Grasshopper 744m Test

[Waspie_Dwarf]

Grasshopper 744m Test | Single Camera (Hexacopter)

On Monday, October 7th, Grasshopper completed its highest leap to date, rising to 744m altitude. The view above is taken from a single camera hexacopter, getting closer to the stage than in any previous flight.

Grasshopper is a 10-story Vertical Takeoff Vertical Landing (VTVL) vehicle designed to test the technologies needed to return a rocket back to Earth intact. While most rockets are designed to burn up on atmosphere reentry, SpaceX rockets are being designed not only to withstand reentry, but also to return to the launch pad for a vertical landing. The Grasshopper VTVL vehicle represents a critical step towards this goal.

Grasshopper consists of a Falcon 9 rocket first stage tank, Merlin 1D engine, four steel and aluminum landing legs with hydraulic dampers, and a steel support structure.

Source: spacexchannel - YouTube

[Peter B]

Ha! Two kinds of awesome - that we can design rockets that fly like that, and that we can design remote control helicopters that can record it.

[Merc14]

Ha! Two kinds of awesome - that we can design rockets that fly like that, and that we can design remote control helicopters that can record it.

Couldn't say it better than that so seconded

[Leonardo]

While I applaud the desire to innovate, there are several major obstacles to this becoming a de facto standard for future launches. Probably the greatest of those obstacles would be cost - not just in monetary terms, but also in fuel.

The rocket has no glide-flight characteristics, therefore both the ascent and descent are completely dependent on thrust from it's primary engine(s). This requires nearly (and possibly more than) double the fuel payload the launch of an expendable rocket of comparable size (minus the weight of cargo expelled before re-entry) requires.

Because more fuel needs to be carried, the rocket must then be much bigger than any expendable rocket when considering comparable lift-capacity.

While there are obvious cost-saving in other materials, and machinery, I don't expect that will be offset by the huge increase in costs of fuel and the required construction of much larger lift vehicles.

[ancient astronaut]

That was cool. Like the shadow of the rocket as it got close to the pad, Awesome stuff there.

[Merc14]

While I applaud the desire to innovate, there are several major obstacles to this becoming a de facto standard for future launches. Probably the greatest of those obstacles would be cost - not just in monetary terms, but also in fuel.

The rocket has no glide-flight characteristics, therefore both the ascent and descent are completely dependent on thrust from it's primary engine(s). This requires nearly (and possibly more than) double the fuel payload the launch of an expendable rocket of comparable size (minus the weight of cargo expelled before re-entry) requires.

Because more fuel needs to be carried, the rocket must then be much bigger than any expendable rocket when considering comparable lift-capacity.

While there are obvious cost-saving in other materials, and machinery, I don't expect that will be offset by the huge increase in costs of fuel and the required construction of much larger lift vehicles.

A Falcon 9 costs around $55M and the fuel to run it costs $200K so a substantial savings if you can reuse most of the machinery

[keithisco]

The question is, can the booster engine be re-used? That is in the Critical Path for cost effectiveness. Lets not forget that 744metres altitude does not equate to a re-entry burn, as ablation shielding is not required. I believe that this was just a simple Proof of Concept for the Avionics, nothing more. Apart from which the new Sabre engine is is truly designed for re-use from an HTOL viewpoint dramatically reducing the costs involved with conventional Space Delivery Systems

[Merc14]

The question is, can the booster engine be re-used? That is in the Critical Path for cost effectiveness. Lets not forget that 744metres altitude does not equate to a re-entry burn, as ablation shielding is not required. I believe that this was just a simple Proof of Concept for the Avionics, nothing more. Apart from which the new Sabre engine is is truly designed for re-use from an HTOL viewpoint dramatically reducing the costs involved with conventional Space Delivery Systems

The vehicle shown is a proof of concept and not meant to deliver payload into orbit and there must be substantial savings possible or they wouldn't be spending the money to develop this thing. I am sure they are a few years away from this being practicable for large payloads but doing it with a 10 story rocket is pretty spectacular.

[Waspie_Dwarf]

I believe that this was just a simple Proof of Concept for the Avionics, nothing more.

You seem to be making the same incorrect assumption that Leonardo is (or rather one of his incorrect assumptions as there are several but I will address that later). The Grasshopper is a test bed for a modification of the existing Falcon 9 first stage. As such this represents more than a simple proof of concept for the avionics. The Grasshopper is essentially a Falcon 9 first stage with only 1 (instead of 9) Merlin 1D engines. The next version of Grasshopper will use all 9 engines and will have legs which are folded against the rocket body at lift off and deploy for landing.

The question is, can the booster engine be re-used?

Yes. The Merlin 1D was designed from the start to be reusable.

Lets not forget that 744metres altitude does not equate to a re-entry burn, as ablation shielding is not required.

As the final goal of this project is a reusable first stage the vehicle will not need to make a re-entry burn as it will not reach orbital velocity. After separation of the second stage the centre engine will fire to reduce velocity. This reduction in velocity means that the vehicle will hit the thicker layers of the atmosphere slowly enough that heat shielding (ablative or otherwise) will not be required.

The aim is to have the first stage fly back to the launch site, lower it's legs and land intact ready for refurbishment and re-use.

The Falcon Heavy will use three of these reusable vehicles as a first stage.

SpaceX is conducting parallel testing during actual flights of the Falcon 9:

Falcon 9 Flight 6's first stage performed the first propulsive-return over-water tests on 29 September 2013. Although not a complete success, the stage was able to change direction and make a controlled entry into the atmosphere. During the final landing burn, the ACS thrusters could not overcome an aerodynamically induced spin, and centrifugal force deprived the landing engine of fuel leading to early engine shutdown and a hard splashdown which destroyed the first stage. Pieces of wreckage were recovered for further study.[65] Elon Musk stated that Falcon 9 Flight 10, in 2014, will be the next attempt to recover a first stage.

Source: wikipedia

[Leonardo]

Thanks for the additional info, Waspie. I can see where the assumptions I made might have led me astray, although I still have reservations regarding the reliability of the approach. I'm glad they are experimenting in the hope of achieving their projected goal, but am skeptical they will achieve it.

[Waspie_Dwarf]

The rocket has no glide-flight characteristics, therefore both the ascent and descent are completely dependent on thrust from it's primary engine(s).

Not so. No vehicle needs thrust to descend, gravity takes care of that. What you need is thrust to break the vehicle and allow it to land.

This requires nearly (and possibly more than) double the fuel payload the launch of an expendable rocket of comparable size (minus the weight of cargo expelled before re-entry) requires.

Where did you get that figure from?

Firstly that is not the way it works. The vehicle size (and therefore fuel load) is the fixed point. You don't increase fuel, you decrease payload size. This of course has the economic down-side you are referring to, same fuel to lift smaller payload = higher cost per weight orbited.

Because more fuel needs to be carried, the rocket must then be much bigger than any expendable rocket when considering comparable lift-capacity.

Not so, see my point above.

However let's assume that this is the case. I'm not sure where you get the "double the fuel load" from. There are several factors you haven't taken into account.

Firstly lets compare the amount of power and therefore fuel needed to get this craft 10 feet into the air compared with getting it from 10 feet in the air back on the ground. It will require considerably less for the latter than the former. Why? Well at lift off the vehicle is fully fuelled at landing it is virtually empty so it has considerably more mass at lift off. Factor in the fact that this is the first stage only and at lift off the engines have to lift not only the fully fuelled Grasshopper but a fully fuelled second stage and the payload. It should already be clear that it takes far less fuel to land the vehicle than to launch it.

Then there is another factor, air drag. This is the enemy at launch, requiring extra power to overcome air resistance. However when slowing the rocket for landing drag slows the vehicle down, which is exactly what you want, once again reducing the fuel you actual need to land.

While there are obvious cost-saving in other materials, and machinery, I don't expect that will be offset by the huge increase in costs of fuel and the required construction of much larger lift vehicles.

As I said before this is not how it will work. The Falcon 9 and Falcon Heavy will be the same size and use the same amount of fuel with a reusable first stage as with out it but will have smaller payloads.

In order to make the Falcon 9 reusable and return to the launch site, extra propellant and landing gear must be carried on the first stage. This necessitates a reduction of about 30 percent to the maximum payload to orbit when compared to the expendable Falcon 9

source: wikipedia

So the question is, will recovering the first stage reduce the costs by 30% Well SpaceX obviously thinks so. The first stage is the single largest component of a launch vehicle. A Falcon 9 uses 10 Merlin 1D engines, 9 of them or on the first stage. The Falcon Heavy will use 3 of the first stage units at lift off and so that is 27 engines which will be recovered and reused.

It is worth noting that once the first stage is regularly recovered SpaceX plan to develop a recoverable second stage, although that will be a more complex issue as that will involve re-entry and heat shielding.

[Waspie_Dwarf]

Thanks for the additional info, Waspie. I can see where the assumptions I made might have led me astray

Hi Leonardo, sorry for the post coming after yours, I wasn't intending to put the boot in, I was already in the middle of writing it and it seemed a shame to waste it.

although I still have reservations regarding the reliability of the approach. I'm glad they are experimenting in the hope of achieving their projected goal, but am skeptical they will achieve it.

I think the advantage they have is that they are modifying existing technologies rather than building something new and complex. The only real modifications are the landing legs and software.

SpaceX are taking a steady, incremental approach to re-usability. The Falcon 9 already works. The engines can already be re-lit in flight. The Grasshopper has now made 8 successful flights proving that the first stage can be landed vertically and that the software works. SpaceX now just have to show they can control the first stage after separation, slow it sufficiently and bring it back to the launch site.

I believe that there approach is far more likely to work than many of the radical new ideas being considered simply because it uses tried and tested hardware.

If it doesn't work then it won't bankrupt SpaceX, they will simply have a successful non-reusable launcher.

[highdesert50]

I am not an MechEng, so perhaps I am missing the obvious. But, wouldn't it be far less costly and simpler to use an enhanced parachute system. Or, perhaps parachute and some thrust e.g. JATO/RATO at near touchdown.

[Waspie_Dwarf]

I am not an MechEng, so perhaps I am missing the obvious. But, wouldn't it be far less costly and simpler to use an enhanced parachute system. Or, perhaps parachute and some thrust e.g. JATO/RATO at near touchdown.

Parachutes still add weight. The parachutes needed to lower the speed of a Falcon 9 v1.1 first stage which weighs over 25 tons would need to be massive and therefore heavy.

Unless you are planning to land at sea (like the shuttle SRBs) then you are still going to need to manoeuvre the vehicle at supersonic speed back over land, which requires engine thrust.

Parachute's alone could not land the vehicle in a horizontal position, it would hit the ground hard and topple over, so it would still need to use rocket motors to make a controlled landing. This would almost certainly require the parachutes to be jettisoned before the powered descent as there would be the risk of entanglement, this would require the addition of pyrotechnics.

In short parachutes are not needed and would simply add weight and complexity.

[Lex540]

Innovations distinguishes between a leader and a follower. nice job. "steve Jobs"