Quote from: Rocket Science on 11/29/2012 01:45 pmQuote from: Crispy on 11/29/2012 11:10 amIt's not a monocoque fuselage. It's a spaceframe, supporting a non-structural skin and internal non-structural tanks. It's more similar to a Zeppelin than an aeroplane or rocket.I would appreciate a link for that if you have one handy..."Application of Carbon Fibre Truss Technology to the Fuselage Structure of the SKYLON Spaceplane"Richard Varvill and Alan Bond, 2004http://www.reactionengines.co.uk/tech_docs/JBIS_v57_x-x.pdfI'm sure the design has moved on quite a bit in 8 years though!
Quote from: Crispy on 11/29/2012 11:10 amIt's not a monocoque fuselage. It's a spaceframe, supporting a non-structural skin and internal non-structural tanks. It's more similar to a Zeppelin than an aeroplane or rocket.I would appreciate a link for that if you have one handy...
It's not a monocoque fuselage. It's a spaceframe, supporting a non-structural skin and internal non-structural tanks. It's more similar to a Zeppelin than an aeroplane or rocket.
Quote from: Rugoz on 11/29/2012 11:41 amIf you sell your flights at 40m that is, otherwise it will only cover operating costs.Good point. Let's split the difference at $30m, on the assumption that the REL figure of $10m covers the operating costs for a launch?
If you sell your flights at 40m that is, otherwise it will only cover operating costs.
Quote from: Jim Davis on 09/02/2010 01:11 pmIt appears at first glance that Skylon, with its widely separated engine nacelles, would be difficult to control if there was a thrust imbalance. Specifically, an inlet unstart would subject the spacecraft to a severe yaw, would it not? Can that inadequate looking vertical tail suffice to control Skylon in those conditions? Or does the other inlet unstart to maintain a thrust balance? Would the mission have to be aborted in such a case? Or does Skylon have such large static margins to make unstarts very unlikely?The answer is we can cope with an engine out throughout the whole but it does mean a mission abort.The exact procedure depends on the nature of the failure and when in the ascent it happens. But the tail fin does play a significant part in the yaw control in many of the cases. Both it and the forward fin may look intuitively small compared with the body but it is because the main body is abnormally large for the vehicle mass (and hence moments) being about half way to a 1930s airship when empty.
It appears at first glance that Skylon, with its widely separated engine nacelles, would be difficult to control if there was a thrust imbalance. Specifically, an inlet unstart would subject the spacecraft to a severe yaw, would it not? Can that inadequate looking vertical tail suffice to control Skylon in those conditions? Or does the other inlet unstart to maintain a thrust balance? Would the mission have to be aborted in such a case? Or does Skylon have such large static margins to make unstarts very unlikely?
The nominal purchase price of a Skylon is $1B, though I believe the price would have to go up if there were only enough interest to generate 10 sales instead of 30. The estimated/targeted ops cost per flight is $5M.
Quote from: WellingtonEast on 11/28/2012 08:27 pmIt then provides a list of typical overpressure per aircraft types at varying height levels:SR-71: 0.9 pounds, speed of Mach 3, 80,000 feet Concorde SST: 1.94 pounds, speed of Mach 2, 52,000 feet F-104: 0.8 pounds, speed of Mach 1.93, 48,000 feet In this context if Skylon is flying at 25KM = 80,000 feet for intercontinental trips - isnt the sonic boom a non issue until landing approaches where it would slow subsonic near populated areas at low altitudes??No, the larger the aircraft, the greater the overpressure
It then provides a list of typical overpressure per aircraft types at varying height levels:SR-71: 0.9 pounds, speed of Mach 3, 80,000 feet Concorde SST: 1.94 pounds, speed of Mach 2, 52,000 feet F-104: 0.8 pounds, speed of Mach 1.93, 48,000 feet In this context if Skylon is flying at 25KM = 80,000 feet for intercontinental trips - isnt the sonic boom a non issue until landing approaches where it would slow subsonic near populated areas at low altitudes??
Regarding lapcat,Overpressure at start of cruise is 85 Pa.Mid cruise its 70 Pa.Concorde: 93 Pa.In general <50 Pa is considered "acceptable" for regular overflight.Everything from herehttp://www.transport-research.info/Upload/Documents/201211/20121105_121021_14924_Final_Activity_Report.pdfpage 12
Regarding lapcat,Overpressure at start of cruise is 85 Pa.Mid cruise its 70 Pa.Concorde: 93 Pa.In general <50 Pa is considered "acceptable" for regular overflight.Some flight times, first subsonic, then mach 5 cruise.Brussels – Sydney 22.25 hours 4.6 hoursBrussels – Los Angeles 10.0 hours 2.5 hoursBrussels – Tokyo 10.75 hours 2.5 hoursBrussels - New York 7.5 hours 1.6 hoursBrussels - Beijing 8.9 hours 4.9 hoursBrussels - Delhi 7.2 hours 5.3 hoursParis - Kourou 7.9 hours 1.7 hoursLos Angeles - Tokyo 9.75 hours 2.0 hoursLos Angeles - Sydney 13.4 hours 2.6 hoursLos Angeles - Singapore 15.7 hours 3.0 hoursLos Angeles - Delhi 14.3 hours 7.5 hoursEverything from herehttp://www.transport-research.info/Upload/Documents/201211/20121105_121021_14924_Final_Activity_Report.pdfpage 12
There are no more 'crash' points where it can all come to a screeching halt. There are only 'issues'.
Can SABRE meet, or exceed, its thrust targets? Can they meet the weight target, or come in lighter? Can they get 200 flights out of the engine, or more?
Quote from: Rugoz on 11/30/2012 12:11 amLos Angeles - Delhi 14.3 hours 7.5 hoursEverything from herehttp://www.transport-research.info/Upload/Documents/201211/20121105_121021_14924_Final_Activity_Report.pdfpage 12Looking at those numbers lapcat could revolutionize business travel in a manner similar to the change from piston engine airliners to jet airliners did.
Los Angeles - Delhi 14.3 hours 7.5 hoursEverything from herehttp://www.transport-research.info/Upload/Documents/201211/20121105_121021_14924_Final_Activity_Report.pdfpage 12
The SABRE engine can reasonably be expected to meet its thrust target (within a moderate range). These days, you can model a rocket design, build your test model & more or less get the predicted thrust.
Quote from: Kharkov on 11/30/2012 02:01 amThe SABRE engine can reasonably be expected to meet its thrust target (within a moderate range). These days, you can model a rocket design, build your test model & more or less get the predicted thrust.This isn't a simple engine and so those words are not applicable
Quote from: Jim on 11/30/2012 03:44 amQuote from: Kharkov on 11/30/2012 02:01 amThe SABRE engine can reasonably be expected to meet its thrust target (within a moderate range). These days, you can model a rocket design, build your test model & more or less get the predicted thrust.This isn't a simple engine and so those words are not applicableCorrect me if I'm wrong but I understood that the stuff in front of the engine was the cutting-edge stuff & the rocket itself was largely similar to every other closed-cycle rocket out there. That was why I said that, once you've modelled it, you should get, within a certain range, the thrust you were expecting from your physical engine.Could someone explain how that's wrong?
Yes Jim, you're entirely right but...The rocket part of it is, IMHO, not that different from other rockets. My point, and perhaps I haven't made it very well, is that, after accumulating experience with rockets for 50 years (other people, that is, certainly not me), engineers can build a rocket, first on the back of an envelope and then inside a computer and calculate what the thrust figures will be and the model will be sufficiently good that when they build the engine, they'll get the thrust figure they expected to get, plus or minus (probably minus) a certain percentage.So I don't think, just my opinion here, that REL is greatly worried that their first actual SABRE will come up with only half the expected thrust or something.It might, or will if that's what generally happens in your experience, end up heavier than expected or not have the lifespan they want or more maintainence requirements than they expect but that's part of engineering. Beyond a certain point, you have to build it to see if it works as expected, for as long as expected and as hard as expected.I think those are the questions that REL will be trying to answer over the next few years.To summarise:I, personally, as a non-engineer, think REL are confident that they'll get X amount of thrust out of their SABRE engine & they're not expecting a thrust figure significantly different.Now they're going to try & make the SABRE engine as light as they can, with as long a lifespan as they can, and with the lowest maintainence requirements they can.
Engine not producing enough thrust for orbit? It is unlikely given the thrust generating element is a chemical rocket engine, and the performance of chemical rocket engines can be very precisely calculated, as we have done the rocket engines we have built and tested.
Yes Jim, you're entirely right but...The rocket part of it is, IMHO, not that different from other rockets. My point, and perhaps I haven't made it very well, is that, after accumulating experience with rockets for 50 years (other people, that is, certainly not me), engineers can build a rocket, first on the back of an envelope and then inside a computer and calculate what the thrust figures will be and the model will be sufficiently good that when they build the engine, they'll get the thrust figure they expected to get, plus or minus (probably minus) a certain percentage.So I don't think, just my opinion here, that REL is greatly worried that their first actual SABRE will come up with only half the expected thrust or something.
Quote from: Kharkov on 11/30/2012 04:52 amTo summarise:I, personally, as a non-engineer...Quote from: Hempsell on 11/12/2012 03:46 pmIt is unlikely given the thrust generating element is a chemical rocket engine, and the performance of chemical rocket engines can be very precisely calculated.
To summarise:I, personally, as a non-engineer...
It is unlikely given the thrust generating element is a chemical rocket engine, and the performance of chemical rocket engines can be very precisely calculated.
The award, expected to be worth around 1 million ($1.3 million) over a year, would support work underway on REL's Synergetic Air-Breathing Rocket Engine (SABRE)
The UK is not part of the ESA launcher program, and would have to join, Ford said when asked if ESA will fund the engine's continued development. But going forward, we've been engaged by the UK Space Agency to go through and plan Phase 3. This will conclude soon.
