Nibb31

Those red tanks are probably the helium tanks to provide pressure to the fuel tanks. Upper-stage engines are typically pressure-fed, especially when they are restartable, because you can't count on gravity to ensure ullage. The reason there are several small ones instead of one big one is probably cost, integration, and spreading the mass. You could probably have a larger tank, but it would affect your CoM, or it would be more expensive, and maybe harder to move around and install. A rocket stage needs performance, but it also needs reliability and needs to be reasonably cheap. It's the combination of all those factors that makes rocket design complicated. Pretty much everything in rocket design has a reason. The people who make this stuff are smart. Different designs are the results of different decisions made on different requirements, but in the end, there are rarely "stupid" designs.

We've been discussing the reason for 2 pages now. By launching a dummy LAS, you save the cost of the attitude motors, the abort motors, and all the avionics that go inside. If they had put a live LAS on EFT-1, people would be complaining about wasting money just to potentially save a prototype that will be retired to a museum after the test anyway. The jettison motors are separate from the abort motors. This is probably because they are solids and have to be fired in two phases, and also because it would be dangerous to jettison the tower with the full thrust of the abort motors.

At this stage, the SRB thrust is only residual anyway, so it wouldn't make much of a difference. Also you would want to avoid any debris hitting the upperstage, so you want to keep as much integrity as you can while the upper stage is in the vicinity.

It also has its own avionics and liquid attitude control engines, as well as separation/jettison motors. It's a pretty complex system. I don't know the exact price difference between a live LAS and an inert one, of course, but several million dollars seems in the ballpark, and it seems reasonable to use that money elsewhere if there is no point in spending it. The LES had its own test campaign to provide data about abort conditions (including the PA-1 test). Data from the launch is not useful for this test, because it will never launch under these conditions again. After EFT-1, Orion MPCV will only ever fly on the SLS, which has a different flight profile. This test flight is only to test high-speed re-entry and some of the avionics systems in space. An abort from the Delta Heavy would not provide much reliable data that would concern an abort from an SLS.

Yes, it's an inert mass simulator. Yes, and having the capsule come down on a parachute instead of blowing up wouldn't turn the bad publicity into good publicity. It would still be a failure. And if the launch is successful, then you get bashed for wasting $10 million on a launch escape rocket for an unmanned prototype (and it's probably much more expensive than that).

Because they are more complex. It's not the man-rating that costs, it's the complexity of the design that is driven from the requirements. A hot-air balloon is man-rated, but it's cheaper than a GEO comsat. Because operators who buy Skylon will not want to wait 25 years to break even. An airliner is profitable way before the end of its operational life. Even 10 years is a long wait for ROI. Right, so we agree that space tourism is not Skylon's market. So then what IS Skylon's market ? What purpose justifies such a huge flight rate at the proposed price point? That is not how these things work... ESA's main purpose is to subsidize the European space industry. Most of the money is provided by France, Germany, and a couple of other big players. The UK is one of the smallest contributors. What each country gets is proportional to what each country puts in, and the decisional power goes to the biggest contributors. ESA is not going to cut the funding that goes to Airbus or Thales-Alenia to spend billions on a small company out of an industrial park in Oxford. The only way ESA will put any serious money into Skylon is if the British Government starts putting serious money into ESA. And I don't see that happening. I don't buy that. The graveyards of marketing are full of products for which somebody thought "build it and they will come". The rare cases where a new product creates a new need are the exception. Dividing the price of orbital launches by a factor of 10 doesn't mechanically multiply the demand by 10... or 100 or 1000. Demand will be driven by need, not price, and there simply is very little need for space.

1) No they won't. They will just talk about the failure. Then they will move on to Kim and Kanye. 2) Even a 5 year old kid can understand that there's no point in spending $10 million just to have pictures of an Orion coming down on parachute in the 1 out of 1000 chances that the Delta rocket blows up.

...And technology. The only stumbling blocks are money and technology. ...And purpose. Oh bugger! Amongst the only stumbling blocks are: money, technology, and purpose. ...And political will. Oh screw that. Nobody expects the Spanish Inquisition.

One of my favorites, the old Super Guppys.

Orion is not reusable. This Orion is just a test article. Who cares if it's destroyed. It's as expendable as all the other Orions that will follow. Once they have flown, they will end up in museums. So no, losing one test article because of the launcher will have no bearing on the Orion program. They will just have to launch another one on the same rocket, or wait until SLS. If the Delta fails, it says nothing about Orion because Orion is not supposed to ever again fly on a Delta rocket. As for image, if the test is a failure, it's a failure. Saving the test article on top will have zero impact, since it has zero value. It's pretty easy to explain to the public that a live LES on an unmanned test article would just cost more for no justifiable reason.

Why spend extra money to save it? It's expendable. It's just going to a museum and it won't contain anything useful if the launch is aborted anyway.

Video tapes are not digital. Even with half the data missing, they can still be read to some extent. Lose too many random bits in a digital stream and your data is corrupted.

Orion doesn't go to Mars on its own. It would be a tiny piece of the Mars spaceship. It wouldn't change anything. Even if the Delta does blow up, it has no bearing on the Orion program.

No it doesn't. The magnetic charge tends to get wiped out after a while. Tapes have to be duplicated on a regular basis. There are departments in NASA whose job is to continuously rewrite data tapes from the old science missions to new tapes before they get corrupted, which is a neverending job as the amount of data continuously grows.

From REL's web site: "SKYLON's fuselage and wing load bearing structure is made from carbon fibre reinforced plastic and consists of stringers, frames, ribs and spars built as warren girder structures. The aluminium propellant tankage is suspended within this, free to move under thermal and pressurisation displacements. The external shell (the aeroshell) is made from a fibre reinforced ceramic and carries only aerodynamic pressure loads which are transmitted to the fuselage structure through flexible suspension points. This shell is thin (0.5mm) and corrugated for stiffness. It is free to move under thermal expansion especially during the latter stages of the aerodynamic ascent and re-entry." There is nothing conventional about a carbon fibre load bearing structure the size of an A380 fuselage, covered with RCC panels that are designed to move under thermal expansion. RCC was used on the Shuttle's wing edges, but has never been used in such a huge structure. It was also damn expensive and fragile. F1 engine parts and exhausts are much smaller and they aren't exposed to the same constraints. Also, F1 teams can afford to replace them after each race, which would be prohibitive for the huge surface of Skylon's TPS. Boeing spent billions just to set up production of the carbon fibre segments for the 787, and they have had all sorts of issues with it. Producing a cylindrical structure is also easier that the ogival shape of Skylon. There are no facilities and no expertise for building stuff like this in such huge sizes. Everything has to be done from scratch, the tooling, the logistics, the supply chain, the training, the manufacturing and testing processes... It's much more complex than the 787 fuselage. It's not about man rating. It's just the cost of designing every single part, bracket, connector, line of code... Mundane parts like the landing gear or engine nacelles, the electronics, tyres, lights, etc... all need to go through testing. The avionics alone are going to be a huge expense, because automated SSTO has never been done before. It's a huge project, much more complex than an airliner, a military cargo plane, or even a supersonic fighter jet. And what are these 60 skylon's going to be launching? Where are the customers queuing up for $16 million launches? 60 vehicles capable of 200 flights, that's 12000 orbital launches. Over 10 years, that's 23 launches a week. Space tourists are not going to pay that kind of money. If you put 20 people on each flight, it's still $800000 per seat. There aren't enough customers with that kind of money to fly 500 people per week to nowhere. There might be a market for a couple of constellations of 100 sats, at $16 million each, that's a few billion, but you're still far from 12000 launches, or even 6000. From the article: "The report, commissioned by the European Space Agency (Esa), was led by Reaction Engines Limited (REL) of Oxfordshire" So basically, ESA paid a few million euros to REL for a report that justifies REL's business case. Ok. Seriously, ESA and its member agencies spend a lot of money every year on reports and trade studies. It's what research institutions do. 5 million euros for a trade study is chump change for ESA. It would be wrong to extrapolate that because they funded a trade study, ESA is going to fund Skylon. In the meantime, they have just committed 8 billion euros to Ariane 6, which is going to be ESA's bread and butter for the next 20 years. Alan Bond has been working on Skylon for nearly 30 years now. Maybe he's right and everyone else is wrong. Maybe NASA, ESA, Boeing, LM, Airbus, BAe, and everyone who works in the industry are dummies. But maybe the reason nobody else has built a space place over the last 30 years is because they actually do know better than him. I think REL has some extremely valuable innovations. I think they could revolutionize space travel. But I also think they are biting off more than they can chew. They should put their technology on the market and reap in the rewards with stuff that the industry actually has a use for. If the need ever arises for an SSTO spaceplane, their technology will probably be part of it, but the industrial effort to build Skylon is way beyond what 4 blokes in a shed can do.

Who builds SuperSonics airframes the size of an A380 these days?

I tried it last night, and it crashes constantly.

I've used AVG for years, but since Windows 8, I've been using Microsoft Security Essentials.

On one hand, I'm trying to move away from Google, because I'm finding them increasingly creepy these days. So I've moved from Chrome/Google Search to Firefox and Duck Duck Go. On the other hand, some of Google's stuff is pretty convenient and I love Android and lots of the integration stuff that comes with it (even though some of it is creepy), so I'm still using Gmail and Inbox and Google Maps... The next version of Firefox will have Yahoo as the default search engine apparently, and Yahoo is taking the opportunity to relaunch itself primarily as a search engine.

Air launch is nothing new (see Stratolaunch, Pegasus, Spiral/BOR, Lockheed D-21, X-15, SpaceShipOne, etc...). Getting to space is all about hitting orbital speed, not altitude. Subsonic air launch doesn't gain you much dV, it only acts as a rather poor first stage. Hypersonic air launch has never been done, because it's hard to get to those flight regimes with anything bigger than a missile. Separation manoeuvers at such high speed are likely to end up badly (like the A-12/D-21 fiasco)

There are engine test facilities in France, UK, Germany, and Sweden at least. They would need government support (ESA at least) to use them though. What they are also going to need is flight experience with the engine. For the subsonic flight regimes, they could test it by mounting it on an old A330 or something similar. For hypersonic, they are going to need a hypersonic wind tunnel or actual flight experience. My doubts are mainly with the actual airframe more than with the engine. Nobody builds ogival fuselages any more. Nobody builds ogival structural tanks, and nobody builds entire airframes out of composite carbon structures with wierd shapes. Nobody knows how much these things are going to cost. Nobody knows how these materials resist to hypersonic airflow, to UV exposure, to thermal cycles, vacuum, and refueling, how much maintenance it needs, how it can be repaired... There is a long way between "this works on paper" and real-world operations. Without knowing this, there is no way to know how much it will cost to operate Skylon. So without such basic information, again, their business model is bogus.

Those figures are bogus, and everyone in the industry knows it. Skylon is bigger than an Airbus A380. Just to build a conventional heavy airliner requires a major airport with a reinforced runway, a production facility the size of a small city, and a supply chain involving hundreds of subcontractors. It took Boeing $32 billion and 10 years to develop the 787, which is just an airliner with fairly mature and well-understood technology, except for the carbon-fiber body. EADS spent $25 billion dollars to develop the A400M, which is just a conventional turboprop cargo plane. Airliners and military aircraft projects have a market, with firm orders years before the first test flight and minimal risk. There currently simply isn't a mass market for hundreds of Skylons with daily or weekly orbital launches, even at the cost of an airline ticket. Which is why EADS, BAE Systems, Rolls Royce or Boeing and Lockheed Martin are not lining up to buy their idea. But Skylon doesn't just have to design an aircraft. They have to invent new technologies, test them, train people to use them, develop manufacturing techniques for them, fund contractors to invest in new tooling and processes, etc... Those conventional aircraft development programs usually reuse tooling, facilities, and construction techniques that are well proven. When they don't (look at the 787), they get cost overruns, delays, sometimes unsurmountable structural problems. Yet REL estimates that Skylon will only cost $12 billion, and that each unit will be cheaper than a good old Airbus A330, although just about everything in Skylon is new, unproven, and unconventional. Now, an A330 costs somewhere around $100 million. If half of that price is development, then to recoup a development cost of $12 billion, they need to sell at least 240 units, which is rubbish. 1100$/kg for a 6 ton payload puts the cost of a flight at $6.6 million. That means that each Skylon will have to fly 15 launches over a period of say 10 years, which means that the market has to absorb over 360 orbital launches per year, at $6.6 million per launch. Sorry, that's not going to happen. The cost estimates are simply not realistic, and therefore neither is their business model.

This is where KSP gives the impression that reaching orbit is easy, when it actually is insanely hard. KSP has the balance of spaceplanes completely off. We are missing a lot of things to make an SSTO spaceplane, but the biggest roadblock is weight. A conventional rocket is basically engines+propellant+tankage+payload. The payload fraction is about 0.5% of the takeoff mass of the rocket, which is achieved by throwing away empty tankage along the way. A spaceplane is engines+propellant+tankage+wings+landing gear+heatshield+hydraulics+payload. That extra stuff that you are carrying all the way to orbit and back is much heavier than a 0.5% payload fraction, meaning that you won't reach orbit with any significant payload. Your particular proposal involves carrying (at least) two sets of engines, which means even more mass. Those jet engines are also going to have to survive hypersonic re-entry, which requires some sort of shielding or fold-away contraption, making it more complex and heavy. Even if those jet engines take you Mach 5, that's still only 20% of the acceleration you need to reach orbital speed (which is ~27000 km/h). There are 3 tricks to make an actual reusable SSTO spaceplane: - Carry less propellant by making the engines more efficient. This is hard, because the same engine has to propel the vehicle from subsonic to hypersonic, both in and out of the atmosphere. - Make the airframe lighter. For example, using a lifting bodies is a way to combine tankage with "wings", but there are physical limits to how light the airframe can be. - Find a business model that makes a reusable spaceplane viable. This is probably the hardest bit because there is no market to absorb the high flight rate that a reusable SSTO is designed for.

Yeah, I pulled those figures off of Wikipedia, and looking at them now, the thrust/Isp/burn times don't make much sense.

The trade studies for a Saturn-N planned a NERVA-derived upper stage (S-N) that would replace the S-IVB in a Saturn V stack. Although it had a significant increase in performance over the S-IVB, it wasn't a magical game changer and it had many drawbacks. S-IVB: Mass empty: 119,900 kg Mass full: 223,900 kg Propellant: LOX/LH2 Thrust (vacuum): 1,001 kN Isp: 421 s Burn time: 475 seconds S-N: Mass empty: 34000 kg Mass full: 178000 kg Propellants: LH2 Thrust (vacuum): 333.6 kN Isp: 850 s Burn Time: 1,200 seconds As you can see, it could burn for 3 times longer, but with 1 third of the thrust, meaning that the actual increase in dV was marginal.