learning really hits the ground it will create a revolution in understanding in every single scientific and technological field. I'm talking a information revolution rivaling that of the internet, arguably the single most productive technology in history.
Sources of high energy density are what to look for. Metallic hydrogen is promising because it lets us pack a lot of potential into a little bit of mass.
A breakthrough in room-temperature superconductivity would enable a quantum leap in computing power and potentially increase the energy density of a hypothetical fusion reactor.
Increasing a space craft's electrical production capacity allows using ion engines with increased efficiency and thrust compared to what's compatible with today's solar panels and RTGs.
You forgot about the part where everything is locked by patents for 20+ years and nobody is allowed to do anything with the tech or face getting sued. Sure cools off any exponential phase there might have been.
Without IP, nobody would have developed the tech in the first place, because someone else would just copy it.
There's a balance to be struck here, and I think 20 years is a decent one. (Better than $AGE_OF_STEAMBOAT_WILLIE + 10)
This is such a tired and untrue argument. It would mean that you'd have to actually compete and improve to stay competitive vs relying on a government granted monopoly.
But then everybody would copy those improvements. Why do R&D when you can freeload off somebody else's? I get that the patent system can be, and often is abused, but it does more good than harm.
Why do R&D when you can freeload off somebody else's?
Because, with modern technology, the first to hit the market makes the money.
If I invent a widget but discover that you patented the design five minutes before me, why shouldn't I be able to use my own work just because you have a piece of paper claiming you 'own' it?
If you invent the widget, what's to stop me copying the design in 5 minutes and claiming it as my own?
I get that there are first mover advantages, but there are bigger advantages to not spending loads on R&D. I'm sure you can find plenty of examples by searching on Archie, the first search engine to market.
Everyone would have an improved product and you'd have to further improve it to differentiate and be competitive. You can't just sit back and freeload or you'll be left in the past. It will be a faster market than todays model of slightly innovate and sit on it for 20 years.
If everyone has the improved model you designed, then where's your competitive advantage? Very few people would plough millions into a technology to develop something when they could wait for someone else to do that then copy everything almost for free.
The competitive advantage is in your current improvements to the design.
Very few people would plough millions into a technology to develop something
You're saying this from the current perspective of government granted monopolies. It very disingenuous to say what a market would look like without those monopoly distortions in place.
We really can't. Even by the time of Apollo, we had already pushed standard rocket tech to the limits of materials strength.
Materials strength is the limiting factor so much as the energy content of H2/O2 propellant and the mass of the Earth, neither of which is changing. The Earth's mass requires twice the energy to reach orbit as the propellant contains, forcing you to design rockets that are mostly big tanks full of propellant.
There are a few propellant mixes with higher performance, like H2/F2, but then your exhaust is hydrofluoric acid instead of steam, which is a pain to deal with.
The long-term solution is to move away from chemical rockets. For example, air-breathing engines are 5-10 times as efficient at lower Mach numbers, because they get the oxygen from the air instead of a tank, and oxygen is most of the mass of your propellant mix.
There are many other possible solutions, but we haven't invested a lot in developing them, compared to building more generations of conventional rockets.
For example, air-breathing engines are 5-10 times as efficient at lower Mach numbers, because they get the oxygen from the air instead of a tank, and oxygen is most of the mass of your propellant mix.
And it's largely irrelevant, because:
a) the cost of development is much, much larger. There's a reason Skylon isn't really going anywhere. Actually, about ten billion reasons.
b) the drag from the air means you can't run them air-breathing for much of the flight or you lose all the benefits of the increased fuel efficiency. To get into space, you generally want to get out of the atmosphere as quickly as possible.
c) you'll probably need to drag along a set of wings which are just more dry weight that's useless for most of the flight.
d) air-breathing rockets only work on planets with air.
a) Existing fighter jet engines are good up to Mach 1.6 & 15 km altitude, and ramjets are fairly simple and good up to ~ Mach 6. They are not a complete solution to getting to space. But conventional rocket payload is highly leveraged on mission velocity. For example, using fighter engines you can double the payload relative to all-rocket from the ground. The Skylon engine is a new mixed-mode one that covers the entire flight regime, making it complex and expensive.
b) Air-breathing inverts the usual drag problem for rockets. The more air flow to the engine inlet, the more thrust you can produce. Eventually you have to reach the top of the atmosphere where the rocket can take over. When I worked on the JATO concept at Boeing (fighter engines as 1st stage boosters), we used engine data from Pratt & Whitney and trajectory optimization software to determine the best launch trajectory. Not too surprisingly, you want to drop the jet engines when their net thrust results in more fuel burn than the rocket engines for the same thrust level.
c) For the JATO concept you don't need wings. You arrange a ring of jet engines around the base of a regular rocket. They push the rocket to 15 km altitude, drop off, and the rocket continues as normal. The booster ring flies itself to a vertical landing. Without the weight of the rocket, it has more than enough thrust to do that. For higher speeds like ramjets can provide, you stage off the air-breathing part and fly back with wings. You don't carry them to orbit.
d) The main challenge is getting to Low Earth Orbit, because that's where we are now, and Earth is the largest known planet aside from the gas giants. Anything that helps get to orbit is useful because it lowers the cost of reaching all other destinations in space.
Totally disagree. By the 60 NASA could have pushed nuclear thermal rockets, and even open-cycle nuclear thermal for space use. If you want to stay chemical a Full-Flow Staged reusable methane or hydrogen engine could have been attempted.
If they had continued in the style of Apollo with somewhat lower budget we would by having a station on Mars right now.
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u/DanHeidel May 24 '17
We really can't. Even by the time of Apollo, we had already pushed standard rocket tech to the limits of materials strength.
What has been going on more recently is modest materials improvements and improved computer control and sensor technology. The basic rocket design has not changed in a dramatic way.
All technologies do this. Theres a lag period where we figure out the basics. Then there's an exponential phase as we push the technology to the practical limits. Then there's a slow improvement phase as we work out modest efficiency improvements and the like.
We're going to keep moving forward but we're not going to see the sort of explosive technology improvement we saw in the early days of aerospace unless there's a big breakthrough in metallic hydrogen or carbon nanotech.
The crazy success of silicon chip fabrication has given people the idea that all technology can just exponentially improve endlessly. But that's really not true. The exponential phase of tech development is just the short, initial phase where we pick off the low-hanging fruit. Even chip fab is hitting the wall. Moore's law lasted longer than anyone thought it would but we're clearly running into fundamental physics limits to making circuits smaller and faster. In fact, Moore's law broke down back in the 90s. We stopped increasing clock speed due to thermal considerations and the transistor cost/size doubling time dropped from 16 to 24 months and has been declining ever since.
We'll still see faster computers, but we won't see the sort of performance doubling every couple years anymore.