Why are advancements in spaceflight technology so slow? We've seen huge jumps in computers and communication technologies, but it still seems like we're using 50 year old technology when it comes to spaceflight.
>>8018188
consumerism
>>8018188
cosmic radiation rapes cmos
To put it simply; Rockets are quite possibly the most inefficient method of travel to date. You need more fuel the more mass you have right? Well the more fuel you have the more mass you have. But the more mass you have the more fuel you need. But the more fuel you have the more mass you need to lift. So scientists are trying to find a way to get to space much easier. As we've seen in the past this process has taken a while. And the rocket was just the first thing that came to mind.
Moving mass is harder than moving information.
>>8018188
expensive
no present consumer use aside from communication satellites
getting any massive object to 7km/s is hard
space will kill you without a lot of precautions
just a few of the reasons why. until there is either a) a widespread desire by a lot of people to live or do something else in space, or b) massively risky investment from some billionaires to do something in space (which is the present course we're on, i guess), space travel will be expensive
>>8018229
this, its called the tyranny of the rocket equation
rockets arent inefficient compared to other engines either, its just the nature of travelling distances way greater than other vehicles need to travel cause them to be huge
>>8018188
Jesus christ can you please fuck off?
This is the REAL world. Anti gravity does not exist, if you want to go somewhere you have to expel mass. If you actually knew anything about the technology that you are crying about as being shit you would know that it's all limited by the Rocket Equation. It's not a case of a bunch of guys saying "meh, let's stick with burning a million gallons of fuel per flight just because". If you need all that fuel to put a few guys in space then it quickly becomes obvious that your pop-sci space hotel fantasies are unfeasible.
You're probably a SpaceX asswad so i'll have to explain reuseable rockets as well. It's only feasible now because of improved computers and most importantly there's actually a market for it now. Even Africans are launching satellites now, this wasn't the case 20 years ago. The military had no need to cut costs because they get the same budget every year no matter what, it doesn't matter if their shit isn't cheap. In fact reuseable rockets are trash to the military because they are less powerful than a disposable one. You don't get anything for free in the world of engineering.
Finally people like you wind me up because a shitload of people put their entire lives into advancing what used to be a firework toy into a machine capable of flying out of the Solar System. We've explored every planet in the fucking system, we have like 3 rovers on Mars right now. But some fat fuck who can't even get a job in McDonalds is shitting on all of it because Star Trek isn't real. Either stop trying to force scientists and engineers to cater to your ridiculous pop-sci fantasies or get an aerospace engineering degree and make your own fucking Starship Enterprise.
This is why we should build Jules Verne's FuckBig Cannon to just railgun shit at escape velocity. As rarely as we would use it, the JVFBC could even be powered by a massive array of batteries and solar panels.
>>8018229
Even if space elevators or launch loops happen wahey, you're in LEO, where are you gonna go next? Mars? Alpha Centauri? Andromeda? Need a rocket for that and it's not going to be any less useless for the job than than it was before space elevators.
>>8018281
That's the name of the equation and names are capitalized.
It's "tyrannic" because it's a gay ass law that makes spaceflight hard.
>>8018259
>JVFBC
Why can't we just launch nukes in a tube to shoot our payload into space.
>but big acceleration puny humans
Just make the tube long and bombs small.
>>8018317
https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion
The hippies won't allow it.
>>8018188
>hey I've got a new idea for a computer program
>codes it
>tries it
>doesn't work
>oh well, I'll try again
vs.
>hey I got a new idea for a space rocket
>throws millions of dollars at it
>launches
>blows up
>well we could try again
>why does no one want to give me money
>>8018254
Rockets are fucking horrible compared to other engines
Major reason is that they have to carry their oxidizer, while an airbreather does not
And because they are simply mechanically better
>>8018269
He's talking about what's necessary get into LEO. Once you're there you can burn to wherever the fuck you want at a snail's pace.
>>8018188
In addition to what others have said (rockets are inefficient, etc.), one reason we haven't seen much improvement in rocket technology since the 1960s is that we pretty much maxed out the efficiency of liquid fuel rockets decades ago. If you take two mol of H2 and one mol of O2, there's only so much chemical energy that their reaction can produce (572 kJ). The chemical rocket engines we built in the 1960s were already near the maximum theoretical efficiency. In principle, we could use more energetic reactions, but there aren't that many that beat out the combustion of hydrogen with oxygen. You could use fluorine as an oxidizer, and they have experimented with this. But fluorine gas is extremely dangerous, toxic, and corrosive. It was deemed not worth the huge hassle and risk for only a modest increase in energy density.
And solid-fuel rockets are even less efficient.
So, the only alternatives are:
- air-breathing hybrid engines (you don't need to carry as much oxidizer with you because you can pull oxygen from the air; the problem is that this only works below a critical altitude when the air pressure is high enough and becomes useless once you get into space).
- non-chemical rockets, such as nuclear fission or fusion. Fission rockets are possible (look up project NERVA) and would yield better energy-weight ratios than chemical rockets. However, no sane government would ever allow them to be built and used in Earth's atmosphere because such a rocket would basically spew radioactive fallout over its entire flight trajectory and probably give millions of people cancer. It could certainly be useful once in space, however.
- space elevator. Conceptually sound, but unless we have a major breakthrough in materials science it ain't gonna happen anytime soon. We can't produce any materials with a high enough tensile strength to build a space elevator.
>>8018641
>tensile strength
I love that word. It makes me think of the truss on an interstellar craft.
>>8018641
- launch track. The idea would be to magnetically accelerate a launch craft along a track (like a maglev train) to give it enough velocity to attain earth orbit. The problems are: A) unless your ship and payload can withstand >10,000 g's of acceleration, your launch track is going to have to be very long. Like, as long as a continent. And it would have to be something like a ramp or sloped track that would have to extend beyond the upper atmosphere. We have no idea how to build anything that large without it collapsing under its own weight. Check out "launch loop" for a concept that kinda theoretically makes sense, but would in practice be an engineering nightmare and would likely cost trillions of dollars to build and operate. A second problem is that even if you could build a functioning launch track, your ship would still need engines to do a burn once in space, in order to enter a stable orbit.
Because the governments and the public sector (particularly those of the US and the Soviet Union) used to successfully develop it, but now that the cuts to the public sector have been made, the huge technological innovations it once provided are gone.
A healthy economy requires a good share of both public and private sector. The private sector alone can't produce enough innovation alone, and would never be able to fund research and development substantially enough. Most of the "innovation" by the private sector was the reuse of the new technologies created by the public sector.
>>8018654
Informedfag, what about the JVFBC?
>>8018188
Because you can't just write a program to launch a rocket. You have to actually build it and debug it when things go wrong. "Just computer more better faster" doesn't work outside of the digital world.
>>8018858
Never heard of it, and Google turns up nothing. What is it?
>>8018255
found the rocket scientist
>Hurr rockets are inefficient
But they really aren't though, especially considering what they do. Looking at the sheer scale of a rocket and all its propellant in relation to their fairly modest payloads, they may SEEM wasteful, but ultimately the fact of the matter is that spaceflight is an energy-intensive prospect, period. And currently (as well as for the foreseeable future), chemical rockets are simply the most efficient means we have of achieving these ends.
Consider this: A Falcon 9 starts out with 395.7 t of propellant, equivalent to about 4475 GJ of chemical energy, and uses it to carry a 13,150 kg payload into LEO, corresponding to about 431.3 GJ of orbital energy. That's an overall efficiency (ignoring the energy of spent stages) of 9.6%. May not sound like much, but for comparison, a ~60 t Airbus A320 climbing to 10 km, equivalent to 5.88 GJ of potential energy, will burn about 2,000 kg of fuel, corresponding to 86 GJ of chemical energy - equating to an overall efficiency of just 6.8%. Yes, you read that right. A Falcon 9 is actually MORE efficient than a passenger airliner.
>>8018939
Top kek
See older replies
>>8019722
In that case, would it be more efficient to launch someone on a suborbital rocket than transport them on a plane?
>>8019722
A Falcon 9 only travels in the vertical direction. An airliner's engines are much more efficient than a rocket, this comparison is skewed because the main source of losses in the case of a passenger jet is drag, whereas a rocket's main source of losses is thermal inefficiency
>>8019889
Rockets spend most of their energy burning sideways mate. Getting high is the easy part, going really fast is the hard part
>>8019889
>A Falcon 9 only travels in the vertical direction.
??????
>>8018229
isn't the ratio something like 9:1 fuel weight to other weight (engines, structural, payload, etc) (?)
also as an example of rockets being inefficient, iirc the saturn V gets 5 inches to the gallon
getting to orbit's a bitch
>>8019927
>Getting high is the easy part, going really fast is the hard part
haha
>>8020117
We can, like, totally go to space maaan
>>8020121
its true tho, that's why blue origami or whatever isn't (currently) a threat to spacex
sure they got the automated return to earth thingy working but it was just straight up and back down, not like spacex with the barge and the orbit and the suicide burn and all that good stuff
>>8019879
>In that case, would it be more efficient to launch someone on a suborbital rocket than transport them on a plane?
In both cases the net efficiency (by the measure I used before) is zero, since you are at no greater energy state once you land than you were at when you took off. So no; and in this case simple energy efficiency is the wrong metric to use.
>>8019889
>A Falcon 9 only travels in the vertical direction.
Wrong.
>An airliner's engines are much more efficient than a rocket
By propulsive efficiency? Not really. Both peak around the same level, albeit at radically different velocities.
>this comparison is skewed because the main source of losses in the case of a passenger jet is drag, whereas a rocket's main source of losses is thermal inefficiency
Thermal inefficiency is the main source of loss in both cases, but second to that is drag for the airliner and wasted kinetic/potential energy (in the form of discarded stages and consumed propellant) for the rocket.
>>8019927
>Getting high is the easy part, going really fast is the hard part
Kek, pic related
>>8018323
>the deaths of ten innocent bystanders per launch
Just so I they can tell me it's going to rain an hour earlier than they could before? No thanks.
>>8020151
that was a 60's prediction
we know now that minute changes in radiation don't effect anything
>>8020132
Thing is blue orangatang is going straight for a reusable rocket, since he has billions of dollars to burn
Elon Musk started SpaceX with only like 200 million dollars
>>8018229
chemical rockets are actually pretty efficient
>>8018188
That's not true, we managed to land on the moon in 1969.
>>8018188
>why are advancements so slow
Because of everything everyone in this thread has said + no one cares to fund it to a great degree. This is why you have billionaires like Elon musk actually competing with government agencies.
>>8018188
Greetings from the Breakaway Civilization!
So, SpaceX hype thread for next week's launch?
>>8020709
Nevermind, I see it was delayed to May 3rd now.
>>8018854
Here's some comedy for you.
>>8018188
>Why are advancements in spaceflight technology so slow?
They're moving at a breakneck pace now, because genuine private industry was allowed to play starting in the early 2000s, although they still had some legal wrangling to do to to get the regulatory agencies to actually do what the law said.
The process started with the Commercial Space Launch Act of 1984, after the Challenger disaster, and the end of the official US policy that all commercial cargoes should fly on the space shuttle (with older launch vehicles being a stopgap until the shuttle was ready). This is what made the EELV program and Orbital's Pegasus possible. They would have been strictly illegal before that point.
However, the law still gave regulators too much freedom to block anything other than a bare minimum of government-favored launch services. The Commercial Space Act of 1998 and especially the Commercial Space Amendments Act of 2004 are what made companies like SpaceX possible.
The 2004 act in particular directed various government agencies to support the development of a private space industry and apply consistent standards. This gave private space companies a powerful weapon to use in court, and in less formal complaints, to defend themselves against maliciously obstructive regulators.
So here we are, 12 years after the legalization of private commercial spaceflight. Two private companies have demonstrated early versions of the essential technology for propulsive landing of all stages and airliner-like reusability, where the cost for launch is dominated by the price of fuel. One is routinely launching orbital payloads and gearing up for orbital manned spaceflight (in a highly reusable capsule) while the other is gearing up for frequent suborbital thrill-rides to space mostly for private customers.
>>8020715
>other is gearing up for frequent suborbital thrill-rides to space mostly for private customers.
While occasionally trying to sabotage the other with things like trying to patent barge landings.
>>8020721
That's just typical business behavior in the USA, though. The Wright Bros did it for the patents. They were in a hurry to develop and demonstrate practical flight because they expected to OWN it, and because in those days you needed a working example to get a patent.
Meanwhile, SpaceX is getting about $5 billion in taxpayer money through NASA. It's contracts for services, sure, but they're mostly of the form, "Develop X technology, and keep it as private property. Build and test fly a reusable vehicle, and keep it as private property." etc. NASA's effectively paying all their development and facility costs for Falcon 9, Falcon Heavy, Dragon, and Dragon V2, AND paying for a fleet of tried and proven reusable boosters and capsules, while also giving them copious advice, analysis, and assistance.
Imagine trying to get started in a business against a competitor getting a $5 billion subsidy and close support from NASA.
>>8020860
Blue Origin isn't in the same business though, they're all about the space tourists whilst working with ULA to make new engines.
It's not like SpaceX has had it entirely fair either, they were practically blocked from bidding on things for a time while ULA held a monopoly because of pork reasons.
>>8020877
>Blue Origin isn't in the same business though, they're all about the space tourists whilst working with ULA to make new engines.
They are absolutely in the same business, they're just taking a different path toward the end goal.
And they're not "working with ULA to make new engines", they're selling ULA they engines they were developing anyway, for their own orbital rocket.
SpaceX and Blue Origin are both on incremental paths toward airliner-like fully-reusable, passenger-capable orbital launch vehicles.
SpaceX is evolving their design from an expendable orbital rocket to a reusable one, while Blue Origin is working on the technology for efficient reusability first, then going orbital. SpaceX's approach is based on cash flow, while Blue Origin's is based on cost minimization.
PHYSICS
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>>8020877
>It's not like SpaceX has had it entirely fair either, they were practically blocked from bidding on things for a time while ULA held a monopoly because of pork reasons.
It's a bit more complicated than that. ULA's launch vehicles and services were developed hand-in-glove with Air Force personnel from the beginning, and ULA was allowed to form in the first place out of recognition that the Air Force's launch requirements are too expensive, specific, and limiting for competing firms to satisfy independently.
These are cutting-edge satellites, often with the need for many last-minute checks and fixes, and sensitive to vibration and acceleration. ULA likes to complain that the Air Force "builds them on the launchpad".
The Air Force requires vertical integration (keeping the satellite upright at all times, and therefore having a workspace at the top of the upright rocket), while SpaceX uses horizontal integration (attaching the satellite before erecting the rocket).
Besides that, even now SpaceX doesn't have a mature launch vehicle. They have a long launch backlog, are constantly changing things on their vehicle, and frequently delay launches. Their schedule remains unpredictable years after they started pushing to be allowed to provide launches for strategically-important defense payloads.
Basically, what has happened here is that SpaceX has enough political pull and legal clout to get the Department of Defense to change the way it launches satellites. Meanwhile, the ULA people are calling foul, because their job could have been far easier and less costly if they could have benefitted from a similar willingness to compromise.
>>8018188
No need for it.
Space race objective was developing and perfecting ICBMs.
Getting to the moon was just a bonus for the future.
We need space elevators.
>>8018188
>Why are advancements in spaceflight technology so slow?
It is a sharp uphill curve that starts into a plateau.
Shit we've only had lightbulbs for about 200ish years. We've gone from that to landing on the moon and putting robots on Mars, Venus, and sent shit out beyond the solar system.
New inventions using newly proven science are not coming along at any real rate anymore. We have pretty much all the technology we are ever going to have or need. We just don't use it in as novel a way as we could. This is due to the fact no one with the funds and means actually gives a shit enough and are not motivated properly. Those of us who really want to do it are too inept at life to actually do it or we'd be making the money and be doing it now (those are dreamers).
>>8018188
What about this glorious beast in development?
https://en.wikipedia.org/wiki/Skylon_%28spacecraft%29
An single stage to orbit reusable spaceplane makes reusable conventional rockets pointless
>>8021553
Not only are space elevators way too hard and expensive, they're not as good as efficiently reusable rockets.
Even if you can managed to construct it, operating it is a problem because of the sheer length. It seems easy to picture an elevator in your mind, but this is an elevator ride for a distance like a trip all the way around the world. Power transmission is a real problem. Then there's the mechanical issue of climbing all that way against gravity.
The energy efficiency of rockets isn't bad. The trouble is that we haven't done any rockets like airliners, that you can just refill and fly again.
>>8021613
Small payload missions might still be worthwhile with cheap rockets
>>8021630
The problem with rockets is that they have to carry all of their own fuel and all of their own oxidiser, and the amount of delta-v needed to get into orbit is crazy high. Ion thrusters and similar things are much more efficient because they only need to carry propellant and a method of generating electricity
>>8021613
>An single stage to orbit reusable spaceplane makes reusable conventional rockets pointless
You've got that the wrong way around, though. Reusable conventional rockets make an SSTO spaceplane pointless.
An SSTO means you're hauling more mass to orbit just to bring back down again. It also only goes to LEO, which isn't a very interesting destination, so you need a second stage anyway. Might as well just make the first stage suborbital and save yourself a lot of trouble.
Spaceplanes are also naturally more mechanically complex and less robust than simpler-shaped entry vehicles, which have fewer functions to compromise between.
>>8021644
>Ion thrusters and similar things are much more efficient because they only need to carry propellant and a method of generating electricity
Ion thrusters are more mass-efficient, but far less energy efficient. They're never going to replace chemical rockets, the power demands would just be too unreasonable in high-thrust applications.
>>8021709
Excpet skylon uses far more efficient air breathing engines for a large amount of its delta-v, so it doesnt have to carry the huge mass of oxidizer that a rocket would. The rocket equation is far less tyrannical on jets than on rockets. Skylon fully loaded is less than half the mass of falcon 9 fully loaded and carries about the same payload to leo.
And i'm not sure what you mean by leo being uninteresting, getting there is hardest and most expensive part of space travel
>>8021738
You dont need particularly high thrust in most situations in space, and there are thruster in development that should can produce enough thrust for pretty much anything you might want to do in space. They will never be powerful enough to get you off the ground of course, so you will need another system for that
>space elevator
Now that is a delicious terrorism target with global consequences when the tip whips around at 8600 mph.
>>8021785
>Skylon fully loaded is less than half the mass of falcon 9 fully loaded and carries about the same payload to leo.
1) Falcon 9's an RP-1 rocket. Skylon's hydrogen fuelled. That alone would account for that difference.
2) The "fully loaded" mass is generally irrelevant. Liquid oxygen is extremely cheap (both in money and energy) and quite dense, so it goes in a small tank.
3) Skylon doesn't carry any payload to LEO. It's a paper rocket, and an SSTO at that. Every ounce of vehicle mass growth during development is an ounce subtracted from payload.
The Skylon D1 specs from the wikipedia page say it would be 83m long with a fuselage diameter of 6.3m and a 27m wingspan. The latest (and largest) version of Falcon 9 is 70m long with a fuselage diameter of 3.66 m. In terms of the amount of hardware, Skylon's much more comparable to Falcon Heavy than Falcon 9.
>>8021785
>i'm not sure what you mean by leo being uninteresting, getting there is hardest and most expensive part of space travel
By that token, getting to space, just getting out of the atmosphere, is the hardest and most expensive part of getting to LEO. On Falcon 9, for instance, it takes 9 engines on the booster to get to space, but just one on the upper stage to go anywhere from LEO to Earth-escape.
If your system only goes to LEO, it needs another stage anyway, same as a system that only goes to space.
>>8021827
Incidentally, Skylon's $/kg *projected cost*, assuming all goes well and the development, facilities, and construction costs can be amortized over many flights, is only about half of Falcon Heavy's $/kg *advertised price* as an expendable.
Even limited reusability will allow SpaceX to blow by Skylon's cost-effectiveness goals.
>>8021827
Skylon lifts the roughly the same payload as falcon 9 and similar rockets, so thats the vehicle it will be competing and so thats the one it should be compared to. If it manages to work as advertised/predicted (and I dont deny that its a big "if") then it will cut the cost/kg to orbit for payloads of that size in half. Falcon 9 being fully reused would cut the cost by about 20%
>>8021846
All any of these vehicles do is get a payload to LEO, the payload can do whatever it likes from there. The upper stage of falcon 9 gets you from a suborbital trajectory to LEO, thats it
>>8021613
>An single stage to orbit reusable spaceplane makes reusable conventional rockets pointless
Except that it's fancy vaporware engines, even by REL's own projections, underperform relative to conventional rockets.
>Excpet skylon uses far more efficient air breathing engines for a large amount of its delta-v, so it doesnt have to carry the huge mass of oxidizer that a rocket would.
All of these gains are completely wasted (and then some) by hauling the extra dead weight required by those heavy engines all the way to orbit. The engines alone literally weigh more than the entire payload - with an SSTO that is seriously no bueno.
Read this closely:
http://forum.nasaspaceflight.com/index.php?topic=24621.225;wap2
It pretty clearly shows that, even assuming everything else about Skylon eventually works as advertised (which itself is pretty dubious), it would be better off with conventional rocket engines than the SABREs.
>>8022024
>Except that it's fancy vaporware engines, even by REL's own projections, underperform relative to conventional rockets.
How so? SABRE is an order of magnitude more efficient in atmosphere than falcon 9 and somewhat more efficient in vacuum. It doesnt produce as much thrust but it doesnt need to since its half the weight and flies aerodynamically at its heaviest
>All of these gains are completely wasted (and then some)
Except they arent. The propellant for the first stage alone of falcon 9 is heavier than the entire fueled up skylon + payload
nasa is a cover for them to keep us trapped on earth
>>8018259
How would a rail/loop launcher even work?
I mean I get the idea, but wouldn't the craft have to leave the launcher at near orbital speeds? Moving that fast inside the atmosphere would cause heating like that encountered upon re-entry. Nevermind the g-forces.
Rockets don't have that problem since they accelerate gradually, and are mostly above the atmosphere before they reach those extreme speeds.
It could work on the moon or maybe Mars, but it seems implausible inside the Earth's atmosphere.
>>8022081
Its possible, but not with people on board
>>8020721
Wait, what?
>>8018255
Agreed. Reaction mass based propellant methods are simply the current best way to accelerate a massive object to orbital speeds, and will most likely remain that way for a very long time.
>>8022158
They are the ONLY thing that actually works so far
>>8020004
But I thought rockets only go up and don't have to go through any horizontal acceleration at all. Everyone knows gravity just ends after a hundred and thirty km.
>>8022162
Well, there is the one program where top Olympic disk throwers attempt to manually launch things into orbit, but that hasn't worked out well so far.
>>8022174
Svetlana?
>>8022174
They gettin swole though
>>8021968
>Falcon 9 being fully reused would cut the cost by about 20%
Who told you this?
How does that make sense to you?
>>8022024
yea air breathing rockets would be great for the first stage, but SSTO spaceplanes is just a meme
>>8022230
The numbers were wrong. The wiki page says spacex could stretch to a 30% saving on a reusable lower stage, the only numbers for fully reusable are musk talking about cutting things by an order or two of magnitude, which is stretching belief to say the least
>>8022232
Why?
>>8022242
Thats them talking about how much they will reduce their prices, when faced with zero competition on pricing
You are assuming they need to do more than just refuel the rocket, mount the second stage back on top, and let er go
>>8022262
They will never ever be able to reuse a rocket without refurbishing it, not in any realistic timeframe
>>8022275
Bullshit, they could do so right now
>>8022289
No, they cannot. Refurbishing the lower stage cost at least 3 million, and theyve never actually flown a refurbished stage to prove its even that cheap, and they absolutely cannot just fill up a recovered lower stage with fuel and launch it again
>>8022291
They've only had 2 first stages landed so far
They want to spend time testing & studying them
>>8022242
>The wiki page says spacex could stretch to a 30% saving on a reusable lower stage
The truth is that SpaceX is reducing prices by 30% for its initial satellite launches on a reused lower stage.
This is far from the full benefit of lower stage reuse. Satellite customers are finnicky, and their payloads are commonly one-of-a-kind, and need babying. They need workspace near the launchpad and all sorts of special considerations. There hasn't been a reason to streamline this. What's a few more million on a $100+ million launch?
By giving a discount of $20 million on the initial relaunch, SpaceX is passing along basically the entire savings of their incremental cost of building another first stage. But that's not taking into account the potential for increasing the launch rate and streamlining pad operations. Their markup on incremental costs must cover their fixed costs.
SpaceX has also been telling customers that they'll eventually be able to do a satellite launch for around $15 million, with an expendable upper stage. For simpler repetitive work, like trucking insensitive cargo to the same orbit, I think I've heard the figure $8 million.
>>8022291
>they absolutely cannot just fill up a recovered lower stage with fuel and launch it again
I suppose they also absolutely cannot just start the engines again after the initial boost, to land propulsively. Those engines need refurbishment! That's why they have teams of trained mechanics in space suits riding Falcon 9 in a secret compartment to quickly climb out and fix that center engine like an Indy 500 pit-stop team so the thing can land.
>>8022308
The first one, they've decided to keep as a trophy. They tested it a little and put it aside.
They might keep the second one as a trophy as well, as the first that landed at sea, but I expect they'll test it more.
I heard they had plans to resume their Grasshopper program at their facility in New Mexico, along with their DragonFly program for the propulsive-landing Dragon, once they recovered some stages to refly. They've got a no-ceiling license there, so they can fly all the way to space to develop their recovery and rapid-reuse systems.
>>8022981
sure lets put millions of dollars of payload and upper stages on a refurbished first stage without so much as a mechanical check to make sure nothing got broken during the landing
I'm as pro spacex as they come dude, but no one sane is just gonna fuel the recovered stage and launch it again straight away. Too risky.
>>8022134
http://www.google.co.uk/patents/US8678321
>>8018255
> Either stop trying to force scientists and engineers to cater to your ridiculous pop-sci fantasies or get an aerospace engineering degree and make your own fucking Starship Enterprise.
This times a fucking billion
I'm laughing my ass off on the fact congress spent 400 million on a europa mission that HAS to have a lander.
>>8023014
>They might keep the second one as a trophy as well, as the first that landed at sea, but I expect they'll test it more.
Second one is going to be relaunched in June (or whenever it gets delayed to) after 10 test burns.
>>8022134
>>8023037
And some more, for shits and giggles.
>Control surfaces for use with high speed vehicles, and associated systems and methods
http://www.google.co.uk/patents/US8991767
>Launch vehicles with ring-shaped external elements, and associated systems and methods
http://www.google.co.uk/patents/US20140263841
The first is the grid fins used on the Falcon 9 and a bunch of Soviet rockets, though the patent mentioned tail-landings as well which the Soviet rockets aren't capable of.
The second might overlap with inflatables like NASAs LDSD test vehicle and similar.
>>8018188
because nasa is state-owned. I bet that in a few decade, SpaceX is going to have completely changed the industry.
>>8023018
>without so much as a mechanical check to make sure nothing got broken during the landing
Yeah man, inspection is exactly the same thing as refurbishment. "No refurbishment" means, "don't even look at it". They also totally don't have any instruments onboard or on the pad to monitor the condition of the vehicle.
>sure lets put millions of dollars of payload and upper stages on a refurbished first stage without so much as
>refurbished first stage
Come on, man.
What they're aiming for is airliner-like reuse. If they're being turned around quickly, between flights, airliners mostly depend on onboard instruments to detect any faults. If they're being stored for a while before being reflown, they also get at least a visual inspection. After a certain number of flights, or the detection of an issue, they get routine maintenance or repair before being reflown, with mechanics actually opening things up, taking them apart, cleaning things, replacing parts, etc.
They're not going to leap straight into that on their first few times successfully recovering a rocket, but because that is their goal, they're also not going to just take the recovered stages all apart and restore them to like-new condition, sparing no expense to ensure their successful reflight. The goal is cheap, fast reuse for many flights. They're not starting from extensive refurbishment and trying to cut down on it gradually. They're starting from careful inspection and ground testing before reflight, and will change the design as necessary as they find parts that don't stand up to reuse without refurbishment.
>>8023018
Thats what cars and passenger aircraft do all the time
>>8023059
>The first is the grid fins used on the Falcon 9 and a bunch of Soviet rockets
No, it's describing something different: a type of fin designed to operate on the way up, and the way down. Not collapsible grid fins for descent only.
>The second might overlap with inflatables like NASAs LDSD test vehicle and similar.
I don't see how...
Both of these are for aerodynamic features of New Shepard and its successor for orbital launch.
SOLAR
FREAKING
LAUNCHPADS
>>8019722
You comparison is retarded.
>>8023107
That's basically the concept of propellant ISRU: you set up a launchpad with a bunch of solar panels on Mars or the moon, and it sits there turning stuff like water and CO2 into rocket fuel and oxidizer.
>>8023107
ELON MUSK OMG PLS DO THIS UR THE ONLY ONE WHO CAN SAVE US
>>8023088
Even if they do managed that kind of reusability, which unlikely at best, they still lose to skylon which costs much less to fuel up, not to mention they are only planning to reuse these rockets 10 or so times, whereas skylon is aiming for 200 launches per vehicle
>>8023346
Skylon is just a meme plane for suckers
It'll never fly
>>8023346
>they are only planning to reuse these rockets 10 or so times
So basically, what you're doing here is spreading lies and seeing what you can get away with?
"Oh, reusing is only going to save 20%! Oh, they're only going to reuse them 10 times!"
Just straight made-up bullshit.
>they still lose to skylon which costs much less to fuel up
Where do you even get these ideas?
Anyway even if Skylon got fully funded tomorrow, it would still require a lengthy development process. Its competition wouldn't be the partially-reusable Falcon 9 and Heavy, it would be the fully-reusable, Raptor-powered successor to Falcon 9.
>>8023346
>planning to reuse these rockets 10 or so
Likelier value were estimated to 3-4 times max, assuming modern materials and manufacturing techniques. Beyond that number the probability of failure becomes ~40%, which is way to high for any customer (even things like student cubesats)
>>8023387
>Likelier value were estimated to 3-4 times max
By who? That is sure as fuck not what SpaceX is saying.
>>8023107
Jesus Christ what the fuck is that?
>>8023374
Why?
>Where do you even get these ideas?
The current version of falcon 9 carries more than twice as much propellant as skylon, the next version of falcon carries even more
>>8023387
Keep in mind spacex have yet to reuse a rocket even once
it was raining this morning and i was hoping I wouldn't have to work, but i did
>>8023234
Nice rebuttal. You have a better comparison?
>>8023395
White paper from a joint study by CNES/Airbus. I'm sure some here will dismiss them as incompetents, but that would really be dishonest given the fact that their rockets are both more powerful, more technologically advanced, and more reliable than SpaceX's. Some other might dismiss it as wishful thinking, but given their business is on the line on this one, I don't believe that either.
>>8023435
Didn't they reuse Grasshopper? Not that that really counts for much...
>>8023480
I dont believe they did, could be wrong though
>>8023488
No they did in fact, launched the same vehicle 8 times, landed it vertically, refurbished it then used it again. It only did very small missions though
>>8018654
It would be considerably more feasible to make a launch track that loops around until the craft reaches sufficient speed, at which point it can switch over from the loop to track B which is the rising ramp.
It wouldnt have to be mucher larger than the LHC for this to be feasible either.
The real unfeasibility is power generation and materials science.
>>8023434
>The current version of falcon 9 carries more than twice as much propellant as skylon
In total mass, yes. That doesn't equal either energy content or cost.
Because it's a pure rocket, Falcon 9's load of propellant is mostly liquid oxygen, which is extremely cheap and takes little energy to produce. The rest is kerosene, only slightly fancier than jet fuel. It's cheap and easy to handle.
Typical O/F ratio for lox/kerosene is 2.5, so over 70% of the propellant load is just oxygen, which is practically free. It's certainly not harder to gather and chill it on the ground than in flight.
Because Skylon uses an air-breathing engine, relatively little of its propellant load is cheap oxygen. Most of it is costly subcooled liquid hydrogen. This is a deep cryogen, so the cooling process and even storage is energy intensive, and the facilities required are expensive.
When you make hydrogen, you start by partially burning natural gas, CH4, into CO and 2 H2. Then you react the CO with H2O to get H2 and CO2. So per 16 units natural gas, you get 6 units hydrogen. Then to cryogenically liquefy it, and keep it liquid, takes about as much energy as it contains in the first place. When you look at burning a ton of liquid hydrogen, you should think of it as burning five or six tons of natural gas.
>>8018229
>You need more fuel the more mass you have right? Well the more fuel you have the more mass you have.
That's true of any internally fuelled vehicle. It's just much more apparent with rockets.
>>8023472
>White paper from a joint study by CNES/Airbus.
You're going to need to provide an actual source for the claim that Falcon 9s could only fly 3 or 4 times, because this, "I remember these people said something like this." is not going to cut it. I am about 90% sure you either misunderstood it or are deliberately distorting it.
>the fact that their rockets are both more powerful, more technologically advanced, and more reliable than SpaceX's
It is to kek. They have nothing nearly as capable as Falcon Heavy. They have nothing remotely comparable with the advanced technology of flyback recovery. Their rockets have also blown up.
What they have are rockets that are older. That's all. Their first Ariane 5 blew up in 1996. Then they blew up another in 2004. They had 2 other serious failures, not putting the payload in the intended orbit. New designs often have subtle bugs that are only discovered by flying.
As for it being advanced, I hope you're not referring to them using hydrogen fuel. Because that's not "advanced". That's 1950s technology.
>>8018188
Have you been asleep for the past year? Advances are coming at breakneck speed! as mentioned here: >>8020715
But also yeah, spaceflight isn't computing. We were already near the limits of physics and materials even back in the 1960s. Further advances will be like airlines, bringing down the cost due to reuse and streamlining operations.
>>8022047
>SABRE is an order of magnitude more efficient in atmosphere than falcon 9 and somewhat more efficient in vacuum.
Which isn't enough to make up for how much this fucking anchor of an engine weighs, when it comes to SSTO.
Think of it this way: it's like saying a 100 HP, 1000-lb inboard marine diesel engine is more efficient than a 100 lb motorcycle engine with the same power. It may be true but it doesn't change the fact that adding all that weight to a little motorcycle is going to make the thing burn more fuel anyways.
Read the link I gave, the math's all there plain as day (provided you understand how the rocket equation works). Skylon would perform better if it ditched the SABRES entirely and replaced them with conventional rocket engines.
>>8023587
Yeah. It's even visible with some high-performance aircraft. As the Concorde flew a route, it would burn fuel, getting lighter and lighter, flying higher and higher in thinner and thinner air where it would burn less and less fuel per mile. Basically the same thing that happens with rockets, only with velocity instead of distance. Hell, just compare the Tsiolkovsky Rocket Equation with the Breuget Range Equation.
It is very pricey and inefficient to send shit into space.
>>8023958
>Read the link I gave, the math's all there plain as day (provided you understand how the rocket equation works). Skylon would perform better if it ditched the SABRES entirely and replaced them with conventional rocket engines.
I don't think it's right, though.
For starters, you need significantly more delta-V if you're doing horizontal takeoff and lifting flight. 9.8 km/s won't get you there, because you're flying and gaining altitude gradually. If you switch to vertical takeoff to avoid it, you need more thrust.
For another thing, SSMEs aren't very efficiently reusable. They needed a lot of refurbishment. They pushed too hard for performance. An efficiently-reusable rocket engine would probably have lower performance, either in Isp or thrust-to-weight, or both.
>>8023958
>Which isn't enough to make up for how much this fucking anchor of an engine weighs, when it comes to SSTO
Why do you keep saying this? Its been established that if the SABRE engines meet their stated specs then then they can will get enough delta-v to reach orbit, the only question is whether or not the engines will works as predicted, and whether they can keep the weight of skylon itself low enough
>>8024395
>Its been established that if the SABRE engines meet their stated specs then then they can will get enough delta-v to reach orbit
Engines don't "get enough delta-v" on their own. They have parameters such as mass, thrust, and specific impulse. The delta-v they provide depends on the vehicle and its payload.
Even if SABRE was ready today, working exactly as predicted, building Skylon at the mass specified, to perform as specified would be a daunting technical challenge.
>>8024411
Skylon, as designed, has enough delta-v to get to orbit, and cheaper than anything except the most optimistic estimates for fully reusable rockets.
At no point have I claimed it would be easy or guaranteed to work as advertised, all I have done is argue against people who seem to think that skylon CANNOT be viable, for some reason never fully explained. It works on paper, the unique technology for the engines works in reality. Its reasonable to think the whole thing has some chance of working
>>8024416
>Skylon, as designed, has enough delta-v to get to orbit
Do you have any idea how easy it is to design a rocket on paper, and what a gulf there is between that and making one actually work? You might as well say, "Skylon, as wished for".
>cheaper than anything except the most optimistic estimates for fully reusable rockets.
The $/kg cost figure they originally tried to sell it with was not much better than Falcon Heavy's price figure, as an expendable.
They made it sound like an extremely ambitious goal mostly by comparing it with ungenerous estimates for the space shuttle's costs, which is basically the most expensive launch vehicle that was routinely operated.
Meanwhile, you could get an order-of-magnitude improvement on the space shuttle's costs just by ordering a Proton.
>the unique technology for the engines works in reality
You mean part of the unique technology for the engines works under lab conditions. The other dozen miracles needed have yet to be unveiled.
>all I have done is argue against people who seem to think that skylon CANNOT be viable, for some reason never fully explained.
Oh, that makes it easy, deciding to argue against a strawman. I suppose when your dad told you wouldn't make it as a rockstar, you came back with proof that rockstars exist and some persons had at some point become them.
Skylon's been implausible through the whole career of the man pushing it, and now he's old and better ideas for reusable rockets are actually reaching a practical stage, so it makes less sense than ever to fund it.
>>8024456
Dude, the company designing it seems to think it can work, the british government seems to think it can work. The initial price (whihc would fall over time) they are claiming is less than half what falcon heavy claims and less than a quarter the current pricing for falcon 9 (which is what its competing with). No one said it isnt going to be hard, but it is certainly possible
>>8018188
The advancement of space flight ultimately came with the fear of falling behind the soviets in the space race. The income for the evolution of rockets ended really when the cold war ended. The U.S. had big dreams about space flight but lacked the economy for it. Big businesses weren't going to invest into something their not going to profit from. However, now, private companies, such as SpaceX and Blue Origin, have started to invest into space flight because of government contracts being implemented, instead of being put into NASA. The answer to your question is that most governments suck at spending money, specifically the U.S.
Bad Economic Spending > Our Future
>>8024466
>Dude, the company designing it seems to think it can work, the british government seems to think it can work.
Remember how that worked out with the space shuttle? Everyone officially thought it would work. In the end, they made something that went to orbit alright, but it came back in no shape to reuse.
Anyway, the company designing it has to say they think it'll work or nobody will give them money, and the British goverment doesn't simply "think it can work". They've given it limited support, not full funding. They may not really care whether it works, and just hope to encourage private investment in a British aerospace firm.
>>8024485
Give me one reason why it CANNOT work
I think people are completely justified in fearing that foreseeable future of spaceflight ending up being endless repeats of the shuttle. That's certainly what SLS is starting to lean toward.
I say give companies the benefit of doubt for this upcoming generation (SLS, etc), but if those both turn out to be duds/turbopork, pressure needs to start being applied in a major way.
>>8024466
>The initial price (whihc would fall over time) they are claiming
There are no price estimates for Skylon, let alone a firm price, only *cost* estimates.
The initial cost would be at least $10 billion. That has to be amortized over the number of flights. Imagine that the program only lasted 200 flights (the space shuttle went 135 flights). Then there'd be a development cost of $50,000,000 per flight, around $3,500/kg, entirely aside from the ongoing operating and facilities costs or interest on the development funds.
The unit cost of a Skylon is estimated at $300 million. Even if it lasts 200 flights, that's $1.5 million per flight. If there's a problem and it only lasts 20 flights, then the vehicle unit cost alone accounts for the full amount of their $1,000/kg goal, with nothing toward development, facilities, maintenance, fuel, or interest.
It can't possibly reach their cost goals without a thousand flights. Their target of $15 million per flight with a 15 tonne maximum cargo is not their "initial price", it's their eventual cost goal for if Skylon is very, very successful and the development costs can be amortized over many, many flights quickly.
Falcon 9 only cost a few hundred million to develop, and each unit only costs around $25 million to build. Do you see how overwhelming the advantage of low development and unit costs is?
>is less than half what falcon heavy claims and less than a quarter the current pricing for falcon 9 (which is what its competing with).
Skylon, as a candidate for development funding, is certainly not competing with current pricing.
Currently on the Wikipedia page: "If all goes to plan, the first ground-based engine tests could happen in 2019, and Skylon could be performing unmanned test flights by 2025."
Test flights in 2025. Can you imagine what SpaceX will be flying by then?
>>8024145
>For starters, you need significantly more delta-V if you're doing horizontal takeoff and lifting flight.
And HOW does this count against the pure-rocket option? It's the airbreathing SABRE that constrains Skylon to a lifting ascent.
>9.8 km/s won't get you there, because you're flying and gaining altitude gradually.
*9.9 km/s
And tell that to the knuckleheads at REL, then, since they seem to believe that's all the dV they need to get Skylon to orbit. Or were you under the impression that the SABRE-equipped Skylon had more than that?
Anyways, it's also worth noting that at least a lifting ascent helps reduce gravity drag, which offsets some of the so-called "Airbreather's Burden."
>If you switch to vertical takeoff to avoid it, you need more thrust.
True, and while that guy's analysis assumed HTHL was retained, there is another analysis earlier in the thread that considers a VTHL Skylon with three SSMEs instead of just two (albeit with somewhat different assumptions), and that option is judged to be viable as well: http://forum.nasaspaceflight.com/index.php?topic=24621.180
>For another thing, SSMEs aren't very efficiently reusable. They needed a lot of refurbishment. They pushed too hard for performance.
Right, so let's completely forget about anything that's tried-and-true and go with an unproven vaporware combined-cycle engine with even more outrageous performance claims and that's even more complicated instead. Yeah, that sounds like an EXCELLENT plan.
>An efficiently-reusable rocket engine would probably have lower performance, either in Isp or thrust-to-weight, or both.
It's worth pointing out that SABRE still claims to have an airbreathing thrust:weight ratio almost as high as has ever been achieved before, while simultaneously having a claimed hypersonic ISP that surpasses some subsonic turbofans (though the H2 fuel source helps account for some of this latter factor). You'd be a fool to think SABRE isn't "pushed hard for performance."
>>8024488
>Give me one reason why it CANNOT work
>>8024456
>>all I have done is argue against people who seem to think that skylon CANNOT be viable, for some reason never fully explained.
>Oh, that makes it easy, deciding to argue against a strawman. I suppose when your dad told you wouldn't make it as a rockstar, you came back with proof that rockstars exist and some persons had at some point become them.
I like how, when people come up with reason after reason why Skylon doesn't make sense, isn't as good as VTVL reusables, and is generally very unlikely to live up to its hype, you keep coming back to this, "But you can't PROVE that it's COMPLETELY impossible!"
Nobody said it was. This is like an argument between people explaining why lottery tickets are a bad investment, and this one guy who came in saying they're a great investment, who keeps retreating to, "Give me one reason why you CANNOT win." and "All I have done is argue against people who seem to think that the lottery doesn't have ANY winners, for some reason never fully explained."
>>8018188
>We've seen huge jumps in computers and communication technologies
Not as huge as you think. Microprocessors have been made in fundamentally the same way for 30 years (Photolithography). Internet architecture has NEVER been significantly changed.
>we're using 50 year old technology when it comes to spaceflight
Dawn launched in 2007 is the first ever spacecraft able to orbit and de-orbit at will thanks to its ion drive that's being used for the very first time
>>8024547
>>For starters, you need significantly more delta-V if you're doing horizontal takeoff and lifting flight.
>And HOW does this count against the pure-rocket option? It's the airbreathing SABRE that constrains Skylon to a lifting ascent.
I'm not talking about it counting against pure-rocket options in general, or defending Skylon. I'm talking about it counting against the specific option of sticking ordinary rocket engines on Skylon.
I don't think this NSF napkin math is very reliable.
Like with this:
>http://forum.nasaspaceflight.com/index.php?topic=24621.180
There are immediate objections to the proposed 3-SSME design, particularly the assumed mass savings.
>>8024395
>Its been established that if the SABRE engines meet their stated specs then then they can will get enough delta-v to reach orbit
>if they meet their stated specs
>if
Exactly. "If." The SABREs are an unproven technology that show zero (or even slightly negative) actual performance improvement over existing liquid engine technology (in the SSTO role anyways), so why on Earth would you go to the trouble of developing a riskier engine that, even by your own projections, doesn't even achieve any useful improvement over proven technology?
>>8024466
>Dude, the company designing it seems to think it can work, the british government seems to think it can work.
It's entirely possible it could work, but even if it does exactly to REL's own projections, it would still be NO BETTER WHATSOEVER than an SSTO with conventional rocket engines instead.
You have to understand, Alan Bond was completely enamored with airbreather SSTOs since even before failed HOTOL project; it's really no surprise he managed to gather enough followers to keep pushing the concept. That doesn't change the fact that after three and a half decades of obsessive dedication, brainstorming and perhaps even distorting the numbers, the proposal is STILL penciling out to be an inferior-but-workable solution to the SSTO challenge at best.
As for the government's involvement, we've seen governments fund dumber projects before. With government funding, especially at the early R&D stage you have to bear in mind that they're usually more interested in the research itself than the overall success of the project. Even if the project fails, the research may still very well yield useful information. For instance, the precoolers are the main focus of recent funding, and while they and the rest of SABRE don't really make much sense for an SSTO, they could still be incredibly useful for future hypersonic SST aircraft or possibly as the first stage of a multistage launch vehicle.
>>8024566
>I'm not talking about it counting against pure-rocket options in general, or defending Skylon. I'm talking about it counting against the specific option of sticking ordinary rocket engines on Skylon.
So you're basically saying that neither version of Skylon (SABRE-powered or hypothetical SSME equivalent) has enough delta-V to reach orbit with the stated payloads? If you say so.
>There are immediate objections to the proposed 3-SSME design, particularly the assumed mass savings.
Well no shit, he posted it in a thread that's naturally packed with Skylon fanboys. But let's go ahead and take a look:
>Rob, there are a few problems with your design (as I understand it).
>VTHL has problems with abort shortly after take off, loose an engine and the trust to weight is less than 1.0, there isn't enough time or energy to transition to horizontal flight for landing.
The SSME is just a convenient and well-published benchmark. If redundancy and abort options are that important, a smaller engine of proportionately similar performance could be used instead, in greater numbers. And it would still be considerably easier and less risky to develop than SABRE.
>I think you need to allow for thrust structure of about 2 tonnes per engine.
Absolute horseshit. Skylon already has thrust structure for 2 engines of a similar thrust class to the SSME, if you're adding any mass for additional thrust structure it will only be for the one additional SSME (or proportionate equivalents), not "per engine."
>3 x SSME are difficult to put on the ends of the wings.
Why? Because they're lighter? This makes even less sense than the previous point.
>The wings would need to be strengthened to withstand the extra thrust (more mass).
Possibly a bit, but I suspect the structure is effectively already there on account of aerodynamic lift loads. After all, they'll have to withstand 2-3 Gs of lift force in their weakest direction for horizontal takeoff and ascent to be viable.
Could this work ??
>>8024595
That is just a retardedly drawn version of how multi stage rockets actually work
>>8024695
Im gonna build it in KSP
With engines as seperated as that on the skylon, does it just destroy itself if it loses thrust on one side?
This alan bond guy seems to have spent his whole life chasing pipe dreams
>>8024771
A sudden loss of thrust would probably put it into a spin which rip it apart
>>8024604
multistage rockets turn to achieve orbital velocity while gaining altitude
this is concerned with making recovery of the jettisoned first stages easier, since the rocket doesn't have to return to earth on an angle
>>8024695
thanks for your support
>>8024703
please let me know how it goes, my gaming rigs broken so I can't do that for myself
>>8024903
You know the earth itself is rotating, yes? So they will need to turn anyways?
Not to mention they need to brake the first stages to return them to earth?
>>8023040
SLS can do it.
>>8018641
>burning a million gallons of fluorine
>>8022024
This. a) it's vaporware b) for that tiny payload even a standard rocket could do SSTO so you may as well just use that.
>>8024933
reminds me of this http://www.tor.com/2012/07/20/a-tall-tail/
even if its bullshit, it's a cool story.
>>8024466
The British government gave it £2 million. Kanye's crib costs more than this.
I'll tell you a story. One day I wanted to make a drone and I wanted it to fly longer than any other drone. I decided to try developing a hybrid generator system. No-one outside of the military had ever done this but the proposition was simple enough on paper. Petrol engine - generator - motors. It was a complete disaster. Spent maybe £5,000 and 2 years on it to no avail. So I gave up and went with batteries like everyone else. Within a month I was getting the performance I wanted just by improving on the tried and tested method.
Moral of the story is that guys like Elon Musk have the right idea; improving on existing technology is the way to run an engineering business. Creating totally new technology is just a black hole that rarely has a bottom. It's rarely worth it, even if your shit works after all that R&D it's going to be inefficient and unsafe as hell because it's so new.
>>8024941
Bruh, my jaw was dropping until I got to dimethylmercury and I jumped out of my chair shouting "no no no no fucking way"
That guy is a fucking madman.
>>8024941
Oh wow great story, I was losing my mind until it got to "red mercur and Chernobyl" then I knew it was fake.
R-right??
>>8024941
>>8024961
>>8024985
There are some elements of truth to it. FOOF was explored as a liquid rocket oxidizer and NAIL SPIKE sounds suspiciously like the Farewell Dossier in which the CIA let the Soviets steal control software for a Siberian pipeline with a line of code that blew the pipeline apart at a certain date.
>>8024585
>>I'm not talking about it counting against pure-rocket options in general, or defending Skylon. I'm talking about it counting against the specific option of sticking ordinary rocket engines on Skylon.
>So you're basically saying that neither version of Skylon (SABRE-powered or hypothetical SSME equivalent) has enough delta-V to reach orbit with the stated payloads?
Can you stop being a jackass for like three seconds? A random guy on an internet forum did a few lines of napkin math, obviously left out some considerations, and you're instantly ready to believe this is 100% equivalent to the detailed analysis of a team of aerospace engineers.
>>I think you need to allow for thrust structure of about 2 tonnes per engine.
>Absolute horseshit. Skylon already has thrust structure for 2 engines of a similar thrust class to the SSME, if you're adding any mass for additional thrust structure it will only be for the one additional SSME (or proportionate equivalents), not "per engine."
We're talking about going from an HTHL to a VTHL that goes straight up by brute force, with the engines on the tips of the wings, and you're laughing off the idea that this would require some reinforcement of the structure.
Skylon C1 was specced to lift off at 275 tons and put 56 tons in orbit. This guy is talking about a 418 ton vehicle that would put 46 tons in orbit. He has simply deducted the difference in mass between SSMEs and SABREs from the empty vehicle. No additional structural mass for a vehicle at 50% greater lift-off weight. If the structural mass grows 50%, there's no payload and it doesn't go to orbit.
...and this is on an SSTO. The main objection to an SSTO is that every gram of additional dry mass must be subtracted from the payload. This is one of the best arguments against Skylon: that as they get closer to an actual vehicle, they'll learn things that require them to add mass, which will reduce the payload.
