Author Topic: The Reaction Engines Skylon Master Thread (1)  (Read 273249 times)

Offline Warren Platts

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Re: The Reaction Engines Skylon Master Thread
« Reply #1110 on: 10/31/2012 06:24 PM »
@ Bob: I agree a numerical simulation is the only way to settle the issue, and that they've probably actually looked at that. Next time Mr. Hempsell pops in, hopefully, he can weigh in on the issue. Not that it's a big deal, but I'd like a little input before I go buying any land on that big plateau east of Quito I found on Google Earth! ;)

@ 93413: I agree you can't just subtract the altitude--the savings is marginal--less than 5% no doubt, yet its real and maybe worth taking into account, other things being equal. One thing, if you're starting from 5 km up already, the drag you're going to experience as you accelerate to supersonic speeds is going to be significantly less.
"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.--Leonardo Da Vinci

Offline 93143

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Re: The Reaction Engines Skylon Master Thread
« Reply #1111 on: 11/01/2012 07:11 PM »
One thing, if you're starting from 5 km up already, the drag you're going to experience as you accelerate to supersonic speeds is going to be significantly less.

The thrust will be significantly less too.  The flight profile is tailored to produce optimal engine performance over the substantial range of airspeeds seen by the intake.  Start the thing cold at the altitude at which it expects Mach 1.2 and you may be disappointed with the results.

I agree, of course, that an actual answer would require an actual analysis (or at least a response from someone sufficiently expert to genuinely see the answer as obvious, if such a person exists).

Online MP99

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Re: The Reaction Engines Skylon Master Thread
« Reply #1112 on: 11/01/2012 07:38 PM »
But, if you ran cargo or passenger SKYLON flights to a resort hotel in a polar, sun-synchronous orbit (which has advantages from the point of view of visitors always having a view of the Earth lit up in daylight)

Night views from ISS seem spectacular. Would be disappointing to go to orbit and not see that.

cheers, Martin

Offline BobCarver

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Re: The Reaction Engines Skylon Master Thread
« Reply #1113 on: 11/01/2012 09:04 PM »
But, if you ran cargo or passenger SKYLON flights to a resort hotel in a polar, sun-synchronous orbit (which has advantages from the point of view of visitors always having a view of the Earth lit up in daylight)

Night views from ISS seem spectacular. Would be disappointing to go to orbit and not see that.

cheers, Martin

How about an orbit that follows the terminator? Very spectacular. If it were the sunset terminator, you would see afternoon to the left and evening to the right as the Earth sweeps below.

Online douglas100

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Re: The Reaction Engines Skylon Master Thread
« Reply #1114 on: 11/01/2012 10:05 PM »
Higher radiation exposure in a polar orbit.
Douglas Clark

Offline BobCarver

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Re: The Reaction Engines Skylon Master Thread
« Reply #1115 on: 11/01/2012 11:34 PM »
Higher radiation exposure in a polar orbit.

Do you have a quantitative comparison (or link to one)? Would it be comparable to passing through the http://en.wikipedia.org/wiki/South_Atlantic_Anomaly ?

Offline baldusi

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Re: The Reaction Engines Skylon Master Thread
« Reply #1116 on: 11/02/2012 04:30 PM »
Look at the profile:

for certain altitudes, as long as you don't stray too far from the Equator, you can get below the worst part of the Belt. But if you go in an exactly polar orbit, you'll be crossing the worst part four times per orbit!

Offline BobCarver

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Re: The Reaction Engines Skylon Master Thread
« Reply #1117 on: 11/02/2012 05:44 PM »
Thanks for the chart. I'm afraid we've wandered off-topic here. But, we have to deal with radiation if we're ever going to leave LEO.  :)

If we can't, then we're doomed as a species.

Offline baldusi

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Re: The Reaction Engines Skylon Master Thread
« Reply #1118 on: 11/02/2012 06:00 PM »
Thanks for the chart. I'm afraid we've wandered off-topic here. But, we have to deal with radiation if we're ever going to leave LEO.  :)
Not really off-topic. The SSO launches are a significant part of the launches market. If Skylon pretends to compete, it will have to be hardened for thousand of passes through the Van Allen belt. Luckily, for a vehicle of its size, it shouldn't be such a problem.
The other issue is one of performance. Will Skylon be able to put any significant payload on the 800km~600km altitude of the normal SSO or will it need an US?

Offline BobCarver

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Re: The Reaction Engines Skylon Master Thread
« Reply #1119 on: 11/02/2012 06:16 PM »
Bond talked about the initial SKYLON being analogous to a DC-3, with follow-on 747 and successive models to come in the future. I have no doubt that much higher orbits will be reached at some model level:

« Last Edit: 11/02/2012 06:24 PM by BobCarver »

Offline 93143

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Re: The Reaction Engines Skylon Master Thread
« Reply #1120 on: 11/02/2012 07:23 PM »
The User Manual indicates a two-tonne payload to an 800 km SSO.  This doubles to four tonnes for 500 km.

Be aware that these are C2 numbers; D1 is a bit smaller due to technological advances, so it might not lose payload as fast to high altitude and inclination.
« Last Edit: 11/02/2012 07:52 PM by 93143 »

Offline BobCarver

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Re: The Reaction Engines Skylon Master Thread
« Reply #1121 on: 11/02/2012 08:13 PM »
The User Manual indicates a two-tonne payload to an 800 km SSO.  This doubles to four tonnes for 500 km.

Be aware that these are C2 numbers; D1 is a bit smaller due to technological advances, so it might not lose payload as fast to high altitude and inclination.

If you were going to take tourists to a high-altitude station, you would have a chioce of using the present design and transferring the passenger module to an in-space transfer vehicle to transport them to the high-altitude station, or building a bigger version of SKYLON to take them there all the way in a single go. The in-space transfer vehicle would probably be the choice near term, of course. We could speculate about what kind of design would be best for this vehicle, but it might be somewhat off-topic here I suspect, if only because REL have not announced the design of such a vehicle. May be a good subject for a "Reaction Engines Skylon Slave Thread."

Offline 93143

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Re: The Reaction Engines Skylon Master Thread
« Reply #1122 on: 11/03/2012 06:52 AM »
Just to be totally clear for all readers, those numbers are for launching from the equator into a 98 sun-synchronous orbit.  Even a low-altitude orbit (~200 km) won't allow much more than 6 tonnes, at least on the C2 (again, D1 might do better).  Launching from a site at 60 latitude adds nearly a tonne to all three numbers.

Launching from the equator into an equatorial orbit, Skylon C2 can haul 11 tonnes to 800 km, or more than 13 tonnes to 500 km.
« Last Edit: 11/03/2012 07:20 AM by 93143 »

Offline Turbomotive

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Re: The Reaction Engines Skylon Master Thread
« Reply #1123 on: 11/04/2012 02:54 AM »
Regarding bird strike issue, maybe a spaceport could have a fleet of birds of prey to scare them off like they do at Wimbledon. Somewhat retro that your Skylon spaceport would have a role for a Chief Falconer, but anyone have any more effective ideas?
"Men might as well project a voyage to the Moon as attempt to employ steam navigation against the stormy North Atlantic Ocean." - Dionysius Lardner, 1838

Offline Warren Platts

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Re: The Reaction Engines Skylon Master Thread
« Reply #1124 on: 11/04/2012 03:32 AM »
Shotguns?
"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.--Leonardo Da Vinci

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