LH2 has a known boil off rate for a given tank and ambient conditions. A factor to be engineered into the design, not a show stopper. Consider that the tanks and heat shields will need to deal with a period of supersonic flight, with a hot skin. This implies to me some insulation. A limited amount of boil off should be part of the design. For a moderately extended hold I don't expect too much trouble driving out a truck to top off the tanks. Longer holds (hopefully very rare) imply return to the hanger.
The propellants are loaded subcooled.Also, the tankage is indeed insulated. It's just that it's inside the spaceframe truss, which is inside the TPS, so you don't see the insulation.What exactly is unrealistic about the payload integration facility?
Not really. This is the first time I have seen it and it has some holes. The first thing I saw that is wrong is the payload integration facility. Totally unrealistic.
And the timeline is just as funny as the two week shuttle turnaround.
It uses LH2, which boils off quickly. They have only talked about the flight vehicle and not the ground support equipment.
How do you "subcool" LH2??
I mean selling launches /before/ all orbital launches have been completed.Just 2 years of flight testing for 400 flights is VERY optimistic, as we can see from SpaceShipTwo and other reusable test-bed vehicles.And yes, I do think that such expensive vehicles will be a hard sell, especially with the significant ground support equipment that will be necessary.There will be a lot of pressure by investors to get earlier income. That's why I think that if Skylon ever happens, Reaction Engines will be initially operating Skylon for customer launches (during the "test program," if you like). And at that point, it'd be really tempting to just continue operating, since they'll already have the infrastructure in place.And of course, customers of Skylon would know this. That's part of why I am skeptical of the "just sell Skylons to people, and ignore the actual launch market." If Skylon ever happens, I really doubt that's how it will work.
REL staff did work on payload integration for the Shuttle. They are aware of the issues around Coupled Loads Analysis, which is why they don't plan to bolt the payloads to the airframe.
Indirectly they have. It's in their references to the use of sub cooled propellants to avoid tank venting. Either the vehicle launches before the system starts to boil or the propellants recycle to long term storage.
Quote from: Robotbeat on 12/05/2015 01:28 amI mean selling launches /before/ all orbital launches have been completed.Just 2 years of flight testing for 400 flights is VERY optimistic, as we can see from SpaceShipTwo and other reusable test-bed vehicles.And yes, I do think that such expensive vehicles will be a hard sell, especially with the significant ground support equipment that will be necessary.There will be a lot of pressure by investors to get earlier income. That's why I think that if Skylon ever happens, Reaction Engines will be initially operating Skylon for customer launches (during the "test program," if you like). And at that point, it'd be really tempting to just continue operating, since they'll already have the infrastructure in place.And of course, customers of Skylon would know this. That's part of why I am skeptical of the "just sell Skylons to people, and ignore the actual launch market." If Skylon ever happens, I really doubt that's how it will work.I actually don't see the point of them doing 200-400 test flights and not at least using a few of them to place actual satellites in orbit. Especially if the first few orbital flights are completed, especially if they are done without any major problems cropping. These won't necessarily be big satellites, but things like cube satellites, small research satellites from universities and schools.
"Payload integration" for aircraft is basically loading the cargo on the plane in a container or strapping it down to deck fittings.
This isn't an aircraft nor is it carrying bulk cargo.
1. It's got wings, takes off from a runway, and flies under its own power, which seems very much like an aircraft to me.2. How do you define bulk cargo? The cargo bay is designed to take virtually anything up to the mass limit. That could include bulk items such as water, fuel and other consumables. It'd need specially designed cargo modules, but it'd be possible.
Quote from: Ravenger on 12/08/2015 04:10 pm1. It's got wings, takes off from a runway, and flies under its own power, which seems very much like an aircraft to me.2. How do you define bulk cargo? The cargo bay is designed to take virtually anything up to the mass limit. That could include bulk items such as water, fuel and other consumables. It'd need specially designed cargo modules, but it'd be possible.1. It goes into orbit, that negates the aircraft designation. It is a launch vehicle.2. It isn't going to bulk cargo in the beginning. It is going to deliver spacecraft
Subcooling doesn't prevent boil off
1. It goes into orbit, that negates the aircraft designation. It is a launch vehicle.
Nonsense. Don't know where to start since so much is wrong in that statement.
A. The need for CLA's is not determined by the method of attachment.
b. ELV's use clamp bands and still some have CLA issues
c. It is more about the spacecraft structural stiffness
d.. A bolted interface was not the driver of shuttle CLA issues
d. Skylon is using an interface that similar if not identical to the shuttle, the trunnion.
1. It gets it's lift from wings while in UK airspace. That makes it an aircraft.2. true. It's set by the wafer thin structural margins of most ELV's and the practice hard mounting to the LV, making for superb coupling between 2 major structures with opportunities to excite all kinds of failure modes. 3. Seriously LV's are the only transport systems that often require the cargo to be redesigned multiple times because it could be shaken to bits, or cause it's carrier can be shaken to bits by the resonance it can excite back into the carrier vehicle. 4. I'd suggest the size and position of any spacecraft fluid tanks might be some effect on things as well. The point is it should have no effect. It should not require an FEA simulation to determine if there is or is not a problem.5. True. But I would ask if CLA was as big a problem with Shuttle as it is with ELV's?
Seriously LV's are the only transport systems that often require the cargo to be redesigned multiple times because it could be shaken to bits, or cause it's carrier can be shaken to bits by the resonance it can excite back into the carrier vehicle.
Quote from: Jim on 12/04/2015 02:32 pmQuote from: francesco nicoli on 12/02/2015 11:01 pmthere is a difference in theory, and there is a difference for Skylon according with REL own plans. You might not like them, you might believe they are unrealistic and that "reality" today is different, but then again if anything that differs from how things are done today is unrealistic for the simple fact that they are not done today, why do you even bother about Skylon? You are right. I shouldn't bother since there is too much nonsense, unsupported conjecture and flat out just wrong statements on this thread. Much of it should be in the scifi section because it isn't reality or come close to it.Good, I'm glad we agree to disagree. Now it would be very kind of you if you could let us continuing our "nonsense conjectures" without further poisoning the discussion..
Quote from: francesco nicoli on 12/02/2015 11:01 pmthere is a difference in theory, and there is a difference for Skylon according with REL own plans. You might not like them, you might believe they are unrealistic and that "reality" today is different, but then again if anything that differs from how things are done today is unrealistic for the simple fact that they are not done today, why do you even bother about Skylon? You are right. I shouldn't bother since there is too much nonsense, unsupported conjecture and flat out just wrong statements on this thread. Much of it should be in the scifi section because it isn't reality or come close to it.
there is a difference in theory, and there is a difference for Skylon according with REL own plans. You might not like them, you might believe they are unrealistic and that "reality" today is different, but then again if anything that differs from how things are done today is unrealistic for the simple fact that they are not done today, why do you even bother about Skylon?
Quote from: ChrisWilson68 on 12/09/2015 12:31 amTo me, having someone who disagrees isn't poisoning the discussion.It depends on how they disagree. A great deal of insight can be gained from disagreements, provided they're presented in a more constructive form than "that's nonsense"
To me, having someone who disagrees isn't poisoning the discussion.