This strikes me as about the most conservative approach to reusable lift vehicles.I would like to see a RLV discussion dedicated just to this. It is ok to generalize two stage to 1.5 stage, and I havent specified whether landing is parachutes, rockets, wings or something else.What actually are the difficulties that prevent us having one right now? Is anyone close to being able to make this work?
Why not a 3 stage RLV?
Quote from: Propforce on 03/11/2010 03:05 pmWhy not a 3 stage RLV?Out of curiosity, where is that image from?
The Kistler K-1 was a good example of a way it could work. TSTO, first stage RTLS recovery with parachutes and airbags, second stage thermal protected reentry to launch site recovery with parachutes and airbags. What prevengted it from working (unresolved technical questions aside) was lack of money.
It's one of my favorite approaches. I'd add Vertical Landing for the first stage. This could be down-range, since most launches are to only one or two distinct orbital inclinations from a given launch site. This approach also lends itself to starting with an ELV second stage, and progressing to an RLV in due course.
I remember someone here claiming quite a small additional weight in fuel for a vertical landing.. Anyone able to support that?
. Evolving from an expendable tsto to a reusable tsto also seems an interesting topic. What design choices in the expendable would let you consider either evolving the 1st stage to reusable and/or evolving/replacing the second stage?
Quote from: Propforce on 03/11/2010 03:05 pmWhy not a 3 stage RLV?At one point, a "trimaran" concept was proposed for the space shuttle, consiting of three "orbiters" sandwiched together, with the two outer ones acting as boosters for the inner one, which would proceed to orbit. I googled for an image, but nothing bubbled close to the surface. Too many seagoing trimarans in the world. The only picture I have is in one of Phil Bono's old books (still in storage).
Quote from: William Barton on 03/12/2010 11:36 amQuote from: Propforce on 03/11/2010 03:05 pmWhy not a 3 stage RLV?At one point, a "trimaran" concept was proposed for the space shuttle, consiting of three "orbiters" sandwiched together, with the two outer ones acting as boosters for the inner one, which would proceed to orbit. I googled for an image, but nothing bubbled close to the surface. Too many seagoing trimarans in the world. The only picture I have is in one of Phil Bono's old books (still in storage).Sounds like a British concept called Mustard. (I have the same Bono book)http://www.astronautix.com/lvs/mustard.htm
That's the one, I just couldn't remember the name (my books will be in storage for about another 4 months; I'll be very happy to have them back!). Apparently, there's an Australian boat company with the initials BAE that makes trimarans...
Here's a picture of Space Shuttle design "evolution". .... the middle one appears to be a 3 stage but only the orbital is a reusable ...
Quote from: KelvinZero on 03/11/2010 08:23 amThis strikes me as about the most conservative approach to reusable lift vehicles.I would like to see a RLV discussion dedicated just to this. It is ok to generalize two stage to 1.5 stage, and I havent specified whether landing is parachutes, rockets, wings or something else.What actually are the difficulties that prevent us having one right now? Is anyone close to being able to make this work?The Kistler K-1 was a good example of a way it could work. TSTO, first stage RTLS recovery with parachutes and airbags, second stage thermal protected reentry to launch site recovery with parachutes and airbags. What prevengted it from working (unresolved technical questions aside) was lack of money.
I wouldn't evolve the first stage. Starting as a VTVL RLV allows incremental testing, gradual expansion of the envelope, with ONE test LV. Plus possible early revenue for sub-orbital payloads.I might consider starting with an expendable second stage and a reusable payload carrier/spacecraft, that performs orbital insertion and possibly acts as a small third stage. This could allow the second stage to be very simple and inexpensive. Just a tank and a low pressure engine. That might be cheaper to expend than flying an RLV.
Quote from: Propforce on 03/12/2010 05:47 pmHere's a picture of Space Shuttle design "evolution". .... the middle one appears to be a 3 stage but only the orbital is a reusable ... I think the middle concept consisted of an S-IC based first stage topped by an air-start orbiter attached to an external tank. - Ed Kyle
Quote from: edkyle99 on 03/12/2010 08:00 pmQuote from: Propforce on 03/12/2010 05:47 pmHere's a picture of Space Shuttle design "evolution". .... the middle one appears to be a 3 stage but only the orbital is a reusable ... I think the middle concept consisted of an S-IC based first stage topped by an air-start orbiter attached to an external tank. - Ed KyleIt sure looks like a S-IC doens't it? I just can't see from this angle if that's a 2nd stage or a strap-on tank.Thanks.
Holy ....I like the last one
Yes, that last one is to make the girls gird their loins...
Quote from: mlorrey on 03/13/2010 05:40 pmYes, that last one is to make the girls gird their loins...Would probably have a big base heating problem though.
The launcher. And idk, I think one of the concerns with the Direct launchers was base heating, and they have just one ET core. That thing has 7 (I think).
Slight problem, more than a 3 core version couldn't be launched at KSC. Obviously even a 3 core would need a massive pad upgrade, but there is a limit to the total amount of lift-off thrust before acoustic damage to the surrounding areas is too great. That limit is about 12 million lbf.
The big question is how is a launch vehicle reused? Personally I never saw the point in reusing a fuel tank. They're relatively cheap to make (shuttle ET, according to studies I've seen costs less than a million bucks when you discount all the administrative overhead) and make for good useful pressurized space in orbit. I'd like to bring up my old ET derived 1.5STO family of HLVs.
Quote from: mlorrey on 03/13/2010 05:28 pmThe big question is how is a launch vehicle reused? Personally I never saw the point in reusing a fuel tank. They're relatively cheap to make (shuttle ET, according to studies I've seen costs less than a million bucks when you discount all the administrative overhead) and make for good useful pressurized space in orbit. I'd like to bring up my old ET derived 1.5STO family of HLVs.Too big (in geometric sense). LH in 1st stage is not the best idea.
Well, 1.5STO is going to use the same fuel on the .5 boost and the 1st stage sustainer motor, unless you want to get hopelessly complex with multiple fuels. I am normally a critic of hydrogen fuelled launch vehicles, though, particularly due to tank size/mass and cryogenic requirements. This launch vehicle family I envisioned is IMHO really the only way to use LH advantageously in as few stages as possible.....
Quote from: indaco1 on 03/01/2010 12:13 pmI repeat I can't see a reason for variable isp.Even for SSTO, varying the Isp (and being able to airbreathe for a good chunk of the ascent) can be very helpful to optimize the vehicle's efficiency.
I repeat I can't see a reason for variable isp.
Wow, just reading about the RD-701. The more I read about the Russian/Soviet space program, the more respect I have for them.
... It definitely deserves more capital invested in it....
...Beyond easy TPS maintenance, low maintenance engines are the second ingredient to an economical RLV.
mlorry:The problem with using the ETs on-orbit is they are flimsy, especially the latest "light-weight" tanks. Other than the hard-backs for mounting the SRBs and Orbiter they are chemically etched iso-grids so thin in places a good kick or punch will rip right through the metal. (Especially on-orbit if they were pressurized)It's one of the main reasons that doing an "in-line" booster is going to take some major redesign work. Actually what we NEED to do is go back to the "heavy-weight" tank design with the lighter alloys since most of the "usable" ET work was done with that design.
Quote from: RanulfC on 03/16/2010 04:59 pmmlorry:The problem with using the ETs on-orbit is they are flimsy, especially the latest "light-weight" tanks. Other than the hard-backs for mounting the SRBs and Orbiter they are chemically etched iso-grids so thin in places a good kick or punch will rip right through the metal. (Especially on-orbit if they were pressurized)It's one of the main reasons that doing an "in-line" booster is going to take some major redesign work. Actually what we NEED to do is go back to the "heavy-weight" tank design with the lighter alloys since most of the "usable" ET work was done with that design.Actually I was thinking of utilizing large Polyvinylidene Fluoride bags/tubes to fit around each tank in orbit, with a 0.5 mm wall thickness, this material is a heat shrink polymer that tolerates high temperatures, high ionization levels, and abrasions as well. Density of this material is only 1.48, so its pretty low mass, and would create a good outer structural containment of the foam but also would provide support to the isogrid tank itself.Also, the tank is built for pressure levels more than twice that of normal sea level pressure (at the top) and significantly more than that at the bottom, so I can't see it as being seriously stressed by being used as habitat space.PVDF normal operating temps are up to 175 C, which is less than the 145 C peak daytime temps one would see in orbit.