back to article Rocket 'Grasshopper' leaps higher than tall building in single bound

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 …

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Boffin

Bravo!

Science - SpaceX has that.

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Re: Bravo!

I will reserve judgement until I hear of more reporters present at their launches, and see less of heavily spliced videos.

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Re: Bravo!

OK, there is a single view video of the same launch. /tin hat.

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Meh

To land vertically?

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.

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Re: To land vertically?

Clearly you should phone up spacex, they've obviously not considered any of that before spending the money developing this.

More constructively:

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.

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Headmaster

Re: To land vertically?

That's drogue *chutes*, as in parachutes.

YW

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But you have to land on a landing pad...

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.

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Re: To land vertically?

Whoops, you should chute me for that mistake. I blame being distracted looking up the spelling of drogue.

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Re: To land vertically?

Nick,

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.

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Boffin

Re: But you have to land on a landing pad...

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.

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Re: But you have to land on a landing pad...

Did you see the amount of flame spilling off the landing pad? It is a much bigger thing to hit something that small. If you miss it, the rocket would likely wreck, perhaps ruining other's property.

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Unhappy

Re: To land vertically?

"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.

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Mushroom

The cost of the fuel required for this sort of thing is also an important consideration.

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More the weight / space I would think

It's fuel they have to lift along with the second stage, and reduces room for fuel to do that lifting.

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Returning the rocket to the launchpad is still a BIG challenge...

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.

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Cost of fuel per Falcon 9 flight: on the order of US$200 000

Cost of manufacturing a new Falcon 9: on the order of US$50 000 000

Bringing some excess fuel along is obviously cheaper than making another rocket.

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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.

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Boffin

Cost of fuel

I had the same thought at first but 100kg of fuel is hell of a lot cheaper than 100kg of rocket engines. Or 100kg of avionics.

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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.

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But you cannot land it arbitrarily...

You have to get the rocket back to a landing pad. That navigation is where all the return-fuel burn comes from.

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Re: It's fuel they have to lift along with the second stage

I imagine that squeezing every last kg into the payload isn't so much of a consideration when you have a reusable system with low launch cost and rapid turnaround.

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@ridley,

S5 could put 120t into LEO and 45t to TLI.

It's getting to orbit not coming back.

You only need a bigger rocket if you're not:

A: Sacrificing payload.

B: Increasing the efficiency of the system.

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Thumb Up

I've often wondered why this wasn't tried before. It seems such an obvious thing to do.

But then again, I admit I have no real idea of the complexity involved.

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Boffin

I've often wondered why this wasn't tried before. It seems such an obvious thing to do.

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.

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Re: I've often wondered why this wasn't tried before. It seems such an obvious thing to do.

No not 2x bigger not even close. Much much much bigger.

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Happy

Re: I've often wondered why this wasn't tried before. It seems such an obvious thing to do.

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?

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Re: I've often wondered why this wasn't tried before. It seems such an obvious thing to do.

Payload fraction on an F9 V1 is 1.986%

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A hop in the right direction

Who knew those old sci-fi movies would accurately predict that this would actually be a landing option? It always seemed ludicrous to me. At least we aren't stuck with all computers looking the way they did 50+ years ago

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Nice

That looks surprisingly impressive.

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Incredible!

The first thing I noticed was the absence of any kind of support gantry before the lift-off. How many millions of tiny corrections must they be making to keep that thing balanced?

Well done, SpaceX!

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I must admit

I didn't realise NASA recovered the shuttle boosters. Seems obvious in hindsight, but I didn't think they would have survived the fall in reusable conditions.

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Re: I must admit

There were huge parachutes involved.

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Re: I must admit

and they are made of half inch maraging steel, because they contain solid fuel.

liquid boosters are usually made of paper-thin aluminum alloys.

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Re: I must admit

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.

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Re: I must admit

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...

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Thumb Up

Some deserted rural landscape instead of huge gantries and buildings?

With a rocket so pristine it looks like something out of a Lonnie Zamora UFO sighting?

Leisurly descending on its own flame?

That seriously looks like Hollywood. Good job!

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I would like to have some reporters on hand, or at least the landing in one continuous unspliced take. There are some peculiar things about that edit.

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Dear DanR2,

please remove tin foil hat, it doesn't suit you.

Since there is a single edit view also available, does that assuage your paranoia?

Jesus, some people just see conspiracy in everything. Why can people not just take things at face value nowadays.

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Face value is overrated.

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No idle talk

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..

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Paris Hilton

Re: No idle talk

> provided it's done properly

How exactly is that?

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Anonymous Coward

Re: No idle talk

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.

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WTF?

Re: No idle talk

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.

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Re: No idle talk

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.

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All kinds of awesome

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Fuel

Where o'where will they put the huge amount of fuel required to land used boosters in this fashion and by carrying all that extra fuel that will significantly degrade the performance of the system.

Tis a cool trick, 'tho!

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Fifteen years earlier

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.

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FAIL

What exactly in "Not NASA" do you not understand?

> 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.

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Re: Fifteen years earlier

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.

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Re: Fifteen years earlier

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.

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