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Nibb31

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  1. Nibb31
    It's so gorgeous, it just makes you want to land on it, doesn't it?
  2. Nibb31
    Nope. It goes like this: 1. Aircraft takes off with rocket flies to launch location, altitude, and azimuth. 2. Rocket release. Core stage ignition. 3. Separation. Upper stage ignition. 4. DC reaches orbit. Upper stage separation. 5. Mission. 6. DC reenters and lands. Both rocket stages are expendable. Upper-stage is cryo (lower stage is TBD), which means that it suffers boil-off on the way up and needs topping up during the flight, which adds complex cryo storage and refueling systems to the carrier aircraft. The wings on the core stage are only to stabilise and point it upwards after the drop, which adds extra weight, control surfaces, and more complex avionics. There is no benefit in terms of cost or delta-v and a whole lot of extra complexity and high-altitude stunt jobs. The aircraft is a very specialized and complex one-off that costs a lot to develop, can only operate from one or two airfields in the world, and spends most of its life in a giant hangar waiting for a launch and eating up maintenance costs. You would really be better off just replacing the whole aircraft boondoggle with a couple of SRBs for a similar gain in dV. The only real advantage is that it can launch rapidly and into any orbit. That flexibility might be useful for DoD launches, but that's about it.
  3. Nibb31
    I don't install tech previews and OS betas, but it can't be worse than 8, can it? I hope they give a cheap upgrade path like they did for Windows 8.
  4. Nibb31
    That word you just used. It doesn't mean what you think it means: "A scientific theory is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation. (...) Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge. This is significantly different from the common usage of the word "theory", which implies that something is a conjecture, hypothesis, or guess (i.e., unsubstantiated and speculative)." Wikipedia There's nothing wrong with being creative. Scientific method implies that when you formulate a conjecture, it has to stand up to criticism. If there is evidence that it's wrong, then it's your duty to admit it and move on to something else. If there is no evidence that it's wrong, then it just stays a conjecture with no value or merit. If you can substantially prove it AND explain it AND repeatedly predict the outcome of any experiments pertaining to it, then you might actually be on to something. Most people admit that science-fiction is more fiction than science. Its role is to entertain, not to provide a valid scientific background. It's a fantasy world where technobabble replaces magic as a plot device. Looking to Star Trek for science or predictions of a plausible future is just like looking a Lord of the Rings as a historical source. Speculation is allowed. Criticism of that speculation is also allowed. That's how you learn and that's how science progresses.
  5. Nibb31
    It depends on the orbit of the asteroid. Asteroids don't stay in one place. You would need a lot of delta-v to rendez-vous with the asteroid, and then a lot of delta-v to go from the asteroid's orbit to your destination's orbit. I don't see how this serves any purpose.
  6. Nibb31
    There is also a whole load of problems with abort and scrub modes. - What happens if you have to scrub a launch after take-off? It's damn risky to land with a fully loaded rocket under the belly. - What happens if you scrub the launch after release of the rocket or if the engine doesn't start? You lose the rocket and you have to abort the DreamChaser. - DreamChaser needs a runway nearby for abort modes. This negates the point of StratoLaunch's "launch anywhere" advantage, meaning that you can't launch from out in the middle of the Ocean. - If DreamChaser is to abort by splashing down in the Ocean, it needs to have a rescue ship prepositioned nearby, which also negates StratoLaunch's "quick response" advantage. I'm sure there are plenty of other abort modes that people can think up. It's simply not going to work.
  7. Nibb31
    You've said that already. The Shuttle had a crappy glide ratio and had similar characteristics to a lifting body: steep descent angle, high sink rate, poor manoeuverability, and no go-around. Like DreamChaser, it would break up it if it wasn't actively flown by the computer during reentry. Those CAPS systems are for light aircraft that weigh 1.5 tons. DreamChaser weighs 11 tons and is made of composites. It's going to hit hard and break, even with a much larger chute.
  8. Nibb31
    No they're not. And DreamChaser is not a space plane. But this topic was to discuss the future (or lack of) of DreamChaser, not to rehash sour grapes about NASA's CCtDev program. Let's keep that in the other thread. SNC doesn't have stockholders. It's a privately-owned company.
  9. Nibb31
    They did make Battleship into a movie. Hollywood is really running out of inspiration.
  10. Nibb31
    A little bit of news that will get the DreamChaser fans drooling: http://aviationweek.com/space/sierra-nevada-turns-international-market-dream-chaser Personally, I don't believe this will ever come to fruition. A scaled-down DreamChaser with a crew capacity of 3 isn't very useful for space tourism, NASA doesn't need it to service the ISS, and it really has nowhere else to go... unless of course Bigelow suddenly comes up with some miraculous customers for his own station. Also, a scaled down DC means that they are basically redesigning it from scratch. The only thing left is the X-28 moldline that they licensed from NASA. Who is going to pay for a whole new development program? And then there are huge doubts about the economical viability of StratoLauncher itself, the most expensive and underperforming first stage ever, as well as its abort and scrub modes, especially for a manned vehicle. But well, it's still interesting I guess.
  11. Nibb31
    Actually, although the framing is breathtaking, I've been a bit underwhelmed by the quality of the pictures released until now. They are very noisy, low resolution, and blurry... It does look like they stuck a pretty low-end camera on it, which is a bit disappointing.
  12. Nibb31
    Well, to be fair, it's not necessarily that bad. First of all, you can't bail out of DreamChaser because the hatch is on the top and you would hit the rear stabiliser. It's supposed to have a backup parachute so you have two options: - If you are going fast enough and high enough, you can try to "glide" unpowered to a landing site. - If you're not, you open the parachute and hope you'll survive the splash down. I don't think a parachute landing on land is survivable. Splashing down on a parachute is a last chance thing. The crew would probably survive, but the vehicle would be a write-off. Note that I use "glide" in quotes. A lifting body behaves more like a cannonball with fins than an unpowered airliner. It's somewhat controlled, but it's still pretty scary with a high descent rate and a steep angle, and you need a lot of speed and altitude to have any cross range.
  13. Nibb31
    We are talking about robustness, not elegance. A lifting body (sorry, DreamChaser is not a plane, it doesn't have wings) might be more elegant, but a capsule is more robust. Ability to landing or splashdown anywhere trumps needing a runway. If something goes wrong during reentry, or if weather does not allow landing, you can land in the ocean or in the desert. And because there would have been only 2 vehicles, if one DreamChaser ditches or crashes, even if the crew survives, 50% of the fleet is put out of order and the program is no longer viable. Also, capsules only reenter ballistically when something goes wrong, but that is what makes them more robust. If a lifting body loses control authority during hypersonic reentry phase, it breaks up. In a nominal controlled reentry, capsules have a positive L/D ratio and can be steered. Parachutes have proven pretty reliable until now. The only LOC event due to parachute malfunction on a spacecraft was Soyuz 1. I've already pointed out several times that DreamChaser's TPS is exposed to MMOD damage during the entire 6 month loiter period on orbit. MMOD strikes are quite frequent on the ISS. The Cupola already has several impacts on it, and it's offers a smaller surface area than DC's heat shield: http://www.nasaspaceflight.com/2014/09/iss-evaluate-mmod-strike-cupola-window/ The risk of an MMOD strike on the heat shield is non-negligeable and might have caused negative points in the evaluation process. Again, capsules are more robust in this respect, because their heat shield is protected until the last minutes before reentry. You are aware that Boeing built the X-37B, right? They know how to build a spaceplane if they need to. But they also know how to design a proposal to respond to an RFP. There are no bonus points for exceeding requirements, for making the prettiest spaceship, or sticking the word "innovative" on your proposal. They took the requirements and built what they felt best met those requirements. They could have built something based on the X-37, and I'm pretty sure there were long design meetings at Boeing where this was debated, but they ultimately felt that a capsule was a better response to NASA's requirements. If they reopen the contest, nobody flies and NASA spends those billions on buying Soyuz seats until the ISS is switched off. At the same time, SNC becomes the most hated company in the space industry.
  14. Nibb31
    That is just speculation. NASA hasn't published the selection criteria or the weight that was attributed to each of them. Since NASA didn't select SNC, we can only assume that: - either SNC's proposal scored below the other competitors, regardless of the price difference. - or NASA disregarded federal law, its own rules, and the selection criteria that it specified itself to illegally favor another competitor. I don't believe NASA is made up of idiots that would go with the latter, so I think that the former is closer to the truth.
  15. Nibb31
    It "could" land at an international airport. However, as it can only fly in a straight line, can't go around, has only one shot at a landing, and has to be safed before being towed away on a truck, it would be a high-priority landing, which would mean clearing the airspace and closing the airport to regular trafic for several hours. No, you're right. There is no go-around capability and diverting is limited. Lifting bodies do not land like aircraft. They come in extremely fast (it's more of a controlled free-fall) and flare a few seconds before touching down. If something goes wrong with the glide slope, or if you reenter in the wrong place, you have to ditch in the ocean or crash in the desert. NASA and the USAF went through a lot crashes during the X-24 and M2-Fx programs in the 60's and 70's. Note that the Space Shuttle wasn't forgiving either. It looked like a gentle landing, but if your were to land like that in an 737, there would be brown pants in the cabin.
  16. Nibb31
    What sort of reasons would those be? There isn't a reason to colonize Antarctica or the Sahara desert, let alone the Moon or Mars, so why would we colonize the most hostile planet in our solar system? Can you explain the relationship between black holes and multiverses? You might as well add pink unicorns and teapots.
  17. Nibb31
    Innovation for innovation's sake is meaningless. They could build a spaceship out of chocolate. That would be innovative. Innovation was not a requirement. The purpose of the CCtDev competition was not to spur innovation. Also, DreamChaser isn't that innovative. It's based on HL20, a 20 year-old design that was based on BOR-4 and X-24 which are 40 year-old designs. It's the latest in a long heritage of lifting-body vehicles that have repeatedly been cancelled and rejected for various reasons. Those reasons might be unrelated to the current competition, but still, it says something about the idea of a lifting body spacecraft: it's pretty, but nobody really needs it. So yes, it's pretty. The *only* reason you guys are fond of it is because it's pretty, but when you balance the pros and cons against other designs, it has no clear benefit over a simpler more robust design.
  18. Nibb31
    Yes, sorry for the confusion
  19. Nibb31
    For this phase of the CCtDev selection, SpaceX bid for 2.6 billion and Boeing bid for 4.2 billion. SpaceX SNC has stated that their bid was $900 million lower than Boeing's, which makes it $3.3 billion. That's pretty much slap bang in the middle, with SNC having the same price differential compared to SpaceX as Boeing had compared to SNC. Cut it the way you want, Boeing's offer was only 20% more expensive than SNC's while having a much higher chance of staying on track and meeting the requirements. Source: http://www.reuters.com/article/2014/09/27/us-usa-boeing-spacetaxi-sierra-nevada-idUSKCN0HM0H720140927 Sure, SNC was cheaper than Boeing, but price isn't the only factor. NASA evidently put a larger value on the lower risk proposals than on cost alone, which is quite justifiable. If the goal of the CCtDev competition was "sexiest spacecraft" or "most innovative solution" or "reusable spaceship that lands like a plane", then DreamChaser might have won, but it wasn't, and there were no requirements for "low-g reentry and crossrange". The goal was to take people reliably and safely to the ISS and back. Exceeding requirements doesn't earn you any points in these competitions. Meeting requirements and milestones does. Boeing's proposal might not look as pretty, but the company knows how to respond to an RFP. Now, what I would really like is to see NASA embrace and fund DreamChaser as an X vehicle, a successor to X-38 and HL-20. There is a use for low-g reentry and lifting bodies, and it's NASA's role to study them, but unfortunately it isn't in this particular program.
  20. Nibb31
    I don't think that the actual crash played a major role. The gear used on the test article was a placeholder only, scavenged from an old F-16 (I think) because the DC's own landing gear hadn't been developed yet. What worried me more than the crash was that they actually rushed the landing test with a placeholder in the first place. There isn't much point in a landing test if you are not using the actual landing gear, unless you are grasping at straws to meet deadlines. Of course, even though the damage was repairable, crashing the ETA meant more delays in the drop tests, more missed milestones. I don't think there has been another drop test since then. Also note that a drop test only models the last few seconds of the mission. There is currently no way to test the performance during reentry and through hypersonic flight without launching it on a rocket. The only actual test data of lifting body reentry comes from the old Soviet BOR-4 test in the early 80's, and we don't know how applicable it is to DreamChaser or how reliable that data is. On the other hand, we are quite familiar with capsule reentry, especially using the Apollo moldline.
  21. Nibb31
    That was my point. Until the official announcement, everything was just speculation and rumors from unnamed sources. One man's speculation is just as good as another's. There is no evidence that your Lurio guy had no more evidence than the other journalists. None of the competitors are planning water landings. Both CST and Dragon land on land. CST is assisted with airbags, Dragon is assisted with SuperDracos. We don't know yet whether Dragon will go propulsive all the way or if it will use parachutes for most of the deceleration. The Boeing proposal was only 20% more expensive than SNC's. SNC's proposal was 20% more expensive than SpaceX's. By your metric, then SNC was "VERY high Cost" too, compared to SpaceX. As to how you can determine "medium risk", with all the uncertainties that were attached to the DreamChaser proposal. Let me recap again: no engines, unconvincing aborts and exposed TPS. You can't deny that the program risk was much higher than the others. I don't think that SNC has a case here. The competition was fair, there is no evidence that it wasn't. Challenging the decision will only introduce delays in achieving the goal of CCtCap, which is assured independant access to the ISS.
  22. Nibb31
    In France, we use astronaut, cosmonaut, taikonaut for Chinese astronauts and spationaut for French ones. It's utterly stupid.
  23. Nibb31
    I don't think the greatest person in history would be an astronaut. Even though they were the best of the best highly skilled test pilots, they were part of a team and they were interchangeable and part of the effort of a nation. If it hadn't been Gagarin or Armstrong, it would have been another astronaut. The engineers and scientists behind them, although less famous, played a bigger role in the events than the actual astronauts. The most important man in history would be someone who changed the destiny of Humanity on his own. I would say it's the Homo Sapiens who one day discovered how to make fire. Unfortunately, his name didn't make it to posterity.
  24. Nibb31
    The hybrid engine is the same one that SpaceShipTwo is struggling with. It's based on the one that was used in SpaceShipOne but they are having problems scaling it up. It simply isn't working properly and they can't get it ready for flight testing, which is causing delays in both SS2 and DC programs, with a high risk that it might never work properly. Both SNC and Scaled Composites are now working on getting a liquid engine for their vehicles. Switching to a liquid engine at this stage in the design process is extremely late. It changes your center of mass, which changes the vehicle dynamics and requires new tanks and redesigned systems. Basically all the glide and drop tests that SNC has done are invalidated by the change. The orbital manoeuvering characteristics might also change. This means more delays and also a high risk that the vehicle might not be ready soon enough for it to be worthwhile (remember the ISS will only be around until 2020-2024). The delays in getting an engine ready is probably the main reason why DreamChaser was not selected, although there are a few other reasons why it was not an appropriate design for the Commercial Crew program. Respected by who? I've never heard of this Lurio guy until today. Who is he? What does he do for a living? It takes more than a "tweet" to make a rumor. There were other analysts and journalists that predicted that Boeing and SpaceX would win. Oh look, rumors from Bloomberg and the Wall Street Journal: http://www.bloomberg.com/news/2014-09-10/musk-s-spacex-vies-with-boeing-to-build-nasa-taxi-to-mars.html http://online.wsj.com/articles/boeing-takes-lead-to-build-space-taxi-1410820865 Rubbish speculative journalism if you ask me, but that's what rumors are about. You can look at these forums. Some other guy on the internet (me actually) predicted that either DreamChaser or SpaceX would get the cut. You could call that another cool rumor. Just pick the one you want to believe. However, the truth is that Boeing getting the contract was pretty certain because they had met all milestones and their design sticks more closely to the quick and safe space taxi that NASA wanted. Boeing was high-cost and low-risk. SpaceX was low-cost and medium-risk. SNC was medium-cost and high-risk. NASA clearly favored low-risk over cost concerns, which makes sense for a program that is to provide "assured access to the ISS".
  25. Nibb31
    It was pretty clear to anyone following the process that SNC was not in a position to win. They had a much riskier design, some fundamental design flaws, and no engine. Rumors are rumors. For each rumor I could find a counter-rumor. And some guy on twitter is not a "source".
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