REL has been developing Skylon since the 1990s, and has done nothing but suck up research dollars ever since. It hasn't ever created a testable engine, let alone a testable plane. The whole idea is a set of nearly insurmountable problems.<p>For just one example, they claim that it will be an enormous plane filled with hydrogen, so on re-entry it will have a large cross section but low mass so it will be slowed by atmospheric friction more rapidly than the shuttle. But it's also going to have wings and turbulent air flow, it's a bad shape for atmospheric re-entry. This is project killer if they can't handle re-entry, and they are no where near a physical test of it.
>The SABRE Engine is a hybrid air breathing rocket engine. In the past, attempts to design single stage to orbit rockets have been unsuccessful largely due to the weight of oxidiser, such as liquid oxygen.<p>Carrying your oxidizer with you allows you to avoid losses related to the accelerating (which is slowing down in the plane's frame or reference) of the unnecessary 80% of the incoming air, ie. nitrogen. Decompressing that nitrogen back in the working chamber (which also decreases the efficiency of the chamber) allows to recuperate back some of that loss. At slow speeds (like typical jet) - most of that loss is recuperated back. The higher the speed the bigger the share of that unrecuperated loss, due to higher temperatures, etc... Granted, thrust-wise having larger working mass moving slowly would usually/theoretically be welcome (larger prop effect, one example in application to rockets - air-augmented rockets like <a href="http://www.astronautix.com/g/gnom.html" rel="nofollow">http://www.astronautix.com/g/gnom.html</a>), yet at higher speeds other things like that mentioned loss, efficiency, complexity/cost, etc. start to become major factors.<p>Additionally the potential amount of oxidizer saved while reaching the orbit is really not that much. Quick mind napkin calculation shows that on the order of several tons per engine which is close to a wash given the additional hardware (thus weight) necessary for such scheme to work.<p>If anything, 2 stage system with returnable 1st stage should work much better/cheaper/robust as we can already see from SpaceX and SpaceShipOne. Developing such first stage - basically a plane for quick acceleration to M5-M8 and returning back to the airport should be pretty simple relatively to any other orbital/suborbital or long-range supersonic effort.
If a plane of this design ever flies, I will purchase a stout fedora and eat it one sitting.<p>There are SO MANY things that can go wrong, esp. at the micro level, which will see the engine turn from a chiller to a block of ice, then melted metal in a fraction of a second. Plus this is being developed in the UK, a country whose aerospace industry lost its entrepreneurial spine when the de Havilland Comets started falling from the sky and never really recovered IMHO.
>Who wouldn’t want to have breakfast on the French Riviera, take a walk along the Great Wall of China in the afternoon, and then cap off the evening by staring at stars above the Alaskan wilderness?<p>Ok, I know this is just aspirational ad copy... but, realistically, this looks very bad with respect to planetary health.<p>We're trying to get people out of cars and into public transit or bikes --this would do the opposite of that. It would allow the wealthy to further increase their carbon footprint. In addition, even if we figure ways to counterbalance carbon pollution, it would in the least increase throughput in a given area due to reduced travel friction. Already some national parks exhibit detrimental effects from too many people visiting -such that some require advanced limited reservations.
How do you shed 400Mwh of heat in an area that small?<p>I would imagine the surrounding air would take some of the heat, but that's an incredible amount of energy to dissipate in such a small area.<p>Call me skeptical.
I’d been happy if we could just get commercial supersonic flight back. NASA is working on quiet supersonic, which will hopefully do the trick:<p><a href="https://www.extremetech.com/extreme/251718-nasas-quieter-supersonic-plane-project-soon-take-flight" rel="nofollow">https://www.extremetech.com/extreme/251718-nasas-quieter-sup...</a>
Should be tagged as 2014. The included video interview is even older, from July of 2012.<p>I can't find any recent news about them. Only what they post themselves, which doesn't seem to have much concrete information: <a href="https://www.reactionengines.co.uk/category/news/" rel="nofollow">https://www.reactionengines.co.uk/category/news/</a>