Ah, the benefits of not having to listen to shareholders. SpaceX can take long term bets, for example moving capital into exploratory programs including the proposed Mars missions, without having to justify it by profit.
Completely off-topic, but what's the latest thinking on space-elevators? Is there any active research on them? I thought that carbon nanotubes or diamond nanothreads were likely candidates for the cable material.
Probably the biggest barrier to space elevators is exactly what SpaceX and Blue Origin are doing - safe, reliable, and eventually (relatively) inexpensive rockets will make the large fixed costs of setting up a space elevator uneconomical.
I think that the best long term way to spur investment in projects like a space elevator would be to make space as economically attractive as possible. In-situ resources, extracted/processed robotically and accessed via low cost rockets is the way to do that.
Once we have a rocket-powered transport network between, say, Earth-orbiting space stations, a moon colony, some near-Earth asteroid mines, fuel depots at lagrange points, a Phobos outpost and robotic factories on Mars, the economic payoff of a space elevator will be more immediate. Plus we could try them out on less massive bodies first, like the moon.
Both Musk and Bezos seem well on their way to reusable boosters. But reusable upper stages is another story.
An upper stage re-enters at around 8 km/s. An ~7 km/s delta V budget plus the need to carry a payload means a very slim dry mass fraction, an egg shell space craft.
Recovering and reusing upper stages will be much harder than reusing boosters.
It seems like there is a wall in reliability with getting chemical rockets much more reliable than about 99% - 99.5%. SpaceX and Blue Origin are doing cool things, but I don't see them being any more reliable than previous generations of chemical rockets.
If an elevator could provide more 9s of reliability, that could be huge.
But cost is also at issue. For cargo, it might make sense to take on 0.5-1.0% risk versus the massive investments necessary for the development of a space elevator.
And when we're talking about human spaceflight, consider the work SpaceX and Blue are putting into in-flight abort and propulsive landing - SpaceX's Crew Dragon should be much safer than the Space Shuttle, for example.
The issues are huge and probably insurmountable. For example: where would you site it? It has to be equatorial so it can be below the geostationary counterweight. Just the motion of the cable from the eccentricity in the earth's rotation and orbit would probably tear the cable apart (imagine what the foundation of the base station would have to be, and how it would buckle and lift as the earth rotates).
The space elevator is an idea that sounds cool but is fucking dumb if you think about it for more than ten minutes, like the idea of accelerating ships to near light speed, when every hydrogen atom in the void will shred your hull like a cosmic ray.
Still a lot of active research going on. The biggest issues that need to be resolved are currently with the cable material. There has been a surprising amount of progress in the last few years with creating longer carbon fibers, but its still nascent and has a minimum of 5-10 years of work. Probably much more.
Then even when the cable strength and length issues are satisfactorily resolved, there are lots of other logistics to deal with.
I think any future barriers to the elevator(s) will be more regulatory than technological in the future.
I'm not sure what "future barriers to the elevator(s) will be more regulatory than technological" means. Like, right now, the barriers are firmly technological.
From the perspective of a hypothetical future in which all the technological problems have been solved, the barriers might be regulatory. But that seems tautological.
80km high track supported by centrifugal force and belt momentum, and tethered by (the same type of cable necessary for a space elevator)? With a belt over 4000 km long capable of 14km/sec without flying apart or overheating?
Between the recent news of SpaceX shipping a test article of its Mars rocket to McGregor (the Raptor engine) and this large contract for material for its Mars Colonial Transporter, SpaceX's Mars plans are shaping nicely.
Hopefully Congress takes notice within the next few years, and funnels the money currently spent on the SLS rocket to Musk's Mars project.
In some ways, not a good sign. Space-X can't make and launch Falcon boosters fast enough now. They're not a big enough company to do many things in parallel. Their unfinished, and late, projects include the Falcon Heavy, the Brownsville TX launch facility, and the crewed Dragon, all of which were supposed to be working by now.
>Space-X can't make and launch Falcon boosters fast enough now.
The bottleneck is not Falcon 9 production, at this point it's largely on the payload side. A faster turnaround would certainly help, but there's only so much optimization that can be done.
The Falcon Heavy is not a priority because (1) much less demand from customers and (2) it's a transitional system between Falcon 9 and built-for-reuse BFR/MCT, so it will have limited use.
Brownsville isn't a case of them being distracted but just underestimating the degree of soil surcharging needed. Crewed dragon is unfinished but hasn't missed any of NASA's deadlines so far.
I do wish that Falcon Heavy would finally launch though.
As a point on the FH, one reason it's delayed is that it has lower priority: now that the Falcon 9 has been upgraded to the full thrust version, it can take many customers who were originally envisioned to go on the Heavy
My only issue with carbon fiber is that it is not very easily recycled. Aluminum, on the other hand, is quite trivially recycled. So while spaceships made from CFRP are great in the short-to-medium term (a single spaceship can get a lot more use), I hope that we figured out how to recycle CFRP sooner rather than later.
Aerospace aluminum isn't as easily recycled as beer cans.
If you're building a space ship you have very tight tolerances and specifics needed for the alloying of the metals you use. The aluminum in aircraft is full of strange things that need to be removed for general use aluminum and definitely need to be removed for building new aircraft.
You're right that melting and re-casting aluminum is really cheap and efficient for beer cans, it's not so much the same for aerospace aluminum.
When it comes down to spaceships, the energy used to produce them is usually a very small portion of the total cost of the mission and we don't make very many of them – recycling isn't and shouldn't be a priority.
The Falcon 9 burns 110,000 liters of kerosene every launch, if it were made of carbon fiber, maybe it wouldn't matter how the structure was disposed.
I never thought about it but I became curious as to what the differences are, here's what I was able to find:
[0] Aircraft grade aluminum alloy's composition roughly includes 5.6–6.1% zinc, 2.1–2.5% magnesium, 1.2–1.6% copper, and less than a half percent of silicon, iron, manganese, titanium, chromium, and other metals.
[1] Aluminum cans are typically 1% magnesium, 1% manganese, 0.4% iron, 0.2% silicon, and 0.15% copper.
There are a lot of metrics that determine the appropriate use of various grades of aircraft level alloys [2]. I guess from the outside some big considerations are how the metal reacts to temperature change and how well a metal cylinder can handle stress while staying light.
>how well a metal cylinder can handle stress while staying light.
Are we talking beer cans or rockets? Maybe they are the same after all :)
All spot on. There are lots of alloys used for lots of different things and economics and availability play their part too. When you're designing your airplane every slight detail matters.
Why would you be worried about recycling spacecraft at this point in history? Up until the last 2 years, practically all spacecraft either burned up in the atmosphere, crashed into the ocean or land, landed permanently on another body, or are now sitting in a museum somewhere if they were designed to return. Recycling the material in spacecraft is simply a non-issue.
Maybe, we need to think about recycling carbon fiber as..
In recycling the fibers get shorter..
Could not that be re-applied to a different industry as far as re-using the carbon fiber? Body Armour for soldiers as the shorter fibers would be of use there?
The resin has a low Tg (temp at which it turns goopy again) - somewhere around 500*F even for 'aerospace' stuff. Whereas recycling aluminum requires roughly double that temperature to begin to melt aluminum.
The carbon fiber is then chopped and used as reinforcement in other material likes plastics. SGL Group, who supplies/partners in production with BMW, even uses reclaimed and production waste in it's production process for the new 7-series.
Carbon fiber is a pretty weird choice for a reusable rocket. Unlike aluminum, it has basically zero tolerance to heat since the fibers are embedded in a matrix made of a polymer glue compound. That's why they call it fiber reinforced plastic.
SpaceX already uses carbon fiber on their rockets in the interstage and payload shroud. They do provide some insulation: they're covered in cork. But most of the rocket body encounters extra low temperatures more than high temperatures.
