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.
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.
That is the party line...
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 )
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.
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.
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.
Quote from: JamesG123 on 11/17/2015 03:43 amThere 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.Quote from: JamesG123 on 11/17/2015 03:43 amThose 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.
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?
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?
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.
Quote from: JamesG123 on 11/17/2015 03:43 am 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 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)...
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.
I think the case of exoatmospheric suborbital refueling will likewise be one of those crazy things that we wonder how we ever lived without.
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.
{snip}Would that the human race could have evolved on a 0.9 G planet, so that these arguments might be moot.
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?
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.
Quote from: HMXHMX on 11/17/2015 04:47 pm{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.
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?
Quote from: john smith 19 on 11/17/2015 03:58 pmX33 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.
Unfortunately, as usual, I can't comment on my current work except to say it isn't SSTO. Close, though.
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.
Quote from: Nilof on 11/19/2015 03:14 amOne 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.
Quote from: Robotbeat on 11/18/2015 12:52 amA 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..."
Quote from: HMXHMX on 11/18/2015 03:28 amQuote from: Robotbeat on 11/18/2015 12:52 amA 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.
Quote from: HMXHMX on 11/19/2015 04:46 pmSince 1969, yes.Thanks for the vote, along with the four other people who want to read it, that makes five. Make that 6
Since 1969, yes.Thanks for the vote, along with the four other people who want to read it, that makes five.
As John Goff said QuoteI think the case of exoatmospheric suborbital refueling will likewise be one of those crazy things that we wonder how we ever lived without.
Quote from: Archibald on 11/19/2015 04:30 pmQuote from: HMXHMX on 11/18/2015 03:28 amQuote from: Robotbeat on 11/18/2015 12:52 amA 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.
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
Quote from: Archibald on 11/17/2015 05:41 pmAs John Goff said QuoteI think the case of exoatmospheric suborbital refueling will likewise be one of those crazy things that we wonder how we ever lived without. 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
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.
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.
I asked an astronaut a related question;QuoteDo 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 repliedQuoteTo, 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...
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 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 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 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.
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.
What subsequent history? Delta Clipper was cancelled for political reasons, not technical reasons.
Quote from: JasonAW3 on 11/20/2015 03:14 pmUntil 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.
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.
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.
Quote from: Elmar Moelzer on 11/20/2015 04:36 pmI 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.
Quote from: RonM on 11/20/2015 05:45 pmQuote from: Elmar Moelzer on 11/20/2015 04:36 pmI 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
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.
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.
Quote from: Elmar Moelzer on 11/20/2015 04:36 pmWhat subsequent history? Delta Clipper was cancelled for political reasons, not technical reasons.The history of all SSTO developments, not just Delta Clipper.
Quote from: Robotbeat on 11/21/2015 12:10 amYou 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.
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.
Quote from: 93143 on 11/21/2015 01:51 amQuote from: Robotbeat on 11/21/2015 12:10 amYou 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.
Quote from: douglas100 on 11/20/2015 09:18 pmQuote from: Elmar Moelzer on 11/20/2015 04:36 pmWhat 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.
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.
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.
Quote from: john smith 19 on 11/20/2015 06:21 amHowever 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.
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.
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...
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.
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.
Quote from: A_M_Swallow on 11/22/2015 03:27 pmCan 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
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.
This certainly contradicts the optimism of those suborbital schemes that are effectively two stage with integration in flight
Quote from: Darkseraph on 11/22/2015 03:35 pmAlmost 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....
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.
Quote from: Darkseraph on 11/22/2015 04:57 amI 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.
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.
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.
Skylon and other SSTO programs are speculative multi-billion dollar efforts that have lots of unknown unknowns.
BAE Systems have just announced that they are putting $30M into Alan Bond's project
Quote from: Darkseraph on 11/22/2015 08:18 pmSkylon 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
This whole idea has been limping along on relatively small amounts of funding for 3 decades because it's not a certain thing.
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.
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.
Quote from: Vultur on 11/21/2015 07:09 pmBut 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. QuoteIt 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."
Quote from: KelvinZero on 11/22/2015 03:57 amThis 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.
It's a correct assumption. There is no turn-key SSTO capability that would be competitive with expendable launch systems.
The low hanging fruit right now is just making the first stage returnable. Even that is very hard to do.
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.
Quote from: nec207 on 11/17/2015 09:21 amWhat 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.
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.
"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).
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).
Quote from: Robotbeat on 11/23/2015 12:04 am"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).
Quote from: Robotbeat on 11/23/2015 12:04 am"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."
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..
Quote from: Proponent on 11/24/2015 11:57 amTo 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. ...
Quote from: Proponent on 11/24/2015 11:57 amTo 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.
Quote from: john smith 19 on 11/24/2015 01:40 pmQuote from: Proponent on 11/24/2015 11:57 amTo 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.
Quote from: Robotbeat on 11/25/2015 12:39 amQuote from: john smith 19 on 11/24/2015 01:40 pmQuote from: Proponent on 11/24/2015 11:57 amTo 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.