Al lot of bullshit going on on this board, let's have a serious discussion about real technology. Which of these systems do you think will be the future of spaceflight? I am behind SpaceX for two reasons 1) they have far more funding 2) their concept is more straightforward and based on existing technology. The US military is also jumping on the reusable rocket bandwagon
http://www.space.com/30196-xs1-military-space-plane-boeing-contract.html
Pic related is Boeing's super original design. Don't worry kids, SS heat shield issues won't happen because it isn't going all the way to orbit.
>>7860703
I'm excited about SKYLON from Reaction Engines - Their SABRE engine is a gamechanging technology that could revolutionise space travel. They are some way away from demonstrating their tech though, so in the meantime SpaceX are the most promising route to advances in Space Travel.
Blue Origin get an honorable mention too
>>7860737
Skylon looks like a good concept but it's hard to see something like that materialising in the UK. Too many questions: who is going to fund it? where is the testing going to take place? what is going to stop it being scrapped after the obvious budget overruns and failures? where is the support for this project going to come from?
I think the moment BAE systems bought into it that it was filed together with a long list of slightly promising projects that ended up in a dead end.
Maybe it is a case of my English pessimism getting to me but I suspect it is also going to get to anyone that could make this thing happen too.
>>7860737
If it works does it mean the end of the scramjet? Supersonic combustion has proven to be very temperamental, the precooler solution could make it obsolete.
>>7860797
The project seems too risky for most investors at the moment. Even the British Government are pretty cagey about handing over their £60 million already promised.
Reaction Engines need to put more effort into their PR with a strong and convincing pitch to investors. Test demonstrations of the technology with positive results are obviously needed too.
Failing that, they need a rich entrepreneur like Richard Branson or Elon Musk to buy them out
>>7860797
I am English too and I feel exactly the same. The product is too big for us to finish. Something will go wrong and it will get canned due to being on a shoestring budget whereas the Americans or Russians would have just plowed more money into it. Nobody in this country even knows about it, so you can forget about public support.
>>7860819
Both these people are working on competing systems, they probably want it to fail.
>>7860737
>Their SABRE engine is a gamechanging technology
No, it isn't. Even if the vaporware comes to fruition, as it currently stands, SABRE's higher advertized ISP is *still* not enough to make up for it's godawful thrust:weight ratio (and thus dead weight on-orbit) in terms of overall performance. If you scrapped the SABREs, replaced them with 3 SSMEs instead and reallocated tank volume to LOX for the appropriate mixture, SKYLON would actually have more payload-to-orbit as a whole.
>>7860811
>end of the scramjet?
It will take decades to prove the technology and longer still before rocket burning engines are phased out
Look at the automotive industry: Electric cars have been around for a while now but combustion engines remain popular
>>7860832
>godawful thrust:weight ratio
Sauce?
>3 SSME
Isn't the whole idea of SABRE to avoid using consumeable rocket boosters which rely on carrying large amounts of fuel?
A reduction in performance or payload capacity is more than outweighed by the benefit of completely avoiding rocket boosters
>>7860832
Rocket engines are actually advanced enough to achieve SSTO. SSTO hasn't failed to materialize because we can't do it, it's because doing it for the tiny payloads that will be allowed by the rocket equation is un-economical. You are saying saying that Skylon's payload could be matched with just a rocket. Well either that is untrue or they are willing to try marketing payloads that everyone else deemed to be too small.
>>7860831
I get the feeling Elon has a genuine interest in science and furthering mankind's space technologies. I very much doubt he'd want to see a novel idea like SKYLON fail.
They barely pose a threat to him since he could buy them at any moment and use their technology as and when he sees fit
>>7860837
Combustion engines will always be better because the energy conversion is more direct and hence more efficient. It's funny that it's the total opposite in the drone world; electric is the standard and petrol hybrids have a hard time getting off the ground (no pun intended). i think it's in large part due to what came first. This is what people will stick with.
>>7860862
>combustion engines are energy efficient
wat
Surely the prevelance of electric drone vehicles legitimises the technology as being efficient enough?
>>7860868
I believe he's talking about the efficiency in terms of energy wasted by burning fuel and then transmitting electricity to the charging station for electric engines vs burning fuel directly in the combustion engine.
>>7860868
Electric drones are short-ranged and inefficient. The electrical batteries and motors are convenient, responsive, and low-maintenance.
Combustion engines, at suitable scale, are certainly more weight-efficient than electric propulsion.
Let me know when you come up with an example of an electric (non-solar) drone that can fly from New York to London.
There are solar-powered electric aircraft, which can fly pretty much indefinitely, but they carry little to no payload and are optimized like mad for low-thrust level flight.
>>7860849
SSMEs aren't consumable boosters. I say this politely before angry anti-Skylon person comes back to shit up this thread like all previous ones.
It does have bad thrust weight because it's an SSTO and an RLV.
>>7860849
>Sauce?
https://en.wikipedia.org/wiki/SABRE_(rocket_engine)
>14:1 @ 220 tons thrust, or 15.71 tons PER ENGINE
By rocket standards, that's abysmal. If you compare it to an SSME which weighs less than 4 tons and makes nearly as much thrust, you're looking at a LOOOOOOT of dead weight that could otherwise be used for payload instead.
>Isn't the whole idea of SABRE to avoid using consumeable rocket boosters which rely on carrying large amounts of fuel?
That's the idea, yes, but given that less than 30% of your on-orbit mass is actual payload and nearly 2/3s of it is dead weight comprised of the engines themselves, there's actually quite a bit of wasted impulse. It doesn't matter if your engine is "efficient" on paper if the majority of the work it does will be simply moving it's own enormous mass.
Somebody's done the math here:
http://forum.nasaspaceflight.com/index.php?topic=24621.225;wap2
Now, don't get me wrong, there are areas where SABRE or something like it could indeed be useful. For instance, the LAPCAT project seems far more credible and competitive to me (though I certainly still wouldn't invest in it). And if Skylon wasn't so hell-bent on being SSTO, they probably actually could achieve a net performance-gain with a 2STO/piggyback launch system, where the SABRES get the stack to mach 5 and then dedicated pure-rocket engines take over for the rest of the trip to orbit (thus avoiding having to carry/accelerate that dead weight all the way to mach 26+). But the proposal that currently is Skylon, constituting an SSTO carrying heavy-ass SABRE engines all the way to orbit, is not competitive with pure rockets even by their own (questionable) numbers.
>>7860851
Yeah, that too. The appeal of SSTO is reusability, but all the same things that complicate reusable SSTO with rockets would still apply to Skylon, and yet REL seems to kinda handwave most of that.f
>>7860892
SSMEs aren't exactly refuel-and-go either, though.
Anyway, SABER and the SSME both suffer from the extreme low density of liquid hydrogen. Ever notice how hydrogen/oxygen engines have much poorer thrust-to-weight ratios than RP-1/oxygen engines? That's because the pumps, fuel lines, cooling channels, etc. all have to be scaled to the density of the propellant.
SSTOs would be better with H2O2/RP-1 or NTO/UDMH propellant. Both the tank mass and the engine mass required to deliver a certain payload to orbit are determined more by density impulse than specific impulse, with a multiplier added for dealing with cryogenic fuels.
>>7860953
>H2O2/RP-1 or NTO/UDMH
that would make it difficult to use atmospheric oxygen as a reactant ie. voiding the premise upon which skylon is based.
>>7860953
>Ever notice how hydrogen/oxygen engines have much poorer thrust-to-weight ratios than RP-1/oxygen engines?
Not really.
https://en.wikipedia.org/wiki/LR-87
>87:1
https://en.wikipedia.org/wiki/LR-87#LR-87_LH2
>95:1
>
>>7860959
SSMEs wouldn't use atmospheric oxygen, either.
>>7860963
https://en.wikipedia.org/wiki/LR-87#LR-87-5
>Thrust / weight: 151.34
https://en.wikipedia.org/wiki/LR-87#LR-87_LH2
>Thrust / weight: (not given)
>Weight: unsourced, guesstimated around 700 kg
Anyway, why would you use an unflown engine from the 1950s as your representative example?
>>7860978
>>7860959
...and the point was made earlier that liquid hydrogen's density is so poor, Skylon has to be bigger than if it were powered by conventional rocket engines.
Its loaded take-off weight is lower because it's mostly full of low-density hydrogen, but its volume and empty mass would be higher.
The SABER doesn't particularly enable a reusable SSTO. If you can make an SSTO work with SABER, you can make it work with any decent engines. Rather, The Reaction Engines guys just assume they can tackle all of the problems of a reusable SSTO without a hitch.
Basically, it's all the same stuff you heard out of the Roton people, who thought it was totally a good idea to make an SSTO space helicopter, and went out of business without building more than a rocket-shaped helicopter (with parts scavenged from a regular helicopter).
>>7861022
I think there would have to be more to it than that, don't you? After all this report by the ESA did not find any such issues:
http://webarchive.nationalarchives.gov.uk/20121212135622/http://www.bis.gov.uk/assets/bispartners/ukspaceagency/docs/skylon-assessment-report-pub.pdf
and they seem to be a reputable source.
>>7861065
>After all this report by the ESA did not find any such issues:
They weren't looking for it, since they're only funding further research on the precooler and not the entire project. Just because SABRE probably isn't useful for SSTO doesn't mean it's not worth investigating.
>>7861022
>SSTO space helicopter
I saw that, were they actually serious??? I thought they were just using the helicopter for simulation.
>>7861070
I'm an EE not an AE so I can't tell whether your chatting rubbish or not but the report clearly deals with many aspects of the SKYLON concept beyond just the precooler like you claim. It also says that no roadblocks have been found to developments so they clearly missed something you didn't. Maybe you should get in touch with them?
>The document concludes that, no impediments or critical items have been identified for either the SKYLON vehicle or the SABRE engine that are a block to further developments. It is clear that the SABRE engine is crucial for the successful development of the SKYLON vehicle.
Either way, this discussion has reached it's conclusion: you disagree with the ESA findings and I am unable to evaluate the validity of your position.
>>7861096
>whether your chatting rubbish
>your
can't believe I've made that mistake
I'm definitely done with this discussion.
>>7861022
I totally understand because the drone business has the same turkeys. Every time someone tries to use a combustion engine solution even though combustion engines are far more powerful on paper by the time you add up the generators or transmission or whatever it ends up having no more lifting capability than a standard electric drone. Pic related is practically the Skylon of the drone world, sounds great on paper but is forever vaporware because it won't work in practice yet they refuse to admit it.
>>7861070
This. No-one is saying the SABRE engine is bad it's just that it is not competitive with rocket-based launch systems. USAF is interested but it's highly likely that they want it for long range hypersonic aircraft because if they wanted to throw payloads that tiny into orbit they would just use a Titan II first stage.
>>7861104
> 5kg payload
> 100 km/h
> 60 minute flights
shit son...
>>7861113
I know right? They must smoke some good shit in Germany.
>>7861065
>this report by the ESA did not find any such issues:
Do you remember that the space shuttle got the go-ahead as a practical way to lower launch costs? VentureStar got years of approvals and funding. The Roton people got millions of dollars in funding, and had various experts saying, "This has all been worked out and looks fine."
The Skylon design shows a ~50 ton empty mass and a ~15 ton payload. If the empty mass grows 30%, it carries no payload. If it grows 31%, it doesn't go to orbit. If the engine gives less thrust or gets lower Isp than expected, or they get more drag than expected, it doesn't go to orbit.
This is the trouble with SSTOs: they barely work even as napkin sketch concepts, so there's no room to fix things as you get closer to the real vehicle.
Compare to SpaceX's Falcon 9 1.1 (before the recent improvements): the empty mass of the realized upper stage was under 5 tons, about a third of what the nominal payload is. The upper stage empty mass could have TRIPLED as they dealt with surprise problems, and it would still take multiple tons of payload to LEO. The lower stage had similar flexibility: at burnout, it was under 30 tons, pushing a loaded upper stage of nearly 100 tons. It could also have tripled in empty weight without compromising the ability to go to orbit. Indeed, to attempt flyback reusability, they stage with a substantial load of fuel, having pushed the upper stage a full 1 km/s less than the speed at staging in expendable mode. This is the margin on the delivered vehicle, not the early estimates.
So with a staged vehicle, you have this tremendous flexibility to correct for overoptimistic estimates late in the design process. It looks even better with a three-stage vehicle (like Soyuz, Saturn V, Ariane 5, or Atlas V with strap-on boosters), which is generally considered to give optimal performance for launch from Earth.
There has not been a single payload sent to orbit from Earth without some form of staging.
>>7861117
Well finally they had the fucking sense to use fuel as the power source for drones. And Yeair has a really tiny capacity. Since it can lift 5kg, I'd just add a 5 liter fuel for it to fly for fucking hours.
>>7861131
>Roton
Their wiki article is pure comedy, I feel kinda bad laughing because I've come up with some wack ideas myself in the past but space helicopter? C'mon why did people take this seriously?
>>7861139
My point is that as with airbreathing rockets it sounds good on paper but when you do it it doesn't work. The generators to convert the engine power will be heavy and inefficient. Maybe they did the calculations and found that it would still marginally be better however as this guy >>7861131 said when you are working with marginal possibilities you may as well not bother trying to build the real thing because things will go wrong and rob your design of it's advantage.
>>7861131
>tfw on some alien planet in another galaxy they are SSTOing everyday because they have Martian-tier gravity.
Oh well all I can say is thank God that Earth gravity isn't so high that even staged rockets wouldn't work. I imagine there's aliens out there on some planet with triple Earth gravity that is stuck there fore eternity, poor fuckers.
>>7861087
>>SSTO space helicopter
>I saw that, were they actually serious???
It's actually not a terrible idea for how to build a tiny launch vehicle. Small launch vehicles suffer more from drag than large ones do, to the point that it can be prohibitive. The original plan was a whole spinning rocket driven entirely by wingtip engines.
At low altitudes, it would enjoy the high specific impulse of a tip-rocket helicopter. In vacuum, it would be spin-stabilized (stabilization is another problem for small vehicles).
It's probably a pretty good way to make a cubesat launcher.
They didn't try and make a cubesat launcher. They scaled it up until, even by their own estimates, it would barely work, they'd need another rocket engine on the main body, the whole thing couldn't spin anymore but instead they'd need the the rotor to be mounted on a bearing, and the rotor would actually offer no net benefit to getting to orbit (it would only be useful for the landing). Then they decided it should be manned.
...and that's how they ended up building a tall helicopter, going bankrupt, and starting XCOR, the suborbital kitplane company, whose first product was proposed in 2003 and announced in 2008 (and started selling $95,000 ride tickets) with flights to begin in 2010. They did not start building their space kitplane until 2013. Then in 2014, they announced flights would begin in 2015. They have announced their space kitplane will not go to space (the karman line), but only to 62 km... they hope.
Space helicopter people, man. Space helicopter people.
>>7861178
Hmm.
>>7861154
>thank God that Earth gravity isn't so high that even staged rockets wouldn't work. I imagine there's aliens out there on some planet with triple Earth gravity that is stuck there fore eternity
Well, orbital velocity only scales with the square root of the strength of gravity, so the delta-V requirement would only be a little higher than going to the moon. The thrust requirement would be three times as much for the same take-off weight, which is doable, especially with solids.
Their typical launch vehicle might look like a Saturn V plus a set of big solid rocket boosters.
I see a lot of considerations here, but have you ever tried to remember what happened with the Space Shuttle and the whole reusability thing?
When it came back from space it needed to be basically overhauled completely in a very expensive way. I can't see why something like Skylon, in case it actually makes it into orbit and back, shouldn't be inspected in its entirety, bolt by bolt, nut by nut.
Skylon may find some kind of application, like a bus ride to the nearest space station, with the capability to land softly like an airliner, but I still can't see how someone would trust a vehicle like that to hold another trip to space without bursting into pieces if not by knowing it underwent some expensive and scrupulous inspection and refurbishment.
>>7861306
If they needed a Saturn V just to get to orbit going to space for them would be like going to the Moon for us so crewed alien spaceflight would almost never happen. They would still throw up satellites though assuming they are war-like. But who knows perhaps they are richer than us and you can pick up a Saturn V in alien Wal-Mart
>>7861360
This is why reuseable rockets are much smarter. You see the reuseable part never goes to orbit so doesn't have to deal with the things that the SS had to.
>>7861360
The space shuttle was a very special screw-up.
For starters, just dropping the external tank was throwing out approximately as much precision aerospace hardware as you'd have used for a conventional launch of the same payload on an expendable rocket.
Correcting for inflation, it cost $86.5 million in the mid-90s. That's just the incremental cost of manufacturing the tank. About the same as the launch price of a Falcon Heavy, which can carry as much to LEO as two space shuttle launches, or send large payloads to higher orbits or escape trajectories.
...and no wonder, it had a volume of 2 million liters, 50% more than all the tank volume of a Falcon Heavy, 3 quarters of which was for deep-cryogenic hydrogen.
Or in a more direct comparison, the Proton rocket, which was established before the shuttle program started and carried a similar payload, had only about 1/4 of the tank volume and cost around $110 million for the entire launch (a price which has stayed reasonable stable ever since). Of course, the manufacturing cost was much less.
Even if every reusable part of the space shuttle was free to develop, free to build, and worked perfectly without maintenance, there was no way for the shuttle to markedly reduce launch costs over a cost-sensitive expendable rocket. It required four times as much expendable tank volume as a conventional rocket, which of course meant new manufacturing costs per launch which were at least comparable to an expendable.
It was just a completely insane design.
nice thread, looks like there are some specialists here...
so, why don't the SABRE people give their idea a spin? why are people so obstinate about doing things gradually?
>>7861522
There's nothing gradual about Skylon. They basically took every radical unproven concept they could think up and threw it all together into the same vehicle. They'd be much better off if they were developing things incrementally, and THEN deciding on a vehicle design based on the technology they successfully prove.
>>7861522
They don't have any product yet
engine likely doesn't even work
These sorts of things ar eall scams
>>7861522
The only thing they have developed is the engine precooler. They have yet to make a prototype of the engine that uses the precooler, let alone the vast gulf between a test engine and an actual flight-worthy SSTO.
It warms my heart to see a tread like this not deathspiral into some shitposting nuclear pulse flat earth SpaceX-btfo tread. Keep it up, good people!
Is reusing the entire body of a rocket as useful as simply recovering the engine?
>>7861490
Honestly I think the point of the space shuttle was to look cool and bring in more funding for NASA. Unfortunately the military took it too seriously and added ridiculous demands that pushed it to its limit.
>>7861854
OP here, I'm so happy, Ive never seen a /sci/ thread so good.
>>7861859
>Is reusing the entire body of a rocket as useful as simply recovering the engine?
Imagine an airline that simply scavenged the engines from its aircraft after each flight, instead of refuelling and maintaining the complete vehicle.
It's possible that you could make engine recovery work, but only if you made a special effort to keep the expendable tanks cheap. You can't have elegantly-constructed, mass-sensitive tanks put together by painstaking hand labor. They have to come out of an automated line, like small arms ammunition.
You need something like the OTRAG approach to tank construction, which used clusters of small-diameter pipes, which came out of pipe-rolling machines for making long oil and gas pipelines.
Mind you, once you start thinking like that, there are ways to make the engines cheap, too. The OTRAG engines were just moulded into the ends of those pipes out of an ablative fiberglass. Pressure-fed with hypergolic ignition (the propellants were diesel or jet fuel and nitric acid blended with extra NTO, with a shot of furfuryl alcohol loaded in the bottom of the diesel pipe for ignition, pressurization was just headspace full of compressed nitrogen gas), there was nothing else to them but valves. Steering was by differential throttling. They worked fine.
OTRAG was shut down for political reasons, not technical ones. It was the "soda can" of expendable designs: expendable parts so cheap they rivalled the affordability of the consumable contents (although it was also designed for evolution toward reusability). Solid-fuel designs can also make very cheap expendables.
>>7862666
Why did they test their rockets in the edgiest of locations? Testing missiles in Libya circa 1980 is like if SpaceX decided to move operations to Iran.
>>7862787
>Why did they test their rockets in the edgiest of locations?
They didn't start there. They started in Germany, and were chased out by political pressure.
Actually, this was one of Werner von Braun's projects. He had been chased out of the US space program by political pressure, too. If you ever wonder how the NASA that could pull off the Apollo Program could turn into the NASA that diddled around in LEO with the space shuttle program from the 1970s to the 2010s, one of the big factors was that bureaucratic careerists with pull in Washington and allies among the more political (i.e. underhanded) sort of contractors were drawn to claim leadership of the successful agency, and pushed out men of vision and competence like von Braun to claim it.
The dodginess of the places they resorted to working in is a measure of how much they believed in their idea and how badly they wanted to make it work.
>>7862666
>Imagine an airline that simply scavenged the engines from its aircraft after each flight, instead of refuelling and maintaining the complete vehicle.
It's not very common on airliners, but droptanks are a thing. In WWII they actually made P-47 droptanks out of paper-mache.
>Mind you, once you start thinking like that, there are ways to make the engines cheap, too.
>Pressure-fed with hypergolic ignition
Pressure-fed engines demand heavy, high-pressure tanks. That, in turn, demands additional stages, which may (arguably) make recovery and reuse more difficult.
It's somewhat paradoxical, because - as long as you're talking about reusable or partially-reusable multistage rockets, the stages that demand the highest performance and investment and flimsiest, lightest construction (that is, the upper stages) are also the ones that are hardest to recover. The ones that can be cheap and rugged without much performance loss (i.e. zero-stage boosters) are also by far the most easily-recoverable.
>>7862827
>>>Is reusing the entire body of a rocket as useful as simply recovering the engine?
>>Imagine an airline that simply scavenged the engines from its aircraft after each flight, instead of refuelling and maintaining the complete vehicle.
>It's not very common on airliners, but droptanks are a thing. In WWII they actually made P-47 droptanks out of paper-mache.
Drop tanks are one thing, "simply recovering the engine" is another.
Drop tanks aren't most of the vehicle. There's not much to them but tanks, with maybe some slosh baffles and a feed pipe, maybe wrapped in a fairing. When you just recover the engine end of a conventional rocket, you're at least dropping a very light and strong fuselage, two huge pressure vessels (one of which is oxidizer-compatible, and usually at least one is cryo-compatible), the plumbing for one propellant to be fed past the other, two tank pressurization systems, an interstage and separation hardware, and most of the dry mass of the vehicle.
They say that recovering the engine end is recovering 80% of the incremental manufacturing cost of the rocket's lower stage. Maybe, but the incremental manufacturing cost is maybe 50% the cost of a launch, and the manufacturing cost of the lower stage ranges from 40-80% of the manufacturing cost of the entire rocket (cryo uppers are expensive). You have to pay for the design, development, and tooling of the engine even if you only make one for actual use.
The rest of the rocket is still going to be a construction project. You're still going to have to inspect and test the assembled vehicle. You're still risking mission failure with unproven, possibly defective hardware each time. You're still limiting your rate of launches to how quickly you can finish these construction processes, so you can't amortize your development, tooling, and infrastructure costs over many flights.
Recovering only the engines is nowhere near the value of recovering the whole, assembled vehicle.
>>7862666
>OTRAG
>Steering was by differential throttling. They worked fine.
I don't think they got to the integration stage of development where they would have tested that design. The only other differential throttle design was the Soviet N-1 moon rocket, which was a disaster.
>>7863005
>I don't think they got to the integration stage of development where they would have tested that design.
They did some flight testing. The attitude control worked fine.
> The only other differential throttle design was the Soviet N-1 moon rocket, which was a disaster.
Not true. It was also used for the DC-X lander.
Differential throttling is preferred by VTVL landing designers. Gimballing is tricky, because you have to keep balance by swinging the bottom end back and forth.
Gimbaling is preferred for launch vehicles because most rockets are stick-shaped, and don't have broad bases. Differential throttling works better the wider you space the engines. You also need some means of roll control, which implies some efficiency loss if you do it with differential throttling, since your engines can't all be pointing exactly straight down.
>>7862923
>You're still going to have to inspect and test the assembled vehicle.
That point is rather moot, if you have to carry out a more thorough inspection on a recovered launch vehicle.
>>7863344
>That point is rather moot, if you have to carry out a more thorough inspection on a recovered launch vehicle.
Why would you have to more thoroughly inspect a recovered complete vehicle than a vehicle cobbled together from recovered parts and untried new parts?
The space shuttle was crap. Don't try and take any lessons from it on what a reusable vehicle should be like. Besides, it was an example of a partly-reusable system, where they dumped the tank and recovered the engines.
A reusable stage should land in shape to just be refuelled and sent up again. If that won't probably work, there's something wrong with it, and it's time to improve your design.
It's like airplanes. Sometimes an airplane lands and needs to be fixed or maintained before it can be sent up again. Or even cars. You shouldn't go on a long road trip without at least checking the oil and tires. But you don't expect "refurbishment" to be necessary between uses, you expect that if you just refill consumables, it should work.
If you do, you're not talking about a reusable vehicle, you're talking about a refurbishable vehicle, a salvageable vehicle.
This is where the debate always falls apart, because you have a discussion over "reusable vehicles" and some of the people carry on as if it means salvageable vehicles, and there's this semantic disconnect.
tl;dr the shuttle program caused massive brain damage
>>7862923
>a very light and strong fuselage
Ah, but you zee, it is ze FUEL zat provides ze strengths!!
>>7863518
orbital rockets push materials to the limit that is the problem. Unless we make some new super material completely reusable rockets will never happen. However refurbished rockets are still a huge step forward.
>>7862062
Not even Musk would look at the whole nuclear pulse splerge thing and think "fuck yeah, this is the shit". However, I can see him being an advocate for putting more nuclear power sources into orbit, such as VASIMR-designs as upper stages. We will be stuck in LEO until someone green-light an expansion in the whole "nuclear stuff in space"-thinking.
>>7863890
>orbital rockets push materials to the limit that is the problem. Unless we make some new super material completely reusable rockets will never happen.
I think that's nonsense.
I've pointed out before how big the margins are for staged rockets: >>7861131
Look at what SpaceX is doing. They're not working on refurbishable rockets. The rocket lands the same way it takes off. It can't land unless it's in good working order. They can put assembled stages through full-length burns before using them.
They do lots of things in rockets that aren't good for longevity, like use ball bearings instead of fluid bearings in the engine turbopumps, or accept some observable chamber and throat erosion instead of increasing things like curtain cooling until there is none, but those are all deliberate design choices.
Developing a reusable vehicle is expensive. The way SpaceX is doing it is to evolve an expendable vehicle to be reusable. That means they're aiming very carefully for the absolute bare minimum of what's necessary for reusability, not because this is the best way to make a reusable vehicle, but because they didn't have money or time to do more if they wanted to get launching payloads and gathering data.
They know there are better ways to make an engine that will last for more cycles, better survive the stresses of atmospheric entry, give more performance margin for flyback, permit more forgiving landing techniques, and require less expensive consumables. That's why they're developing Raptor.
Returning a small upper stage is not like returning the shuttle. The shuttle was a parallel-staged near-SSTO with high payload, downmass, and cross-range performance requirements. This made it both very large and very mass sensitive, and precluded simple or robust entry solutions. A normal-size upper stage can just return like a capsule. Ablative heat shields can last for multiple, or even many flights.
>>7864728
>Look at what SpaceX is doing. They're not working on refurbishable rockets. The rocket lands the same way it takes off.
The Space Shuttle was SUPPOSED to be the same deal (2-week turnaround without Orbiter refurbishment was in the design intent), but risk-intolerance put an end to that idea. I think Falcon 9 will be slightly better-situated in this regard since it can and usually will be launched unmanned. Also, for the manned launches, Falcon 9/Dragon Crew will have abort capability throughout the entire ascent, but I suspect even that won't be good enough for NASA and they'll still demand full refurbishment (or even brand-new rockets) for every manned flight.
>They do lots of things in rockets that aren't good for longevity, like . . . accept some observable chamber and throat erosion
>Ablative heat shields can last for multiple, or even many flights.
Why the double-standard here? If you're willing to tolerate an ablative heat shield only good for a finite number of uses, why do you have such a problem with ablative nozzle throats?
>>7865581
>>Look at what SpaceX is doing. They're not working on refurbishable rockets. The rocket lands the same way it takes off.
>The Space Shuttle was SUPPOSED to be the same deal
The shuttle didn't land the way it took off. It didn't need its main propulsion system to be in good operating condition to land, which could be a couple of weeks after it took off.
>(2-week turnaround without Orbiter refurbishment was in the design intent), but risk-intolerance put an end to that idea.
Lots of things put an end to that idea, starting with the rate of external tank production, and a lack of commitment to that "design intent" as non-negotiable. Risk-intolerance wasn't really an issue. They were downright reckless in their determination to pretend that it wasn't a steaming pile of crap and carry on the program.
Washington wouldn't fund it unless the military wanted it. The military knew it wouldn't save money or increase launch availability, so they wouldn't sign off unless it offered unique capabilities; they demanded that it be able to launch to a polar orbit, grab a satellite, and land with it after one orbit, almost certainly intending for NASA to admit this ridiculous demand couldn't be met. They weren't ready for the level of dishonesty and bad faith NASA was willing to perpetrate. Nixon pushed it as a jobs/pork/spoils program. After NASA picked their side boosters, Nixon picked a new committee to revisit the decision, and they picked the option that had been dead last of the four bids: cozy defense buddy Thiokol's segmented solid boosters.
The engineers were told to make all this crazy shit work, or take a hike, and only people who gave wildly overoptimistic estimates were given important positions.
>ablative nozzle throats
Very different thing from unwanted throat erosion.
>>7865581
can you stop comparing everything to the monumental fuck up that was the space shuttle? not everything is the same.
>>7865693
>The shuttle didn't land the way it took off.
Irrelevant.
>It didn't need its main propulsion system to be in good operating condition to land
Requiring the main propulsion system to be functioning for landing is a liability, not an asset. (But don't get me wrong, the Shuttle had PLENTY of fundamental liabilities of its own.)
>which could be a couple of weeks after it took off.
Or it COULD land within hours of launch if needed. Prior to EDO, all Shuttle missions were 10 days or less, and only two of the five Orbiters were ever fitted with EDO at all (and only for 14 missions in total). And again, I fail to see how the capability of remaining in orbit prior to reentry is detrimental to reusability.
>Lots of things put an end to that idea, starting with the rate of external tank production
ET production could have theoretically reached one every two weeks, but in practice they never even came close to this turnaround rate - closest they got was 9 launches in 1985. Prior to 51-L, a lack of available missions may have been the limiting factor, but afterwards, risk-intolerance and extensive inspection/refurbishment requirements definitely became the main limiting factor.
>They were downright reckless in their determination to pretend that it wasn't a steaming pile of crap and carry on the program.
Perhaps their expectations were unrealistic, but the same could be said about SpaceX as well. But at least SpaceX has the benefit of everything being expendably-priced should it prove unfit for reuse; with the Shuttle orbiter that wasn't the case at all (though it somewhat was for the SRBs and to a lesser extent the SSMEs themselves).
>Very different thing from unwanted throat erosion.
Explain it to me then; just what are you referring to? Most wear-and-tear on the SSMEs was turbopump-related; I'm not aware of any throat erosion and only a handful of cases of nozzle/chamber damage.
>>7865916
>>The shuttle didn't land the way it took off.
>Irrelevant.
>>It didn't need its main propulsion system to be in good operating condition to land
>Requiring the main propulsion system to be functioning for landing is a liability, not an asset. (But don't get me wrong, the Shuttle had PLENTY of fundamental liabilities of its own.)
It's not irrelevant, and it's not simply as simple as being a liability or an asset.
Consider Just-In-Time manufacturing. In JIT manufacturing, you don't have parts bins. If there's a bad part, or any stage of the process has a problem, the whole assembly line stops.
Terrible, right? Big disadvantage, compared to being able to limp along and catch up. But not really, because there's a human factor involved: it forces the managers and engineers to deal with problems that they might otherwise accept as mere inefficiencies.
If you land the same way you take off, with the same systems required to be in good operating condition, then if you successfully land, you should be ready to refuel and fly again. There's no option to limp along with a "refurbishable" vehicle, so there's no temptation to do so. You only get stages back reliably if they're are worth recovering.
>ET production could have theoretically reached one every two weeks
What are you basing that on? I know you're not basing it on the factories they built and workforce they hired and trained. The external tank was a titanic piece of high-performance, low-defect-tolerance, low-mass-tolerance hardware.
Not even counting the boosters and OMS tanks, the ET was four times the tank volume that you'd need for all stages of a launch vehicle that could lift the same payload as the shuttle. It cost roughly as much to manufacture as a complete launch vehicle that could lift the same payload as the shuttle. In today's money, the ET cost about $105 million. A complete Proton launch cost about $135 million (in 2015 dollars) when the shuttle was under development.
>>7865987
>But not really, because there's a human factor involved: it forces the managers and engineers to deal with problems that they might otherwise accept as mere inefficiencies.
Sounds like a project management problem to me.
>If you land the same way you take off, with the same systems required to be in good operating condition, then if you successfully land, you should be ready to refuel and fly again.
Absolutely not. In no way is a powered descent even remotely comparable or equivalent to legitimate inspection and testing, and operating the Falcon 9 this way would actually entail an even higher degree of risk-tolerance than the Shuttle (since the Shuttle verified engine and systems function in the last few seconds of every countdown and could abort then and there if a fault was detected; whereas if a fault is detected during F9 descent there's jack-shit you can do to prevent the rocket from being destroyed by it). You can't POSSIBLY spin this into a positive.
>There's no option to limp along with a "refurbishable" vehicle, so there's no temptation to do so.
Sure there is. But the key difference with Falcon 9 is, there's much less INCENTIVE to do so, since the rocket is so expendably-priced. If refurbishing is going to be anywhere near as costly as it was with the Shuttle, then they'll simply scrap it and build a new one instead. The ability to fall-back on total-expendability is the Falcon 9's biggest advantage over the Shuttle (with unmanned launch capability, greater abort options and reduced dead-weight being 2nd, 3rd and 4th).
>What are you basing that on?
https://en.wikipedia.org/wiki/Criticism_of_the_Space_Shuttle_program
>While not reducing absolute operating costs, more launches per year gives a lower cost per launch. Some early hypothetical studies examined 55 launches per year (see above), but the maximum possible launch rate was limited to 24 per year based on manufacturing capacity of the Michoud facility that constructs the external tank.
continued from >>7865987
So you can see it's not really reasonable to expect the shuttle external tank to be produced at a much higher rate or lower cost than a complete expendable rocket.
You can say "theoretically, the Saturn V could have launched every 2 weeks", in the sense that it's physically possible, but it wasn't possible with the program they actually implemented. There wasn't enough floor space, not enough equipment, not enough trained and reliable people. It's not clear that they could have trained enough people for that, without redesigning the vehicle to be simpler to produce.
>>They were downright reckless in their determination to pretend that it wasn't a steaming pile of crap and carry on the program.
>Perhaps their expectations were unrealistic, but the same could be said about SpaceX as well.
Their "expectations" were dishonest. Nobody involved believed them.
http://www.washingtonmonthly.com/features/2001/8004.easterbrook-fulltext.html
What SpaceX is experiencing is difficulty and delays in scaling up production. They're still just a few years into the big rocket business. Up until 2010, they basically just a development/prototyping crew. They didn't have a production model until mid-2013, and since then they've done sixteen launches, twenty-one if you count the Falcon 9 1.0s. The whole Apollo Program was only 28 orbital flights
They've had to buy and build facilities, hire and train staff, sort out processes, get production tooling made, etc. The design stuff they're doing is all reasonable and fine. A delay of a couple of years getting a major aerospace factory up to speed is par for the course, especially with today's bureaucratic Air Force poking around in everything to certify them as a provider.
People point at the Falcon Heavy delays as if that's a separate failure, but a Falcon Heavy is basically three Falcon 9s. If they can't build enough Falcon 9s, they certainly can't afford to start using them up three at a time.
>>7866080
> (since the Shuttle verified engine and systems function in the last few seconds of every countdown and could abort then and there if a fault was detected; whereas if a fault is detected during F9 descent there's jack-shit you can do to prevent the rocket from being destroyed by it)
What are you even saying? You're comparing the shuttle's lift-off to the F9 landing? Verifying engine and systems before liftoff is completely standard, and F9 does it, too.
>operating the Falcon 9 this way would actually entail an even higher degree of risk-tolerance than the Shuttle
Tolerating what risk? The risk of failing to recover a non-working vehicle and an unknown cost-burden to make it work? I've pointed out what a mixed blessing the option to limp along is.
Remember that the shuttle needed a successful recovery to not kill its crew, and to not throw away a crew compartment, orbital maneuvering system, and other spacecraft systems that had nothing to do with launch.
>>7865735
No. Like it or not, as far as reusability goes, the Shuttle is the only thing we have to compare to Falcon 9. Obviously there are some VERY important differences and Falcon 9 is clearly much better off in general, but ignoring the lessons of the Shuttle program entirely and claiming there are zero parallels at all and no comparisons to be made is no way to go about things.
>>7866154
>What are you even saying? You're comparing the shuttle's lift-off to the F9 landing? Verifying engine and systems before liftoff is completely standard, and F9 does it, too.
I'm saying that simply achieving an intact powered landing is in no way a substitute for proper inspections (and refurbishments) like you seem to be claiming it is, any moreso than the pre-launch countdown checks are.
>Tolerating what risk?
Losing the entire stage if there's a problem with the main propulsion, as opposed to simply losing whatever components are faulty.
>cost-burden to make it work
>limp along
See, this is where you're wrong. You're acting like recovering a stage/vehicle intact is fundamentally an obligation to reuse or refurbish it. It is not. You're still completely free to scrap it entirely if you suspect that it's unfit for reuse. Short of that, nothing about an un-powered landing precludes you from testing, inspecting and/or refurbishing to whatever degree is reasonable.
It frankly baffles me that you're trying to spin the risk of catastrophic stage-1 loss on descent into a positive...
>Remember that the shuttle needed a successful recovery to not kill its crew
Of the Orbiter, yes. Just like F9 requires successful recovery of Dragon Crew in order for crew survival. Failure of F9 stage-1 recovery has about the same consequences as failure to recover an STS SRB.
>and to not throw away a crew compartment, orbital maneuvering system, and other spacecraft systems that had nothing to do with launch.
So.... things that Dragon would need to recover anyways in order to be reused?
>>7866361
>simply achieving an intact powered landing is in no way a substitute for proper inspections (and refurbishments)
You're saying that having the vehicle actually work in real-world conditions is "in no way" a substitute for inspections. This is backwards, and clearly motivated entirely by the failures of the shuttle, and not by the example of other vehicles.
>Losing the entire stage if there's a problem with the main propulsion, as opposed to simply losing whatever components are faulty.
You're not "simply losing whatever components are faulty", though. You're losing the use of the vehicle until those components can be replaced. You're losing the the labor of identifying and replacing them. You're losing confidence in your ability to avoid faults.
Factory operations are predictable and consistent. You can automate things. You can train people to do things in exactly the same way every time. Repair operations are unpredictable and complex. The repaired thing usually isn't as good as the new thing.
This is different from routine maintenance, which has the aim of preventing failures, and which can be made as regular and predictable as the operation of the assembly line.
>You're acting like recovering a stage/vehicle intact is fundamentally an obligation to reuse or refurbish it. It is not. You're still completely free to scrap it entirely if you suspect that it's unfit for reuse.
If you decide to discard it, you gained nothing. If you put effort in before deciding to discard it, you lost.
There are clear advantages to just deciding not to invest in any repair capability, in keeping all consideration of repairability out of the design and construction, in not buying any repair tools, training any repairmen, or building any repair garages. Especially in such a performance-sensitive vehicle.
>things that Dragon would need to recover anyways in order to be reused?
Dragon's just a payload, not a launch vehicle.
>>7866405
>>7866361
I want to say a little more about Dragon not being a launch vehicle.
When you're trying to make a launch vehicle economically reusable, you can't afford a lot of back-up safety systems. The shuttle was basically: have a normal, successful landing or everyone dies.
Crew Dragon will be able to:
- escape from an exploding rocket on the launch pad
- blast away from a failed rocket during any stage of ascent
- survive in orbit as long as supplies hold out, to wait for a rescue mission (not limited by fuel cell power like the shuttle)
- abort rapidly from any point of its orbit and land almost anywhere on Earth, including the oceans, where it would bob around until a rescue could be arranged, rather than wait for a targetted return trajectory
- land propulsively
- land propulsively on redundant thrusters if some fail
- land softly by parachute with propulsive assist from the thrusters
- land roughly by parachute with shock-absorbing legs
- splash down in water by parachute
- land by backup secondary parachute
It's basically only going to be fit for reuse if it has a routine propulsive landing on a landing pad, which is by far the lower priority compared to keeping the crew alive.
When they do a reusable upper stage, it can return separately from any crew vehicle on top of it. It can be designed with entirely different priorities.
>>7866405
>You're saying that having the vehicle actually work in real-world conditions is "in no way" a substitute for inspections.
It isn't. At all. There are all kinds of problems that might not be immediately obvious through normal usage. Sure, with your car you tolerate the risk since at worst you'll probably only end up dead on the side of the road. With an airplane, risks are higher, but even so a basic pre-flight inspection and 100-hour overhauls are good enough. But with spaceflight? This is a high-risk business. So unless you're willing to accept the one-in-five odds of catastrophic failure or whatever it may be, you damn well take a good hard look at everything before you send it up again.
Plus, did you even CONSIDER the fact that F9 only lands with a single engine running? How the hell does the landing even remotely prove that the other eight are good to go?
>You're losing the use of the vehicle until those components can be replaced.
As opposed to losing use of the vehicle... forever.
>You're losing the the labor of identifying and replacing them.
As opposed to the labor of building an entire new stage to replace the one you crashed.
>You're losing confidence in your ability to avoid faults.
As opposed to... losing it anyways, AND losing confidence in your ability to avoid catastrophic firey crashes, AND losing a significant portion of evidence to diagnose said faults and address them in the future.
Goddamn, you are one STUPID motherfucker.
>Factory operations are predictable and consistent. You can automate things. You can train people to do things in exactly the same way every time. Repair operations are unpredictable and complex. The repaired thing usually isn't as good as the new thing.
Sounds to me like you're opposed to reusable rockets altogether.
>This is different from routine maintenance
In the aerospace world, this IS routine maintenance. Get used to it.
>>7866525
>With an airplane, risks are higher, but even so a basic pre-flight inspection and 100-hour overhauls are good enough.
Commercial airliners do not typically undergo 100-hour overhauls between flights. They typically refuel, reload, and fly.
>But with spaceflight?
Okay, so here's your argument: space is magic, so reusability is all going to be space shuttles forever at best.
Where space is legitimately different is that the depleted stages can land without any crew, passengers, or cargo onboard, so landings are not a safety issue. Another difference is that powered flights are *very* short.
>>Factory operations are predictable and consistent. You can automate things. You can train people to do things in exactly the same way every time. Repair operations are unpredictable and complex. The repaired thing usually isn't as good as the new thing.
>Sounds to me like you're opposed to reusable rockets altogether.
Sounds to me like you're EXACTLY who I was talking about in this post:
>>7863518
Refurbishable vehicles and reusable vehicles are not the same thing. Refurbishable vehicles are not very interesting to invest in or discuss.
>In the aerospace world, this IS routine maintenance. Get used to it.
You don't know what you're talking about. Aerospace maintenance covers the whole range from car-like to shuttle-like.
>>7861143
Uhm.... this thing does not have a tail rotor. It would spin like crazy
>>7866525
m8 your argument is basically that "space is different and the space shuttle is the limit there because no one has done better".
>>7866995
Well, it's driven by tip jets, not an engine. The body would only be pulled to spin in the same direction as the rotor is spinning, by the friction of the rotor bearing. Either reaction control thrusters or a small motor in the rotor mount would be able to keep it from spinning. I'm not sure what they used in the Roton ATV.
>>7866525
>Plus, did you even CONSIDER the fact that F9 only lands with a single engine running? How the hell does the landing even remotely prove that the other eight are good to go?
This is a valid point, but this is the heart of my argument:
>>7865987
>You only get stages back reliably if they're are worth recovering.
It's not about considering vehicles and flights one-by-one. There's nothing special about the engine used for landing. It's just like the others. If bad things happen to the engines during launch or on the way down, you're not going to get reliable recovery.
How do you trust ammunition? You can't test shells before you use them. Instead, you develop a trustworthy process that produces vanishingly few duds. If you start getting ones that don't fire, you go back to the factory and fix the problem there. If you reload shells, you don't try and repair damaged brass.
You can get things reliable by painstaking individual confirmation and extensive touch labor to restore anything that looks iffy, or you can make the process good enough that individual confirmation and correction isn't necessary. Low-cost things take the latter strategy.
Wow, I never knew the Space Shuttle was such an emotional issue.
I used to think that you could just press the ignition and go when I saw it on TV as a kid. I always fantasized about stealing one and flying away into space. It's not that easy is it?
>>7861490
You seems smart anon.
what about orion are we doing it right?
>>7867632
Well I mean, if a saturn five is all ready to go and you ignite some fuel, you'll go somewhere.
>>7861490
>It was just a completely insane design.
thats what happens when you let the CIA dictate design.
>>7868364
After decades of redesign by committee, Orion is no longer capable of withstanding the nuclear blasts intended to propel it through space.
>>7868453
The capsule,man.
Thanks anyway.
>>7868463
>The capsule,man.
Sure, now it's a capsule.
But seriously, Orion's bad. The capsule's twice as big and heavy as the Apollo capsule (to have 4 crew rather than 3), on a rocket half as powerful. What's it supposed to be for? The combination's only fit for a lunar flyby, what should be a development mission.
Orion was inelegantly and conservatively designed to go up on Ares I, a rocket as powerful as Delta Heavy, and dock with an earth departure stage launched by Ares V, for a total launch capability 150% of a Saturn V.
It's a bloated "return to Apollo glory" program that has had all the ambition trimmed out of it without being cancelled.
>>7868501
Im not trying to be a smart-ass here, but what would you have made instead? It is quite a leap forward from the Apollo capsule, with regards to supplies(range) and so on, or so i've read.
In the end, i'm just happy that they are actually making something, even though it might be wasting half its bugdet on political pork and so n
>>7869799
If it can't go to Mars it's not a leap forward.
>>7869799
>Im not trying to be a smart-ass here, but what would you have made instead?
Crew Dragon's better in pretty much every way. So much better that Falcon Heavy / Dragon missions will be more capable than SLS/Orion, never mind the cost.
Crew Dragon:
- has a far more advanced heat shield, which can withstand higher atmospheric entry speeds or be reused without refurbishment (with Orion they decided to copy the Apollo one, and struggled to do so)
- is self-sufficient without a separate service module at a mass lower than just the Orion capsule without service module
- can soft-land on Earth at a landing pad and with most components for reuse (Orion discards most of its valuable components splash-lands in no condition for reuse, then search and rescue is required)
- can land at a targetted location on Mars with a substantial load of crew or supplies
- is designed to spend years in space if necessary (Orion's endurance is 3 weeks)
Crew Dragon is equally suitable for a budget-conscious LEO program (launched on Falcon 9) with reuse and an ambitious BEO program (launched on Falcon Heavy). It's everything Orion should have been.
>It is quite a leap forward from the Apollo capsule, with regards to supplies(range) and so on, or so i've read.
>or so i've read.
You've been reading some bullshit. The supplies depend entirely on the service module. The capsule itself is twice as heavy. That's the part that's just for atmospheric entry (and abort operations). You can hang out in there, but you're not going to be comfortable for more than a short ride.
The Orion that survived the cancellation of the Constellation Program is the Orion design intended merely for transportation to and from the ISS (launching on the single-stick SRB-derivative Ares I), not the Orion/Altair meant for lunar missions.
Orion's advantages over Crew Dragon are: larger pressurized volume and higher lift-drag ratio (which gives a gentler ride and longer cross-range maneuvering capability).
>>7869966
>>7869799
By the time SLS/Orion is working, there won't be any reason to ever use it. You might not be able to do all the exact same things in the exact same way with Falcon/Dragon, but you can accomplish all the same objectives earlier and at far lower cost, and accomplish many objectives that are beyond the reach of SLS/Orion.
The next-generation plans for SLS (spend years doing upgrades to hopefully equal what NASA could do in the 60s, and vague ideas about a ruinously expensive flag-planting mission on Mars sometime after everybody currently important at NASA is retired) fall even farther short of SpaceX's next-generation plans (airliner-like reusability with huge capacity upgrades and specialized development for mass migration to Mars).
