So much potential
If it works, it'll be amazing.
Brit firm Reaction Engines has successfully tested its engine design's precooler heat exchanger – a key step on the path to getting its SABRE donk up and into space. The Synergetic Air Breathing Rocket Engine (SABRE) designed by Reaction is designed to get an attached space vehicle up to Mach 5.4 before switching to liquid …
Unfortunately dumping them into the sea would not work. Sharks or other man-eaters would, out of professional courtesy, not touch them or you would get Greenpeace launching protests at the introduction of criminals into the food chain.
A far more sensible option would be to tether them in bunches of 10 behind the engine in order to test the minimum distance for those observing the afterburner.
That said, dropping them all into the middle of the Atlantic might work!
That said, you would indeed prove that those who say that climate change is man made because the combined hot air from said politicians would quickly melt the icebergs, causing sea levels to rise dramatically and causing most of the UK to be flooded. (Unless you live in the Mountains of Scotland. )
So sure. that would be one way to solve Brexit... flooding London along w most of low lying Europe.
Then on the other side of the pond, most of the US East coast would be under water. Think of all of those yuppies on Wall Street treading literal water.
So much potential .... to pollute the atmosphere ever more by making launches simpler and cheaper. I guess its not enough to screw up the stratosphere with burnt kerosene from the thousands of jets up there at any one time, lets make sure we mess up every level of the atmosphere and dump even more CO2 into it for .... what purpose exactly? Perhaps it can launch micro satellites which have a lifetime of a few weeks and are essentially space junk the minute they're launched. Or some idiot space tourists to gormlessly stare at the view.
The engine burns liquid hydrogen, which, since it contains no carbon, cannot emit CO2. The exhaust product would be water vapor. (Water vapor is also a greenhouse gas, but since excess water vapor rains out of the atmosphere it's not a major concern.)
That's not to say it doesn't have a carbon footprint; actually producing, compressing, and chilling the hydrogen is pretty carbon-intensive with current technology. There's nothing precluding doing it with renewable energy, mind, it's just not currently economically feasible when producing it from natural gas is an option.
actually producing, compressing, and chilling the hydrogen is pretty carbon-intensive with current technology
Not really. With *current technology* we can do it for free, the input being water, by-product Oxygen. The fact there hasn't been any investment to scale up isn't the fault of existing technology, it's the fault of governments and people like Elon Musk who are sending the world down the wrong path. We could all be driving HICEVs by now with fairly minimal investment.
If by "Musk" you mean SpaceX, they are moving from kerosene to methane, and methane can be made carbon-neutral if anyone actually cares. Which they probably don't as the number of rockets launched is too few to matter.
You can make methane carbon neutral, burning it carbon neutral not so easy.
Also I meant Tesla obviously but now you mention it, all that NASA research into liquid hydrogen burning in oxygen rocket engines, pissed away. https://www.youtube.com/watch?v=MjQ0j1a9RcA
It's already pretty common -- the Delta IV Heavy uses LH2 for all stages, for example. Some other boosters do use RP1 (kerosene), especially in the first stage, because it's both easier to handle and more energy-dense by volume. (LH2 is more energy-dense by weight, but bulky.) It's worth noting that countdown aborts and scrubbed launches due to hydrogen leaks are pretty common on Delta IV missions.
As part of the LAPCAT project REL developed a new design of combustion injector that is expected to generate 1% of the NOx of existing combustors.
The SABRE 4 cycle splits the system into 2 separate combustion chambers this is now much more viable.
While burning Hydrogen does only produce water you have to get that Hydrogen from somewhere. There are 2 major way to get the stuff:
1) Electrolysis of water - hugely inefficient and unless the power is from a renewable source will generate lots of CO2
2) Catalytic breakdown of hot natural gas with superheated steam - this really produces a lot of CO2 and needs a fair amount of power to get it running hot enough.
There are less polluting ways to get Hydrogen such as biological methods but they are either very small scale or still in the laboratory stage.
"unless the power is from a renewable source will generate lots of CO2".
I suspect even powering a large fleet of Sabre-engined Skylons would not make a significant uptick in the global production of H2.
Is this a case of the perfect is the enemy of the good?
Hydrogen and oxygen are not just lying around waiting to be collected and used. Unlike coal, oil, and gas.
The energy intensity of producing the materials is the most relevant part of the CO2 impact. Yes, if all electricity production was renewable it would be fine, but that is far from the case.
You might find the energy use of cement and aluminium production interesting.
The trick here being you have to pre-warm the fuel anyway, so using it as a heat sink for the helium precooler coolant kills two birds with one stone.
Some earlier proposed designs used simpler schemes where the liquid hydrogen was used directly as a coolant. The problem is this causes a lot of materials problems. Steel and some other metals become brittle with prolonged exposure to hydrogen.
It's not just the low temperatures. Hydrogen embrittlement happens because the hydrogen molecules are small enough to get between the grain structures that make up steel. Once in there they combine with carbon to make methane. The methane molecules are then trapped because they're too big to get back out. This creates internal pressure, a lot like how water freezing in a tiny pavement crack will wedge it open.
Don't hold your breath. It's a fantastic engine concept but its target Skylon space plane sadly stands little chance of taking off from the 5.9km long runway it needs, and putting a payload into orbit. On paper it could put 12.5 tons into LEO with a fuel reserve of 0.5% however like any SSTO spacecraft any additional dry mass that inevitably creeps in during the design and build process directly reduces the payload capacity in a ratio or one to one.
Exactly how much mass it can launch looks like it won't matter. There's a growing mood for self assembly satellites. Put smaller bits into orbit, have them bolt themselves together. What matters then is speed of repeat launches, where Skylon looks good.
Doing it this way is attractive, because the cost of an integration facility on earth for an enormous satellite is very expensive. It's much cheaper to have a smaller facility that can handle one sub-sat at a time, you can sub bits of work out more easily, it's appealing because modularity makes design work a hell of a lot easier, etc.
So, Skylon might not end up being the biggest launcher with the best £/kg, but if customers are saving big time elsewhere and don't need a whole year of SpaceX launches to assemble the spacecraft in orbit (time to operational is also money), it does look quite good.
The people pitching one of the 18-40 TSTO VTO ELV's that are desperately scrabbling for market?
The infrastructure to do that does not actually exist. It'll have the compatibility issues of VHS/Betamax/V2000 multiplied by a 1000.
Now how will they get that tinkertoy satellite to GEO? Or to escape velocity?
Skylon's T/O buys you a full size GEO comm sat and the stage to get it there (or to escape velocity, or just below, but with a big payload).
There are issues, and if we compare it to current/future rockets, it probably isn't the way forward for space launches, Methane/Hydrogen rockets are probably the future.
But as an engine, it is amazing tech and could lead to supersonic, environmentally friendly air travel.
I'm more excited about that than I am about the space launch capabilities in the near term.
You're about 1 generation behind the D2. That's 15 tonnes.
What you don't seem to know about Skylon (because you've just cut-and-pasted a generic SSTO idea perhaps) is it is the only SSTO that offers VTO TSTO payload fraction IE 3-4% of GTOW as payload.
And the 3000 sec Isp (during air breathing mode, but that's enough) buys it a lot of weight growth in a way rocket based VTOL designs just don't have.
My knowledge on Skylon was from reading the 2003 concept paper (which I still have). The mass budget of 12.5 tons came from there (by adding the payload and fuel reserve numbers) so OK it was a while ago so there must be a latter version and it's now 15 tons.
The ISP of 3000 air breathing is irrelevant. That great ISP helps put the dry mass of the Skylon plus the payload and the 0.5% fuel reserve into LEO. If the dry mass goes up (it will) the payload will go down by the same amount. If you study the mass budget table in the design paper this should be apparent.
The good news is that now its 15 tons (or 17 tons according to some sources) they have a lot more to play with . The bad news is that Skylon is still just an idea 15+ years later.
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