sgt_flyer

Well, one of the main issues you'll get with parachutes, is their inherent lack of precision landing (the parachutes' canopies making a huge drag surface for sideway winds - so it's almost impossible to make pinpoint landings with those. (Unless it's a steerable design - but are controllable through gliding, which'll give you horizontal velocity, so it's not suitable for landing on legs. Mixing engine / fin steering with parachutes assist would prove to be quite unreliable - you only need a small random change in wind pushing the canopies away to overcome the rocket's other steering capabilities. Besides, waters at sea are rarely calm so an inflatable system would need to be able to cover everyhting on the booster to prevent salt water from getting in. (And if a tall thing like a booster would topple due to heavy seas, the booster would likely be very damaged with it's top impacting water at these kind of speeds (rocket boosters are not meant to handle much sideways forces) Afterwards, a small emergency drogue chute (which could be cut before landing) could eventually help recover from bad boosters angles - but you'll need to cut it away after it's done it's job, to prevent it from interferring with the landing / postlanding. (Though if the rocket is moving with a bad angle, a drogue / parachute could easily fail to deploy because the relative winds force it back into it's housing) Other methods for reusable stage with pinpoint landings would be to use winged flyback boosters- But those winged boosters came with lots of tradeoffs : you need to include landing gears, eventually jet engines, wings and the support structures to resist to both vertical and horizontal forces, giving you a stage with a quite bad dry weight. There are researches on those systems anyway - old Energia II uragan concept would have used zenith rockets fitted with deployable wings as side boosters, current Angara could be using Baikal boosters (provided they get them out of concept / mockup phases) And from the US, there's the Starbooster concept. Now, spaceX worked a lot to give their falcon 9 the lowest possible dry weight - so all those kind of heavy equipments would be almost out of question - ok they have to keep additional fuel + lox for the flyback phase - but winged flyback style also has to keep fuel to run the jet engines they need to get back home (in addition to the dry weight created by having to haul such engines) So, the spaceX system is quite a good call - with the added benefit of allowing you to be able to launch heavier payloads with the same rocket (but they don't recover the stage) without any hardware difference (rockets with winged style booster would also need to design standard expendable boosters to achieve the same versatility)

Well, barring scifi like breakthroughs, i guess a space elevator would end up being the most efficient way to get into orbit, from various bodies

Well, if the grid fins were stuck in a bad angle, not sure that the rocket could have made the touchdown fully upright to begin with (not accounting winds, which could easily push on the top of the empty rocket stage - the engines are heavy, but create drag, while the top is a lightweight rounded surface - with sidewinds and non working grid fins, the rocket could have started to topple before touchdown anyway.

Well, that's the media for you 'a rocket crashed onto a barge' is going to be much more catchy than 'the rocket accomplished it's main objective flawlessly' Else, given the size of the barge (the figures i found gives it approx 90x40meters), so if the engine exhaust hit the containers instead of the X, i'd say around 40m off the mark (though, if the steering grid fins were stuck in a bad position, the rocket could have been in a bad angle before crashing)

i think the landing precision is not in question - they stated the rocket ran out of hydraulic fluid to drive the grid fins before the landing - so the rocket could not steer itself during the landing attempt. they'll have 50% more hydraulic fluid for the next attempt (especially as all minor trajectory corrections will happen in the last minutes of the flight - the grid fins are put to heavy use during these last few moments)

I've seen it at least once before in one of spaceX livestreams

Do you plan to add a 'reaction' from The controllers if you buzz the tower ?

Mmh, other news channels speaks about AirAsia flight QZ8501 Contact seems to have been lost at 07h24 local time (it was due to arrive at 08h30 local time) The pilot requested ATC for a change of course and climbing to 38000 feets to avoid the bad weather. The plane is an airbus A320-200 Statement made about 155 passengers on board, + 2 pilots and 5 cabin crew 1 Singapore 1 Malaysia 1 France 3 South Korean 156 Indonesia http://www.airlinereporter.com/2014/12/breaking-air-asia-a320-missing-indonesian-airspace/ Edit : nationalities numbers update

One of the problems with this kind of launch, is that you'll be limited to launches to specific orbital angles (you won't be able to do a polar launch for example, because you need to stay lined up with your landing strip.) Returning the thing by barge would be costly and lenghty (most reusable designs can only achieve rentability by having a high turnaround rate, so you'll almost be faster to partially refuel the first stage and launch it back to it's starting point. Nevertheless, you'll have to maintain several additionnal landing zones in other countries to be able to cover various launch angles (which would veery expensive - having classic 'airports' prepped for the shuttle's emergency transoceanic abort mode on each flight was already costly , you'll have to add to that a full logistic chain if you plan to do it on each launch) You'll also need a correct weather on both ends at each launch. Besides, the SSME's would be severely underperforming for this kind of mission : They are built to sustain a very long burn in near vaccuum conditions (which is not the kind of conditions experienced by a first stage - so you'll have to make new nozzles adapted for it.) And they don't have that mich thrust at sea level, compared to other LH2/LOX engines (so you'll need SRB's anyway) The 3 SSME's, with their 1860kN of thrust at sea level each, would have a TWR < 1 if they where trying to only lift a fully fuelled external tank (625 tons) - without any upper stage or orbiter (For comparison, a single RS-68A has more than 3000kN of thrust at sea level for a delta-IV rocket) So, for your kind of first stage, i think it would be easier to start directly from a delta-IV rocket 1st stage and make it reusable instead of starting from the Space Shuttle subsystems Now, if your first stage has a similar size and shape to a space shuttle, maybe you'll be able to use boeing's shuttle carrier plane to transport it

For 'maple seed' rotation, there have been several experiments on that for reentry capsules. http://www.wired.com/2012/10/nasa-capsule-helicopter-hybrid/ That's called autorotation and it's a known and practiced helicopter emergency landing technique in case of engine failure (Basically, they let the blades pick up speed (and store cinetic energy) with a specific blade angle of attack (which already limits the descent rate), then change the blades AOA to generate lift from the stored cinetic energy just before landing, flare the helicopter to kill forward velocity, stabilize and land with no power (Though the added complexity and pilots training is a bit complex, it would allow a much more controlled a softer landing than parachutes.)

maybe try to avoid the additional complexity of centrifuges : simply 'deploy' the hab module from the space ship atop of a truss or a cable, with a counterweight made of other spacecraft systems the other way, and make the whole spacecraft spin on itself. (so no need of bearings, and no need to spacebuild a huge circular structure) the only thing to address in these cases is how to maintain the antenna's alignement towards earth

Depends if i have a replica of a real rocket with it's launch pad or not For soyuz style, i release the stock clamps + decouple the launch arms (which 'holds' the whole counterweight system for physics load), so the rocket 'holds' herself. then, from throttle at zero, stage the engines and increase throttle (which makes a nice cinematic launch as the rocket's boosters weight leaves the arms, which are pulled away by their counterweights) For ariane V style, i first start the main engine (and throttle up to full thrust), then activate the SRBs and release the clamps

the only homemade reverse hybrid rocket engine concept i've seen used compacted ammonium nitrate protected by a thin plastified nitrocellulose layer (to prevent water from ruining the ammonium nitrate - the nitrocellulose will completely combust with almost no residue during ignition) with LPG as fuel. - though he didn't gave much more informations beside that. here you use KNO3, so i don't know if simply compacting the KNO3 together like he did with ammonium nitrate would be enough.

I thought teflon above 350° Decomposes and the byproducts were toxic ? Not the kind of stuff you'll want to work with in amateur rocketry. (Can cause the deaths of animals at least)

http://cs.astrium.eads.net/sp/spacecraft-propulsion/bipropellant-thrusters/220n-atv-thrusters.html The ATV uses 4x490N engines as main propulsion, and 28x200N engines for RCS manoeuvers. All of those are hypergolic bipropellant pressure fed engines Edit : quick note though - Orion's service module will have a different layout of engines than the ATV. It'll have an array of 8x490N engines (the same as those 4x490N on the ATV) which are planned to be clustered around a refurbished Space shuttle AJ10-190 27kN OMS engine. (The 8x490N engines are there as a backup) and 24x200N RCS engines. Orion SM shares technology with ATV's SM (solar panels, onboard electronics, etc) and will be built by ESA, but they are not the same. http://www.spaceflight101.com/orion-spacecraft-overview.html

Ok, for sure, it'll depend to how much you can invest in amateur rocketry - regarding oxygen, maybe look with diving gear stores - the initial tank buying can be expensive for sure, but the refills will not be that much. (That, or oxy-fuel welding equipments (not acetylene ones, those are expensive) Of course, if you want to do that on long term, once you have a bottle, you'll need an industrial oxygen concentrator to do your refills yourself.

Well, some questions, is what you want to accomplish with it (launch an actual hybrid rocket, or only use a ground testbed to further refine your knowledge on how this kind of engine works) Then, you asked about using a solid oxidizer and a liquid fuel - are there some technical reasons for that ? Or would you also be ready to use solid fuel and liquid oxidizer ? In this case, this guy here http://makezine.com/2012/10/11/homemade-hybrid-rocket-engine/ built an homemade hybrid rocket engine using plexiglas as a solid fuel and oxigen as oxydizer. - of course, in this ground test, he uses external means to feed oxydizer to the engine - and the engine was not meant for running more than a few seconds. In any case, any kind of pyrotechnics can be dangerous - (i know one guy who lost his hand with fireworks) so always assume the worse can happen and prepare for it (and then add another safety margin on your precautions for good measures)

Well, they use lifting body techniques with the cone shape, which would be disturbed by other shapes. (Basically, they still have their numbers from apollo, no need to remake the wheel ) The apollo capsule had an offset gravity center, so the heat shield was not perpendicular to the reentry vector. This offset during reentry allowed the capsule to steer it's course during reentry, simply by making the air 'bouncing' off the shield at an angle. (Which allows for a much wider reentry corridor, if you come in too steep, turn the capsule to deflect air downwards - in return the capsule goes upwards. On the other end, if you came in too flat and risks bouncing out of atmo, turn the capsule so the heat shield deflects the air upwards. This also allows to fine tune the final landing spot.) The specific cone shape allows for a bigger 'range' of deflection than a soyuz bell shape would be able to. (However, keep in mind that soyuz is primarily made for leo operations, with much slower reentry speeds (and easier to predict reentry angles), whereas apollo / orion is meant for moon / interplanetary returns (so this extra amount of body lift could be useful - without having to expose anything else than the heat shield)

I'm sorry, i can't let you do that

Well, regarding the 2nd stage (EPC), they still change various things about how the fuel tanks will be built (ariane V used a common bulkhead design, Ariane 6 EPC will not use a common bulkhead anymore - worse dry mass, but more economic to build) For the 3rd stage, the expander cycle vinci engine has yet to fly once. (The ariane 5 ECA Cryotechnic upper stage use a gas generator cycle) that's quite an evolution for EU, because they never used this kind of cycles in their engines. Also, the original vinci engine project would have used an extendable nozzle in order to shorten the interstage - they decided to directly use a fixed long nozzle again to make the engine more economic to produce - at the expanse of the added weight of the longer interstage. At least, the vinci engine will be restartable. (In contrast with the current ESC-A which is not restartable) In the end, it's really a whole new rocket (Though the Ariane 5 midlife evolution would have changed quite a lot too - the vinci based upperstage, + upgraded SRBs (the vega serves as a test bed for the technology needed for those SRB upgrades - the carbon composite SRB casing used in the P80 + it's nozzle simplifications, they wanted to make a multisegment version of it to replace ariane V EAPs)) Still, i'm eager to see how will perform those carbon composite casings (at least, EU takes no risks in wanting to use only single segment P120s for ariane 6, both economically and security wise:)) Guess we'll have to wait for ATK dark knights to see huge multisegment SRBs with composite casings

Regarding the kind of components Ariane 6 will use - the SRBs will be based onto a similar technology than the vega rocket first stage - which uses a carbon fiber composite casing instead of Ariane 5's Steel casing SRBs. (Though, those will be single segment (the single segment p80 has 2103 kN of thrust for 109s of burn time 7.3 tons of dry mass , vs 2 and a (short) half segment EAPs 7080kN for 140s of burn time, 33 tons of dry mass) So, what do you think about these composite casings for SRBs ? (Which kinda makes sense, especially as the current EAPs are recovered but not reused) Besides, i think ATK will look with interest at how it devellops, given it's dark knight SRBs for SLS will also use composite casings.

Yes, it looks quite the same, but ariane 6 will be bigger (The proposed arianne 6 with two boosters would have more payload to GTO than H-IIa with 4 boosters) At least, on the video link you gave, the upper stage will be restartable (which is a huuuge plus over current ariane V non restartable upper stage)

Well, lets see how much spaceX 'reusability' lowers launch costs - because that'll only lower the price of the rocket itself - on the other end, as hardware costs go down, they'll increase ground crew costs by a substantial margin too. (That, plus the need of a fast turnaround to keep the usefulness of reusability) Besides, only the partially reusable falcon 9 heavy would be able to compete with Ariane 6 payload capability. and it will be a truly complex piece of hardware - and the non reusable falcon 9 heavy has not even flown once yet. (The non reusable falcon 9 1.1 has a payload of 5 tons to GTO - while ariane 5 had problems with that, as they had orders for putting 6 tons satellites to GTO (so they had to find 'lighter' satellites also going to GTO to pair them with the heavier satellites) - so Falcon 9 1.1 already can't compete on this market) Sometimes, you can't split up the payload into several lighter ones so launch costs per kg is only a part of the equation

Seems the current proposed version would use a 4.6m EPC (5.46m for ariane V) Which should still be using a vulcain 2 engine (or a revision of this engine for the new rocket) The planned vinci engine for the second stage would be using a fixed nozzle (they don't want an extensible nozzle anymore to save on building costs) - the length of the nozzle + the fact that it will be a LH2-lox upper stage will make a really tall upper stage. For the SRB's, it seems they will try to use the same SRBs as the one used for Vega's first stage. (Or at least, an evolution of it both rockets would use) The actual SRB on Vega, the P80, is a single segment SRB, which is derived from Ariane V multisegment SRBs. The ariane 64 version would have a 11t payload to GTO, and the 62 6.5t. So a quite conservative evolution in the end - to try to reuse as much of the reliable existing systems as they can and sharing components across various rockets to limit devellopment and production costs. Let's see how it will end up

Hehe yeh, hydrogen dioxide (HO2) would end up being an incomplete molecule (it would be missing one electronic pairing) the complete molecule is hydrogen peroxide (H2O2) - at the temperatures and pressures of a NTR, having peroxyde inside it would quickly make a boom (as we already can't heat peroxyde to boiling point at 1 ATM without it going boom)