SpaceX Unveils Heavy-Lift Vehicle Plan
I don't agree.djolds1 wrote:Reusability does not equal low cost. If the Shuttle taught us anything, it should have taught us that.KitemanSA wrote:The important thing is cost/kg to orbit. Seems rapid turn-around reusability is the prime desire.
I think that the appropriate lesson to take away from STS is that reusability does not guarantee low cost. It all depends on the actual design.
Without all the hand-work replacing fragile tiles and rebuilding overstrained engines after each flight the STS costs would have dropped dramatically.
It's all in the design decisions and Shuttle should have never been treated as anything but an experimental vehicle.
On nasaspaceflight.com, I was involved in an exchange in which I wound up assuming (very generously, I thought) 10 GW out of a Polywell with a 1 m bore (remember, if you run the magnets near their critical field, power out increases as diameter decreases) and a 2.5 m diameter vacuum chamber (good luck fitting the conversion system in there without arcing). Fully shielded, it came out in the vicinity of 100 Mg. This reactor is not capable of powering a constant-Isp all-rocket VTOL SSTO; delta-V for zero structural mass peaks below 6 km/s at 600 seconds Isp.
But it would be awesome for an airbreathing spaceplane... too bad it's probably far too small to make sense...
But it would be awesome for an airbreathing spaceplane... too bad it's probably far too small to make sense...
That's the same argument for why True Communism actually works - it just hasn't been done right yet.zapkitty wrote:I don't agree.djolds1 wrote:Reusability does not equal low cost. If the Shuttle taught us anything, it should have taught us that.KitemanSA wrote:The important thing is cost/kg to orbit. Seems rapid turn-around reusability is the prime desire.
I think that the appropriate lesson to take away from STS is that reusability does not guarantee low cost. It all depends on the actual design.
Remanufacturing, which is basically as expensive as just building a new throwaway one-off, if not moreso as systems optimized for modular retrieval and reassembly have inherent structural weaknesses or expensive over-engineering versus a unitary one-off disposable unit.zapkitty wrote:Without all the hand-work replacing fragile tiles and rebuilding overstrained engines after each flight the STS costs would have dropped dramatically.
Vae Victis
If it's rocket-propelled then not at the anemic power ranges 93143 was aiming for with his concept...Betruger wrote:So no joy on flying CVs?
For my HLV based on the Martin Marietta air-augmented design I'm thinking more along the lines of 2 10-meter containment structures @ ~300 GW apiece
But for your airborne CVs you'd be using some form of props or turbines, ducted fans or whatever... assuming you didn't want the carriers for LEO ops
... and that's much more efficient than rocket propulsion. Some crude math using the engine output vs lifted weight of the Mi-26 cargo copter gives about 34 GW to lift a Nimitz-class carrier.
So four of 93143's 10 GW modules is more like it for your flying CV and that would leave you about 6 GW to run the carrier on... better carry two more 10 GW modules for backup and to give you ample power for weapons.
So, yeah.... flying carriers is easy with polywells
Er... no...djolds1 wrote:That's the same argument for why True Communism actually works - it just hasn't been done right yet.zapkitty wrote:I don't agree.djolds1 wrote:Reusability does not equal low cost. If the Shuttle taught us anything, it should have taught us that.
I think that the appropriate lesson to take away from STS is that reusability does not guarantee low cost. It all depends on the actual design.
... we're assuming that the argument for or against RLVs is not a religious assertion or a political doctrine, right?...
... I know, I know... that very concept is heresy...
... the "True Communism" argument always suffers from a lack of methods to actually make pure communism work... and for good reason... but saying an RLV hasn't been done right yet would be more akin to the Wright Brothers saying that powered flight hadn't been done right yet.
They had their reasons and their experiments and their math and eventually they made it work.
The shuttle costs were vastly inflated by politically-oriented decisions to garner funding and cargo for flights. The oversized cargo bay and the oversized wings, segmented solids instead of monolithics... the list is substantial. These led to the choice of the tiles amidst glad-handing that they could take the stress.
And the engines... can't really place much blame there once their size was determined by the shuttle's size... if you have to run the engines within a hair's breadth of their tolerances just to get to orbit then they're simply not going to last that long without overhauls.
But still, without the bloat brought on by political chicanery, "contractmandering" and bad faith by said-same contractors aggravated by the NASA admin... the original NASA concepts for the shuttle would have been far more reusable and much cheaper.
.... er... why do you think I pointed it out and argued against it?djolds1 wrote:Remanufacturing, which is basically as expensive as just building a new throwaway one-off...zapkitty wrote:Without all the hand-work replacing fragile tiles and rebuilding overstrained engines after each flight the STS costs would have dropped dramatically.
The metal TPS for the original shuttle designs just wouldn't have had the problems the tiles did, and a lighter shuttle would have had smaller engines and would have been able to not run those engines to death at every launch... which would have greatly extended their life between overhauls.
So the shuttle experience is neither an argument for or against reusability... because despite the original intentions of the project actual reusability took a back seat to politics and funding... even though the funding was largely obtained through promises of reusability.
Did anybody the watch the New Space Video posted here a few weeks ago? Steve Howe – Director, Center for Space Nuclear Research
was there talking about their new and improved NTR design that uses Tungsten based fuel. This fuel allows much higher temperatures and therefore much higher exhaust velocities. It should have an ISP of at least 950, probably even above 1000.
On SpaceX heavy lift design: I am a fan of SpaceX and I think that they have achieved amazing things, but I think that a heavy lifter like that is a waste of money. I would much rather see them build a fast turnarround RLV.
The argument that "the Shuttle prooved that RLV is not cheap" is flawed on so many points, I dont even know where to start.
1. The Shuttle was a failed design in about every aspect. To many people had their say in its design and it had to do to many things at once. It had to be a crew launcher, a heavy lifter, a space station. It also had to have a huge crossrange so the military could do their black ops with it. Of course they never did as many then, as they claimed. It was not very save and therefore never had a high flightrate
2. The Shuttle is not a real RLV. It is more a "partially refurbishable" launch system. Pretty much everything has to be taken apart inbetween launches and then serviced and put together again. The tank is completely lost too. The whole pre- launch process is ridiculously complicated and expensive. No, the shuttle is not an RLV.
So that argument is bollocks.
was there talking about their new and improved NTR design that uses Tungsten based fuel. This fuel allows much higher temperatures and therefore much higher exhaust velocities. It should have an ISP of at least 950, probably even above 1000.
On SpaceX heavy lift design: I am a fan of SpaceX and I think that they have achieved amazing things, but I think that a heavy lifter like that is a waste of money. I would much rather see them build a fast turnarround RLV.
The argument that "the Shuttle prooved that RLV is not cheap" is flawed on so many points, I dont even know where to start.
1. The Shuttle was a failed design in about every aspect. To many people had their say in its design and it had to do to many things at once. It had to be a crew launcher, a heavy lifter, a space station. It also had to have a huge crossrange so the military could do their black ops with it. Of course they never did as many then, as they claimed. It was not very save and therefore never had a high flightrate
2. The Shuttle is not a real RLV. It is more a "partially refurbishable" launch system. Pretty much everything has to be taken apart inbetween launches and then serviced and put together again. The tank is completely lost too. The whole pre- launch process is ridiculously complicated and expensive. No, the shuttle is not an RLV.
So that argument is bollocks.
Concur. Indeed, I think of it as a "rebuildable" launch system. But if you have to tear the thing down to its components and rebuild it every time, how does this save over just building a new one? We need a rapid turn-around, REUSABLE launch vehicle analgous to an airliner. That would be cheaper than any ELV.Skipjack wrote: 2. The Shuttle is not a real RLV. It is more a "partially refurbishable" launch system.
Ok, I will admit that there MAY be some circumstance where a single use ELV might be the only way to go (Footfall comes to mind). But such circumstances are hopefully never to come.
Cool page from P&W: http://www.pwrengineering.com/data.htm
Musk emphasized in a recent interview with SpaceVidcast that "the SpaceX heavy lift slides shown at the recent propulsion conference are just rough concepts and not part of any grand long term plan."
So I guess he is just putting it out there that SpaceX has a strategy for heavy lift, if NASA or someone else wanted them to do it (and would pay for it).
So I guess he is just putting it out there that SpaceX has a strategy for heavy lift, if NASA or someone else wanted them to do it (and would pay for it).
Nah, the nose shock wave will get eaten up by the intakes. That makes the intake outer edge where the leading shock wave will be, and the trailing shock wave will be at the tail. With a distance between the two of less than 140 ft, it will have a smaller shock wave than the Concorde, however on launch, it shock wave will be straight up so nobody on the ground will feel it. The vehicle on reentry with large empty internal fuel tanks will have a very very low surface loading so it will lose most of its velocity at a very high altitude, it will likely be subsonic around the time it passes through 100,000 ft on its return flight.KitemanSA wrote:Air augmented side (downhil) of an augmented aeroplug combined rocket/ramjet engine? Note the different size rocket engines on either side too. Just a guess.DeltaV wrote:Why the asymmetrical design for the Martin Marrietta air-breathing SSTO Nova R10R-2?
Boy, that'll rattle a few windows when it passes supersonic!
