Grasshopper jumps sideways

Old news ... August 14th!

http://www.nbcnews.com/science/spacexs-grasshopper-test-rocket-flies-sideways-successfully-6C10923106

and
http://www.spacex.com/media

Photos, videos, 325m, ...

/dps

--
Ieri, oggi, domani

Snidely formulated the question :
Old news ... August 14th!

http://www.nbcnews.com/science/spacexs-grasshopper-test-rocket-flies-sideways-successfully-6C10923106

and
http://www.spacex.com/media

Photos, videos, 325m, ...

The sideways-ness shows up better in the NBC link's video, as the
landing is about 2m from the takeoff point. I'm not sure what the
maximum horizontal displacement was ... 50m to 100m ?

/dps

--
I have always been glad we weren't killed that night. I do not know
any particular reason, but I have always been glad.
_Roughing It_, Mark Twain

On 8/17/2013 5:03 AM, Snidely wrote:
Snidely formulated the question :
Old news ... August 14th!

http://www.nbcnews.com/science/spacexs-grasshopper-test-rocket-flies-sideways-successfully-6C10923106


and
http://www.spacex.com/media

Photos, videos, 325m, ...

The sideways-ness shows up better in the NBC link's video, as the
landing is about 2m from the takeoff point. I'm not sure what the
maximum horizontal displacement was ... 50m to 100m ?

/dps

================================================== ===

It's needed progress. Space technology is gaining on the sf writers
of the 1930's and 40's. Not bad -- for America. I recall words seen
a few decades ago: "...As God and Heinlein intended."

Titeotwawki -- Martha Adams [Sat 2013 Aug 17]

Snidely formulated the question :
Old news ... August 14th!

http://www.nbcnews.com/science/spacexs-grasshopper-test-rocket-flies-sideways-successfully-6C10923106

and
http://www.spacex.com/media

Photos, videos, 325m, ...

The sideways-ness shows up better in the NBC link's video, as the landing
is about 2m from the takeoff point. I'm not sure what the maximum
horizontal displacement was ... 50m to 100m ?

From what I understand 100m. (One article said 330', so I'm assuming someone
converted from 100m.)



/dps


--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net

On 8/18/2013 11:10 AM, Greg (Strider) Moore wrote:
Snidely formulated the question :
Old news ... August 14th!

http://www.nbcnews.com/science/spacexs-grasshopper-test-rocket-flies-sideways-successfully-6C10923106


and
http://www.spacex.com/media

Photos, videos, 325m, ...

The sideways-ness shows up better in the NBC link's video, as the
landing is about 2m from the takeoff point. I'm not sure what the
maximum horizontal displacement was ... 50m to 100m ?

From what I understand 100m. (One article said 330', so I'm assuming
someone converted from 100m.)

/dps

========================================

It's an interesting topic to think about. In today's world,
it's a challenge to write the software. And seems to me, the
properties of the Grasshopper change as it flies: its center
of mass moves down and its weight changes as it consumes
fuel; and for lateral translation, you must tilt it to start
the translate and tilt it again to stop it. Thus the thing
had to tilt four times to translate out and return to its
starting point. The tilts were very visible as it flew, and
a little disconcerting. Having seen rockets flying directly
up only, for the past several decades, here is one that does
it differently. Well, ...Yay!

Titeotwawki -- Martha Adams [Mon 2013 Aug 19]

On 8/19/2013 9:05 PM, Martha Adams wrote:
and for lateral translation, you must tilt it to start
the translate and tilt it again to stop it. Thus the thing
had to tilt four times to translate out and return to its
starting point. The tilts were very visible as it flew, and
a little disconcerting. Having seen rockets flying directly
up only, for the past several decades, here is one that does
it differently.

The lunar landers must have done that, so rocket-powered lateral
translation is hardly a new concept.

Still, the Grasshopper is an amazing feat, done on a relatively tiny
budget over a relatively tiny time frame.

In article ,
says...

It's an interesting topic to think about. In today's world,
it's a challenge to write the software.

I think this is debatable. One thing that modern electronics gives you
is speed and processing power. This isn't like the Apollo or shuttle
days where you had to minimize every bit of data you stored and had to
count every cycle you needed to execute your code. Remember the 1201
and 1202 errors on Apollo 11? How about the shuttle code which wasn't
quite right related to some aerodynamics issues on reentry?

Even kids these days are doing amazing things with hardware and software
on $25 computers (e.g. Raspberry Pi). Back when I was a teenager, I
spent well over $1000, in late 1980's money, on a C-64, 1541 floppy
drives, printer, and misc. electronics bits to interface to the C-64's
user port. Kids these days can do far more with far less cash and they
can do it using higher level programming languages than assembler and 8
bit C-64 Basic.

And seems to me, the
properties of the Grasshopper change as it flies: its center
of mass moves down and its weight changes as it consumes
fuel; and for lateral translation, you must tilt it to start
the translate and tilt it again to stop it. Thus the thing
had to tilt four times to translate out and return to its
starting point. The tilts were very visible as it flew, and
a little disconcerting. Having seen rockets flying directly
up only, for the past several decades, here is one that does
it differently. Well, ...Yay!

This flight was much more "tame" than the "death swoop" maneuver
successfully pulled off by DC-X. It's exciting because it's being done
on a large scale on a demonstrator based on flying hardware and on a
"reasonable" budget. It's not exciting because it's truly breaking new
ground technologically.

Jeff

--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

In article ,
says...

On 8/19/2013 9:05 PM, Martha Adams wrote:
and for lateral translation, you must tilt it to start
the translate and tilt it again to stop it. Thus the thing
had to tilt four times to translate out and return to its
starting point. The tilts were very visible as it flew, and
a little disconcerting. Having seen rockets flying directly
up only, for the past several decades, here is one that does
it differently.

The lunar landers must have done that, so rocket-powered lateral
translation is hardly a new concept.

To be fair, that was in vacuum and in lunar gravity. That said, DC-X
certainly demonstrated more maneuverability than Grasshopper has so far.

The software for control systems for a DC-X or Grasshopper like vehicle
aren't *that* hard to write. Look at what the quad-copter
hackers/builders have been doing with modern electronics and control
system software. Except for the scale of the vehicle, what they're
doing isn't that much different than Grasshopper. In many ways, quad-
copters need faster, more efficient, control systems due to their small
scale (small moments of inertia which result in very fast changes in
attitude for relatively small changes in forces created by each of the
electric motors.

Still, the Grasshopper is an amazing feat, done on a relatively tiny
budget over a relatively tiny time frame.

It's also promising, because it's being done with hardware that's
derived from the (proven) Falcon 9 first stage. As such, incorporating
the lessons learned from Grasshopper into the Falcon 9 launch vehicle
will therefore be relatively straight forward.

Jeff

--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

On 8/20/2013 8:52 AM, Jeff Findley wrote:
The lunar landers must have done that, so rocket-powered lateral
translation is hardly a new concept.

To be fair, that was in vacuum and in lunar gravity.

Except for the smaller thrust needed in the lunar gravity, I'm not sure
I see the difference. Also remember that the first true "test flight"
of the lunar lander was an actual manned flight. Pretty gutsy! (As was
the first flight of the space shuttle, but that's another subject.)

In article ,
says...

On 8/20/2013 8:52 AM, Jeff Findley wrote:
The lunar landers must have done that, so rocket-powered lateral
translation is hardly a new concept.

To be fair, that was in vacuum and in lunar gravity.

Except for the smaller thrust needed in the lunar gravity, I'm not sure
I see the difference. Also remember that the first true "test flight"
of the lunar lander was an actual manned flight. Pretty gutsy! (As was
the first flight of the space shuttle, but that's another subject.)

Yes, to a first order approximation, they are the same.

But a deeper look reveals that aerodynamics of a rocket engine during
vertical landing in 1 atmosphere of pressure (especially if that
atmosphere is moving relative to the landing surface) is not the same as
in near vacuum. Yes, this is a detail, but an important one for an
object as tall as a Falcon 9 first stage.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer