/sci/ - Science & Math

[Anonymous No.6085362]

SpaceX's Grasshopper reusable rocket test program has flown again, this time to a 744 meter height.

https://www.youtube.com/watch?v=9ZDkItO-0a4

This is the first Grasshopper, used mainly for hovering and landing tests. The Grasshopper 2 will be flying soon, and is intended to fly at supersonic speeds and go beyond the karman line.

[Anonymous No.6085373]

The orbital rocket the Grasshopper 2 is based on, the Falcon 9 1.1, went to orbit for the first time two weeks ago:
https://www.youtube.com/watch?v=PU7Li5rX_OQ

It's designed to function as a reusable vehicle, but is cheap enough to fly as an expendable (as the most cost-effective expendable on the market, in fact) while they work out the bugs.

[Anonymous No.6085406]

This is good shit.
People like to focus on huge payloads, a space bus like the shuttle or Falcon Heavy but most of the work can be done with much smaller payloads.
It's just more sensable, efficent engieneering.

[Anonymous No.6085481]

FREE MARKET

FUCK YEAH

[Anonymous No.6085543]

>>6085362
Hi Elon, love your work.

[Anonymous No.6085553]

yeah its pretty neet, shit got real when flames and shit came out though

[Anonymous No.6085616]

>>6085362

I like the camera.

[Anonymous No.6085673]

>>6085616
Yeah, there are a lot of neat multicopters on the market now.

[Anonymous No.6086033]

Thread needs an image of the Falcon Heavy.

[Anonymous No.6086926]

Apparently this will be the last grasshopper test with the free standing leg configuration. up next is Falcon 9 Reusable tests at Magregor and then New Mexico.

[Anonymous No.6086928]

>>6085373
And here's the transcript of the post launch teleconference: http://shitelonsays.com/transcript/spacex-press-conference-september-29-2013-2013-09-29

[Anonymous No.6086960]

>>6085362
Is re-usability like that actually feasible for ground-orbit-ground? Doesn't that mean they have to carry more than twice as much fuel for the same payload, massively decreasing payload weight per flight? Or does reusability decrease the cost of a flight so much that needing twice as many flights for the same payload mass is still a net reduction in cost?

[Anonymous No.6086963]

Is that really a useful concept?
You need at least twice as much gas and rockets are basically mostly just cheap metal tubes.

[Anonymous No.6086985]

>>6086963
>You need at least twice as much gas and rockets are basically mostly just cheap metal tubes.

Congratulations, everything you just said was wrong.

[Anonymous No.6086996]

>>6086960
No becasue the return trip is gravity and air friction assisted, it only needs to carry a fraction more fuel and burn to add resitance just enough to keep it inside an acceptable terminal velocity envelope. besides the fuel contrary to belief is the cheap part (partly becasue they use a less efficient but cheaper fuel), the ship and all the engineering turn around time and person ell on station is the expensive part.

[Anonymous No.6087004]

>>6086996
I'm well aware that the fuel is cheap (SpaceX is using LOX/Kerosene, AFAIK), but you're right, it's completely obvious that they only need just a little more fuel and I'm retarded.

[Anonymous No.6087008]

>>6086960
>>6086963
The fuel is cheap. With stuff like kerosene and oxygen, it's less than 1% of launch cost. Most of the cost of launch is constructing and testing the rocket, which has to be built of very strong, light materials to exacting standards.

Even limited lower-stage reusability is expected to immediately cut $/lb prices in half, despite reducing maximum payload by about 30%. Upper stage reusability is expected to cut payload in half (together with lower-stage reusability, payload will be down to 30-40% compared to the expendable), but when the whole rocket becomes reliably reusable, $/lb launch prices can fall to a few percent of the expendable price, eventually being dominated by the price of fuel.

And then they can redesign for a cheaper fuel, like methane, and go to a larger rocket which takes less organizational overhead to launch.

This is a path which can eventually lead to breaking not only the $1,000/lb barrier, and the $100/lb barrier, but the $10/lb barrier.

[Anonymous No.6087011]

>>6086996
>>6087004
Actually, due to non-linear factors in launching rockets, it does end up taking in the neighborhood of twice as much fuel (and rocket) to send up the same payload.

[Anonymous No.6087023]

>>6087011
I know that's why I said a fraction. One half is a fraction, but I guess not everyone has graduated with his factorial PHD yet, I forget sometimes.

[Anonymous No.6087029]

Wow, that's as far as I walk in 7 minutes.

[Anonymous No.6087031]

>>6087029
Uphill both ways? Or just up and down

[Anonymous No.6087041]

>>6087029
>100m/minutes
Do you ride a mobility scooter?

[Anonymous No.6087047]

>>6087029
Check out their history of flight tests, though:
https://en.wikipedia.org/wiki/Grasshopper_%28rocket%29#Flight_tests

Flights 6 and 7 were exceptions, because they wanted to test a new navigation system and sideways maneuvering, but other than that, every flight was at least twice the height of the one before it.

They're being cautious, but they're making steady progress.

[Anonymous No.6087049]

>>6087041
no he is probably just rich and from a cold climate city

[Anonymous No.6087141]

>>6087029
You can walk 700 meters up into the air?

[Anonymous No.6087160]

>>6085362
I know this is going to sound stupid, but how do rockets start off slowly yet end up so fast? Is there an increase in thrust, or does thrusting with a certain force over a long period of time result in an increase in speed?

[Anonymous No.6087178]

>>6087160
It's a constant slow acceleration. There is an increasing cost to accelerate due to air resistance square increasing as the rocket accelerates which creates a maximum achievable velocity d at a given altitude x.

However as it's altitude x increases the air density decreases which increases the limit d^2.

[Anonymous No.6087189]

>>6087160
Some rockets actually accelerate very quickly from the start, particularly solid-fuel rockets. Also: they look like they're accelerating slower than they are simply because they're so big.

For the most part, rockets produce a constant thrust. But they lose mass over time, due to burning up fuel. This means they start out accelerating slowly (most of the thrust is simply spent countering the pull of gravity), and then accelerate faster and faster. Additionally, the air gets thinner as they go higher, reducing drag and increasing the efficiency of the rocket nozzle.

[Anonymous No.6087190]

>>6087160
Yes, thrusting with a certain force over a long period of time results in an increase in speed.

See, force is mass times acceleration. Acceleration multiplied by time is velocity. Ergo, if you exert thrust over a period of time, you'll be going faster than when you started.

[Anonymous No.6087195]

>>6087160
>>6087190

But to actually answer your question, as the rocket burns, it uses up fuel, so it becomes lighter, which means that the same thrust causes it to accelerate faster. So not only does it speed up as it travels, the rate at which it speeds up also increases.

And furthermore, the further you go up, the thinner the air is, so there's less air resistance. Not only does the acceleration from the thrust increase as the rocket travels, but the resistance drops as well, so it accelerates even faster.

[Anonymous No.6087856]

>>6085362
>>6085616
>that moment when it starts descending
> RIGHT AT THE QUADCOPTER

holy fuck, I thought they were trying to crash into it! Being that close gives you some amazing footage, though! Their engineering team must be delighted to get such great feedback on a test.