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.
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?
Really, there are three different basic conops; single sats to GEO, cargo to a depot, and passengers to a station. Single GEO launches make sense to be equatorial, tourist stations will probably high inclination, and depots probably at 23-28 degrees (ecliptic aligned). The single GEO launches make sense to be equatorial, and so the first real Skylon base will probably be there. But if it works and is economical, I could imagine a proliferation of other launch sites in Europe and North America.
The best sites for freight operations may be islands in the Atlantic, Indian and/or Pacific Oceans, assuming an equatorial orbit destination. 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), a launch site nearer the poles wouldn't be unreasonable as there would be no advantage to an equatorial spaceport for such a mission. Your passenger traffic is likely to be European, American, Chinese, Korean, Arabian and Indian. Europeans and Americans might find a spaceport on an island in the Atlantic more convenient, while the Asian nations would probably like to use an island in the Pacific. Indians and Arabs would prefer a site either in some remote location within their countries or an island in the Indian Ocean.Probably the bigger consideration is noise from the takeoff, as Hempsell has pointed out numerous times, which argues for sparsely-populated island locations for siting launch facilities.
There's another problem with Quito or most other inland launch sites: sonic boom. Skylon doesn't take off vertically like a rocket, but gradually ascends to 28.5 km over 620 km before switching to rocket mode at Mach 5.5. That's going to create a carpet of sonic boom like Concorde did, except probably worse because Skylon is much bigger and much faster. Concorde was banned from supersonic flight over land. Coastal launch sites may be de rigeur, at least in democratic countries. -Snip-Sparsely-populated islands near the equator sound like the best place for launch sites, but islands that are big enough for a 5.5 km runway tend to have quite substantial populations, while ones that have few inhabitants tend to be too small. Ascension Island is a possibility in the Atlantic, but although it already has a 3 km runway, it might be tricky to fit a 5.5 km one because the island is rather mountainous. I don't see why it would be preferable to Kourou.I don't see what's wrong with coastal sites like Kourou, Alcantara and Cape Canaveral.
Cape Canaveral (28 degrees north, wouldn't Hawaii (21 degrees north) be better?), USA, raises an important question.
Aside from my earlier post recommending the coastal town of Lamu, Kenya
I'd also like to note that Ascension Island does have room for a 5.5Km runway on it's southern side, some distance from where the inhabitants seem to live on the northern side. The downside is that the east-west-facing runway would need to span three rivers/large streams.
That said, it would keep a UK spaceplane operating from UK soil.
That said, Alan Bond (I'm sure of this but I still can't find the video that had him saying so) said that if the STRICT/STERN Expansion/Deflection nozzles work then they'd shave 1Km to 1.5Km off that takeoff run so the 4Km start-to-rotation distance reduces to 2.5Km to 3Km reducing the whole thing to 4Km to 4.5Km. That should simplify things at Ascension as they do seem to have some space at the southern end of the existing runway.
Quote from: Kharkov on 11/04/2012 12:05 pmCape Canaveral (28 degrees north, wouldn't Hawaii (21 degrees north) be better?), USA, raises an important question.Okay, Cape Canaveral isn't ideal for equatorial orbits, but where would you find space for something as noisy as the Space Shuttle in Hawaii?
Launching from the equator is only a factor when you want to get to GSO. Cape Canaveral only shaves off ±50m/s delta-V compared to equator, but it benefits from having most infrastructure in place + short supply lines. You don't want to launch Skylon from Quito, Alcantara, Honolulu, Easter Island, or whatever remote atoll (and DEFINITELY NOT Kenya, PLEASE) just for the sake of a few m/s of delta-V. Long supply lines and lack of infrastructure make those options a no-go.
With regards to runways, the spaceport location is up to the operator, if they want to offer the most flexible service they should set up at the equator with eastern ocean views (like existing launch vehicles), but specialists services could be located elsewhere – the performance to high inclinations like Sun synchronous is slightly improved by high inclination launch sites. The User Manual shows the performance for launch sites up to 60 degrees latitude. We assumed sea level sites, since we pictured the takeoff being close to an ocean. Altitude should provide a slight improvement in performance but may also impact the take off speed – so an even longer runway please. We have not evaluated the impact of high altitude launches.
Repeating what I said earlierIf you buy into the highly unlikely scenario that Skylon will actually work, then the loss of payload capacity due to launch latitude really doesn't matter. Because concept is supposedly going to drastically reduce the cost of launches; multiple launches can be used to achieve a given mass to orbit vs optimizing the capacity on a given launch or launch site. French Guiana was chosen for ELV's and not an RLV that supposedly going to change space launch. Other costs will dictate launch location rather than performance considerations (i.e it might be more economical to launch from Europe vs French Guiana, due to additional logistical costs)
Jim, you have a reputation as a smart guy and it's probably well deserved. But, there are a lot of smart guys who have looked at the SKYLON design and said it will work.