VentureStar is it possible now

RobertDyck · 2016-04-18 21:52:27

Well, depends what you're talking about. Is this a SSTO shuttle, with nuclear engines? If so, the orbiter can land on it's own wheels with engines attached.

Is this for an ITV? That's "Interplanetary Transit Vehicle", term from NASA's Design Reference Mission aka Mars Semi-Direct. ITV is a deep space habitat with propulsion stage. If that's the case, I would suggest leaving it in orbit. Propellant could be transferred on-orbit to refill the tank(s), or a new tank attached. Russia already has a working propellant coupling. Progress transfers UDMH and N2O4 with every flight. European ATV did too, using the same Soyuz docking hatch with propellant coupling. Are you thinking LH2? That changes things. For example neoprene rubber is usually used for "O" rings; don't know if Russia's coupler uses one, but rubber gets brittle at LH2 temperature.

However, you just suggesting using STS to recover an engine module. Sounds like the design ULA proposed.

I have one issue with this info-graphic. It says "Helicopter Acquisition, Trailing Line Engagement". They do realize helicopter blades have down-wash? That's why helicopter recovery is done with a hook on a long line dangled from the helicopter. That hook used to grab the parachute/parafoil. Their little hand-drawn graphic looks like they intend to grab a line on the helicopter belly. Rotor down-wash will blow any such line away, preventing capture. Do they want to recover the parafoil undamaged? Then the trailing line will have to be designed for capture by a hook dangled far enough under the helicopter that down-wash is disperse.

Last edited by RobertDyck (2016-04-19 14:25:47)

Tom Kalbfus · 2016-04-18 23:18:39

RobertDyck wrote:

Hubble Space Telescope was designed to be re-captured by Shuttle and brought down for periodic maintenance. The reason it wasn't was fear the government would never authorize re-launching if it was ever brought down. Same with your reusable nuclear engine.

Nuclear physics requires a certain minimum critical mass to get the reactor to start. That results in more fissionable material than is necessary for one trip to Mars and back. It could easily have enough material for 10 round trips. However, propellant is the issue. You could build a spacecraft with a reusable TMI/TEI engine, and refillable propellant tank. It may be easier to just replace the whole tank. Russia currently transfers propellant to ISS.
But this thread was supposed to be about a reusable SSTO, not interplanetary.

Why would you want one? If we already have a reusable bottom stage, all you need then would be a reusable top stage to place on top of it. With a reusable bottom stage and a reusable top stage, you have a reusable vehicle. Why would you want to sacrifice payload to transport unnecessary structural mass into orbit and then bring it down again? Those bottom stage rockets are heavy. Anyway with just one vehicle, you are again limited on what sort of payload you can bring to orbit and to which orbit you can bring it too. With reusable stages, you select the stage which best suits the mission. Bottom stages can come in different sizes, the engineering in them isn't as extreme, so you can design conservatively. The bottom stage doesn't have to reach orbit all by itself, and neither does the top stage, a greater fraction of each stage would be payload, and the top stage doesn't have to haul the enormous engines of the bottom stage into orbit like the Shuttle had to.

Antius · 2016-04-19 04:29:57

Tom Kalbfus wrote:

RobertDyck wrote:
Hubble Space Telescope was designed to be re-captured by Shuttle and brought down for periodic maintenance. The reason it wasn't was fear the government would never authorize re-launching if it was ever brought down. Same with your reusable nuclear engine.
Nuclear physics requires a certain minimum critical mass to get the reactor to start. That results in more fissionable material than is necessary for one trip to Mars and back. It could easily have enough material for 10 round trips. However, propellant is the issue. You could build a spacecraft with a reusable TMI/TEI engine, and refillable propellant tank. It may be easier to just replace the whole tank. Russia currently transfers propellant to ISS.
But this thread was supposed to be about a reusable SSTO, not interplanetary.
Why would you want one? If we already have a reusable bottom stage, all you need then would be a reusable top stage to place on top of it. With a reusable bottom stage and a reusable top stage, you have a reusable vehicle. Why would you want to sacrifice payload to transport unnecessary structural mass into orbit and then bring it down again? Those bottom stage rockets are heavy. Anyway with just one vehicle, you are again limited on what sort of payload you can bring to orbit and to which orbit you can bring it too. With reusable stages, you select the stage which best suits the mission. Bottom stages can come in different sizes, the engineering in them isn't as extreme, so you can design conservatively. The bottom stage doesn't have to reach orbit all by itself, and neither does the top stage, a greater fraction of each stage would be payload, and the top stage doesn't have to haul the enormous engines of the bottom stage into orbit like the Shuttle had to.

Does seem that whenever we have a discussion on the feasibility of SSTO the conclusion we invariably arrive at is that TSTO is better all round. The technology is more practicable and affordable and the payload mass as a fraction of take-off mass is always greater. The bottom line is that launch vehicles are not like aeroplanes. Getting into space can effectively be divided into two phases - booster phase, which involves pushing above the atmosphere and gaining enough kinetic energy to reach orbital height and orbital injection phase, which involves building up orbital velocity. The design requirements of the two phases are best served by a two stage vehicle with the lower stage serving as booster and the upper stage used to build orbital velocity. With a reusable SSTO we are effectively forcing one stage to serve both functions and to carry all the weight needed for both.

RobertDyck · 2016-04-19 04:46:26

Antius wrote:

Does seem that whenever we have a discussion on the feasibility of SSTO the conclusion we invariably arrive at is that TSTO is better all round.

No, there are just people who don't want to believe anything new can be done. To quote a sit-com called "Married With Children": "You are what you were." That is all you will ever be is what you were. Obviously that sit-com did not seriously believe in this, it was criticism of those who give advice.

Dan Golden said NASA can't operate as long as spacecraft drop off major chunks during flight. To be truly practical, he needs a spacecraft that can be operated as an aircraft.

SpaceNut started this thread when I pointed out VentureStar would have worked. We have the technology, just not the will. Corporate executives at Lockheed-Martin wanted to gouge NASA just the same as they did with Shuttle. Part of VentureStar's mandate was to ensure they wouldn't. That's what killed it, not anything technical.

Tom Kalbfus · 2016-04-19 07:38:53

You have one stage that works, it would be much easier to build something reusable that goes on top of it, rather than a complete SSTO.

Antius · 2016-04-19 08:37:22

RobertDyck wrote:

Antius wrote:
Does seem that whenever we have a discussion on the feasibility of SSTO the conclusion we invariably arrive at is that TSTO is better all round.
No, there are just people who don't want to believe anything new can be done. To quote a sit-com called "Married With Children": "You are what you were." That is all you will ever be is what you were. Obviously that sit-com did not seriously believe in this, it was criticism of those who give advice.
Dan Golden said NASA can't operate as long as spacecraft drop off major chunks during flight. To be truly practical, he needs a spacecraft that can be operated as an aircraft.
SpaceNut started this thread when I pointed out VentureStar would have worked. We have the technology, just not the will. Corporate executives at Lockheed-Martin wanted to gouge NASA just the same as they did with Shuttle. Part of VentureStar's mandate was to ensure they wouldn't. That's what killed it, not anything technical.

I'm not saying its not possible, I'm saying its not desirable.

For it to work, non-fuel mass fractions have to be razor thin - basically structure and payload cannot be more than about 8% of take-off mass. That means high pressure pump-fed engines, ultra-lightweight tapered fuel tanks, slim safety factors, sub-systems that weigh very little. And this isn't good for a vehicle that has to survive severe thermal gradients and structural stresses. The amount of engineering that needs to go into the vehicle jumps significantly. That means high capital and operating costs, whether it's reusable or not. And those costs are averaged over relatively small payload fractions, which are smaller precisely because you are carrying a lot of unneccesary booster-stage weight over the second launch phase.

RobertDyck · 2016-04-19 10:29:06

Antius, what you described applies to every launch vehicle. Period. Without all that, a launch vehicle will never get off the ground, will never lift its own weight. So don't claim it applies to just this or that thing that you want to argue against.

Today a Boeing 787 Dreamliner has an estimated cost of US$224.6 million each. Typical capacity is 242 passengers depending on seating configuration. That's full, no empty seats. Work that out per passenger. If you fly just once then throw the vehicle away, how could you ever afford to operate an airline. That is what reusable craft are about.

No one has yet built a fully reusable TSTO. It was the initial design for Shuttle, requirements laid down in 1968. But wasn't built. There are people who claim even that couldn't be built. It's basically older technology than Shuttle, I'll let you argue which parts are how old. Yes some people claim it would never work. Their argument is the one from the sad sit-com: "You are what you were."

SSTO was supposed to reduce operating cost. It was supposed to be something actually new. Remember, TSTO is 1968 technology.

kbd512 · 2016-04-19 12:59:08

Rob,

I think you're missing Antius' point. Thus far nobody has built a SSTO because the payload fraction is pitiful and the structural mass has to be so low that the materials to fabricate such a structure simply didn't exist at the time STS was in development. Every attempt has failed thus far and every one of those projects had substantially overran its budget before cancellation. It's not technically impossible, but it is a first order multi-discipline engineering problem with meager returns.

Elon Musk hit the nail on the head when he stated why he'd given up on air launch. The primary problem is speed. The StratoLaunch vehicle can climb to 60K ft, but the "second stage" is released at a low subsonic velocity and then that stage has to accelerate the payload an additional 17,000 mph.

My personal belief is that the solution is a LOX / RP1 fueled X wing lifting body that uses in-flight refueling at 60K from another vehicle so the vehicle can remain reasonably sized. Obviously LOX / LH2 are NASA's favorite propellants, but vehicles using those fuels require structures so large that the drag, aerodynamic heating, and dynamic loads are at or near the limits of what the best materials available can withstand. If the lifting body doesn't require separate tankage for the turbofans and rocket motors and doesn't have to take off fully fueled, then the vehicle can be more reasonably sized for a given payload mass and still attain orbit.

Tom Kalbfus · 2016-04-19 13:02:02

Antius wrote:

RobertDyck wrote:
Antius wrote:
Does seem that whenever we have a discussion on the feasibility of SSTO the conclusion we invariably arrive at is that TSTO is better all round.
No, there are just people who don't want to believe anything new can be done. To quote a sit-com called "Married With Children": "You are what you were." That is all you will ever be is what you were. Obviously that sit-com did not seriously believe in this, it was criticism of those who give advice.
Dan Golden said NASA can't operate as long as spacecraft drop off major chunks during flight. To be truly practical, he needs a spacecraft that can be operated as an aircraft.
SpaceNut started this thread when I pointed out VentureStar would have worked. We have the technology, just not the will. Corporate executives at Lockheed-Martin wanted to gouge NASA just the same as they did with Shuttle. Part of VentureStar's mandate was to ensure they wouldn't. That's what killed it, not anything technical.
I'm not saying its not possible, I'm saying its not desirable.
For it to work, non-fuel mass fractions have to be razor thin - basically structure and payload cannot be more than about 8% of take-off mass. That means high pressure pump-fed engines, ultra-lightweight tapered fuel tanks, slim safety factors, sub-systems that weigh very little. And this isn't good for a vehicle that has to survive severe thermal gradients and structural stresses. The amount of engineering that needs to go into the vehicle jumps significantly. That means high capital and operating costs, whether it's reusable or not. And those costs are averaged over relatively small payload fractions, which are smaller precisely because you are carrying a lot of unneccesary booster-stage weight over the second launch phase.

Much easier to put a reusable booster underneath it, that way the mass fuel fraction of the vehicle can be lower, and it can haul more cargo into orbit., and both parts can then return to Earth and be reused. Reusability even if the vehicle splits in two is more desirable than getting it all in one stage, and also its an easier feat to accomplish, we can get out in space sooner, while a SSTO that is not ready yet, can't do anything! Frankly I would have been surprised if the Venture Star worked as promised and revolutionized space travel allowing airliner like prices and space hotels.

I think the space hotels would come sooner it we tried something easier to get into space, and with the revenue coming from launch services from reusable two stage vehicles, we can fund and attract additional investor dollars to develop an SSTO, because now the public can see that it would be possible, if we have an example of something that is reusable that already is profitable, the rest is just about lowering costs and increasing profit margins. Because NASA right now does not make a profit, it is not a self-funding space program. I think SpaceX potentially could be.

If we can get the launch costs down low enough, we could colonize Mars and the Moon for profit! No need to go to Congress other than to pass the necessary legislation to allow space companies to be profitable and capitalize on space assets and resources! The great thing about Mars is that is can be strip mined and developed without the EPA getting in the way, same goes for the Moon, if we did the same with Antarctica, there would be screaming and hollering from all sorts of environmental lobbies, even though very little actually lives there compared to most other places on Earth.

Tom Kalbfus · 2016-04-19 13:08:44

RobertDyck wrote:

Antius, what you described applies to every launch vehicle. Period. Without all that, a launch vehicle will never get off the ground, will never lift its own weight. So don't claim it applies to just this or that thing that you want to argue against.
Today a Boeing 787 Dreamliner has an estimated cost of US$224.6 million each. Typical capacity is 242 passengers depending on seating configuration. That's full, no empty seats. Work that out per passenger. If you fly just once then throw the vehicle away, how could you ever afford to operate an airline. That is what reusable craft are about.
No one has yet built a fully reusable TSTO. It was the initial design for Shuttle, requirements laid down in 1968. But wasn't built. There are people who claim even that couldn't be built. It's basically older technology than Shuttle, I'll let you argue which parts are how old. Yes some people claim it would never work. Their argument is the one from the sad sit-com: "You are what you were."
SSTO was supposed to reduce operating cost. It was supposed to be something actually new. Remember, TSTO is 1968 technology.

We have this

And we have this.
All we have to do is find a way to put these two pieces together, I mean marrying the technology together of both of these vehicles to produce a two stage to orbit reusable vehicle. There are a lot of technologies that when into Shuttle development that can be used to develop a reusable upper stage for the reusable lower stage falcon rocket. The bottom stage lands, the upper stage glides to a runway landing. Now imagine that both parts can be put back together and be launched one more time. Is that so hard to imagine?

Oh that reminds me ever hear of DynaSoar?

Imagine a rocket that looks like this, except that the bottom stages are reusable falcon rockets. Such as the Falcon Heavy for instance.

Lets put an updated "DynaSoar" on top of a Falcon Heavy rocket like this one. Does this sound like a great idea to you?

Last edited by Tom Kalbfus (2016-04-19 13:14:13)

RobertDyck · 2016-04-19 13:17:18

kbd512,

I did get his point, but you're not getting mine. Those issues are true of absolutely *EVERY* launch vehicle development. They aren't unique to VentureStar. Materials necessary weren't available at the time of development of Shuttle (aka STS), but were at the time of development of VentureStar.

Contractors like Boeing and Lockheed-Martin have been accused of deliberately causing cost overruns to increase their profit, so NASA included a clause in the contract that said the contractor had to share the cost of any overrun. And at the time many felt Lockheed-Martin should never have been given the contract for VentureStar, because they were the ones responsible for the mushrooming cost of Shuttle. You can debate whether that was true, but that was the belief at the time. So when Lockheed-Martin bid on the contract, NASA management had to cover their ass by putting a very firm clause in the contract to ensure they didn't cause a cost overrun again. But then a composite tank for X-33 was sent to garbage. Lockheed-Martin said it was an accident, but some people were suspicious. NASA had carefully tested all technologies for VentureStar on other vehicles before X-33, and X-33 was a 1/4 scale model. Then Lockheed-Martin made a last minute change to the tank, the only untested technology, and hanger test of that tank proved it didn't work. Management at Lockheed-Martin declared this to be an overrun, so wanted NASA to pay for it. NASA management activated the clause in the contract that said Lockheed-Martin had to share that cost, but Lockheed-Martin had no intention to comply.

That's what killed it. Not anything technical. All the technical arguments are simply CYA!

I'm not married to VentureStar, but I'm saying if they stuck to the original design, it would have worked. VentureStar was supposed to be successor to Shuttle. If it was built, we would have had a working vehicle right now. And VentureStar was one design for a fully reusable launch vehicle.

RobertDyck · 2016-04-19 13:23:50

Tom Kalbfus wrote:

Lets put an updated "DynaSoar" on top of a Falcon Heavy rocket like this one. Does this sound like a great idea to you?

It's called DreamChaser.
However, Falcon upper stage isn't reusable.

Tom Kalbfus · 2016-04-19 13:29:11

RobertDyck wrote:

Tom Kalbfus wrote:
Lets put an updated "DynaSoar" on top of a Falcon Heavy rocket like this one. Does this sound like a great idea to you?
It's called DreamChaser.
However, Falcon upper stage isn't reusable.

Doesn't look too hard to recover. If the shuttle portion can be recovered and the three bottom rockets can be recovered. What if we simply expanded the orbiter to swallow the middle stage? That would be a much easier feat than a fully reusable one stage rocket to orbit.

Last edited by Tom Kalbfus (2016-04-19 13:29:33)

RobertDyck · 2016-04-19 13:38:02

Ok. But now try to get funding to do that. NASA has become risk averse, and all money is sucked by SLS and Orion. I like SLS, but not Orion. Bottom line is they don't have money for that. And SpaceX has their own plans. It would take some lobbying to get funding to launch DreamChaser on Atlas V. Hopefully that will happen. Would like to see it launch on Falcon, for exactly the reason you stated, but current plans are Atlas V.

Tom Kalbfus · 2016-04-19 15:43:51

RobertDyck wrote:

Ok. But now try to get funding to do that. NASA has become risk averse, and all money is sucked by SLS and Orion. I like SLS, but not Orion. Bottom line is they don't have money for that. And SpaceX has their own plans. It would take some lobbying to get funding to launch DreamChaser on Atlas V. Hopefully that will happen. Would like to see it launch on Falcon, for exactly the reason you stated, but current plans are Atlas V.

Can they recover Atlas V stages? or are they depending on government funding and the whims of Congress?
Government funding has its limits, otherwise we would have people on Mars by now, and also there is the requirement of pork-barreling jobs to all the districts of the various influential congressmen and Senators, and that's going to cost extra! The formula becomes, "how many jobs does it take to get Congressman X to vote yes on approval for the funding, as a contractor, you don't really care, so long as your bottom line gets take care of, but the thing is, if space travel stays expensive, then a space colony is never going to get off the ground, because it will always be hundreds of billions of dollars, and congressmen don't care whether hundreds of billions of dollars is spent on space in their districts or on building bridges in their districts. So you have a funding competition between space and other things which always leaves your space funding vulnerable, as the pie is limited, and investments in space doesn't make it grow.

This was the vision that proponents of the space shuttle put forward in the 1970s, so how many billions of dollars did it take to make that vision a reality and take this picture? Imagine if we could send this picture back in time to the Early 1970s, and we sold them on that this is what the space shuttle can do, isn't it great? What story doesn't this picture tell? The hideous expense of the thing, the space station isn't a private thing, but a multi-billion dollar pork barrel project by a government that doesn't care about how much it costs, only that it has won the upper hand over other ways to spend hundreds of billions of dollars temporarily and so became a reality, not because of the Shuttle but in spite of it! What we need is a vehicle that will make it profitable to build space stations in orbit, something the shuttle was supposed to do, but never did!

Last edited by Tom Kalbfus (2016-04-19 15:55:03)

RobertDyck · 2016-04-19 16:55:41

If you want to do would-a could-a should-a, then I would have preferred what NASA actually proposed. Shuttle was supposed to be fully reusable TSTO, with lifting body orbiter, 7 astronauts plus 11 metric tonnes of supplies. Cargo hold was for supplies only, not nearly as long or as wide. They planned to separate cargo from crew, using Saturn 1B for bulk cargo, or whatever came after. Plans for ISS were 2 Skylab workshops launched wet, plus air lock and multiple docking adapter each launched with a manned Apollo mission. Total 4 launches of Saturn 1B, each of which cost less than a single Shuttle launch. And 6 months from first launch to US core complete. Continue Apollo to the Moon; they built Saturn V and Apollo spacecraft for Apollo 18, 19, and 20. When Shuttle was under construction, there was debate of a Skylab reboost module launched on Saturn 1B. But NASA management at the time wanted to focus on Shuttle, so they focused everything on Shuttle with the hope it would fly soon enough to save Skylab.

Apollo CM was smaller and lighter than Orion. It would be better for Mars. There were plans for an Apollo with 4 seats and PICA heat shield for Mars.

SpaceNut · 2016-04-19 18:40:10

The "DynaSoar" aka modern version Dream chaser rides atop of an Atlas V to allow for human rating of the booster rocket but Atlas V will likely be phased out due to the cost and the Russian engine flap....over nothing....and be moved to the ULA's new rocket most likely....

Looking back at page 1 posted image I see why the mass fraction and payload become an issue with the cargo bay simular to shuttle which means that its a sealed area which adds mass to isolate it from the fuel tanks walls....and since the tanks are still part of the plane as it reaches towards orbit they become a mass penaly for final orbital speed....

Tom Kalbfus · 2016-04-19 20:10:30

The difference is, the wings are useless until the ship needs to land. With a falcon, the same engines which send the ship into space are also used to land the stage. You do need to set aside fuel for landing, but atmospheric resistance does most of the work in slowing down the ship. The ship reaches terminal velocity, so the rocket engines need only slow down the stage from terminal velocity for a soft landing on the platform. Landings take much less fuel than reaching orbit!

SpaceNut · 2016-04-19 21:08:44

Actually there is a fuel allotment set aside to land the first stage of the Space X rocket.. its 40%...

Capsule for Space x is currently not a re-useable

RobertDyck · 2016-04-19 21:11:22

It's absolutely amazing that SpaceX got it to work. Definitely a new development, something that could never have been done in the 20th century. But don't exaggerate; a descent shuttle uses a lifting body, not wings.

kbd512 · 2016-04-19 21:39:08

RobertDyck wrote:

kbd512,
I did get his point, but you're not getting mine. Those issues are true of absolutely *EVERY* launch vehicle development. They aren't unique to VentureStar. Materials necessary weren't available at the time of development of Shuttle (aka STS), but were at the time of development of VentureStar.

Not quite. The materials that the prototype was made of, when scaled out, would not have provided the lift capability the LM was contractually obligated to provide. As a result, someone at LM decided to try using composite tanks. The sub-scale test articles to prove that the composite tanks could withstand the structural loads applied to them and adequately contend with the environment created by the LH2 worked, but LM had a hell of a time making that work. When the tech was scaled up to the sizes required of the X-33 demonstrator, IIRC they had three successive pressure test failures. In other words, while it may have been possible to fabricate really small LH2 tanks, the technology wasn't there to fabricate larger LH2 tanks.

RobertDyck wrote:

Contractors like Boeing and Lockheed-Martin have been accused of deliberately causing cost overruns to increase their profit, so NASA included a clause in the contract that said the contractor had to share the cost of any overrun. And at the time many felt Lockheed-Martin should never have been given the contract for VentureStar, because they were the ones responsible for the mushrooming cost of Shuttle. You can debate whether that was true, but that was the belief at the time. So when Lockheed-Martin bid on the contract, NASA management had to cover their ass by putting a very firm clause in the contract to ensure they didn't cause a cost overrun again. But then a composite tank for X-33 was sent to garbage. Lockheed-Martin said it was an accident, but some people were suspicious. NASA had carefully tested all technologies for VentureStar on other vehicles before X-33, and X-33 was a 1/4 scale model. Then Lockheed-Martin made a last minute change to the tank, the only untested technology, and hanger test of that tank proved it didn't work. Management at Lockheed-Martin declared this to be an overrun, so wanted NASA to pay for it. NASA management activated the clause in the contract that said Lockheed-Martin had to share that cost, but Lockheed-Martin had no intention to comply.

Those evil corporations are out to make money and give people jobs! Oh, the horror! And NASA continues to let cost plus contracts. And Congress continues to wonder at why there are cost overruns.

As long as our government continues to contract with them, they will happily continue taking the American taxpayers to the cleaners. If ever someone wised up, there'd be a lot of moaning and groaning as the gravy train ground to a halt.

RobertDyck wrote:

That's what killed it. Not anything technical. All the technical arguments are simply CYA!

Actually, VentureStar would not have provided the lift capability that it was contractually obligated to provide. It died over a money argument, but wouldn't have worked even if money was no object. There were two options. Sacrifice payload or improve the state-of-the-art. LM wanted to try the latter. It didn't work. LM didn't want to keep paying for obscenely expensive test articles.

RobertDyck wrote:

I'm not married to VentureStar, but I'm saying if they stuck to the original design, it would have worked. VentureStar was supposed to be successor to Shuttle. If it was built, we would have had a working vehicle right now. And VentureStar was one design for a fully reusable launch vehicle.

I'm saying they could've stuck with the original design if we wanted a working SSTO, but it would not have provided the desired lift capability. The composites weren't used just because engineers were bored. NASA provided a spec that the mature materials technology of the time could not meet.

Tom Kalbfus · 2016-04-19 21:59:03

SpaceNut wrote:

Actually there is a fuel allotment set aside to land the first stage of the Space X rocket.. its 40%...
Capsule for Space x is currently not a re-useable

What about the Orion? Is that reusable? For the amount of money NASA is spending on it, it should be!

Tom Kalbfus · 2016-04-19 22:02:37

RobertDyck wrote:

It's absolutely amazing that SpaceX got it to work. Definitely a new development, something that could never have been done in the 20th century. But don't exaggerate; a descent shuttle uses a lifting body, not wings.

It just so happens that the shape which uses the least structural mass for a given volume is a sphere. If you make it a cylinder, as most rockets are, you use more structural mass for that given volume, if you use a lifting body, you need even more structural mass than you would need for the cylinder. It you tail-land a rocket, you can keep its cylinder shape, thus saving mass that would otherwise go towards its lifting body.

kbd512 · 2016-04-19 22:24:19

Tom Kalbfus wrote:

RobertDyck wrote:
It's absolutely amazing that SpaceX got it to work. Definitely a new development, something that could never have been done in the 20th century. But don't exaggerate; a descent shuttle uses a lifting body, not wings.
It just so happens that the shape which uses the least structural mass for a given volume is a sphere. If you make it a cylinder, as most rockets are, you use more structural mass for that given volume, if you use a lifting body, you need even more structural mass than you would need for the cylinder. It you tail-land a rocket, you can keep its cylinder shape, thus saving mass that would otherwise go towards its lifting body.

Here on Earth shape plays a significant role in drag and spheres create a lot of drag. Aerodynamic lift, which does necessarily produce drag, requires less fuel consumption to lift a heavier-than-air object of a given mass in comparison to pure thrust. As SpaceNut pointed out, you need quite a bit of fuel to land a rocket using pure thrust and drag. A HTHL lifting body can be refueled in-flight. A rocket can't, at least not yet.

As I have stated before, short load the fuel for takeoff, refuel in-flight, and use the rocket motors to produce the velocity required to take the vehicle to orbit. Transferring RP-1 should be no different than transferring JP-8. No insanely large cryogenic gas cans and no requirement to carry every last drop of fuel required to attain orbit on liftoff / takeoff.

Antius · 2016-04-20 05:41:25

If you air-to-air refuel at 40,000 feet, you shave about 0.5km/s off of your delta-V. That doesn't sound like much. On the plus side, if that 0.5km/s had to be provided by rocket thrust from ground level without refuel, both engine efficiency and propulsive efficiency would be low, due to the need to operate engines at 1 bar and the simple fact that the rocket is accelerating from zero. So inflight refuelling might make the difference between an SSTO that is workable and one that is not. Even with that advantage, it would be difficult to sacrifice the need for LOX/H2 fuel if you wanted to achieve a vehicle with a half decent payload ratio. A compromise might be to top up with LOX only, which is much easier to transfer than LH2.

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#26 2016-04-18 21:52:27

Re: VentureStar is it possible now

#27 2016-04-18 23:18:39

Re: VentureStar is it possible now

#28 2016-04-19 04:29:57

Re: VentureStar is it possible now

#29 2016-04-19 04:46:26

Re: VentureStar is it possible now

#30 2016-04-19 07:38:53

Re: VentureStar is it possible now

#31 2016-04-19 08:37:22

Re: VentureStar is it possible now

#32 2016-04-19 10:29:06

Re: VentureStar is it possible now

#33 2016-04-19 12:59:08

Re: VentureStar is it possible now

#34 2016-04-19 13:02:02

Re: VentureStar is it possible now

#35 2016-04-19 13:08:44

Re: VentureStar is it possible now

#36 2016-04-19 13:17:18

Re: VentureStar is it possible now

#37 2016-04-19 13:23:50

Re: VentureStar is it possible now

#38 2016-04-19 13:29:11

Re: VentureStar is it possible now

#39 2016-04-19 13:38:02

Re: VentureStar is it possible now

#40 2016-04-19 15:43:51

Re: VentureStar is it possible now

#41 2016-04-19 16:55:41

Re: VentureStar is it possible now

#42 2016-04-19 18:40:10

Re: VentureStar is it possible now

#43 2016-04-19 20:10:30

Re: VentureStar is it possible now

#44 2016-04-19 21:08:44

Re: VentureStar is it possible now

#45 2016-04-19 21:11:22

Re: VentureStar is it possible now

#46 2016-04-19 21:39:08

Re: VentureStar is it possible now

#47 2016-04-19 21:59:03

Re: VentureStar is it possible now

#48 2016-04-19 22:02:37

Re: VentureStar is it possible now

#49 2016-04-19 22:24:19

Re: VentureStar is it possible now

#50 2016-04-20 05:41:25

Re: VentureStar is it possible now

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