Science - SpaceX has that.
Elon Musk's private space program jumped another 40 meters just before Christmas, with the VTVL "Grasshopper" rocket successfully lifting more than its own length into the air and safely setting down again. The test follows one from September which involved lifting a few feet, and a November test of a couple of meters, but …
Fuel costs may actually be affordable but capacity and payload of the extra fuel necessary for this kind of thing would be huge. One reason NASA didn't consider it was not that the technology was too complex but that the rocket would have had to be 3 times the size.
Payload/weight have always been an issue in aviation and space flight and bigger does not always translate to better. Still good effort but I think the concept is a dead end unless gravity can be eliminated on earth.
Clearly you should phone up spacex, they've obviously not considered any of that before spending the money developing this.
The fuel costs for a $60 million falcon 9 launch is only about about $200k.
The fuel required to accelerate a fully fueled rocket with payload to about 4000 mph massively dwarfs that required to slow down a now almost empty rocket sans payload falling at terminal velocity (the air resistance should slow it most of the way to that and drogue shoots can be added if needed).
NASA is not that interested in saving money and many of their missions are 'one offs' where the cost of an expendable launch vehicle is insignificant next to the development costs of the payload.
Sticking the landing with parachutes is fine, Soyuz does that. Even today, Soyuz targets a 24-mile diameter circle in the Kazak desert. In 2008, they missed the circle by over 250 miles.
The issue is navigating to a landing pad and sticking the landing there. That navigation will use a lot of fuel.
And yet the later members of the Gemini series managed to land within 1 nautical mile of their target, despite loosing any effective directional control below about 65000 ft.
Keep in mind this is a stage, not a capsule. Historically no capsule has had any aerodynamic controls at all. It's all been done to shifting the centre of mass.
You need to look at rocket trajectories, stage 1 at burnout is 50 miles downrange and at 200,000+ feet altitude, there is no significant air to slow you down. The stage would continue 200 miles downrange until gravity finally pulls it down into thicker air. Your concept would only work if there was a landing platform on vertical pontoons (for stability in rough seas), for it to land on. Then it would take a couple of days to secure and be barged back to the launch site.
"NASA is not that interested in saving money and many of their missions are 'one offs' where the cost of an expendable launch vehicle is insignificant next to the development costs of the payload."
Actually it's worse than that.
The rule of thumb for spaceflight is
Launch cost L
Payload cost 2L
Operations cost over life of satellite/probe/lander 3L
In theory the cost of launch should have no connection to payload cost or operations but in reality it's the yardstick for estimating them.
What happens when launch cost L becomes << than the other 2 costs is unknown, as is the effect of making recovery from orbit (downmass) substantially cheaper.
Flying the rocket back to a launchpad on Earth is a question of lift-economics. The Shuttle guys in the 70s said that having 75% of the payload be the reusable orbiter would be overtaken by improved lift-economics. That never happened. Some of it was due to old technology of NASA's rockets.
Most of it is probably unchanged though.
If SpaceX has a payload of W and a ascent-rocket+fuel load of X, an ascent-stage fuel burn of Y and a return-rocket+fuel load of Z, then the initial lift must do W+X-Y+Z. Since Z must 'lift' approx X-2Y+Z, the return rocket to launchpad system (even with some parachute assist) will take a substantial amount off the limit of W.
The cost of fuel, as you point out, is not the problem it is the cost of a vastly bigger rocket that would be required that is the problem.
IIRC the Apollo capsule had a mass of about 5.5 tonnes and the Saturn 5 had a mass of about 3500 tonnes. Doubling the mass of the capsule would NOT mean adding a few tonnes of fuel but making the whole rocket vastly bigger.
More fuel means you need a bigger rocket which has a bigger mass so you need more fuel which mean you need a bigger rocket which means you need more thrust and more fuel so you need a bigger rocket and bigger engines, repeat etc etc. Carrying enough fuel/rocket up so that you can use it to come back down seems a non starter to me.
You are assuming they have to fly it all the way down at a thrust necessary to achieve escape velocity, which clearly is not the case. Firstly gravity will bring the rocket back down meaning you just have to use thrust/chutes/etc to steer it and keep attitude then initiate a burn close to the ground to slow it sufficient to prevent damage on contact with the pad. All this means the amount of fuel needed is vastly reduced from your calculation, which assumes escape velocity thrust all the way which would result in the rocket either zooming away or hovering at apogee.
Payload fraction of a typical 2 stage liquid fueled rocket c3%.
It's estimated that the recovery hardware costs 1/2 of that payload, but as no one has ever succeeded in doing it no one really knows (and frankly no one's had the balls to seriously try).
So rocket needs to be 2x bigger to deliver same payload.
However propellant wise it's a winner. F9 launch c$60m. Propellant c$200k.
Usual payload mass fractions for ELV's are around 3-3.5% of GTOW. if (as Musk estimates) F9 will achieve 4% of GTOW as PMF and he looses 50% (giving a 2% PMF) of that for the recovery fuel and hardware that roughly a rocket x2 as big to lift the original payload.
How do you calculate the rockets size?
The solid rocket boosters are, in essence, large steel tubes filled with high explosives. Liquid fuel rocket engines are much more easily damaged, and their outer shells don't tend to be as thick and durable as the shuttle SRBs, so "lob it in the ocean and come pick it up later" isn't really an option, as SpaceX learned in their earlier test flights.
If only they were large steel tubes, more a series of steel rings connected together by dodgy joints into what resembles a steel tube.
There was a video of the british Blue Streak rocket (liquid fueled) on TV (British Space Race?) and it showed that the skin on the blue streak was literally paper thin, unless pressurised it could not support its own weight...
Say what you want, but I rather like the staged, deliberate, "let's keep an eye on as many variables as we can control" approach to basically nuking the established rocket industry.
I wish them the best of luck - it's never a bad thing to shake up an established industry, provided it's done properly and as far as I can see, this is done right. 2013 is going to be very interesting..
Well, if you wanted to and had sufficient funds, you could give away- utterly free- a high-end smartphone to every person in the world.
The Smartphone industry would then be massively disrupted, but it'd do bugger all to really help anyone. You'd end up with a mound of waste, presumably little in the way of customer support, and the established suppliers would be utterly wiped out. Maybe not Apple as they've got the whole Cult thing going for them, but they'd certainly suffer.
SpaceX are just being better and cheaper than everyone else- but sustainably. So long as they continue making launches (and strides forwards like this) they'll continue making money at the expense of the less good market incumbents.
You are thinking all wrong and socialistically.
> Well, if you wanted to and had sufficient funds, you could give away- utterly free- a high-end smartphone to every person in the world.
MAGIC MONEY FOUNTAIN! MAGIC PRODUCTION CHAIN!
> The Smartphone industry would then be massively disrupted, but it'd do bugger all to really help anyone.
On the contrary. About a trillion dollar that were magically sitting in your bank [how?] have suddenly been disbursed through your factories to upstream suppliers and their workers. Everyone has suddenly a free smartphone. This liberates money that people wanted to spend for other things.
> SpaceX are just being better and cheaper than everyone else- but sustainably.
How does that make sense? Why would anyone be "better and cheaper than everyone else- but sustainably"? Hell, get everyone as customer RIGHT NOW. That's what drives improvement in the competition, dontcha know.
There's a company in Yorkshire (England) that makes Valve Packs. Their growth has been pretty constant and rather slower than it could be- if they grew too fast they wouldn't necessarily be able to keep up with demand or train staff fast enough to keep up quality. It'd also limit their ability to take on specialised projects.
If they got everyone as a customer right now, they'd fall over and lose their reputation. All their money would go into production rather than R&D, and you'd have a totally different company.
As they're going now, they'll dominate the industry in a few years- and still have a reputation for good customer service, excellent tech, reliability and as people who deliver on time and on budget. This is a sustainable business model.
The point was, I believe, that SpaceX are developing cool new technologies and pushing forwards with reliable products. So they've got the present sorted and are even turning a profit- while creating more and more impressive and diverse products and features that will sustain them in the future. This is the way to run a company in the long term- running in and taking stacks of orders is a great way to run a business for a short time, but in the long term you'll need more meat on that plans' bones.
The DC-X Delta Clipper hover tests did more and better fifteen years ago. You can find video of the various test flights on the Web.
The extra weight and complexity of a softlanding recovery system eats into payload meaning the need for much larger rockets for the same capability with more stuff to go wrong, and the recovered rocket motors, pumps etc. will need extensive refurbishment afterwards. The Shuttle was a reusable spacecraft after all and it cost a lot more per flight than an equivalent one-shot launcher would have for the same payload. Saying that it had other benefits that outweighed the extra costs.
> The DC-X Delta Clipper hover tests did more and better fifteen years ago.
Yeah, I remember. But so what? Typical meatball project. Wakypedia says: "In a post-accident report, NASA's Brand Commission blamed the accident on a burnt-out field crew who had been operating under on-again/off-again funding and constant threats of outright cancellation. The crew, many of them originally from the SDIO program, were also highly critical of NASA's "chilling" effect on the program, and the masses of paperwork NASA demanded as part of the testing regimen."
More and better. Does not fly.
DC-X was not 100 feet tall, nor would it ever be capable of getting to orbit. just because something was done before with a very different vehicle does not make this any less difficult, or impressive.
as far as "the recovered rocket motors, pumps etc. will need extensive refurbishment afterwards" - really? Elon Musk repeatedly tells anyone who will listen that that was the whole problem with the shuttle, too much refurbishment. EVERY SpaceX engine is designed to be used multiple (ten at least) times without any refurb, precisely because he doesn't want to repeat history.
The Grasshopper is not capable of getting to orbit either. The DC-X flew higher, for longer and further crossrange than the Grasshopper has. I suspect the goal of a orbit-capable rocket's first stage landing as the DC-X and Grasshopper do is physically impossible due to mass fraction constraints, given the fuel/oxidiser combo of LOX/LH2 (the best known) as used on the DC-X only gives an Isp of about 320 or so at sea level and the LOX/RP-1 Musk engines are even worse with a sea-level Isp of 250-odd.
The RS-68 Block 1 motors used at the start of the Shuttle program were supposed to be rated for ten flights before rebuilds were necessary; in the real world they were rebuilt after every flight. Later variants including the RS-68A Block 2 motors were rebuilt after every flight too but they were easier and cheaper to refurbish.
"The Grasshopper is not capable of getting to orbit either. "
True. It's a control systems and concept of operations demonstrator.
"The DC-X flew higher, for longer and further crossrange than the Grasshopper has."
" I suspect the goal of a orbit-capable rocket's first stage landing as the DC-X and Grasshopper do is physically impossible due to mass fraction constraints,"
Then by extension you would have considered the ultimate goal of the DC-X programme (sometimes called the DC-1), a single stage to orbit vehicle with no major maintenance between flights, to have been absurd
"The RS-68 Block 1 motors used at the start of the Shuttle program were supposed to be rated for ten flights before rebuilds were necessary; in the real world they were rebuilt after every flight. "
The RS-68 did not exist during most of the Shuttle programme.
It's the expendable engine on the Delta IV and as such has 1 use, although like all liquid rocket engines it's capable of multiple test firings.
The manufacturer ID # for the Space Shuttle Main Engine (which I think is what you're talking about) is RS-25.
You might like to review the rocket equation, the thrust to weight ratio of the Merlin 1d and approximate current payload fraction of the F9. It's all down to how much of the orbital velocity each stage has to supply.
Yep, RS-25 not RS-68 as you said. Mind fart on my part, sorry.
As for the SSTO fully-recoverable Delta Clipper concept, yes I would regard it as absurd. The energy budget is against it -- there isn't a disposable rocket today that can do SSTO even with LOX/LH2, the best fuel/oxidiser combo available (the weird experimental fluorine fuel combos don't give much extra Isp advantage over LOX/LH2). The Shuttle was closest to the SSTO concept but it still required the SRB strapons to get off the pad at all. Skylon (or whatever it's called this week) is airbreathing for a good chunk of its initial ascent so isn't a true SSTO rocket and besides it's still mostly a paper exercise.
What the prototype DC-X proved was that the vertical-landing system was possible and could be implemented in hardware, and they did this fifteen years ago. The amount of fuel and oxidiser required to softland a first stage, SpaceX's intent, is not the real problem as a residual few tonnes will go a long way when the tanks are nearly empty and the first stage is down close to its dry weight at separation, assuming they don't fly-till-dry as most staged rockets do today. The real problem is the extra mass of the landing gear etc. and the other equipment needed to achieve the soft landing as this has to be launched along with the rest of the rocket costing extra fuel to reach the same velocities.
SpaceX have also been working on a rocket-landing variant of their Dragon capsule but how much of the payload and volume of the capsule would be taken up by fuel tanks, rocket motors, pop-out legs etc. they're not talking about much. It's already quite cramped in there as it is.
"As for the SSTO fully-recoverable Delta Clipper concept, yes I would regard it as absurd. The energy budget is against it -- there isn't a disposable rocket today that can do SSTO even with LOX/LH2,"
You appear to think that people don't do VTOL SSTO because of this "energy budget"
It's not. The problem is the loss of payload. Historically both the Titan II 1st stage is believed to have been SSTO capable, as (probably) was the Russian engined Atlas III. A payload of 3-3.5% of the whole payload of a TSTO is historically common state of practice. Musk is aiming at 4% so his reuseable TSTO will still have 2% of its GTOW as payload after the recovery hardware and fuel is added to each stage.
"The Shuttle was closest to the SSTO concept"
Only in the sense that if you only counted the payload bay capability it gave an SSTO payload fraction (1% of the whole stack) in a structure of 4 parts, 3 of which dropped off before orbit. Not most people's definition of "single" stage.
"Skylon (or whatever it's called this week) is airbreathing for a good chunk of its initial ascent so isn't a true SSTO rocket and besides it's still mostly a paper exercise."
Skylon (as it's been called for the last 30 years) is not designed to be a pure rocket. Which is why it gives the TSTO payload fraction with SSTO operations. As of now a complete sub-scale SABRE engine is in design, the next phase being construction and ground test. I'd suggest that fact you can have the full TSTO payload fraction "cake" and enjoy SSTO is why it's getting funding.
"The real problem is the extra mass of the landing gear etc. and the other equipment needed to achieve the soft landing as this has to be launched along with the rest of the rocket costing extra fuel to reach the same velocities."
Sounds like Spacex should build a simulation to study exactly how much mass this adds and study the control problems of landing a high aspect ratio tank structure (you might have noticed that VTOL SSTO concepts tend to be rather squat. There are good reasons for this. They don't work so well when you're starting with a TSTO stage).
"SpaceX have also been working on a rocket-landing variant of their Dragon capsule"
That variant will retain landing parachutes. As for "cramped," relative to what? It's a completely different problem, which will need to be addressed in a different way.
Being pedantic to be polite... The Shuttle's ET could have been carried to orbit; it was nearly empty at Main Engine Cut Off (MECO) and there were BOTE plans at one time to collect them in orbit to build a space station and/or orbital tank farm for fuel and consumables for Moon and Mars missions etc. but that presumes a much greater operational presence in space than actually happened -- I saw suggestions in the 70s that an expanded Shuttle fleet (8 to 10 airframes) could be carrying out fifty flights a year but of course this never happened. The ET was ditched before orbit was achieved to ensure it would come down somewhere predictable in the Pacific rather than letting drag deorbit it randomly weeks or months later. The Shuttle was unique in that its main engines burned from takeoff to orbit, a critical part of an SSTO design I think you would agree.
The Soyuz capsules already use rocket braking to soften their landing but it's not a zero-zero landing system, it just takes some of the energy out of the ground impact after the parachutes have bled off most of the vertical speed.
As for the Dragon capsule being "cramped", I'd compare it to the Shuttle's accommodations which were spacious in comparison for the same planned crew capacity, seven. It's also missing a toilet, one of those luxuries that you get to appreciate after your tenth day in orbit from what I've been told. No shower either.
Dragon capsule cramped? So what. It's just a taxi. Admittedly a 6 seater one though, so it does have a capacity to launch more people than the current options.
As to it's landing capability - the rockets being used for landing are also the ones that are required for the LES, so it's weight you have to carry anyway. Legs - yes, they add some mass. Let's hope SpaceX have done the sums eh! Since they are spending multi millions on it...one woudl assume they have worked it out using, you know, maths'n'shit.
As to the first stage reuse - plans are for high altitude supersonic tests of the grasshppper (or similar) in 2013. So looks like an exciting year.
Please either watch Musks' interviews on this stuff, or read up on it, they answer all the questions.
A taxi to where? The ISS is due for decommissioning in a few years time -- given the US current budgetary difficulties the agreed mission extension past 2016 is looking less and less likely to happen unless the other partners dig into their pockets, something they've been noticeably reluctant to do in the past. I suppose there might be flights to the Chinese space station if it gets internationalised. There's Bigelows large balloons filled with hot air, true vapourware, and... that's it.
The Shuttle flew space labs in its versatile cargo bay, it had the airlocks and volume to allow mission specialists to perform multiple EVAs for assorted projects such as Hubble repair, satellite recovery, military missions and ISS construction. The Dragon capsule is spam-in-a-can, Apollo-era tinned monkey without the end-game of a boots-and-banners mission to the Moon to beat the damned Commies to justify any flights at all.
"Being pedantic to be polite... The Shuttle's ET could have been carried to orbit; it was nearly empty at Main Engine Cut Off (MECO) and there were BOTE plans at one time to collect them in orbit to build a space station and/or orbital tank farm for fuel and consumables for Moon and Mars missions etc."
I was aware of that. I think the design went a bit beyond the BOTE stage but parts of NASA seemed to feel it was "Skylab" all over again and wanted the new shiny made-to-order space station (they would not even allow flight experiments to be attached to one of the access doors). 2 (or was it 3?) design iterations later they got it.
And not to be pedantic but the first S in SSTO stands for "Single." Actually the STS payload could have been substantially higher if NASA had recognized that lower tank pressures directly lead to lower tank mass (and within 150m/s of orbital velocity tank mass translates more or less directly into additional payload). SSME tests indicated it could comfortably support lower tank pressures.
"The Shuttle was unique in that its main engines burned from takeoff to orbit, a critical part of an SSTO design I think you would agree."
IMO the SSME was one of the "crown jewels" of STS development. Had all upgrades been implemented it would have been even better(at least 300lbs lighter, more if you can dump the 6 stage LP LOX drive turbine, less inspection etc). The issue was (given its size) how to make effective use of its capabilities.
"The Soyuz capsules already use rocket braking to soften their landing but it's not a zero-zero landing system, it just takes some of the energy out of the ground impact after the parachutes have bled off most of the vertical speed."
Irrelevant in this context. This is a stage, not a capsule. The aspect ratio of diameter to height is part of what makes it tough.
"As for the Dragon capsule being "cramped", I'd compare it to the Shuttle's accommodations which were spacious in comparison for the same planned crew capacity, seven. It's also missing a toilet, one of those luxuries that you get to appreciate after your tenth day in orbit from what I've been told. No shower either."
The Shuttle was designed to be the sole on orbit accommodation for the 7 person crew for up to 14 days. Crewed Dragon, CST-100 and Dream Chaser are designed to be buses to the ISS, not camper vans.
I note you seem to hold some views which seem to contradict each other.
You admire the Shuttle, which managed to kill 14 crew after being declared "operational," while being unimpressed by the Mercury, Gemini and Apollo capsules, which across 3 programmes killed 3 crew in test and none in operation.
You appear to be unaware large solids have intrinsic safety issues (critical diameter) and are not quite as simple to design as they appear, but disregard this as a problem. You don't appear to have a problem with the original SRB contract award either, which given their performance did not seem to justify their premium pricing (about $50m above the original awardee) .
You point out Grasshoppers ability was demonstrated by DC-X 15 years ago but view that programme's ultimate goal as absurd. You don't really have a reason for this you just think it was. Do you view Grasshoppers goal as absurd as well?
Summing up you're a fan of winged vehicles and large solid boosters, even if they are quite expensive and have killed more crew than other designs. That might sound an unfair characterisation, and I'm always happy to listen to other people's PoV, and I've sometimes changed mine as a result. Rather than down vote me why don't you just explain your views?
>> The real problem is the extra mass of the landing gear etc. and the other equipment needed to achieve the soft landing as this has to be launched along with the rest of the rocket costing extra fuel to reach the same velocities
Could it be that SpaceX intends to get around this problem by keeping the landing gear on the ground and lowering the stage onto the gear with extreme precision?
"RS-232 has nearly sent me into orbit a couple of times..."
So true. So true.....
Joking aside the 422 version is quite popular for some launch vehicles. The differential signal format makes it much more resilient to electrical noise (lots of high current pulses flying around).
"The shuttle wasn't designed to need that much refurbishment between flights, it just happened somewhere betweeen design and reality. I wish Elon all the luck in the world."
No it happened when Nixon's OMB required it be built to a fixed constant yearly amount despite high inflation in the US during the development and the fact that no major aerospace project had that funding profile.
The architecture was the only one that could come close to meeting that budget profile. That design, and that apparent lack of someone in overall charge of the project, who understood the issues between sub systems and could trade their performance accordingly, are the reasons STS was what it was.
But I'll believe that this is practical when I see it being used in the marketplace. I have a hard time seeing rocket boosters lifting a craft to something like mach 5 or mach 7 several tens of miles downrange, and then the detached boosters turn around and fly back home and land vertically.
I'd think the amount of extra fuel, structural weight and complex control and telemetry systems to make this work would more than outweigh the cost of using a good old-fashioned "let's fire it and drop it in the drink" reusable booster like the space shuttle had.
" and then the detached boosters turn around and fly back home and land vertically."
The trick (or part of it) is to avoid having to "fly" them back. It's more like a sort of controlled "fall" back from orbit.
"I'd think the amount of extra fuel, structural weight and complex control and telemetry systems to make this work would more than outweigh the cost of using a good old-fashioned "let's fire it and drop it in the drink" reusable booster like the space shuttle had."
That's what Spacex is trying to find out. But those SRB's took serious refurbishment (At one time the new cost was equal to the refurb cost, which sounds highly suspicious to me). And of course transporting roughly 1million lbs of explosive from Utah to Florida per booster. Do you think having a solid rocket booster mfg plant in a landlocked state and making them so big they cannot fit in one piece onto a train was a bit of a design oversight?
For range safety reasons most if not all US orbital launches fly over the ocean and the first and subsequent stages end up crashing in open water. The SpaceX recovery system will require the first stage to actually reverse course to come back to land, even if it doesn't return to the original launch site. This is a lot more expensive in fuel than simply arresting a vertical drop to a zero-zero landing after parachutes have taken most of the energy out of the fall from twenty miles up. They are also talking about similarly recovering the second and third stages, possibly with heatshields which also adds to the weight penalty.
The interesting point is that the first stage will in effect be a guided missile with the possibility of it going astray and ending up in, say, downtown Miami or some other populated area instead of returning to the desired landing spot. How they are going to cover the insurance costs on that I don't know.
The Thiokol deal was basically that there was only really one company in the US that has experience with big solid-fuel motors and that happens to be in Utah. Their main business was producing military IRBM and ICBM motors for Peacekeeper, Trident and Polaris and the like. When the decision was made to go with SRBs on the Shuttle they were pretty much the only US business who could produce the goods. I don't know why NASA didn't go with the alternative of liquid-fuelled strap-on boosters like several other launchers such as the venerable Soyuz use, but then again the Ariane5 uses solid-fuelled boosters too.
@ Robert Sneddon
Exactly the point I was trying to make regarding the use of ocean as downrange for launches. After you've left Cape Canaveral or Vandenberg, the next piece of terra firma to land on is going to be Bermuda or Hawaii. So to make this work you'd have to boost your payload up to several thousand miles an hour, separate and then turn the boosters around and fly back to Vandenberg or Cape Kennedy. Both of those coastlines (Southern CA and central Florida) are heavily populated, so there are no real alternatives to land anywhere else.
Seems to me that structurally that 180 degree turn at such speed would be very stressful on the booster, which would still be in the atmosphere, and would take a great deal of fuel to perform that maneuver. So not only would you have a structurally larger booster, to carry all that extra fuel and control systems, but it would have to be a structurally more rugged booster too, to handle the stresses of performing the turnaround maneuver in the atmosphere.
At that point, I would think it would become impractical. Maybe you can actually orbit the boosters and have them land back home (or at Edwards AFB or Kwajelain some place like that) after completing pretty much a full orbit, but then you have to worry about re-entry, while carrying lots of explosive fuel to make the vertical landing .
"So to make this work you'd have to boost your payload up to several thousand miles an hour, separate and then turn the boosters around and fly back to Vandenberg or Cape Kennedy."
No. Following separation the stage continues to coast to high altitude. At that point the wind resistance is practically zero (close to space vacuum) and the force needed to spin it round is pretty low. Those 9 engine bells make pretty good air brakes. Those two details make a bigdifference to feasibility. How big is the key question.
"At that point, I would think it would become impractical. "
Well that's part of the point of these tests. You might like to revise you views given that how you think this is going to fly is incorrect.
"This is a lot more expensive in fuel than simply arresting a vertical drop to a zero-zero landing after parachutes have taken most of the energy out of the fall from twenty miles up."
The Shuttle SRB's separated at c43miles. The question is how much fuel is needed for this manoeuvre, which I guess is one of the questions these tests are designed to answer.
"he interesting point is that the first stage will in effect be a guided missile with the possibility of it going astray and ending up in, say, downtown Miami or some other populated area instead of returning to the desired landing spot. How they are going to cover the insurance costs on that I don't know."
Well I'll take a wild guess as see if they are going to approach it like the blind landing certification of 1 failure per billion hours of operation. I'll also note that "guided missile" is in fact more like a rapidly rapidly decelerating set of propellant tanks, which will probably emergency vent at high altitude before anything serious happens, rather than the classic exploding shower of bits beloved of military self destruct systems. Bad news for anyone directly under them who does not look upward in time.
Just like any aircraft crash in fact (although with less debris).
"The Thiokol deal was basically that there was only really one company in the US that has experience with big solid-fuel motors and that happens to be in Utah. "
No. In the late 1960s IIRC there were at least three mfg of big solids in the US. The original competition gave them the lowest score. I think Lockheed won but proposed constructing a propellant loading site at the Cape. The administrator of the time (Webb) required a re-marking and the rest is history. In reference to the SLS I asked if you could bulk mfg them and store them as complete SRBs upright in (basically) pits blasted in the Utah desert (something there is no shortage of). Another poster explained the SRB mix would slump as it's nothing like the ICBM mix.
As for using solids it was all about meeting the budget.
Kind of strange watching that footage, when I consider that the last time I saw a rocket rise off the pad and hover like that was the attempted launch of Vanguard I. It's also weird to watch when the only other times I saw rockets settle down gently to the ground and stop like that was in bad old sci-fi movies.
"Kind of strange watching that footage, when I consider that the last time I saw a rocket rise off the pad and hover like that was the attempted launch of Vanguard I"
Well there was also that Lunar Lander Simulator that Buzz Aldrin was flying (the flying bedstead IIRC was one of it's nicknames).
Jet engine to cancel 5/6 of the mass so the lander rocket engine though it was in 1/6 g.
Good thing they went ahead and fitted the ejector seat anyway though.
...Well there was also that Lunar Lander Simulator that Buzz Aldrin was flying (the flying bedstead IIRC was one of it's nicknames).
Jet engine to cancel 5/6 of the mass so the lander rocket engine though it was in 1/6 g.
Good thing they went ahead and fitted the ejector seat anyway though.
Seriously, man... the LLRV was a wicked-assed machine -- literally. From all accounts, astronauts training to fly the LM swore by the LLRV, and at it. Neil Armstrong was nearly killed in the LLRV training for his Apollo mission.
"Seriously, man... the LLRV was a wicked-assed machine -- literally. From all accounts, astronauts training to fly the LM swore by the LLRV, and at it. Neil Armstrong was nearly killed in the LLRV training for his Apollo mission."
I think it was Buzz Aldrin but it was their instantaneous recognition that a)something was wrong b)they could not fix it and c)time to eject that demonstrated they were the 1st choice for the first Apollo landing.
Proving that one man's wicked ripping fun is another man's insanely dangerous kamakaze death ride.
Having read descriptions of it I still can't tell if the on board computer helped you compensate for the weight changes as the fuel ran out. The lack of this is one of the things which makes the various rocket belts built over the years (I did not know that Bell built both the rocket belts and this simulator) so tricky to fly (and why there are few people licensed to fly a rocket belt than pilot an LM).
That there are so many rocket scientists on here who know this cannot work. They should really apply for a job at SpaceX and tell them where they are going wrong,. Or perhaps, just perhaps, they should read up on what Musk has said about mass fraction, weight of landing gear, possible payloads etc.
EVERY SINGLE QUESTION raised by the 'rocket scientists' posting above have been answered by Musk in either print or in video. I'd suggest doing some research, rather than simply posting your often incorrect analysis here.
"ITS A FSCKING PROTOTYPE NOT AN END DESIGN"
It's not even that. It's more like a proper X vehicle. It's mission is to gather information so the real vehicles can be be built. The X1, X2 and X15 (and most in between) never turned up as actual production aircraft but what was learned drove most supersonic US aircraft and missile design for decades(including the space Shuttle)..
Thumbs up for making the point.
Obsolete junk. What really needs to be done is throw lots of money at the Skylon people. Real, surface to space jet/rocket hybrid engines which look EXACTLY like the engines from just about every one of the more awesome sci-fi spaceships? (The atmospheric capable ones at least!) I'll buy that for a dollar!
Skylon engines for lift-off/re-entry, and an ion drive for interplanetary (Luna, Mars etc) propulsion, would make colonizing the solar system WAY more awesome than tooling around with what is, lets face it, Nazi developed terror weapons from the 1940's. Lets 21st century this shit already!
http://www.bbc.co.uk/news/science-environment-17864782 <-THIS is cool, can't wait for flight tests.
http://www.freewebs.com/battlestarguardianbsr65/Viper_Mk_II.jpg Three Skylon engines!
http://www.spacegamejunkie.com/wp-content/uploads/2011/08/X-wing_SWGTCG.jpg Four of them!
http://www.thescifiworld.net/img/wallpapers/users/foomandoonian_01_1024x768.jpg (These ones actually have jet-intakes, as seen in the show when Mal boots some guy into one of them)
Many many more of course, the concept design for the Skylon plane itself is fairly obvious in it's origins after all.
Can't we have spaceplanes now please? They're way better than dumb old ROCKETS, pah!
"Obsolete junk. What really needs to be done is throw lots of money at the Skylon people. Real, surface to space jet/rocket hybrid engines which look EXACTLY like the engines from just about every one of the more awesome sci-fi spaceships? (The atmospheric capable ones at least!) I'll buy that for a dollar!"
Sold! To the man with £12Bn in his bank account.
What's that. You don't have £12Bn in your account?
Skylon's capabilities are indeed very impressive. They are also still highly speculative (but becoming less so each year). And that is there estimated total budget.
I see some people have pointed out the difficulty of returning to the launch site, or the amount of fuel required to reach the landing site.
Has anyone got a link to the explanations by Musk regarding what the ultimate plan is? Logically you would time separation such that the returning booster could simply go ballistic with gravity doing the work. Aim for one of the Shuttle alternate landing sites such as the one in Spain. That would minimise the fuel required
I don't think the first stage has anything like the energy at separation to make it across the Atlantic on its own. The Spanish landing strips for the Shuttle abort plans required the Shuttle to continue in powered flight for several minutes with or without the SRBs. Going by other boosters (as actual data about the Falcon series is not easily findable) the first stage of a three-stage stack like the venerable Saturn V separated about 50km up at about 3km/s velocity, maybe 2km/s ground track and I expect the Falcon's profile is similar.
Thinking about it, one solution for SpaceX would be to buy a redundant aircraft carrier and land the spent first stage on that somewhere out in the Atlantic. It would solve the safety problems of bringing the stage back over land and populated areas and would save on fuel needed to fly it back along its track as the carrier landing could be done at a point based on weather predictions for wind drift etc. at the end of the stage's ballistic track rather than have it reverse course. It would also allow Musk to one-up Larry Ellison and his Mig-29...
"I don't think the first stage has anything like the energy at separation to make it across the Atlantic on its own."
You're probably right. If it coasts to maximum altitude it's forward speed is zero. At this point it could fall vertically or be given a reverse thrust which starts it on a parabolic fall back to the area of the launch site.
"The Spanish landing strips for the Shuttle abort plans required the Shuttle to continue in powered flight for several minutes with or without the SRBs. "
With the SRB's providing c90% of the thrust (and being impossible to shut down without the loads tearing the stack to pieces) I'd suggest that would be with the SRB's attached. I think you'll find the technical term for the crew of a Shuttle that has one or both it's SRB's detach while still firing was "dead."
"The first stage of a three-stage stack like the venerable Saturn V separated about 50km up at about 3km/s velocity,"
The Saturn V stack used 2 stages to achieve orbit. The third was the Earth departure stage for the Moon. Given most flights were to the Moon (or around it) that's the configuration that tended to fly. The usual rule of thumb is the delta-V for orbit with 2 liquid stages is about 50/50 between the 2 stages. Black Arrow was unusual. It's first stage supplied about 1500m/s. A big chunk was supplied by the 3rd stage Waxwing solid. This fact is under appreciated by people who have seen it in a museum. Orbital velocity is about 7950m/s but losses typically bump it up to about 9100-9200m/s. Shaving those losses pays very big dividends.
This stuff might look to you like the "same old same old" but it's not. Building a new gas generator LOX/RP1 rocket engine (albeit one with a pretty good T/W) is rocket engineering. Likewise building a good lightweight tank structure is also engineering. There is lots of prior art on these areas.
Actually learning how to land a stage of a TSTO vehicle is rocket science. Yes that aspect ratio makes a hell of a difference which DC-X (along with other SSTO concepts, especially those of Philip Bono) designed out. But you cannot build a TSTO that shape. Musk is trying to square the circle, which is why this is "super damm tough." As old maps put it "Here be monsters," and yes he may fail. But his team have gone further than any previous AFAIK with dealing with real world size (and shaped) hardware.
You might find the work of John Carnack and his team at Armadillo aerospace instructive. From PC game programing to hardware hacking on large scale. Reading through their back posts is highly instructive, especially how supposedly trivial issues can bite you. How what seem to be fairly easy performance specs require top class components and near semiconductor levels of cleanliness.
Keep in minds most of there stuff has been relatively well behaved liquid fuels. Not giant explosive SRB's or vicious hypergolics.
SRBs are incredibly well-behaved compared to LOX plus anything with carbon and/or hydrogen in it and a lot easier to handle and store, one reason most military missiles use solid fuels these days. The material they're made of (an auminium powder and perchlorate mix plus a binder in the case of the SRBs) doesn't explode, it burns rapidly (and there is a difference, pressure shockwaves in the supersonic and hypersonic regime and such).
The loss of the Challenger was due to a flame leak at an SRB joint which cut into the liquid-fuelled External Tank "bomb" and set it off. If the flame had been directed towards the outside of the stack away from the ET then the Challenger would probably have survived and made it to orbit.
I don't know what fuel the Dragon capsule's LES is going to use. I presume it will be storable hypergolics such as UDMH and N2O4, not something I'd be comfortable sharing such a compact capsule with in quantity.
"SRBs are incredibly well-behaved compared to LOX plus anything with carbon and/or hydrogen in it and a lot easier to handle and store, one reason most military missiles use solid fuels these days."
Solids make excellent weapon systems. Except the filling of the Shuttle SRB's, which slumps over time.
There virtues (storage vessel is combustion chamber, mechanical simplicity, once started never go out) are either irrelevant to commercial use or active liabilities. LOX is dangerous due to it's concentration and temperature. In time it warms up and diffuses into the air. In contrast both solids and hypergolics are intrinsically dangerous. Solids don't evaporate and a cloud of UDMH is an effective chemical weapon.
When solids are built, moved or stacked they are classed as an explosive and the expenses are those of an explosive, not a set of propellants which can be moved separately.
"The material they're made of (an auminium powder and perchlorate mix plus a binder in the case of the SRBs) doesn't explode"
Under normal circumstances, but solids have exploded and the combustion of 1.1 million lbs of explosive is pretty serious. The normal physics of operation are deflagration but it can move into the detonation regime (and has) and the transition process is not that well understood. It used to be thought hybrids were immune to this, but even they are not.
"If the flame had been directed towards the outside of the stack away from the ET then the Challenger would probably have survived and made it to orbit."
Highly doubtful. At that point you have a case weak spot and increased burning area of the grain. You now have a thrust vector acting on the stack it was never designed for. If this SRB fails you've now got massive force imbalance on the stack. If it does not you have a (growing) side force until the SRB burns out (prematurely) leaving the other (because you cannot shut them down) SRB to rip the stack apart.
As for the contention that only Thiokol could build large solids and my recollection there were at least 3 companies that could perhaps you should look at this little item on Shuttle design choices and mfg selection.
"I don't know what fuel the Dragon capsule's LES is going to use. I presume it will be storable hypergolics such as UDMH and N2O4, not something I'd be comfortable sharing such a compact capsule with in quantity."
Agreed but they are the common state of practice. Again what does that have to do with Grasshopper, which is mostly LOX/RP1?
"I wonder how well this would work on Selene or Mars?"
Obvious answer. Badly.
Mars atmospheric pressure is about 1/1000 of Earth sea level at Mars sea level.
The Moon is worse.
Air drag is an integral part of the process. While the lower gravity of Mars or the Moon helps I don't think the balance of forces works out too well in either case. I think you'll need more terminal thrust (but OTOH the propellant to do so weighs less). Lots of testing needing.
Thumbs up for the question.
So here's my problem with this whole idea - it will probably require a pilot onboard for political/regulation reasons. For a start, the US requires that private and commercial aircraft have pilots in US airspace, just look at the trouble private operators are having getting approval to use drones which are a lot less potentially explosive. And then think of the image problem of having your robot rocket, complete with super-hot plume and residual rocket fuel, if it comes down and torches a residential area. Just ask yourself why commercial airliners have a minimum two cockpit crew, despite the tech for automated flight having been available for years.
NASA and the US government can get away with drones and robot shuttles because they are the government, it will be a lot harder to get permission as a private company. The only way round that is to include a pilot/astronaut, which then requires a much heavier launch vehicle due to life support The only other option would seem to be launching outside the US, which removes the advantage over the relatively cheap European, Russian and Chinese rockets. Remember, most customers are one-off users, the re-use saving is an advantage to the operator, not necessarily to the customer. To me the spaceplane idea such as SpaceShipTwo, where the whole launch vehicle returns under pilot control, seems a more practical and politically-acceptable idea.
"To me the spaceplane idea such as SpaceShipTwo, where the whole launch vehicle returns under pilot control, seems a more practical and politically-acceptable idea."
Despite its name SS2 is sub orbital.
It's maximum speed is about M3.
And no the airframe is unlikely to manage roughly 7x increase in speed (and the roughly 49x increase in kinetic energy) needed to reach orbit.
".....And no the airframe is unlikely to manage roughly 7x increase in speed (and the roughly 49x increase in kinetic energy) needed to reach orbit." Don't be silly, the whole idea of SS2 is the launch vehicle carries the orbiter to a high altitude, saving the orbiter from having to carry the extra fuel and engines required to reach that altitude. The orbiter, effectively a small shuttle, then separates and uses it's own rocket engine to shoot into orbit. The launch vehicle is analogous to the boosters on the Shuttle, only it takes off and lands like a plane and is re-useable.
"Don't be silly, the whole idea of SS2 is the launch vehicle carries the orbiter to a high altitude"
Again I would suggest you look up the performance of the White Knight 2 / Space Ship 2 combination. While having a pilot may be comforting it's not the way Musk is planning to do it. As he walked away from PayPal with $1Bn in cash I don't he's likely to commit to something he has not fully thought through. Just an impression.
Virgin Galactic have said SS3 might be orbital.
VTOL experiments have been done since the 1950's (Search for "tailsitters")
Rocket thrust since the 1960's (NASA's Apollo lander simulator the "flying bedstead").
But never with a tank structure with this aspect ratio and this size. It's huge.
This combination makes for a relatively "floppy" vehicle and a very tricky control problem. Take a broom handle and try balancing on your fingertip. It's not quite as simple as it seems.
Now imaging the boomstick is 2 hollow chambers with fluid sloshing about in the bottom 1/10th of both. Tricky, is it not?
"The Flying bedstead is a British VTOL Prototype, built in the 50's."
Same nickname different concept.
The 1950's vehicle was the test bed that led to the thrust vectoring (by swiveled nozzles) Pegasus used on the Harrier.
We are talking about the NASA LM simulator using IIRC a turbojet to cancel most of the Earth "gravity" and the actual LM descent engine (possibly with the actual computer) to do the rest.
Their similar because neither had a recognizable fuselage, just a frame work with a seat in it.
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