Quote from: adrianwyard on 04/08/2015 03:38 pmIf you reread my posts you'll see they go like this (with positive fanboi vibe now added in):1] "Hey fellow-Skylon fans, I just realized that Skylon's re-entry will push the state of the art further forward than anything before it. How come no-one ever mentions that? More than any spacecraft before it, Skylon actually 'flies' in on the canards. How cool. Passively stable re-entry vehicles are for wimps. :-)"Perhaps because no spaceplane before it had cannards? The importance of trim was one of the big discoveries of the HOTOL project. Putting the engines on the wing tips is a big change. Skylon is designed to avoid the continuous "fluttering" of control surfaces the Shuttle used to keep it stable. You're assuming it will be unstable. That's not a given.
If you reread my posts you'll see they go like this (with positive fanboi vibe now added in):1] "Hey fellow-Skylon fans, I just realized that Skylon's re-entry will push the state of the art further forward than anything before it. How come no-one ever mentions that? More than any spacecraft before it, Skylon actually 'flies' in on the canards. How cool. Passively stable re-entry vehicles are for wimps. :-)"
An interesting question is could it be stable enough to allow a human pilot to fly it without a computer in the loop to stabilize it. That would make it a very exciting prospect for some potential customers. Quote2] "Wouldn't it be awesome if Skylon could take-off and land at regular airports? I know our friends at REL have already worked out how to make it take off in the shortest distance, but I'm just such a fan that I can't help but think about ways to improve Skylon. So, how about adding canards at the back to aid in earlier rotation. Probably a silly idea, I know."Then you're missing the biggest issue of all. The huge noise level. It's not just the thrust it's the exhaust velocity for air/H2 is much higher than air/kerosene mixture. While OK for occasional takeoffs or emergency landings (which will be unpowered) it's most unlikley there will be fully fueled take offs from any regular airport.
2] "Wouldn't it be awesome if Skylon could take-off and land at regular airports? I know our friends at REL have already worked out how to make it take off in the shortest distance, but I'm just such a fan that I can't help but think about ways to improve Skylon. So, how about adding canards at the back to aid in earlier rotation. Probably a silly idea, I know."
"While adding redundant control surfaces (e.g. horizontal stabilizers on the tail) would indeed mean you'd still have those available if the front canards were to fail, wouldn't the failed/stuck surfaces cause you control problems that your remaining surfaces might not be able to overcome?"
Rather than repeat myself here, I'll refer interested parties (if there are any) back to my initial post on this If you've read anything that indicates the Skylon shape will be more passively stable than the Shuttle during belly-first entry, I'd be very interested in that reference. As you know, the Shuttle was not stable, and its orientation needed to be active maintained with the body flap and elevons.
EDIT: Perhaps we can agree that placing the engines on the wings makes Skylon more symmetrical than the Shuttle in terms of entry (pre-aerodynamic, ~45 degree nose-up) configuration, which is an advantage. But where the orbiter was a simple, relatively compact double-delta, Skylon is a complex shape, and spindly, meaning ISTM that it will have more pronounced forces at the nose and tail that need to be dealt with.
Right. The cases mentioned in my (non fanboi) post were 1] initial delivery to Korou, and 2] recovery after abort: http://forum.nasaspaceflight.com/index.php?topic=36826.msg1355300#msg1355300. I 'worry' that self-ferry even in these rare, special cases might not be possible. And noise is certainly a factor.
"You're probably right. Better to put extra effort into making sure the canards always work. (And are sized for self-ferry in addition to orbital take-off)."
I'm confident everybody in this conversation is within 10% agreement, so to go on would say more about the hazards of forum-based communication than anything else. For example, lkm says "Hempsell has already stated on the thread that any ordinary sub-3km runway can launch a self-ferry Skylon". Which should settle the issue, right? But in the cited comment Hempsell actually says the following - in 2012 - "we currently believe believe Skylon would be able to use sub-3 km runways".I take that to mean it's not a 100% done deal, and so a topic for conversation. But when I raise the topic of self-ferry, and speculate on the usefulness of greater control authority if it turns out to be marginal on shorter runways JohnSmith19 asks me: "why you think the control surfaces which are sized to control a fully loaded Skylon won't be able to cope with the loads imposed by a vehicle that's 150 tonnes lighter in self ferry and over 200 tonnes lighter during re entry? That seems illogical."Just because I'm interested in the self-ferry case doesn't mean I think it can't be done (and REL are liars). But by the same token, REL said they currently believe it can be done, which means there's a chance it might be tricky. That's what makes me raising the issue legit, rather than 'illogical'.Same thing with Skylon entry. Just because I note that it's rarely talked about - and will not be a walk in the park - doesn't mean that I think it's impossible. But neither do I think it's established that no further work is necessary.___To conclude: I don't think anyone here is saying that self-ferry and entry 1] require no further design and testing, or 2] will clearly fail as designed. If you are, then let's continue, otherwise let's change the subject.
To conclude: I don't think anyone here is saying that self-ferry and entry 1] require no further design and testing, or 2] will clearly fail as designed. If you are, then let's continue, otherwise let's change the subject.
Lots more jobs appearing on the Reaction Engines websitehttp://www.reactionengines.co.uk/careers.html
nice! are these new jobs or sobstitutions of people that left?anyway, SpaceX is so close now. The others cannot afford to to ignore reusability any more. Although I am seriously afraid someone at ESA will fall into the Siren's trap of a "REUSABLE ARIANE 6 BY 202X"........
I still wonder whether the UK government, or REL themselves, sent an application for funding at the Commission for the new Juncker fund. This is not public ownership in the classical way... If they didn't, I would at least like to undestand why
http://www.reactionengines.co.uk/press_release.htmlNew press release from Reaction EnginesLooks like the USAF agrees with ESA with regards the feasability of the SABRE concept
http://www.reactionengines.co.uk/press_release.htmlNew press release from Reaction EnginesLooks like the USAF agrees with ESA with regards the feasibility of the SABRE concept
Quote from: Mutley on 04/15/2015 03:02 pmhttp://www.reactionengines.co.uk/press_release.htmlNew press release from Reaction EnginesLooks like the USAF agrees with ESA with regards the feasibility of the SABRE conceptNo, feasibility is the wrong word. AFRL "investigations examined the thermodynamic cycle of the SABRE concept and found no significant barrier to its theoretical viability provided the engine component and integration challenges are met." They found that it can happen but have not ruled on that it will happen.
"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."
Quote from: Mutley on 04/15/2015 03:02 pmhttp://www.reactionengines.co.uk/press_release.htmlNew press release from Reaction EnginesLooks like the USAF agrees with ESA with regards the feasability of the SABRE conceptFrom the press release:Quote"Although application of the SABRE for single stage to orbit space access remains technically very risky as a first application, the SABRE may provide some unique advantages in more manageable two stage to orbit configurations."Given the huge projected development cost of the SSTO version, I kind of agree with that.They could, for example, leave the atmosphere at lower speed, in order to reduce aerodynamic pressure, and reenter at Mach 15 or so instead of orbital speed. The vehicle would then land downrange similar to the Hopper concept and could be towed back to Kourou.An upper stage with Vinci could do the rest. It would probably fit into the vehicle (with a longer bay obviously).Any other ideas?