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The Grasshopper Can Fly Sideways
Phoghat writes "I'm of a 'certain age' and as a child grew up watching shows like "Rocky Jones, Space Ranger and others popular at the dawn of the space age. They always showed rocket ships sitting on their tails and blasting off, and landing, straight up. The shuttle went up that way but had to land like a plane, and anything else was considered impossible or impractical. Now, the Space X's rocket Grasshopper can not only do that, but has demonstrated sideways flight also."
I almost called dupe from SpaceX Grasshopper Launch Filmed From Drone Helicopter but this is new stuff.
I am Slashdot. Are you Slashdot as well?
XKCD just covered this! Good timing for the question.
TL;DR: Heat shields aren't going away because they are efficient.
And a rocket's motor is at the back. Of course it is going to point down to counteract. No matter which way you point the rocket, the motor must point mostly down.
When I see vertical-takeoff-vertical-landing my first thought is Armadillo Aerospace and their years of work on those rockets. Now that Armadillo is largely mothballed, have some of their guys turned up at SpaceX?
Never approach a vast undertaking with a half-vast plan.
The Space shuttle can fly in over a thousand different directions -at the same time- if its heat shield is damaged.
Sig Follows: "Suppose you were an idiot. And suppose you were a member of Congress. But I repeat myself." -- Mark Twain
Diverts like this are an important part of the trajectory in order to land the rocket precisely back at the launch site after re-entering from space at hypersonic velocity."
While watching the video, I just imagined the "gas" gauge needle sinking fast to 'E'.
Having to carry all the extra fuel to land like that is going to drastically reduce the payload.
That's why space missions usually land some other way - parachute, blow up balls, crash land, etc ... more room for equipment.
Heat shields are the efficient way to slow from orbital speeds for reentry (e.g. the Shuttle), but conveniently for recovery the first stage isn't orbital. Grasshopper is basically a modified Falcon 9 first stage, and the goal of the testing is recovery of the first stage of Falcon 9-R, which is much easier than reentry from orbit..
We're not talking single stage to orbit here, and recovery of the second stage would certainly involve a heat shield. The first stage is a different animal. SpaceX seems to be intending to use a boost-back trajectory concept. I look forward to seeing how that works. (The controlled water "landing" attempt will be something to see, too, of course.)
The moon has considerably less gravity and atmosphere to worry about for VTOL. So if it's practical on the moon in 1969, it's reasonable it would take the better part of a century to become practical on Earth given that rocket technology hasn't changed that drastically since the Nazis were launching V-2s (or depending on how you define drastically, since the Chinese were launching emperors, see Wan Hu).
Is he the Wan Hu was legendarily blew himself up with rockets?
Am i the only one who wondered when the summary was going to get to something relevant to entomology? I was really baffled. I didn't know what rockets had to do with bugs :/
bad comparison. the LM actually operated in reverse. it landed at a site, then took off. that is very different from taking off and then landing back at that exact same site. furthermore, the part that took off was a totally seperate piece with its own rocket engine, so technically it was two craft (or two stages) performing two seperate operations, not one craft performing both. the grasshopper is also far far larger than the LM, and exercising greater degree of control and precision in a heaver gravity and different atmosphere.
and while you alude to the crew capsules landing without fuel, the current crop of LAUNCHERS in use, are disposable single use entities, which means you apparently missed the entire point of this experimental rocket is to validate the concept of a reusable launcher, which would dramatically reduce costs.
short version: shutup
The guy who said the election was rigged won the presidency with the second-most votes.
Whooosshhh
The Grasshopper Flies, Heavy, Man!
burbleburbleburble...
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
It's usually used as code to say "I'm old" -- we just don't like to say it that way.
Well, actually, "certain age" is used to mean that you know enough that you're certain about everything you say. That the terminology is used by those typically above average age is just a probabilistic occurrence because of the small window of time it's applicable to those of the other age range.
For instance: The teenage girl was at a certain age...
Trouble is, the DCX never made it to orbit (not even close) whereas the Falcon 9 has.
This is a modification to the existing F9 platform. IIRC, they expect it to reduce the payload capacity by about 25~30%. And yes, they intend to salvage the upper stage too. If they can do that, they'll reduce costs to a few million$ per launch. (About $250k in fuel; skirt/solar module for the Dragon; launchpad services, etc..)
They generally launch from Cape Canaveral, though they are trying to get the legislature to approve a launch site in Texas too.
XML is like violence. If it doesn't solve your problem, you're not using enough of it. --AC
Am i the only one who wondered when parent poster was going to get to something relevant to walking trees? I was really baffled. I didn't know what Ents had to do with bugs.
Am i the only one who wondered when the quoted text was going to get to something relevant to recursion? I was really baffled. I didn't know walking a tree had nothing to do with bugs.
Am i the only one who wondered why the quotes were forming some strange iterative behavior? I was really baffled. I didn't know why the stack trace was missing several parent posters; Probably -O dead code elimination, self referential side effect, or a GOTO bug.
I post therefore I was.
I always found this video to be impressive. It's a little scary in a terminator sort of way too.
Ten thousand dollars of extra fuel saves you 30 million dollars of rocket parts. Seems dead simple to me.
When our name is on the back of your car, we're behind you all the way!
We used to call it "thrust vector control". I worked in the Morton-Thiokol TVC lab for a while. The video shows a really excellent example of the technique, which is not new or controversial.
You can do TVC with hydraulics (heavy, but parts are easy to source and last longer) but you'll get better impulse numbers for the vehicle as a whole if you can divert some proportion of the pressure from the combustion chamber into mechanical actuators that change the direction the nozzles are physically pointing. With multi-nozzled rocket motors (regardless of whether they have multiple combustion chambers or not) you can point some thrust down and some to the side (which appears to be happening in the video) and get this kind of behavior.
Similar things can be done with moving vanes in the exhaust plume, but those will erode even faster than the mechanism described above, and will be far slower to change the thrust vector. Erosion of parts that have high pressure hot gasses flowing through them is a huge issue in rocketry, although fairly well understood at this point. External aerodynamic vanes like the space shuttle's wings will obviously work too, and won't erode much (during liftoff) but they are also slow and clumsy.
When I say the technique's not new, I do not mean to denigrate the achievement. I can confidently state that it's really, really hard to do it as well as is being shown in this video. I would love to be able to work with these guys, because they are clearly just full of the right stuff.
Another alternative system to TVC is separately fueled ACMs - Attitude Control Motors - such as vernier thrusters or the solid fuel ACMs on hypersonic crusie missiles. When you use gimballed nozzles to achieve TVC, though, you can potentially have the entire force of the main thrusters available for attitude control, and the fuel delivery system can be much more concentrated and simple.
Graphical overview of the common methods of TVC here
Didn't you know Elon Musk is Tony Stark.
Am I the only one who clicked through to this while scanning headlines, thinking it referred to living creatures?
"No matter how cynical you get, it is impossible to keep up." -- Lily Tomlin
The moon has considerably less gravity and atmosphere to worry about for VTOL. So if it's practical on the moon in 1969, it's reasonable it would take the better part of a century to become practical on Earth
Ok, look at the videos of the tests of the moon landers and systems here on earth ... under our own gravity.
You are correct that rocket tech really hasn't changed, yet somehow you think today we can do it but back then we couldn't?
Your post is utterly conflicted.
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
The is a first stage. There is no re-entry. It pretty much goes up and falls back down. Historically we'd let it fall in the ocean, then maybe salvage parts of it.
This lets it fall back down ... in a controlled manner, to where it started from, with little to no damage.
That changes the equations a little
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
Well, it's certainly cheaper than having some internet billionaire salvage your rocket parts off the sea floor for you.
Of course with precedents like Howard Hughes, the Glomar Explorer and project Jennifer and Robert Ballard finding the Titanic while secretly researching the Scorpion & Thresher wrecks , it leads one to wonder what internet billionaire Jeff Bezos is really up to.
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
Thanks to George Pal we already know that when a rocketship lands on its tail on another planet a bevy of beautiful space women will attack in their high heels.
I deny that I have not avoided attaining the opposite of that which I do not want.
Soyuz uses parachutes to fall at 7.2m/s. Then about a 0.5s before landing, six solid-fueld soft landing engines fire to slow the vehicleâ(TM)s descent rate to 1.5 m/s just 0.8m above the ground.
Is anybody else disappointed that TFA doesn't have slow-motion video of an actual grasshopper (the insect) flying sideways? That'd be pretty cool.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
My post makes a few points, but I don't see the conflict.
1) Rocket tech hasn't changed much. This, we agreed on.
2) It was practical to do it that way on the moon in 1969.
3) It has not been practical to do it on Earth up to this point.
4) The main difference in practicality between Earth and the moon has to do with atmosphere (or lack thereof) and gravity.
Don't confuse practical with possible. I never said we couldn't do it on Earth, just that we've had better ways due to the slow evolution of rocket technology and that might finally be changing.
Using the same engine, rather than treating the engine as a disposable object that only performs one burn in its lifetime. Most rocket engines can't be throttled, can't be shut down and then restarted in flight or otherwise.
The tricky part is going to be for any stage to have enough delta-V to return to the pad after lifting a payload to orbit. Also, as far as I can tell, this takes a drag chute for lower stages, and a re-entry shield for upper ones.
Bruce
Bruce Perens.
How about the Moon and Mars? It seems to me that the fuel capacity of Dragon isn't enough to do both lunar descent and ascent just on the Super Draco thrusters and the trunk's fuel capacity.
Bruce Perens.
Insignificant. The Dragon is volume constrained anyway, so there is spare lift capacity. You could pack it to the gills and still have unused capacity to lift extra fuel.
When our name is on the back of your car, we're behind you all the way!
[I haven't read or understood what this is about]
Yup, that's about right.
This has never been about deorbiting, but about recovering the
never-made-it-to-orbit-in-the-frist-place first stage of a multistage rocket.
This is a nice step in Musk's plans to make the 1st stage of Falcon 9 re-usable... but before people swoon over this apparent realization of SciFi fantasy and start talking of warp drives and teleporters, a few points are in order:
1. This has been demonstrated before by several other teams (DC-X being most famous, and Amazon's Jeff Bezos, with his Blue Origin vehicle, being hardly noticed). The thing the grasshopper demonstrates is not that the general concept works, but rather that Musk's team has mastered it and, more importantly, done it with an actual first stage of an actual launch vehicle (this part is the unique, and very cool part)
2. This is not proof that winged space planes (like the shuttle) or lifting bodies (like SNC's Dreamchaser) are obsolete or a dead-end. Musk is planning to use a small quantity of residual first stage propellant to land an otherwise-empty first stage for re-use; the scheme would fail if there was any added mass (like a payload). Shuttles brought tons of payload back to Earth to a gentle runway landing, and lifting bodies are similarly tasked with returning payloads. (yes, I know, Musk plans a propulsive landing for his manned capsules... but that's NOT what grasshopper demonstrates and that's a subject for a different discussion as there are many substantive differences, though this experience will certainly pave the way for that effort)
3. The fact that this one technique (of balancing a tall empty beer can on a pillar of fire and steering it around before landing it) is being demonstrated in the real world does not automatically prove that any other dreams of Roddenberry, Heinlein, Asimov, etc are any more practical or likely to appear in the near future than they were two years ago
Well done, Space-X, keep it up!
While I love the DC-X, and I thought it should have continued development, the Grasshopper is a bit more impressive as it is a few times larger. It should be pointed out that much of the engineering research that went into the DC-X has been "borrowed" by SpaceX and used on a practical basis.
Then again, it should be a cautionary tale as there were some disasters with the DC-X as well.
The scale of things here is something to point out. The LEM was just 18 feet tall, where as the Grasshopper was a full 10 stories tall (a little over 100 feet). That much larger size has many more problems that need to be addressed as not everything scales upward as just simply larger parts on everything. Quite often things that work on a scale model simply won't work on a larger version of the idea.
As far as why this wasn't done in 1969 but can be done today, it is missing that a whole lot of technological progress has happened in the meantime. I agree with you that it has take time to develop things like guidance computers which weigh as much as a mouse along with some significant progress in materials science that has allowed for some of the current generation of rockets to be developed. Simply put, the Grasshopper couldn't have been built much earlier.
No wonder Kwai Chang Cane had a hard time catching one.
Tracy Johnson
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