Falcon 9 Reusable Rocket's Maiden Flight Captured By Drone

Falcon 9 Reusable Rocket's Maiden Flight Captured By Drone

The launch and landing of the Falcon 9 Reusable rocket is a remarkable technical achievement and makes for an impressive bit of video, too.

Going to space is an expensive business, in no small part because so much of the stuff that gets you there is throwaway: A whole rocket goes up, but only a little bit of it comes down. It's essentially a multi-million-dollar Bic lighter that you flick once and then throw into the toilet, and that's an awfully wasteful way to go about things.

To help reduce those costs, SpaceX is developing a reusable version of its Falcon 9 rocket, the creatively-named Falcon 9 Reusable, that when complete will be able to maneuver, land and be reused in future missions. A multi-story Roman Candle may not the most aerodynamic vehicle in the world but this new video, shot from a drone, demonstrates that they can be handled effectively.

You can see in the video that the rocket launches, hovers and lands with its legs extended, but SpaceX said it will soon begin tests with the legs retracted. And if this all seems a bit familiar, you're likely thinking of the very similar Grasshopper program from last year. SpaceX said the Falcon 9R program represents "the next step toward reusability," and that by moving to its rocket development facility in New Mexico, it will be able to test at higher altitudes than are permitted in Texas and "prove out landing cases that are more flight-like."

This is the future. It's pretty cool, wouldn't you say?

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This is neat, but I still can't quite see how commercially viable it will be. Mostly because of this image:

image

That's a pithy description of what's known as The Tyranny of the Rocket Equation, and the basic gist of it is that as delta-v (change in velocity) increases, fuel consumption increases exponentially. A reusable rocket, by necessity, means it's going to go and then come back, and that could be a very big problem.

If it's meant for use purely in Earth orbit, then the most severe parts of the problem are mitigated (because gravity can be relied upon to power the return trip's acceleration), but it'd still need sufficient fuel to counter the momentum of the fall before it actually hits the ground.

From the video, they seem to have at least a somewhat working resolution to the "we need to carry a whole bunch of extra fuel for the return trip, which means a lot more dead weight for the initial launch, which means more fuel for the launch, which means more weight, which means more fuel, etc" chain problem, so they're getting there, but I'm doubtful they're gonna buck the tyranny of physics.

You might want to reword the title from "Captured by Drone" to "Documented by Drone" for a good 30 seconds I was looking for the part in the article where a drone managed to capture a flying rocket.

Hey guys

Why don't we use rail gun technology to catapult space ships out of earth's gravity to reduce dead weight.

Agayek:
From the video, they seem to have at least a somewhat working resolution to the "we need to carry a whole bunch of extra fuel for the return trip, which means a lot more dead weight for the initial launch, which means more fuel for the launch, which means more weight, which means more fuel, etc" chain problem, so they're getting there, but I'm doubtful they're gonna buck the tyranny of physics.

According to wikipedia, they've already successfully decelerated the booster for a simulated landing over the ocean. I believe the test occurred during their latest resupply mission for the ISS.

http://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program#Test_flight_history

Dragonbums:
You might want to reword the title from "Captured by Drone" to "Documented by Drone" for a good 30 seconds I was looking for the part in the article where a drone managed to capture a flying rocket.

Yeah, I thought this was about someone testing out a new rocket and then the government captured it.

hawk533:
According to wikipedia, they've already successfully decelerated the booster for a simulated landing over the ocean. I believe the test occurred during their latest resupply mission for the ISS.

http://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program#Test_flight_history

Oh, I have absolutely no doubt that they're able to do it. My concern is merely the economic viability of it. I'm just not sure the massive increase in required fuel load is actually cheaper than building an intentionally-disposable rocket.

Agayek:

hawk533:
According to wikipedia, they've already successfully decelerated the booster for a simulated landing over the ocean. I believe the test occurred during their latest resupply mission for the ISS.

http://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program#Test_flight_history

Oh, I have absolutely no doubt that they're able to do it. My concern is merely the economic viability of it. I'm just not sure the massive increase in required fuel load is actually cheaper than building an intentionally-disposable rocket.

Firstly, fuel is cheap. Relatively speaking, of course. The cost of the fuel is about 3% the total cost of an expendable rocket. Even if they had to double the amount of fuel, would you rather spend $100m on a whole new rocket or $6m on more fuel? The principle is no different to a car really - filling a tank of petrol is expensive, and even more so if you make the tank bigger. But it's a heck of a lot cheaper than buying a new car for every trip.

Secondly, the actual additional amount of fuel they need to carry is not as massive as you might expect. Because when you re-enter the atmosphere the air gets thicker and thicker the closer to ground you get, the majority of the slowing down will be taken care of by drag. So they won't be using the engines to slow from orbital velocity (18,000mph), just terminal velocity through the atmosphere (about 200mph). For a first stage that has just accelerated a fully fuelled rocket and payload to about 4,000mph before separation, 200mph is nothing. And given that most of the fuel has gone, it's much lighter as well during the descent so less delta-v is required to decelerate and land softly.

Britpoint:
Firstly, fuel is cheap. Relatively speaking, of course. The cost of the fuel is about 3% the total cost of an expendable rocket. Even if they had to double the amount of fuel, would you rather spend $100m on a whole new rocket or $6m on more fuel? The principle is no different to a car really - filling a tank of petrol is expensive, and even more so if you make the tank bigger. But it's a heck of a lot cheaper than buying a new car for every trip.

Except that, as per the tyranny of the rocket equation, it's an exponential increase in fuel. See the image I posted above. That's why I'm raising it as a concern. I'd definitely view a $100m one-time-use rocket as a superior choice to spending $150m on fuel for every trip.

Secondly, the actual additional amount of fuel they need to carry is not as massive as you might expect. Because when you re-enter the atmosphere the air gets thicker and thicker the closer to ground you get, the majority of the slowing down will be taken care of by drag. So they won't be using the engines to slow from orbital velocity (18,000mph), just terminal velocity through the atmosphere (about 200mph). For a first stage that has just accelerated a fully fuelled rocket and payload to about 4,000mph before separation, 200mph is nothing. And given that most of the fuel has gone, it's much lighter as well during the descent so less delta-v is required to decelerate and land softly.

I'm not sure you understand what delta-v is, it has nothing to do with mass.

That said, you're largely correct. As I said above, if it's for use purely as a ferry to Earth orbit, then the majority of the problems are mitigated if not rendered irrelevant. It'd still need to carry the dead-weight of the fuel to deorbit and then counter its final velocity, but as you said, that's a comparatively small value, so it's not really that big a deal. Any use that goes a reasonable distance from Earth however, will run smack dab into fueling problems.

Agayek:

I'm not sure you understand what delta-v is, it has nothing to do with mass.

That said, you're largely correct. As I said above, if it's for use purely as a ferry to Earth orbit, then the majority of the problems are mitigated if not rendered irrelevant. It'd still need to carry the dead-weight of the fuel to deorbit and then counter its final velocity, but as you said, that's a comparatively small value, so it's not really that big a deal. Any use that goes a reasonable distance from Earth however, will run smack dab into fueling problems.

Oddly enough, mass is a critical component of any delta-v equation. It's the fundamental principle of the Tyranny issue, in fact: the more acceleration you want for a given mass, the more fuel you need to accelerate it, which itself adds more mass, ad infinitum.

His point was that the rocket is coming down largely empty. SpaceX reserves about 30% of the first stage's boost capacity for recovery tests at the moment, and the most recent test was largely successful at a soft landing on water after a successful launch.

As for how significant it is...

Yeah.

SpaceX's stated goal is $500/lb to LEO. Which is about an 80% reduction in cost vs their current cost, which is itself the lowest in the industry. The fuel used by the first stage costs a whopping $200,000. Out of the $56,000,000 or so that the entire rocket costs.

$500 per lb ($1,100 per kilo if you prefer) is mind-bogglingly cheap by today's standards.

Impressive? Not really. We already have reusable VTOL aircraft that are significantly more advanced and capable than that rocket. Call me when it gets out of the atmosphere.

That's the most future-y headline I've ever seen. I can't wait until the day I wake up and my holographic ocular implant reads to me the headline "Martian Androids Displeased With Intergalactic Warpgate as Resource Wars Continue Between Chinese-American Alliance and the PlasmaLaserBlackHoleTimeMachine Warlords of Exoplanet Omega."

De- orbiting is not as simple as just falling and starting the engines a few thousand feet above the ground. They will not slow down enough in the upper atmosphere to get to the point where they will be going only 200 mph' terminal velocity only applies to something dropped and starting at zero. I honestly don't think a capsule could carry enough fuel for a soft landing coming out of orbit. At least not without deploying a drogue chute to slow their momentum. And momentum is the key word.

 

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