Author Topic: Why was there lots of research into space planes and or single-stage-to-orbit  (Read 35941 times)

Offline nec207

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Why was there lots of research into space planes and or single-stage-to-orbit (or SSTO ) in the 90's?

But we are not doing it today? Why is that?

There was lots and lots and lots of research into space planes and or single-stage-to-orbit (or SSTO ) in the 90's by NASA and the European space program than they all abandoned it? All the different X-programs and such just to name some.

In the 90's it was rage many different yes different concepts and ideas of different space planes and or single-stage-to-orbit.

Than they all abandoned it.

But we are not doing any research into space planes and or single-stage-to-orbit like in the 90's.

Some say money or political will support to get people back interested into NASA.

Going to the moon or mars sound better in public eye than doing  research into space planes and or single-stage-to-orbit (or SSTO ) :o :o :o

Or that space planes and or single-stage-to-orbit was more costly than using rocket with two to three stages with space capsule.

I know the space shuttle was bad idea and cost them more money in long term than using a rocket with two to three stages with space capsule.



Online Robotbeat

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Because it sucked up all the money just to build the suborbital prototype which didn't work. Lots of reasons why it didn't work, only a few of them are technical.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline ChrisWilson68

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nec207, have you considered the idea that abandoning space planes and single-stage-to-orbit was the right decision?  Perhaps not forever, but for the near future it seems there are better places to make investments.

Right now, with our current technology, single-stage-to-orbit is a bad idea.  The margins are slim enough with two-stage-to-orbit.  Staging has some disadvantages, but single-stage-to-orbit has much worse disadvantages.

That's not likely to change without some fundamental technological breakthrough, such as a high-Isp engine.

With space planes, the trade-offs are less clear-cut.  Boeing and SpaceX, the two winners of commercial crew contracts, both chose capsules over space planes.  And NASA chose a capsule for Orion.  So, there's some evidence capsules are the better choice.

Offline JamesG123

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There was very little money (relatively) spent on the various SSTO and USSP projects.  At the time, no it wasn't really practical.  But then we didn't really try that hard.   Those that achieved any kind of success (Delta Clipper) were quickly squashed by the politically powerful STS and "big rockets" lobby in NASA, the USAF, and Congress.

Lots of books and web info about it.

Won't be done today because it would be "expensive".  There isn't the money available to develop a parallel advanced lift architecture when the traditional model, with its entrenched interests, is sucking all of the money away.  The Government wants big expendable rockets, and that is what Government gets.
« Last Edit: 11/17/2015 03:57 am by JamesG123 »

Offline ChrisWilson68

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There was very little money (relatively) spent on the various SSTO and USSP projects. All of them that actually made it past the paper stage approached the problem(s) with the contemporary technology/materials. Not much was spend on new tech.  At the time, no it wasn't really practical.  But then we didn't really try that hard.

When limited resources are available, they should be spent on the most promising paths forward.  Single-stage-to-orbit is very clearly not the most promising path if you want to actually accomplish the most in space over the next several decades.

Those that achieved any kind of success (Delta Clipper) were quickly squashed by the politically powerful STS and "big rockets" lobby in NASA, the USAF, and Congress.

Lots of books and web info about it.

Delta Clipper didn't really show any way forward to a practical single-stage-to-orbit system.  There were plenty of reasons not to move forward with it that have nothing to do with political pressure.

Offline JamesG123

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That is the party line...

Offline ChrisWilson68

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That is the party line...

I'm not part of any party.  I'm not just saying it because I just blindly believe what I'm told.  I'm saying it because there's a lot of evidence it's true.

Offline pathfinder_01

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Why was there lots of research into space planes and or single-stage-to-orbit (or SSTO ) in the 90's?

But we are not doing it today? Why is that?

Budget cuts and an over emphasis on space(i.e. The forgotten A) in NASA. In the 80ies and 90ies NASA still had X-Planes and all sorts of experimental aircraft. That part of NASA has all but been forgoten in recent years.


Quote
There was lots and lots and lots of research into space planes and or single-stage-to-orbit (or SSTO ) in the 90's by NASA and the European space program than they all abandoned it? All the different X-programs and such just to name some.


In the 90's it was rage many different yes different concepts and ideas of different space planes and or single-stage-to-orbit.

Than they all abandoned it.

But we are not doing any research into space planes and or single-stage-to-orbit like in the 90's.

Some say money or political will support to get people back interested into NASA.

Going to the moon or mars
sound better in public eye than doing  research into space planes and or single-stage-to-orbit (or SSTO ) :o :o :o


Not really. Mars was off the table during the Clinton administration due to the way the space exploration initiative bombed in the press for Bush. It was the but of jokes. Congress riduculed it. It made Saturday Night live. It was DOA.

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Or that space planes and or single-stage-to-orbit was more costly than using rocket with two to three stages with space capsule.

Not really. The was no way an capsule would have been developed in the 90ies. It would have been seen as inferior and disposable.

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I know the space shuttle was bad idea and cost them more money in long term than using a rocket with two to three stages with space capsule.

Replacing the shuttle after Challenger was not going to happen. Having spent so much money developing the shuttle there was no will to spend more money on another manned spacecraft. Frankly if not for Columbia, the shuttle would still be flying today.

Offline A_M_Swallow

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There was very little money (relatively) spent on the various SSTO and USSP projects.  At the time, no it wasn't really practical.  But then we didn't really try that hard.   Those that achieved any kind of success (Delta Clipper) were quickly squashed by the politically powerful STS and "big rockets" lobby in NASA, the USAF, and Congress.

Lots of books and web info about it.

Won't be done today because it would be "expensive".  There isn't the money available to develop a parallel advanced lift architecture when the traditional model, with its entrenched interests, is sucking all of the money away.  The Government wants big expendable rockets, and that is what Government gets.

NASA is currently organising the development of Orion, Dragon, CST-100, Blue Origin and Dream Chaser with associated launch vehicles. More Earth to orbit systems are not needed.

However SSTO landers for the Moon and Mars that are also able to ascend could be very useful.

Offline nec207

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nec207, have you considered the idea that abandoning space planes and single-stage-to-orbit was the right decision?  Perhaps not forever, but for the near future it seems there are better places to make investments.

Right now, with our current technology, single-stage-to-orbit is a bad idea.  The margins are slim enough with two-stage-to-orbit.  Staging has some disadvantages, but single-stage-to-orbit has much worse disadvantages.

That's not likely to change without some fundamental technological breakthrough, such as a high-Isp engine.

With space planes, the trade-offs are less clear-cut.  Boeing and SpaceX, the two winners of commercial crew contracts, both chose capsules over space planes.  And NASA chose a capsule for Orion.  So, there's some evidence capsules are the better choice.

What technological breakthrough is needed to make space planes and or single-stage-to-orbit (or SSTO possible? What  major problem holding back space planes and or single-stage-to-orbit?

Offline nec207

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There was very little money (relatively) spent on the various SSTO and USSP projects. All of them that actually made it past the paper stage approached the problem(s) with the contemporary technology/materials. Not much was spend on new tech.  At the time, no it wasn't really practical.  But then we didn't really try that hard.

When limited resources are available, they should be spent on the most promising paths forward.  Single-stage-to-orbit is very clearly not the most promising path if you want to actually accomplish the most in space over the next several decades.

Those that achieved any kind of success (Delta Clipper) were quickly squashed by the politically powerful STS and "big rockets" lobby in NASA, the USAF, and Congress.

Lots of books and web info about it.

Delta Clipper didn't really show any way forward to a practical single-stage-to-orbit system.  There were plenty of reasons not to move forward with it that have nothing to do with political pressure.

I think the problem was more political than an engineering problem that came into be here. In the 80's and 90's NASA had no plans going to moon or Mars. And so the main goal was on reusable craft and cost issue. Those goals got changed where main goal now is to go to the Moon and Mars. And going to Moon or Mars in space planes and or single-stage-to-orbit would be headache so gone with some thing they know best.

Today there no NASA goal for reusable craft or craft that lower space cost. NASA goal today is we don't care about cost that just get people to moon or Mars ASAP.

Now when we send people to moon and Mars 4 to 8 times people are going to lobby congress it to costly than they will cut all programs like they done before in the past. Well than NASA goal changed and say may be we should look into reusable craft because going to moon and Mars is too costly.

To some think is done to NASA look forward every 10 years the goal changing.

Now with media and news the range is going to Mars and to lesser the moon. And wants we been there done that the hype will be over. And will be back to doing LEO's again.

 

Offline nec207

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There was very little money (relatively) spent on the various SSTO and USSP projects.  At the time, no it wasn't really practical.  But then we didn't really try that hard.   Those that achieved any kind of success (Delta Clipper) were quickly squashed by the politically powerful STS and "big rockets" lobby in NASA, the USAF, and Congress.

Lots of books and web info about it.

Won't be done today because it would be "expensive".  There isn't the money available to develop a parallel advanced lift architecture when the traditional model, with its entrenched interests, is sucking all of the money away.  The Government wants big expendable rockets, and that is what Government gets.

NASA does not care about cost.  What NASA does care about and goal is to send astronauts to moon, asteroid and other moons and mars and such to do scientific research and space probes and rovers every where.

JamesG123 I think the main problem is NASA has no goal of doing research into lowering space cost or colonization of space. That is the news media and press not doing proper job and the mass public misinterpreting that when they read NASA to send humans to go to moon and Mars it will not stop.

And there no way taxpayers are going to allow NASA to send people to moon and Mars costing billion dollars every year!! Well taxpayers may allow 4 to 8 trips tops to the moon and Mars but no more.

I think the problem is breakdown of communication of the media and press of hype over going to Mars will lead to colonization. And that is NOT NASA goal. Going to the moon and Mars and other moons and asteroid is pure scientific not colonization.

I think if the public really know what was going on people would be less media hype.

And when we get some Mars rock,water and soil samples there would be no political justification of people on Mars.

Offline john smith 19

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Why was there lots of research into space planes and or single-stage-to-orbit (or SSTO ) in the 90's?
Asked and answered numerous times. Search the site for details or read

"Facing the Heat Barrier" TA Heppelheimers excellent description of the time or

"Halfway to anywhere" by G. Harry Stine.

You make no distinction between "Spaceplanes" and SSTO. The original Shuttle concept was  a 2 stage "spaceplane" with both winged stages. Many people only think of vertical  SSTO but winged SSTO is a concept and gives much better margins if you can develop a suitable engine, but it's no use for landing on Mars as it needs a runway.
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But we are not doing it today? Why is that?
It is being done today. Search under Skylon, XCOR Lynx and Dream Chaser.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Ravenger

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What technological breakthrough is needed to make space planes and or single-stage-to-orbit (or SSTO possible? What  major problem holding back space planes and or single-stage-to-orbit?

Reaction Engines' Sabre air-breathing rocket engine is a good candidate, but there's a dedicated thread for that and the proposed SSTO Spaceplane Skylon on this forum. Well worth a read.

Reaction engines website here: http://www.reactionengines.co.uk/

Offline Jim

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Those that achieved any kind of success (Delta Clipper) were quickly squashed by the politically powerful STS and "big rockets" lobby in NASA, the USAF, and Congress.


BS.  Not true at all.  Let's stick with facts and not this nonsense

Offline Jim

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That is the party line...

No, it is the reality shared by the rest of us.

Offline pathfinder_01

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What technological breakthrough is needed to make space planes and or single-stage-to-orbit (or SSTO possible? What  major problem holding back space planes and or single-stage-to-orbit?

Two different questions a space plane does not need to be single stage to Orbit, see the Space Shuttle, X-37, Dream Chaser and SSTO does not need to be an space plane(however being some type of airplane could be helpful in terms of being capable of generating lift.)

SSTO is possible now, but the problem is SSTO while carrying a practical payload and most SSTO concepts require re usability. The issue is with materials. Mathematically it is possible to get to orbit using chemical rocket in an single stage. It is just that the materials we have to build the SSTO out of are too heavy to allow this concept to work with current technology but technology changes. Lighter weight structures and heat shields would allow this concept to work as well as engines like the sabre(which could allow you to get much higher and faster without using on board oxygen and can double as both an jet and rocket engine.).  We can build an SSTO now, but it won't be able to haul much into orbit and it won't be reusable. It simply would not be practical at the moment.

Space planes are better suited than capsules for certain things. The return to the capsule is being driven by different dynamics. For Orion and CST-100 reusing Apollo's shape saves research and development(esp. for Orion). For Space X, wings don't fit the company philosophy. For Dream Chaser "wings" allow much more selection of places to land as well as reduced G-forces on the crew.

In terms of BEO. Space planes could find an role as an mars mission as the earth reentry vehicle. There is debate on wither on not an the crew can survive the G-forces from that fast an reentry in an capsule. For lunar missions there was an interesting concept floated of using an version of dream chaser as an lunar craft or using the shuttle's cargo bay to haul up an capsule and crew and docking it with an pre-positioned stage launched by Titan in LEO.  While wings can be useless in space, they can be handy at the end of the mission.
« Last Edit: 11/17/2015 02:45 pm by pathfinder_01 »

Offline john smith 19

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Those that achieved any kind of success (Delta Clipper) were quickly squashed by the politically powerful STS and "big rockets" lobby in NASA, the USAF, and Congress.


BS.  Not true at all.  Let's stick with facts and not this nonsense
I would suggest neither view is quite fair.  Let's look at a few facts.

DC-X
$65m. Built a complete vehicle. Got to M3. Flew it 10s of times. Got demonstrated you could build a rocket powered with LH2/LO2 that could be turned around in (IIRC) 28 hrs without a)Removal of engines from the vehicle. b)Taking the engine apart once you'd done so. A feat believed impossible at the time. The DC-Y was planned to solve the materials problems and get to orbit.

X33
$1.1Bn. Planned X craft to show needed SSTO technology to deliver a commercial VTOHL SSTO. Consumed all it's NASA build budget and a fair chunk of it's testing budget. No complete airframe built. LM Pitched "A" team in bid, seemed to have employed "B" team on implementation. OTOH Ensured  LM's ELV business would not be threatened for decades.

X30/NASP
$1Bn. No complete airframe built. Consumed that much before study found the Principal Investigators proposal report was built on wrong numbers for the actual physical properties of the air, amongst other things.

I would also note the lobbying campaign by unknown lobbyists in Congress against DCX follow on programmes described in "Halfway to Anywhere."

Might I suggest the different outcomes reflect where the programmes came from.

DCX came from the now defunct Strategic Defense Initiative organization who needed something to deploy the large number of space based devices needed to support Regans "Start Wars" defense programme. The did not care how it got done, just that it got done. The did not demand the usual endless paperwork to do it either.  AS Jess Sponable (PM on it, and now PM for the XS1) commercial procurement was much cheaper than DoD rules.

X33 seems to have been captured within NASA by the "Let's get lots of new tech developed" arm. This is a very bad idea for an X plane project. It's competitors used the simplest approach possible to solve the problem. However the programme also had a requirement that the winner pitch their money into building the follow on vehicle if the prototype flew.  LM pitched the most. It didn't fly. They therefor committed (in reality) nothing while their competitors were more cautions (perhaps they expected to fly something ?) were prepared to commit less. I'm not sure if it suffered under NASA's BAU documentation requirements.

X30NASP. A USAF general wanted a capability and was given a huge budget to get it just when an ambitious PI showed up with a plan to achieve it. He did not look that gift horse in the mouth very hard. A fool and (someone else s ) money are easily parted.  :(
« Last Edit: 11/17/2015 04:05 pm by john smith 19 »
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Elmar Moelzer

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I always get a bit melancholic when I look at the famous painting of Gary Hudson's Phoenix SSTO. It was such an inspiring vision of the future of space transportation. Gary certainly believed in the feasibility of the concept (even with the state of technology back then)...

Offline HMXHMX

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I always get a bit melancholic when I look at the famous painting of Gary Hudson's Phoenix SSTO. It was such an inspiring vision of the future of space transportation. Gary certainly believed in the feasibility of the concept (even with the state of technology back then)...


And I still do, but the debate is no longer worth having on my part, far as I am concerned. 

All I'll say is that it is mass fraction, not Isp, that needs to be improved, and additionally, if one develops an SSTO and if falls short of expectations, it can be salvaged as an operational system by various expedients such as a zero-stage, air-launching, sled-launching, recoverable strap-ons, etc.  If you start your design process with a goal of two-stages, you'll never magically reach SSTO capability.  But if you start with an SSTO goal, you might get there by incremental improvements that come from learning due to higher flight rates with time.

Would that the human race could have evolved on a 0.9 G planet, so that these arguments might be moot.  :)

Offline Archibald

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Quote
All I'll say is that it is mass fraction, not Isp, that needs to be improved, and additionally, if one develops an SSTO and if falls short of expectations, it can be salvaged as an operational system by various expedients such as a zero-stage, air-launching, sled-launching, recoverable strap-ons, etc.  If you start your design process with a goal of two-stages, you'll never magically reach SSTO capability.  But if you start with an SSTO goal, you might get there by incremental improvements that come from learning due to higher flight rates with time.

Would that the human race could have evolved on a 0.9 G planet, so that these arguments might be moot.

Goddam big Earth with its huge gravity pull !!

How about suborbital refueling ?
http://selenianboondocks.com/2009/11/random-thoughtsorbital-access-methodologies-vii-air-launched-glideforward-tsto-with-exo-atmospheric-suborbital-refueling/

As John Goff said

Quote
I think the case of exoatmospheric suborbital refueling will likewise be one of those crazy things that we wonder how we ever lived without.
;D
Han shot first and Gwynne Shotwell !

Offline JasonAW3

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     Almost wish I could organize a superkickstarter to get billionaires to fund an independant research group to actually develope a working Lifting Body SSTO system.
My God!  It's full of universes!

Offline john smith 19

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All I'll say is that it is mass fraction, not Isp, that needs to be improved,
Careful  here. There is certainly true for vertical SSTO, where if the thrust does not exceed the lift it simply won't take off. I don't think the situation is so clear cut (or investigated) for horizontal takeoff.
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and additionally, if one develops an SSTO and if falls short of expectations, it can be salvaged as an operational system by various expedients such as a zero-stage, air-launching, sled-launching, recoverable strap-ons, etc.
Absolutely true.
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If you start your design process with a goal of two-stages, you'll never magically reach SSTO capability.  But if you start with an SSTO goal, you might get there by incremental improvements that come from learning due to higher flight rates with time.
Definitely.
Quote
Would that the human race could have evolved on a 0.9 G planet, so that these arguments might be moot.  :)
IE where 1g is about 8.83m/s^2
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline NovaSilisko

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I'm just thankful we didn't evolve on a planet with 25% more gravity. We'd be, in short, quite screwed.

I do agree Earth has too much, though. We should do something about it.
« Last Edit: 11/17/2015 06:43 pm by NovaSilisko »

Offline A_M_Swallow

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{snip}
Would that the human race could have evolved on a 0.9 G planet, so that these arguments might be moot.  :)

There is a 0.376 g planet ready and waiting.

Offline Proponent

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Was there any particular factor that lead to the resurgence of interest in SSTO in the mid-1990s?  I'm guessing it was just a desire to take a second crack at cheap Earth-to-orbit transportation, after the failure of the Shuttle.  But was there some other trigger that I'm missing?

Offline JamesG123

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Was there any particular factor that lead to the resurgence of interest in SSTO in the mid-1990s?  I'm guessing it was just a desire to take a second crack at cheap Earth-to-orbit transportation, after the failure of the Shuttle.  But was there some other trigger that I'm missing?

There was money available. The Reagan/Bush Administrations were interested in new space ideas (SDI, New Frontiers),  and Congress was willing to cough up some (but not enough) money.

Offline rayleighscatter

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X33 seems to have been captured within NASA by the "Let's get lots of new tech developed" arm. This is a very bad idea for an X plane project.
It's the very intent of the X programs though. With a few rare exceptions, research is the main intent, not a sustaining program.

Offline HMXHMX

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Was there any particular factor that lead to the resurgence of interest in SSTO in the mid-1990s?  I'm guessing it was just a desire to take a second crack at cheap Earth-to-orbit transportation, after the failure of the Shuttle.  But was there some other trigger that I'm missing?

Yeah, I am afraid I was the factor (for rocket-powered SSTO, not NASP).  I convinced Max Hunter, and together we convinced Jerry Pournelle and Danny Graham, and they convinced the Vice President, and one thing led to another... :(

Max used to tell me it was easy to start a riot but hard to control it once started.  Man, was he ever right.
« Last Edit: 11/17/2015 11:21 pm by HMXHMX »

Offline HMXHMX

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{snip}
Would that the human race could have evolved on a 0.9 G planet, so that these arguments might be moot.  :)

There is a 0.376 g planet ready and waiting.

That we perhaps can't live on (in my view) due specifically to the lower gravity.  But that's the subject of a different forum posting, which generated more heat than light...so best stay away from it here!

Online Robotbeat

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A lot of that "heat" was my fault.

HMXHMX, what are you up to? BTW, do you have a nice summary document of DC-Y/DC-X or any of the other high-mass-fraction vehicles you worked on?
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline edkyle99

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Why was there lots of research into space planes and or single-stage-to-orbit (or SSTO ) in the 90's?

But we are not doing it today? Why is that?
Because it costs far less to develop smaller, lighter, more capable expendable launch vehicles.

 - Ed Kyle

Offline Vultur

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I think SSTO is entirely achievable with current technology - the Mercury Atlas was dang close in the early 60s, and its engines had unimpressive Isp and TWR by modern standards.

A propane/LOX (probably the best compromise between density and Isp - it's only a tiny bit less Isp than methane with much greater density) VTVL SSTO would probably work fine and not even be much of a stretch.

Offline HMXHMX

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A lot of that "heat" was my fault.

HMXHMX, what are you up to? BTW, do you have a nice summary document of DC-Y/DC-X or any of the other high-mass-fraction vehicles you worked on?

Unfortunately, as usual, I can't comment on my current work except to say it isn't SSTO.  Close, though.  But in response to the document request, I can only offer up an ancient paper:

http://www.spacefuture.com/archive/history_of_the_phoenix_vtol_ssto_and_recent_developments_in_single_stage_launch_systems.shtml

Note especially the appendix:

http://www.spacefuture.com/archive/a_single_stage_to_orbit_thought_experiment.shtml

I probably should finish up the book draft I started around 1992 (Single Stage: The 30 Year Quest for the Reusable Spaceship).  It's only half done since I put it on the shelf about 1993 or so, and I have no idea if I'll ever re-write it, since now it needs to be renamed "...The 60 Year Quest..."  :)

Offline john smith 19

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X33 seems to have been captured within NASA by the "Let's get lots of new tech developed" arm. This is a very bad idea for an X plane project.
It's the very intent of the X programs though. With a few rare exceptions, research is the main intent, not a sustaining program.
Yes and no.

Successful X programmes have a very small (typically 1) goal. X1 was "Exceed M1 in level flight" to the X15 "Cruise at high enough Mach for long enough that the whole airframe "soaks" and we can see how it changes" (not the wording, but the key idea). Then use that data to populate the design handbooks for the next generation of vehicles.

Successful X programmes did this with the simplest possible approach. The simplest way to exceed M1? Stick a big rocket in back. Otherwise you're stuck with not only a tough task (which should be why your running one in the first place) but the need for a lot of additional stuff to a)Work and b)Work at the performance level needed for vehicle.

This multiplies the risk of failure.
X33 supposed goal was to demonstrate SSTO but it also needed

The lifting body shape to work (ultimately never tried in a crewed vehicle before the Dream Chase prototype flew) .
The complex shaped LH2 composite tank (although it turned out an aluminum tank with the same mass either was available or was within the design capability of the team)
The linear plug nozzle engine, when no plug nozzle of any description had flown and which get a major redesign during the programme, making the vehicle even more rear heavy, and hence complex to control, like the Shuttle.
The (lightweight) metallic TPS.

LM would say all of this was essential to making SSTO but neither of the other thought so. It was however all very exciting technology and if it all worked together the design would have been a triumph. And it all needed to work as you could not replace most of the major parts without a huge redesign of the rest.

But none of it worked (or got to the stage it could be tested) to where a flight vehicle was flown.

The only thing that worked perfectly about LM's bid was their ability to win it in the first place.  :(
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Elmar Moelzer

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Unfortunately, as usual, I can't comment on my current work except to say it isn't SSTO.  Close, though. 
Oh, I cant wait to hear what that is! Glad to hear that you are back in action, Gary!

Offline Nilof

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One other approach that hasn't been mentioned yet is beamed power propulsion, which escape dynamics is working on. It is still at Robert Goddard levels of TRL and scale compared to chemical propulsion, but it is great to see someone finally taking on the task of maturing the technology to some extent and actually building hardware rather than present powerpoint slides. The key complete unknown here is what engine thrust to weight ratios are possible with such designs.
« Last Edit: 11/19/2015 07:59 pm by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline TrevorMonty

One other approach that hasn't been mentioned yet is beamed power propulsion, which escape dynamics is working on. It is still at Robert Goddard levels of TRL and scale compared to chemical propulsion, but it is great to see someone finally taking on the task of maturing the technology to some extent. The key complete unknown here is what engine thrust to weight ratios are possible with such designs.

The beamed power approach trades a large LV for large expensive ground facilities. I don't think it will work out financially but the idea has merit for lunar landers. The power could be beamed from Solar Power Satellite, which could also be used for beaming power to lunar facilities the other 99.99% of the time.

Offline NovaSilisko

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One other approach that hasn't been mentioned yet is beamed power propulsion, which escape dynamics is working on. It is still at Robert Goddard levels of TRL and scale compared to chemical propulsion, but it is great to see someone finally taking on the task of maturing the technology to some extent. The key complete unknown here is what engine thrust to weight ratios are possible with such designs.

Now you've got me wondering what it would have been like if Goddard had a website and blog.  ;)

Offline A_M_Swallow

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One other approach that hasn't been mentioned yet is beamed power propulsion, which escape dynamics is working on. It is still at Robert Goddard levels of TRL and scale compared to chemical propulsion, but it is great to see someone finally taking on the task of maturing the technology to some extent. The key complete unknown here is what engine thrust to weight ratios are possible with such designs.

The beamed power approach trades a large LV for large expensive ground facilities. I don't think it will work out financially but the idea has merit for lunar landers. The power could be beamed from Solar Power Satellite, which could also be used for beaming power to lunar facilities the other 99.99% of the time.

Different materials have different boiling points, specific heat capacity and latent heat of vaporization. Can lunar and Mars regolith be used as propellant in beamed power landers? Something that can just be scooped up and crushed makes for a cheap ISRU fuel.

Alternatively water and carbon dioxide could be used.

Offline Archibald

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A lot of that "heat" was my fault.

HMXHMX, what are you up to? BTW, do you have a nice summary document of DC-Y/DC-X or any of the other high-mass-fraction vehicles you worked on?

Unfortunately, as usual, I can't comment on my current work except to say it isn't SSTO.  Close, though.  But in response to the document request, I can only offer up an ancient paper:

http://www.spacefuture.com/archive/history_of_the_phoenix_vtol_ssto_and_recent_developments_in_single_stage_launch_systems.shtml

Note especially the appendix:

http://www.spacefuture.com/archive/a_single_stage_to_orbit_thought_experiment.shtml

I probably should finish up the book draft I started around 1992 (Single Stage: The 30 Year Quest for the Reusable Spaceship).  It's only half done since I put it on the shelf about 1993 or so, and I have no idea if I'll ever re-write it, since now it needs to be renamed "...The 60 Year Quest..."  :)


You never stopped since, what, the late 60's ? I wish you publish that book someday.
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Offline HMXHMX

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A lot of that "heat" was my fault.

HMXHMX, what are you up to? BTW, do you have a nice summary document of DC-Y/DC-X or any of the other high-mass-fraction vehicles you worked on?

Unfortunately, as usual, I can't comment on my current work except to say it isn't SSTO.  Close, though.  But in response to the document request, I can only offer up an ancient paper:

http://www.spacefuture.com/archive/history_of_the_phoenix_vtol_ssto_and_recent_developments_in_single_stage_launch_systems.shtml

Note especially the appendix:

http://www.spacefuture.com/archive/a_single_stage_to_orbit_thought_experiment.shtml

I probably should finish up the book draft I started around 1992 (Single Stage: The 30 Year Quest for the Reusable Spaceship).  It's only half done since I put it on the shelf about 1993 or so, and I have no idea if I'll ever re-write it, since now it needs to be renamed "...The 60 Year Quest..."  :)


You never stopped since, what, the late 60's ? I wish you publish that book someday.

Since 1969, yes.

Thanks for the vote, along with the four other people who want to read it, that makes five.  Now if I could just find 50,000 more.  :)

Someday.

Offline savuporo

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Single stage to orbit, or single stage to orbit AND back down again ? The latter is much harder.
Orion - the first and only manned not-too-deep-space craft

Offline Nilof

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One thing that is rather striking about beamed propulsion SSTO's is how ridiculously low their initial mass is for a given payload. This is particularly noticeable when considering launch assist options.

For example, the Stratolaunch carrier aircraft can only carry a rocket capable of putting 6 tonnes into orbit when restricted to solid fuel Pegasus variants. With an 800 Isp spacecraft, the possible payloads with the initial masses that the carrier craft can carry easily go up to 20+ tonnes. Popup stages get a similar size reduction.

EDIT: while I'm at it...
Since 1969, yes.

Thanks for the vote, along with the four other people who want to read it, that makes five. 
Make that 6 :)
...and 7.
« Last Edit: 11/19/2015 11:21 pm by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Elmar Moelzer

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Since 1969, yes.

Thanks for the vote, along with the four other people who want to read it, that makes five. 
Make that 6 :)


Offline Asteroza

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Fund an SSTO book through Patreon? I think you can rig it by number of participants rather than a deadline...

Offline jongoff

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As John Goff said

Quote
I think the case of exoatmospheric suborbital refueling will likewise be one of those crazy things that we wonder how we ever lived without.
;D

I'm not entirely sure how serious I was when I wrote that comment. There may have been some tongue-in-cheekage going on. Not that the idea is 100% stupid, just a bit crazy.

~Jon

Offline jongoff

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A lot of that "heat" was my fault.

HMXHMX, what are you up to? BTW, do you have a nice summary document of DC-Y/DC-X or any of the other high-mass-fraction vehicles you worked on?

Unfortunately, as usual, I can't comment on my current work except to say it isn't SSTO.  Close, though.  But in response to the document request, I can only offer up an ancient paper:

http://www.spacefuture.com/archive/history_of_the_phoenix_vtol_ssto_and_recent_developments_in_single_stage_launch_systems.shtml

Note especially the appendix:

http://www.spacefuture.com/archive/a_single_stage_to_orbit_thought_experiment.shtml

I probably should finish up the book draft I started around 1992 (Single Stage: The 30 Year Quest for the Reusable Spaceship).  It's only half done since I put it on the shelf about 1993 or so, and I have no idea if I'll ever re-write it, since now it needs to be renamed "...The 60 Year Quest..."  :)


You never stopped since, what, the late 60's ? I wish you publish that book someday.

Since 1969, yes.

Thanks for the vote, along with the four other people who want to read it, that makes five.  Now if I could just find 50,000 more.  :)

Someday.

Add me to the list, if I wasn't already one of the original four...  :-)

~Jon

Offline jongoff

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I personally think the conventional wisdom against SSTO RLVs is oversold. Technically speaking I think they're completely feasible, the tech necessary is high-enough TRL to be believable. We just haven't proven markets that need flight rates high enough for them to shine compared to expendable TSTOs yet.

~Jon

Offline john smith 19

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I personally think the conventional wisdom against SSTO RLVs is oversold. Technically speaking I think they're completely feasible, the tech necessary is high-enough TRL to be believable. We just haven't proven markets that need flight rates high enough for them to shine compared to expendable TSTOs yet.

~Jon
As people observed the pressure stabilized tank versions of Atlas were close and a launch of one of those with when they re-engined with a Russian engine as an an SSTO could have settled this a decade ago.

However the real problem with SSTO is that historically your payload goes down from about 3% of GTOW to 1% or less for the same GTOW.

When commercial investors plug those numbers into their cost models they immediately say "Build a TSTO instead."

So far only SABRESkylon has proposed an engine and vehicle architecture that can deliver the same payload fraction as a TSTO.

The thread title packs quite a lot in. I don't think the XCOR Lynx will qualify as SSTO but it's certainly a space plane.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Archibald

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As John Goff said

Quote
I think the case of exoatmospheric suborbital refueling will likewise be one of those crazy things that we wonder how we ever lived without.
;D

I'm not entirely sure how serious I was when I wrote that comment. There may have been some tongue-in-cheekage going on. Not that the idea is 100% stupid, just a bit crazy.

~Jon

Sorry, didn't wanted to embarass you in any way
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Offline spacetech

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I personally think the conventional wisdom against SSTO RLVs is oversold. Technically speaking I think they're completely feasible, the tech necessary is high-enough TRL to be believable. We just haven't proven markets that need flight rates high enough for them to shine compared to expendable TSTOs yet.

~Jon
IMHO You might be half right... half "wrong" on this one.

SSTO RLV seems like the holy grail of affordable spaceflight.. but isn't over 50% of the cost of most rockets is in the first stage? If SpaceX (or ULA) can get the first stage back, and reuse it, then the launch cost is reduced significantly.

What about a 1.5 stage-to-orbit spaceplane with boom refueling after take-off? SR-71 style... take off with half-tank, then refuel. Not exoatmospheric, but has benefits.

I asked an astronaut a related question;
Quote
Do you think there is a launch rate that makes spaceplanes (HTOL) more efficient than a F9/Dragon rocket and capsule? Not sure SpaceX could cycle SLC-39A in less than 24 hours.
And Dan Tani replied
Quote
To, me, it's not a launch rate function, but rather a cost to orbit function. Once the cost is right, the market will take care of the rate.
He's probably right... 

Offline john smith 19

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I asked an astronaut a related question;
Quote
Do you think there is a launch rate that makes spaceplanes (HTOL) more efficient than a F9/Dragon rocket and capsule? Not sure SpaceX could cycle SLC-39A in less than 24 hours.
And Dan Tani replied
Quote
To, me, it's not a launch rate function, but rather a cost to orbit function. Once the cost is right, the market will take care of the rate.
He's probably right...
In marketing terms that's "price elasticity" Historically the  demand has been very inelastic to price and the supplier prices have gone up, basically because governments have a need to launch payloads and that's not going to to away.

SX think once they get a reusable 1st stage their lowered costs will allow them to offer a capability Vs price that enough people will want that the market will grow despite the loss of capability IE You get say 50% of the expendable version for less than 50% of the expendable cost then your cost per lb has gone down. Otherwise you just bought 1/2 a payload for 1/2 the price, which is no improvement on pricing.

Time will tell the market is elastic at the price SX want to offer the F9SR, when it becomes available. Given the next F9 launch is currently showing an NET of December and FH NET than April 2016 this may be a while.  :(
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline kch

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What about a 1.5 stage-to-orbit spaceplane with boom refueling after take-off? SR-71 style... take off with half-tank, then refuel. Not exoatmospheric, but has benefits.

How about that?

http://www.ai.mit.edu/projects/im/magnus/bh/analog.html

;)

Offline JasonAW3

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Until someone can come up with a near nuclear level, compact, safe, self contained, low mass, power supply that can provide enough power to make a significant change to the mass ration to orbit, (higher than 10% of total mass) it is very unlikely that we will see any true SSTO or lifting body designs in any viable use.

With current technology, it SHOULD be possible to make a SSTO design, so long as you are trying for Low Earth Orbit and NOT trying to reuse the rocket.
My God!  It's full of universes!

Offline douglas100

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 I was enthusiastic for SSTO in the 90's, especially Delta Clipper. But I also remember some who said it wouldn't work back then. In the light of subsequent history I've (reluctantly) changed  my opinion and now think that TSTO is the way to go.

I think JasonAW3's post is spot on.

EDIT Slight clarification.
« Last Edit: 11/20/2015 03:40 pm by douglas100 »
Douglas Clark

Offline Elmar Moelzer

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I was enthusiastic for SSTO in the 90's, especially Delta Clipper. But I also remember some who said it wouldn't work back then. In the light of subsequent history I've (reluctantly) changed  my opinion and now think that TSTO is the way to go.
What subsequent history? Delta Clipper was cancelled for political reasons, not technical reasons.

I personally think the conventional wisdom against SSTO RLVs is oversold. Technically speaking I think they're completely feasible, the tech necessary is high-enough TRL to be believable. We just haven't proven markets that need flight rates high enough for them to shine compared to expendable TSTOs yet.
I agree with that. Of course any government could artificially create the market, if they really wanted to. For a country like the US it would be peanuts compared to other expenses.
I am wondering whether TSTO RLVs are needed as an intermediate step so the market has time to gradually grow and adjust to the lower prices. Then we can move on to SSTOs in an attempt to lower launch costs even further.

Offline JasonAW3

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I find it kind of interesting that the DARPA Reusable rocket concept has just quietly disappeared.  I haven't heard anything about it in about a year now.
My God!  It's full of universes!

Offline RonM

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I am wondering whether TSTO RLVs are needed as an intermediate step so the market has time to gradually grow and adjust to the lower prices. Then we can move on to SSTOs in an attempt to lower launch costs even further.

As previously mentioned, currently TSTO vehicles are cheaper than SSTO. It's not a matter of the market, it's technology.

Offline john smith 19

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Until someone can come up with a near nuclear level, compact, safe, self contained, low mass, power supply that can provide enough power to make a significant change to the mass ration to orbit, (higher than 10% of total mass) it is very unlikely that we will see any true SSTO or lifting body designs in any viable use.

With current technology, it SHOULD be possible to make a SSTO design, so long as you are trying for Low Earth Orbit and NOT trying to reuse the rocket.
Do you know NERVA's T/W was designed to be 5.3:1 for an Isp of 825 secs.according to the 4th edition of  Sutton? All applications were for upper stages outside the atmosphere.

MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline douglas100

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What subsequent history? Delta Clipper was cancelled for political reasons, not technical reasons.

The history of all SSTO developments, not just Delta Clipper.
Douglas Clark

Offline JasonAW3

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Until someone can come up with a near nuclear level, compact, safe, self contained, low mass, power supply that can provide enough power to make a significant change to the mass ration to orbit, (higher than 10% of total mass) it is very unlikely that we will see any true SSTO or lifting body designs in any viable use.

With current technology, it SHOULD be possible to make a SSTO design, so long as you are trying for Low Earth Orbit and NOT trying to reuse the rocket.
Do you know NERVA's T/W was designed to be 5.3:1 for an Isp of 825 secs.according to the 4th edition of  Sutton? All applications were for upper stages outside the atmosphere.

Yep.  Knew that, but what is NEEDED is a power supply of nuclear output level, but is NOT nuclear, if possible, or safe if damaged and shut down.

     Fusion could work, IF we could ever figure out how to sustain a fusion reaction.
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Offline 93143

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Until someone can come up with a near nuclear level, compact, safe, self contained, low mass, power supply that can provide enough power to make a significant change to the mass ration to orbit, (higher than 10% of total mass) it is very unlikely that we will see any true SSTO or lifting body designs in any viable use.

I gather you have a low opinion of the viability of Skylon?  The SABRE 4 engine in that application seems to have an average airbreathing Isp in the general vicinity of 4000 seconds or so through at least Mach 5, leading to an average Isp of around 680-690 seconds over the whole orbital trajectory, resulting in a vehicle mass ratio of about 4.4. And thanks to the ultralight precooler and the powered compression it enables, the engine looks to be light enough for that to work - the current payload fraction is about 4.6% after margins.

Do you know NERVA's T/W was designed to be 5.3:1 for an Isp of 825 secs.according to the 4th edition of  Sutton? All applications were for upper stages outside the atmosphere.

*cough*

Add in LOX (or air) augmentation for the early boost phase, and...
« Last Edit: 11/20/2015 10:51 pm by 93143 »

Offline jongoff

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I am wondering whether TSTO RLVs are needed as an intermediate step so the market has time to gradually grow and adjust to the lower prices. Then we can move on to SSTOs in an attempt to lower launch costs even further.

As previously mentioned, currently TSTO vehicles are cheaper than SSTO. It's not a matter of the market, it's technology.

To a point. Once either your overall mass ratio or Isp or both improve to a certain level, TSTO stops being easier. If you had to do intercontinental aircraft flight, without refueling, and without modern materials/engines, you might believe that a two stage aircraft would be cheaper too. If enough details shift, the added performance benefit of TSTO will be swamped by the added cost/risk/complexity of staging. We're nowhere near that point yet, but I can see for many niche markets where an SSTO could be more economical, assuming it was highly reusable.

~Jon

Offline HMXHMX

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I am wondering whether TSTO RLVs are needed as an intermediate step so the market has time to gradually grow and adjust to the lower prices. Then we can move on to SSTOs in an attempt to lower launch costs even further.

As previously mentioned, currently TSTO vehicles are cheaper than SSTO. It's not a matter of the market, it's technology.

To a point. Once either your overall mass ratio or Isp or both improve to a certain level, TSTO stops being easier. If you had to do intercontinental aircraft flight, without refueling, and without modern materials/engines, you might believe that a two stage aircraft would be cheaper too. If enough details shift, the added performance benefit of TSTO will be swamped by the added cost/risk/complexity of staging. We're nowhere near that point yet, but I can see for many niche markets where an SSTO could be more economical, assuming it was highly reusable.

~Jon

Exactly.  The development of aircraft went through this 'stage.'

Once PMF is sufficiently high, there is very little (and some would argue no) advantage to staging.  The was demonstrated mathematically by NASA Langley thirty years ago.

Offline RonM

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I am wondering whether TSTO RLVs are needed as an intermediate step so the market has time to gradually grow and adjust to the lower prices. Then we can move on to SSTOs in an attempt to lower launch costs even further.

As previously mentioned, currently TSTO vehicles are cheaper than SSTO. It's not a matter of the market, it's technology.

To a point. Once either your overall mass ratio or Isp or both improve to a certain level, TSTO stops being easier. If you had to do intercontinental aircraft flight, without refueling, and without modern materials/engines, you might believe that a two stage aircraft would be cheaper too. If enough details shift, the added performance benefit of TSTO will be swamped by the added cost/risk/complexity of staging. We're nowhere near that point yet, but I can see for many niche markets where an SSTO could be more economical, assuming it was highly reusable.

~Jon

Yes, one day technology might make SSTO RLV more economical, but not today. That's why I put "currently" in my comment.

Even saying TSTO RLV is economical is a bit of a stretch. I'm confident that SpaceX will succeed, but my opinion doesn't count. They'll have prove it. ULA Vulcan is designed to eventually recover the engine pod. However, their design still throws away the first stage core because they don't think the SpaceX approach will be economical.

I do agree that one day we'll have highly reusable SSTO vehicles. Just don't know how far down the line that will be.

Online Robotbeat

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There are some pretty good benefits to staging at Earth, though, even with excellent mass fractions. You can separate out sea-level, high-thrust and vacuum-optimized, lower-thrust. With SSTO, you have to throttle way back or shut off a bunch of your engines to keep from crushing the stage.

With TSTO, you can flyback the stage quicker than you can fly back the whole SSTO rocket, thus in principle getting you much faster turnaround for 90% of your rocket. Additionally, 90% of your rocket doesn't need significant TPS or the careful inspection that might require.

I also think that stage integration can be automated with some sort of large jig. We automate loading and unloading shipping containers, over ten thousand units weighing up to ~30 tons each in just a few hours. Mating two rocket stages, both empty, could be done very quickly.

...but there are a lot of advantages to SSTO, especially for passengers. You can test all your engines before committing to launch (hold-down), and you don't have any staging events. That helps keep reliability high.

I agree with Jon and HMXHMX that SSTO RLV can be done (and nuclear-thermal would be a bad way to do it. Very heavy! With very low density propellant that would nonetheless require a lot of energy to produce, which would matter when you're talking tens of thousands of flights per year.). It will be done someday because of the safety advantages.

In regards to HMXHMX's secret project: Something near SSTO performance but not quite would be point-to-point transport, perhaps with hypersonic skipping/reboosting to keep reentry accelerations modest. Or, it could be that SpaceX has hired him for MCT. :P
« Last Edit: 11/21/2015 12:12 am by Robotbeat »
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Offline TrevorMonty

I find it kind of interesting that the DARPA Reusable rocket concept has just quietly disappeared.  I haven't heard anything about it in about a year now.
The XS1 program is alive and well. All 3 contenders have received additional fund to perfect their design before down selecting to one late 2016.

Offline 93143

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You can separate out sea-level, high-thrust and vacuum-optimized, lower-thrust. With SSTO, you have to throttle way back or shut off a bunch of your engines to keep from crushing the stage.

Not necessarily.

For example, TAN combines altitude compensation with deep throttling (and impulse density optimization if you want it) as an inherent feature of the concept.  You could probably run a LANTR the same way, and the mass ratio would be much lower.

SABRE 4's dual-chamber design handles altitude compensation nicely, and Skylon's low takeoff T/W and mass ratio virtually eliminate the throttling issue.  An aneutronic fusion SSTO with heavy air augmentation (the only kind of fusion SSTO likely to work IMO, leaving aside Orion) could easily be done in such a way as to incorporate altitude compensation, and the mass ratio could be very low.

Offline Elmar Moelzer

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What subsequent history? Delta Clipper was cancelled for political reasons, not technical reasons.

The history of all SSTO developments, not just Delta Clipper.
There was not much after that, other than Roton (which failed for many reasons, among others lack of investor confidence) and the X33 (which was actually a suborbital pathfinder for the much larger Venture Star). The latter failed because NASA chose the most ambitious of all proposals and then failed to go through with it when the inevitable problems appeared (because it was the most ambitious).
Personally, I always thought that the Lockheed proposal was a terrible choice.
Either way, none of these proof anything to me.

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You can separate out sea-level, high-thrust and vacuum-optimized, lower-thrust. With SSTO, you have to throttle way back or shut off a bunch of your engines to keep from crushing the stage.

Not necessarily.

For example, TAN combines altitude compensation with deep throttling (and impulse density optimization if you want it) as an inherent feature of the concept.  You could probably run a LANTR the same way, and the mass ratio would be much lower.

SABRE 4's dual-chamber design handles altitude compensation nicely, and Skylon's low takeoff T/W and mass ratio virtually eliminate the throttling issue.  An aneutronic fusion SSTO with heavy air augmentation (the only kind of fusion SSTO likely to work IMO, leaving aside Orion) could easily be done in such a way as to incorporate altitude compensation, and the mass ratio could be very low.
Yes, necessarily, as you point to in your post. With thrust-augmentation, you have to turn off the thrust augmentation as you get higher. So yes, you necessarily have to throttle way back.

There may be clever ways to do this, such as thrust augmentation, but there's overhead to all these clever ideas. Overhead = dry mass. Doesn't mean it's not worth doing, but it's not a free lunch.
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Offline 93143

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So yes, you necessarily have to throttle way back.

That's arguable in the TAN case, depending on how broad your definition of throttling is...

...but in the Skylon case I don't think it's tenable.  C1 was at something like 56% throttle at MECO (= higher thrust than at takeoff, actually) with a 3 gee limit, because the mass ratio simply wasn't high enough to require deeper throttling.  D1's mass ratio is even better (plus the rocket mode is slightly less tightly coupled with the airbreathing mode, so the thrust may not need to rise as much at switchover).

Quote
There may be clever ways to do this, such as thrust augmentation, but there's overhead to all these clever ideas. Overhead = dry mass.

I'm not so sure about that.  TAN seems to result in very high T/W in booster mode.  The Aerojet paper shows a high-pressure hydrogen engine with an initial T/W of 45 ending up at 119 after augmentation with kerosene.  TAN isn't so much a feature of the engine as it is an extra engine sharing the same bell.
« Last Edit: 11/21/2015 10:26 am by 93143 »

Offline Nilof

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The integration cost of staging really depends on how it is done. You could have a system similar to the Soyuz LRB's where the stage 0 boosters simply fall off when they stop burning. Integration is very simple and separation failures are unheard of in the history of the R-7 family. Well, you may get the Foton-M failure mode, but that could be prevented with a pad holddown system like on the Falcon 9.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline hkultala

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You can separate out sea-level, high-thrust and vacuum-optimized, lower-thrust. With SSTO, you have to throttle way back or shut off a bunch of your engines to keep from crushing the stage.

Not necessarily.

For example, TAN combines altitude compensation with deep throttling (and impulse density optimization if you want it) as an inherent feature of the concept.  You could probably run a LANTR the same way, and the mass ratio would be much lower.

SABRE 4's dual-chamber design handles altitude compensation nicely, and Skylon's low takeoff T/W and mass ratio virtually eliminate the throttling issue.  An aneutronic fusion SSTO with heavy air augmentation (the only kind of fusion SSTO likely to work IMO, leaving aside Orion) could easily be done in such a way as to incorporate altitude compensation, and the mass ratio could be very low.
Yes, necessarily, as you point to in your post. With thrust-augmentation, you have to turn off the thrust augmentation as you get higher. So yes, you necessarily have to throttle way back.

There may be clever ways to do this, such as thrust augmentation, but there's overhead to all these clever ideas. Overhead = dry mass. Doesn't mean it's not worth doing, but it's not a free lunch.

Optimal nozzle size for sea level high thrust is in the same range as optimal nozzle size for vacuum low thrust.

Se TAN actually SAVES mass on the nozzles due no need to have two separate similarily-sized nozzles in the initial phase of the flight.

Offline douglas100

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What subsequent history? Delta Clipper was cancelled for political reasons, not technical reasons.

The history of all SSTO developments, not just Delta Clipper.
There was not much after that, other than Roton (which failed for many reasons, among others lack of investor confidence) and the X33 (which was actually a suborbital pathfinder for the much larger Venture Star). The latter failed because NASA chose the most ambitious of all proposals and then failed to go through with it when the inevitable problems appeared (because it was the most ambitious).
Personally, I always thought that the Lockheed proposal was a terrible choice.
Either way, none of these proof anything to me.

(My bold)
Exactly. And that suggests to me that people lost faith in the concept and returned to trying to re-use two stage vehicles. Although Jon Goff makes a persuasive argument it doesn't look at the moment that anyone is minded to spend serious cash to revive it.

Agree totally about NASA's choice of Venture Star. Ironically Lockheed went from Venture Star to Atlas V after the collapse of the X-33.
Douglas Clark

Offline Elmar Moelzer

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(My bold)
Exactly. And that suggests to me that people lost faith in the concept and returned to trying to re-use two stage vehicles. Although Jon Goff makes a persuasive argument it doesn't look at the moment that anyone is minded to spend serious cash to revive it.

Agree totally about NASA's choice of Venture Star. Ironically Lockheed went from Venture Star to Atlas V after the collapse of the X-33.
Money, not technical problems. Just plain money. Lockheed has no interest in advancing the state of the art in spaceflight. They only care about money. The AtlasV pays just as well (Airforce has money and cares comparably little about cost and ULA had a monopoly anyway) and did not cost as much to develop as an SSTO would have. So why bother?

Offline Vultur

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However the real problem with SSTO is that historically your payload goes down from about 3% of GTOW to 1% or less for the same GTOW.

But how closely correlated are cost and GTOW?

It seems to me that the best way to get cheap access to space would be to go to larger sized vehicles [for the same payload] in return for broader margins and thus less need for very high precision manufacturing & lots of inspection. For any # of stages.

Materials are relatively cheap compared to expertise and time IIRC.

IE I think a really good SSTO would be very large.

Quote
The thread title packs quite a lot in. I don't think the XCOR Lynx will qualify as SSTO but it's certainly a space plane.

Agreed - as are SpaceShipTwo and DreamChaser, and as is the X-37B (currently operational though unmanned). Most spaceplane concepts aren't SSTO, at least currently.

Offline Nilof

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However the real problem with SSTO is that historically your payload goes down from about 3% of GTOW to 1% or less for the same GTOW.

But how closely correlated are cost and GTOW?

It seems to me that the best way to get cheap access to space would be to go to larger sized vehicles [for the same payload] in return for broader margins and thus less need for very high precision manufacturing & lots of inspection. For any # of stages.

Materials are relatively cheap compared to expertise and time IIRC.

IE I think a really good SSTO would be very large.

An SSTO inherently has less margin than a TSTO though, since it is much more vulnerable to mass increases. If your intent is to increase margins, the easy way to do that is to increase the number of stages rather than increasing the size of the vehicle. Materials are cheap, but custom large factories and transportation infrastructure that can accommodate huge vehicles are not.

The main issue is this: can a near term SSTO reasonably carry a payload as heavy as or heavier than its dry mass? If not, the majority of the performance goes into lifting tankage, structure and plumbing into orbit rather than payload.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Vultur

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An SSTO inherently has less margin than a TSTO though, since it is much more vulnerable to mass increases.
I didn't intend a TSTO vs SSTO comparison, but SSTO concept vs SSTO concept.

A SSTO (or any other vehicle) can accept a higher structural mass fraction (and thus more structural margin) if it is larger for the same payload, assuming equal materials.

Quote
custom large factories and transportation infrastructure that can accommodate huge vehicles are not.

Factories, sure, but if you're custom building a factory anyway, then you don't need transportation infrastructure  - build at launch site/launch from build site.

Also, any good rapidly reusable SSTO should be able to self ferry.

Quote
The main issue is this: can a near term SSTO reasonably carry a payload as heavy as or heavier than its dry mass? If not, the majority of the performance goes into lifting tankage, structure and plumbing into orbit rather than payload.

Sure, but a SSTO should be able to achieve more rapid reusability than a TSTO. I can't see getting to true gas-and-go reusability with a TSTO... though SpaceX may yet prove me wrong.

Offline KelvinZero

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Sure, but a SSTO should be able to achieve more rapid reusability than a TSTO. I can't see getting to true gas-and-go reusability with a TSTO...
This certainly contradicts the optimism of those suborbital schemes that are effectively two stage with integration in flight ;)

Offline Darkseraph

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I find it a bit hard to believe that the breakthroughs needed to make a reusable SSTO practical are going to be easier to achieve than just making staging more reliable. The compromises in margins that have to be made to make such a vehicle lift any payload to orbit will almost certainly reduce its reliability over multiple flights. But for a reusable vehicle, you want as many flights as you can get out of the hardware. It is probably better just to use staging with an expandable upper stage.

I think SSTO is one of these 'Holy Grail' technologies that attracts more attention than it deserves, bordering on pathological science.

"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." R.P.Feynman

Offline hkultala

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I find it a bit hard to believe that the breakthroughs needed to make a reusable SSTO practical are going to be easier to achieve than just making staging more reliable.

Making complex things extremely reliable is very hard and very expensive. The easiest way to improve reliability is to make things simpler.

Quote
The compromises in margins that have to be made to make such a vehicle lift any payload to orbit will almost certainly reduce its reliability over multiple flights. But for a reusable vehicle, you want as many flights as you can get out of the hardware. It is probably better just to use staging with an expandable upper stage.

If you think further into future and want to make space access _really cheap_ you cannot afford _anything_ expandable.

Quote
I think SSTO is one of these 'Holy Grail' technologies that attracts more attention than it deserves, bordering on pathological science.

I'd say it depends on the greater picture and implementation. SSTO for just to make SSTO does not make sense. But if that SSTO improves reliability or makes reuse cheaper, then it's good. Bad SSTO however can just make reuse harder, if the very high required mass fraction prevents installing a landing system, and then SSTO does not make sense.

Skylon is good example where SSTO makes sense, the whole system is thought out very well.

But just launching a F9 first stage without second stage could reach orbit, but it would not make any sense as a launcher as it cannot return from orbit and payload would be much worse than with second stage; reusable first stage + expandable second stage is both cheaper and gives much better payload.
« Last Edit: 11/22/2015 11:08 am by hkultala »

Offline A_M_Swallow

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Can a combined upperstage and capsule be developed?
Like the Shuttle it may have to come in horizontally. With the cab/cargo hold at the front and engine at the back it will be very light weight in the middle when out of fuel.

Offline Darkseraph

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Almost every scheme I have seen to achieve SSTO doesn't make the vehicle simpler, it makes it more complex and reduces margins just for the sake of being SSTO.
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." R.P.Feynman

Offline edkyle99

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Can a combined upperstage and capsule be developed?
Like the Shuttle it may have to come in horizontally. With the cab/cargo hold at the front and engine at the back it will be very light weight in the middle when out of fuel.
Start with an X-37B, a relatively small spacecraft that can maneuver in and return from low earth orbit.  It weighs maybe 5 tonnes at liftoff (I suspect more) which requires an Atlas 5-501.  That's two expendable stages, each using state-of-the-art propulsion.  I would wonder what cheaper, possibly reusable solution could replace that 501.  Thinking about that just for a minute reveals the challenge. 

 - Ed Kyle

Offline A_M_Swallow

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Can a combined upperstage and capsule be developed?
Like the Shuttle it may have to come in horizontally. With the cab/cargo hold at the front and engine at the back it will be very light weight in the middle when out of fuel.
Start with an X-37B, a relatively small spacecraft that can maneuver in and return from low earth orbit.  It weighs maybe 5 tonnes at liftoff (I suspect more) which requires an Atlas 5-501.  That's two expendable stages, each using state-of-the-art propulsion.  I would wonder what cheaper, possibly reusable solution could replace that 501.  Thinking about that just for a minute reveals the challenge. 

 - Ed Kyle

I am quite happy with a TSTO providing both stages come back. The Falcon 9R is getting the first stage back. Plenty of capsules can come back so that leaves the upper stage.

The Falcon 9 fairing is 13.1 metres high and 5.2 metres in diameter. The upper stage is 3.66 metres in diameter.

The capsule and the upper stage would no longer need to separate, parts of the RCS would need moving to the back of the upper stage and the whole thing would need covering in a thermal protection system. The whole thing would need wheels or floatation devices. p.s. Delete the capsules main engine.
« Last Edit: 11/22/2015 04:51 pm by A_M_Swallow »

Offline TrevorMonty

Almost every scheme I have seen to achieve SSTO doesn't make the vehicle simpler, it makes it more complex and reduces margins just for the sake of being SSTO.
If you talking about crew carrying vehicle, I doubt it would be built because of safety. Just look at recent F9 US failure. Cryo fuels and crew in same vehicle/stage is not a good idea.
Can a combined upperstage and capsule be developed?
Like the Shuttle it may have to come in horizontally. With the cab/cargo hold at the front and engine at the back it will be very light weight in the middle when out of fuel.

Offline Vultur

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This certainly contradicts the optimism of those suborbital schemes that are effectively two stage with integration in flight ;)

Like SpaceShipTwo? Yeah, it's cool and I'd be glad to see it (or any suborbital tourism) succeed, but I don't think it's a particularly good idea.

Suborbital to the Karman line is so easy to achieve with conventional rockets that there would be plenty of margin left over to reuse the vehicle, so I really don't see the point of the SS2 design.

Online Robotbeat

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Almost every scheme I have seen to achieve SSTO doesn't make the vehicle simpler, it makes it more complex and reduces margins just for the sake of being SSTO.
If you talking about crew carrying vehicle, I doubt it would be built because of safety. Just look at recent F9 US failure. Cryo fuels and crew in same vehicle/stage is not a good idea....

It's possible to have ejection pods for the crew, ala DC-I.

And it's not the cryo part that's bad. Cryo is fine, and actually makes your materials stronger (if properly engineered).
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Offline Vultur

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I find it a bit hard to believe that the breakthroughs needed to make a reusable SSTO practical are going to be easier to achieve than just making staging more reliable.

That assumes breakthroughs ARE needed. I don't think they are.

SSTO-level mass fractions have already been achieved (since the early 60s), current engines are probably good enough, vertical propulsive landing was done by DC-X and SpaceX is working on it currently.

The remaining question is TPS, IMO. PICA-X or metallic TPS may well be good enough, but I don't know enough to judge that.

Offline Zond

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In regards to HMXHMX's secret project: Something near SSTO performance but not quite would be point-to-point transport, perhaps with hypersonic skipping/reboosting to keep reentry accelerations modest. Or, it could be that SpaceX has hired him for MCT. :P
Hmmm, who currently is building a launch platform for which you would only need near SSTO performance and who are searching for a rocket to go with it? Does it start with Strato and end with launch? :)
« Last Edit: 11/22/2015 07:43 pm by Zond »

Offline Darkseraph

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I find it a bit hard to believe that the breakthroughs needed to make a reusable SSTO practical are going to be easier to achieve than just making staging more reliable.

That assumes breakthroughs ARE needed. I don't think they are.

SSTO-level mass fractions have already been achieved (since the early 60s), current engines are probably good enough, vertical propulsive landing was done by DC-X and SpaceX is working on it currently.

The remaining question is TPS, IMO. PICA-X or metallic TPS may well be good enough, but I don't know enough to judge that.

It's a correct assumption. There is no turn-key SSTO capability that would be competitive with expendable launch systems.

Skylon and other SSTO programs are speculative multi-billion dollar efforts that have lots of unknown unknowns. Investors are not beating down the door with those billions, because it is far less than certain. The low hanging fruit right now is just making the first stage returnable. Even that is very hard to do. 
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." R.P.Feynman

Offline Hanelyp

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The recent Falcon 9 upper stage failure would have been caught on the first flight of a reusable stage.  The capacity for a first flight of a new vehicle off the line to carry a less critical payload on first launch is good for safety.

SSTO margins have been demonstrated for expendable rocket stages, but the structural margins, TPS, and other assorted systems for stage recovery have a way of eating into already slim payload margins.

Offline Bob Shaw

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Skylon and other SSTO programs are speculative multi-billion dollar efforts that have lots of unknown unknowns. Investors are not beating down the door with those billions, because it is far less than certain. The low hanging fruit right now is just making the first stage returnable. Even that is very hard to do. 

Actually, BAE Systems have just announced that they are putting $30M into Alan Bond's project - and, of course, it was British Aerospace, one of the predecessor companies which were absorbed into BAE Systems, which supported the early HOTOL research which has now become Skylon. The EU has also contributed $77M.

http://www.baesystems.com/cs/Satellite?c=BAENews_Release_C&childpagename=Global%2FBAELayout&cid=1434570674020&pagename=GlobalWrapper

Offline 93143

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The recent Falcon 9 upper stage failure would have been caught on the first flight of a reusable stage.  The capacity for a first flight of a new vehicle off the line to carry a less critical payload on first launch is good for safety.

Last I heard, each individual Skylon was supposed to be flown to orbit and back four times before being delivered to the customer.

Skylon and other SSTO programs are speculative multi-billion dollar efforts that have lots of unknown unknowns.

I think you may be underestimating Skylon's level of technological maturity, but it's hard to tell because your complaints are so vague.  The development program is expensive mostly for the same reasons bringing an airliner to market is expensive; it's large-scale integration and testing/certification, not basic R&D.  REL has been working this for a long time, doing the risk reduction and technology development (which is now done), and has subjected important questions to independent analysis (e.g. the VKI's engine modelling, or DLR's reentry modelling).  The whole thing has been looked at in some detail by the ESA, which found no reason not to expect successful development.  The D revision of the vehicle design was intended to guarantee feasibility (given a successful engine development) and carries substantial margins, and as of mid-2012, nothing in the design was below TRL 4.

Almost every scheme I have seen to achieve SSTO doesn't make the vehicle simpler, it makes it more complex and reduces margins just for the sake of being SSTO.

Dry payload fraction roughly equivalent to the Delta IV, wet payload fraction substantially higher than any launch vehicle ever built, structural safety factor 1.5 (the same as an airliner), mass growth allowance "consistent with AIAA guidelines" (= at least 15% IMO, maybe more, depending on how far along REL thinks their design is - the truss for C1 had a 15% margin) with a payload margin on top, and a payload sensitivity to engine performance of about 1% per second of launch-averaged Isp (baseline is about 687 seconds for Skylon D1.5 with SABRE 4, meaning a small fractional loss of engine performance results in roughly 7 times that fractional loss of payload).  All of this is due primarily to the novel engine concept, which depends mostly on the extremely lightweight high-efficiency precooler, which has already been manufactured and tested and is known to work (there are a few other minor novelties in the engine and airframe, but they have not been neglected).

This is not to say Skylon is the only possible alternative to VentureStar, or that it will definitely perform exactly as projected.  But as a concept, it is something like an existence proof.  There are potential alternatives to the conventional ultralight hydrolox rocket SSTO, and in principle a clever idea can have a large impact on the engineering.

BAE Systems have just announced that they are putting $30M into Alan Bond's project

They're also on board as a development partner.  The relatively small size of the investment may be misleading.
« Last Edit: 11/22/2015 10:15 pm by 93143 »

Offline Darkseraph

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Skylon and other SSTO programs are speculative multi-billion dollar efforts that have lots of unknown unknowns. Investors are not beating down the door with those billions, because it is far less than certain. The low hanging fruit right now is just making the first stage returnable. Even that is very hard to do. 

Actually, BAE Systems have just announced that they are putting $30M into Alan Bond's project - and, of course, it was British Aerospace, one of the predecessor companies which were absorbed into BAE Systems, which supported the early HOTOL research which has now become Skylon. The EU has also contributed $77M.

http://www.baesystems.com/cs/Satellite?c=BAENews_Release_C&childpagename=Global%2FBAELayout&cid=1434570674020&pagename=GlobalWrapper

I was aware of those investments, but they aren't really huge votes of confidence. It is well below what the full system would cost to develop. They'll have avoided closing shop for another couple of years.

This whole idea has been limping along on relatively small amounts of funding for 3 decades because it's not a certain thing.
« Last Edit: 11/22/2015 10:04 pm by Darkseraph »
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Offline john smith 19

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This whole idea has been limping along on relatively small amounts of funding for 3 decades because it's not a certain thing.
Anyone who watched Mark Zuckerberg offload what is basically a server farm and bunch of developers on the US stock market for $104 Bn and a P/E ratio (or how long it would take to double your holding if all its profits were handed out to stock holders every year) measured in centuries, would have realized that peoples perception of how much a company is worth (and therefor how much they are willing to invest) has very little to do with technology or risk and a great deal to do with the sales abilities of its promoters.
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Offline john smith 19

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But how closely correlated are cost and GTOW?
According to conventional "cost estimating relationships" mass --> cost so lighter --> better but the graph seems quite shallow.

People have noted that Xerox's CER's (yes the office equipment people) used complexity IE number of parts, as the key factor.  My instinct is that is more accurate. Note, multiple copies of the same part are not too bad, it's all those unique parts, and the shedload of design and test documentation that goes with them, that costs the real money.
Quote
It seems to me that the best way to get cheap access to space would be to go to larger sized vehicles [for the same payload] in return for broader margins and thus less need for very high precision manufacturing & lots of inspection. For any # of stages.
The notion you're looking at is the "Big dumb booster" concept.

Google "Sea Dragon."
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Offline john smith 19

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Exactly.  The development of aircraft went through this 'stage.'

Once PMF is sufficiently high, there is very little (and some would argue no) advantage to staging.  The was demonstrated mathematically by NASA Langley thirty years ago.
It's quite interest 2 companies (one in the UK and one in Germany IIRC) planned (and financed) these concepts during the 1930's despite Lindberg's "single stage" crossing of the Atlantic nearly a decade earlier, proving they were obsolete.   :(

And AFAIK no one started with a "partially" transatlantic aircraft and "refined" it to full transatlantic range.

That took new aircraft designs, built around sufficiently reliable engines.

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Online Robotbeat

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But how closely correlated are cost and GTOW?
According to conventional "cost estimating relationships" mass --> cost so lighter --> better but the graph seems quite shallow.

People have noted that Xerox's CER's (yes the office equipment people) used complexity IE number of parts, as the key factor.  My instinct is that is more accurate. Note, multiple copies of the same part are not too bad, it's all those unique parts, and the shedload of design and test documentation that goes with them, that costs the real money.
Quote
It seems to me that the best way to get cheap access to space would be to go to larger sized vehicles [for the same payload] in return for broader margins and thus less need for very high precision manufacturing & lots of inspection. For any # of stages.
The notion you're looking at is the "Big dumb booster" concept.

Google "Sea Dragon."
"Big dumb whatever" works in a lot of areas, but in aerospace, you have the brutal exponential rocket equation. If you try "big dumb" you necessarily have to have several stages. It's still possible, though at the expense of needing more stages, which means more expense. And you still have a much higher GLOW for the same payload, which means a bigger launch pad (or launching at sea, with all the complications involved).

"Big dumb" may be a valid first stage design criteria, I'm not sure. But for the upper stage, where your mass overhead directly eats into your payload, you are likely to be much better off with the typical approach of trying to lightweight the crap out of everything and picking the highest performing materials possible, especially for an RLV (which can be reused). Making everything out of silver or something just as expensive clearly makes sense (obviously silver isn't that strong for its mass, just using an example).
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Offline KelvinZero

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This certainly contradicts the optimism of those suborbital schemes that are effectively two stage with integration in flight ;)
Like SpaceShipTwo? Yeah, it's cool and I'd be glad to see it (or any suborbital tourism) succeed, but I don't think it's a particularly good idea.
I was being a bit facetious, referring to ideas where a sort of upper stage in orbit aerobrakes down to meet a suborbital vehicle and then pushes it to orbit.  8)

Offline Vultur

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It's a correct assumption. There is no turn-key SSTO capability that would be competitive with expendable launch systems.

OK, but that's a much weaker statement than saying it requires breakthroughs. It requires development of the vehicle but not really new technology.

The vehicle isn't "off the shelf"/previously demonstrated but I think all major components needed are, except the landing software which SpaceX is working on right now.

Quote
The low hanging fruit right now is just making the first stage returnable. Even that is very hard to do.

The first few SpaceX attempts failed, but I'd expect it to be routine fairly soon (say in 2 years).

And the problems were with the very end of the landing - I don't think they would have been any worse if it was coming back all the way from orbit (though it would need a TPS).

I was being a bit facetious, referring to ideas where a sort of upper stage in orbit aerobrakes down to meet a suborbital vehicle and then pushes it to orbit.  8)

Ah OK - sorry, I thought you meant SS2 as two stages (carrier aircraft plus spacecraft...)

Yeah I've seen those kinds of ideas, but I don't understand what advantage they are supposed to have over either a plain TSTO or plain SSTO.

Although, the specific rapid-reusability problems I had in mind involved ground operations, and those issues wouldn't apply to that kind of system.

But IMO you might as well go straight to a real SSTO.

Offline nec207

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What technological breakthrough is needed to make space planes and or single-stage-to-orbit (or SSTO possible? What  major problem holding back space planes and or single-stage-to-orbit?

Two different questions a space plane does not need to be single stage to Orbit, see the Space Shuttle, X-37, Dream Chaser and SSTO does not need to be an space plane(however being some type of airplane could be helpful in terms of being capable of generating lift.)

SSTO is possible now, but the problem is SSTO while carrying a practical payload and most SSTO concepts require re usability. The issue is with materials. Mathematically it is possible to get to orbit using chemical rocket in an single stage. It is just that the materials we have to build the SSTO out of are too heavy to allow this concept to work with current technology but technology changes. Lighter weight structures and heat shields would allow this concept to work as well as engines like the sabre(which could allow you to get much higher and faster without using on board oxygen and can double as both an jet and rocket engine.).  We can build an SSTO now, but it won't be able to haul much into orbit and it won't be reusable. It simply would not be practical at the moment.

Space planes are better suited than capsules for certain things. The return to the capsule is being driven by different dynamics. For Orion and CST-100 reusing Apollo's shape saves research and development(esp. for Orion). For Space X, wings don't fit the company philosophy. For Dream Chaser "wings" allow much more selection of places to land as well as reduced G-forces on the crew.

In terms of BEO. Space planes could find an role as an mars mission as the earth reentry vehicle. There is debate on wither on not an the crew can survive the G-forces from that fast an reentry in an capsule. For lunar missions there was an interesting concept floated of using an version of dream chaser as an lunar craft or using the shuttle's cargo bay to haul up an capsule and crew and docking it with an pre-positioned stage launched by Titan in LEO.  While wings can be useless in space, they can be handy at the end of the mission.

But that is what I said before that no one replied to me on here. Under Bush he decided to go to the moon and canceled all research into cheap affordable reusable craft for getting people and payload into space.

Going to moon in SSTO or space plane would been way more of a technology and emerging problem than getting into space. It would of taken longer and cost way more money into R&D.

Under President Obama he pushed for going to Mars and an Asteroid. Going in a SSTO or space plane to Mars and an Asteroid would of been even more of technology and emerging problem and cost very yes very large number of R&D.

Gong into space is in SSTO or space plane is a technology and emerging problem and going to moon and beyond would been even more of a technology and emerging and lots of R&D.

And politics look at short term goals not long term goals. The public was losing interest into space so after  the shuttle accident the politicians used it as a PR to get people more into space and public support.

Selling people the political PR to get NASA support. And going into space and building a space station was been there and done that . Time to go beyond low orbit. That us canceled all research into cheap affordable reusable craft for getting people and payload into space and push beyond low orbit to get public support.

Offline nec207

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     Almost wish I could organize a superkickstarter to get billionaires to fund an independant research group to actually develope a working Lifting Body SSTO system.

Don't have to!!!! NASA is going to spend trillions of money to send people to moon and mars and after 4 to 8 trips it be like a the Apollo program.

The public and politicians will say we spent trillions and trillions of money going to the moon and mars and we can no longer support trips to moon or mars or moon or mars base.

Than they will say that spend money into cheap space access and cheap affordable reusable craft to the moon and mars and beyond!! But by that time it will be the year 2050!!!



Offline john smith 19

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"Big dumb whatever" works in a lot of areas, but in aerospace, you have the brutal exponential rocket equation. If you try "big dumb" you necessarily have to have several stages. It's still possible, though at the expense of needing more stages, which means more expense. And you still have a much higher GLOW for the same payload, which means a bigger launch pad (or launching at sea, with all the complications involved).

"Big dumb" may be a valid first stage design criteria, I'm not sure. But for the upper stage, where your mass overhead directly eats into your payload, you are likely to be much better off with the typical approach of trying to lightweight the crap out of everything and picking the highest performing materials possible, especially for an RLV (which can be reused). Making everything out of silver or something just as expensive clearly makes sense (obviously silver isn't that strong for its mass, just using an example).
Before commenting further I suggest you read what the originator of the idea has to say for himself on the subject.

http://www.sfo.org/library/schnitt/

You should note his goal was minimum cost design. Being "big" and (relatively) "dumb" was the result.

Incidentally Russian rockets, which have racked up 100s of launches without failure, follow some of the MCD principles, with a safety factor of 2, rather than the 1.25  of US ELV's (and SF of 1.5 for human rated ELV's).
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline Nilof

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Incidentally Russian rockets, which have racked up 100s of launches without failure, follow some of the MCD principles, with a safety factor of 2, rather than the 1.25  of US ELV's (and SF of 1.5 for human rated ELV's).

...And the Russians do this by having lots of stages, with 4-5 stages to GEO being rather common. The path they have followed is making staging extremely simple and reliable and integration easy even with a lot of stages.
« Last Edit: 11/23/2015 05:54 pm by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline edkyle99

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Back to the X-37B example. 

Assume first a spaceplane orbital mass at 5-ish tonnes (like X-37B). 

Assume the spaceplane can carry enough propellant to perform its own LEO insertion burn (perhaps 1,500 m/s delta-v) with an ascent  propellant mass fraction of 0.4 (spaceplane GLOW of 8 tonnes).

Assume spaceplane propulsion ISP = 320 seconds.

Assume a 500 kg payload on the spaceplane.

Assume a single booster stage, powered by two SLS-style RS-25 engines, 430 seconds average ISP for the trip. 

If the booster can carry 282 tonnes of usable propellant with a gross liftoff weight of 302 tonnes, LEO can be achieved.  We're pushing the mass-fraction envelope, hard.  With the spaceplane, total liftoff mass is 310-ish tonnes.

All of this is very big IF, of course.

The result of this attempt to use one big stage results in - one big stage.  It would be more than one-third larger (volume-wise) than a Delta 4 CBC and about 40% as large as a Shuttle External Tank - and it would only put 5.3 tonnes in LEO x 28.5 deg and only 500 kg of usable payload.  That's Minotaur 1 class.

 - Ed Kyle
« Last Edit: 11/23/2015 05:21 pm by edkyle99 »

Online Robotbeat

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"Big dumb whatever" works in a lot of areas, but in aerospace, you have the brutal exponential rocket equation. If you try "big dumb" you necessarily have to have several stages. It's still possible, though at the expense of needing more stages, which means more expense. And you still have a much higher GLOW for the same payload, which means a bigger launch pad (or launching at sea, with all the complications involved).

"Big dumb" may be a valid first stage design criteria, I'm not sure. But for the upper stage, where your mass overhead directly eats into your payload, you are likely to be much better off with the typical approach of trying to lightweight the crap out of everything and picking the highest performing materials possible, especially for an RLV (which can be reused). Making everything out of silver or something just as expensive clearly makes sense (obviously silver isn't that strong for its mass, just using an example).
Before commenting further I suggest you read what the originator of the idea has to say for himself on the subject.

http://www.sfo.org/library/schnitt/

You should note his goal was minimum cost design. Being "big" and (relatively) "dumb" was the result.

Incidentally Russian rockets, which have racked up 100s of launches without failure, follow some of the MCD principles, with a safety factor of 2, rather than the 1.25  of US ELV's (and SF of 1.5 for human rated ELV's).
Oh trust me, I'm familiar with the idea.
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Offline the_other_Doug

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I will note that Russian rockets have racked up hundreds of launches, but not without failures.  Look up the failure rates of Proton and Soyuz launchers, among others, sometime.  There have been some rather high-profile failures over the past few years.
-Doug  (With my shield, not yet upon it)

Offline Proponent

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"Big dumb whatever" works in a lot of areas, but in aerospace, you have the brutal exponential rocket equation. If you try "big dumb" you necessarily have to have several stages. It's still possible, though at the expense of needing more stages, which means more expense. And you still have a much higher GLOW for the same payload, which means a bigger launch pad (or launching at sea, with all the complications involved).

"Big dumb" may be a valid first stage design criteria, I'm not sure. But for the upper stage, where your mass overhead directly eats into your payload, you are likely to be much better off with the typical approach of trying to lightweight the crap out of everything and picking the highest performing materials possible, especially for an RLV (which can be reused). Making everything out of silver or something just as expensive clearly makes sense (obviously silver isn't that strong for its mass, just using an example).
Before commenting further I suggest you read what the originator of the idea has to say for himself on the subject.

http://www.sfo.org/library/schnitt/

You should note his goal was minimum cost design. Being "big" and (relatively) "dumb" was the result.

To quote Arthur Schnitt himself, "The MCD analysis showed that first stages, as part of a multi-stage expendable SLV, should be the least sophisticated; and that the optimum degree of hardware sophistication increases with each successive, upper stage."
« Last Edit: 11/24/2015 12:00 pm by Proponent »

Offline john smith 19

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To quote Arthur Schnitt himself, "The MCD analysis showed that first stages, as part of a multi-stage expendable SLV, should be the least sophisticated; and that the optimum degree of hardware sophistication increases with each successive, upper stage."
Exactly.

Save the cutting edge, wafer thin margin  tech for the uppermost stage.

Which sort of flips SX's plans on their head.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline savuporo

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BTW, Musk just claimed that F9 first stage is a SSTO
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Offline HMXHMX

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BTW, Musk just claimed that F9 first stage is a SSTO

Of course it is.  If it has a PMF >0.95, it can't help but be able to fly to the reference LEO orbit.  And with sequential engine shutdown it can certainly stay below 4-5 Gs, unlike another first stage (the Titan II) which is also an expendable SSTO.

Offline KelvinZero

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BTW, Musk just claimed that F9 first stage is a SSTO
Hey, you know that dumbish-idea of some massive infrastructure that catapults the rocket off the launch pad, saving the first few seconds of slowly building up speed which apparently uses a fair bit of fuel..

..well I was just thinking: Suppose you had a single stage to orbit that you were happy with, apart from negligible payload to orbit, then at that point how attractive does that extra boost at the launch pad look in terms of payload to orbit? What is the mathematical relationship roughly?

Offline savuporo

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Hey, you know that dumbish-idea of some massive infrastructure that catapults the rocket off the launch pad, saving the first few seconds of slowly building up speed which apparently uses a fair bit of fuel..
No end to these ideas, huh. Including building a launch pad at Volcán Cayambe
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Online Robotbeat

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To quote Arthur Schnitt himself, "The MCD analysis showed that first stages, as part of a multi-stage expendable SLV, should be the least sophisticated; and that the optimum degree of hardware sophistication increases with each successive, upper stage."
Exactly.

Save the cutting edge, wafer thin margin  tech for the uppermost stage.
...
Which is, in fact, exactly what I said.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Online Robotbeat

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To quote Arthur Schnitt himself, "The MCD analysis showed that first stages, as part of a multi-stage expendable SLV, should be the least sophisticated; and that the optimum degree of hardware sophistication increases with each successive, upper stage."
Exactly.

Save the cutting edge, wafer thin margin  tech for the uppermost stage.

Which sort of flips SX's plans on their head.
If you have a fully, rapidly reusable first stage, then yeah, Minimum Cost Design would lead you to use cutting edge tech on the first stage while relaxing the cutting-edge-ness on the (expendable) upper stage.

Different assumptions give you different conclusions.
« Last Edit: 11/25/2015 12:40 am by Robotbeat »
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Offline john smith 19

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To quote Arthur Schnitt himself, "The MCD analysis showed that first stages, as part of a multi-stage expendable SLV, should be the least sophisticated; and that the optimum degree of hardware sophistication increases with each successive, upper stage."
Exactly.

Save the cutting edge, wafer thin margin  tech for the uppermost stage.

Which sort of flips SX's plans on their head.
If you have a fully, rapidly reusable first stage, then yeah, Minimum Cost Design would lead you to use cutting edge tech on the first stage while relaxing the cutting-edge-ness on the (expendable) upper stage.

Different assumptions give you different conclusions.
I suggest you read his articles again.

His point is to do with what NASA have called the "exchange rates" IE 1 unit of extra mass means what do you lose from final payload.

For the 1st stage not much. So go big (which is pretty cheap), go simple (to keep it cheap) and go expendable.

But this was back when avionics were heavy and (very) expensive. So that changes things a bit. Likewise piston pumps are much simpler to make but Whitehead's team reckons the crossover point was only about 5000lbs, so we get back to turbopumps. OTOH CAD driving CNC changes the economics of that problem quite a lot.

But his conclusion still says "pay mass to avoid cost."

Trouble is that means you leave all the reusability in the upper stage, as well as the return from orbit issues.

And just a reminder SX still does not have a reusable first stage. Currently I'm thinking it'll be available before Q417.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¬cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline HMXHMX

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To quote Arthur Schnitt himself, "The MCD analysis showed that first stages, as part of a multi-stage expendable SLV, should be the least sophisticated; and that the optimum degree of hardware sophistication increases with each successive, upper stage."
Exactly.

Save the cutting edge, wafer thin margin  tech for the uppermost stage.

Which sort of flips SX's plans on their head.
If you have a fully, rapidly reusable first stage, then yeah, Minimum Cost Design would lead you to use cutting edge tech on the first stage while relaxing the cutting-edge-ness on the (expendable) upper stage.

Different assumptions give you different conclusions.
I suggest you read his articles again.

His point is to do with what NASA have called the "exchange rates" IE 1 unit of extra mass means what do you lose from final payload.

For the 1st stage not much. So go big (which is pretty cheap), go simple (to keep it cheap) and go expendable.

But this was back when avionics were heavy and (very) expensive. So that changes things a bit. Likewise piston pumps are much simpler to make but Whitehead's team reckons the crossover point was only about 5000lbs, so we get back to turbopumps. OTOH CAD driving CNC changes the economics of that problem quite a lot.

But his conclusion still says "pay mass to avoid cost."

Trouble is that means you leave all the reusability in the upper stage, as well as the return from orbit issues.

And just a reminder SX still does not have a reusable first stage. Currently I'm thinking it'll be available before Q417.

I'd slightly rephrase "pay mass to avoid cost" to "burn propellant to avoid cost" since propellant is the cheapest mass to buy and use aboard a lunch vehicle.
« Last Edit: 11/26/2015 05:09 am by HMXHMX »

Online Robotbeat

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To quote Arthur Schnitt himself, "The MCD analysis showed that first stages, as part of a multi-stage expendable SLV, should be the least sophisticated; and that the optimum degree of hardware sophistication increases with each successive, upper stage."
Exactly.

Save the cutting edge, wafer thin margin  tech for the uppermost stage.

Which sort of flips SX's plans on their head.
If you have a fully, rapidly reusable first stage, then yeah, Minimum Cost Design would lead you to use cutting edge tech on the first stage while relaxing the cutting-edge-ness on the (expendable) upper stage.

Different assumptions give you different conclusions.
I suggest you read his articles again.

His point is to do with what NASA have called the "exchange rates" IE 1 unit of extra mass means what do you lose from final payload.

For the 1st stage not much. So go big (which is pretty cheap), go simple (to keep it cheap) and go expendable.

But this was back when avionics were heavy and (very) expensive. So that changes things a bit. Likewise piston pumps are much simpler to make but Whitehead's team reckons the crossover point was only about 5000lbs, so we get back to turbopumps. OTOH CAD driving CNC changes the economics of that problem quite a lot.

But his conclusion still says "pay mass to avoid cost."

Trouble is that means you leave all the reusability in the upper stage, as well as the return from orbit issues.

And just a reminder SX still does not have a reusable first stage. Currently I'm thinking it'll be available before Q417.
And I suggest you read my post again. I said "f you have a fully, rapidly reusable first stage..."
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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