Any thoughts on an AJAX core, but instead of AV boosters, use Falcon 9 V1.1, using either 6 or 8 boosters and air starting the core at booster jettison?
Quote from: davamanra on 01/07/2014 03:02 pmIt's been a while since I've been on this forum, and I've done a cursory search for this subject without success. This thread SEEMS to be the appropriate for this subject, so here goes! What about using 3 or more boosters on an SLS/HLV? You could configure the boosters for a lower thrust, longer duration burn, as well as throttling back the main engines until booster burn out. The SLS Block II payload of 130mt is nice, but I would like to see a SHLV in the future for much more ambitious projects.The following thread that I started discussed this concept. For numerous reasons, the short answer is no.http://forum.nasaspaceflight.com/index.php?topic=27563.msg840654#msg840654
It's been a while since I've been on this forum, and I've done a cursory search for this subject without success. This thread SEEMS to be the appropriate for this subject, so here goes! What about using 3 or more boosters on an SLS/HLV? You could configure the boosters for a lower thrust, longer duration burn, as well as throttling back the main engines until booster burn out. The SLS Block II payload of 130mt is nice, but I would like to see a SHLV in the future for much more ambitious projects.
Quote from: davamanra on 01/07/2014 03:02 pmIt's been a while since I've been on this forum, and I've done a cursory search for this subject without success. This thread SEEMS to be the appropriate for this subject, so here goes! What about using 3 or more boosters on an SLS/HLV? You could configure the boosters for a lower thrust, longer duration burn, as well as throttling back the main engines until booster burn out. The SLS Block II payload of 130mt is nice, but I would like to see a SHLV in the future for much more ambitious projects.That could certainly work, but it would require a complete redesign to SLS. SLS is designed like STS, with two top-lifting boosters attached to an upper thrust beam. So you can't add more than just the two. To add more, you might need an upper thrust cross beam, and two more boosters, or come back to a traditional bottom lift booster system where you can add boosters around the core and attached them into the core's MPS. Or you could have two booster pairs on each side attached to a strongback which is then attached to the upper thrust beam. That's probably the only way to could have more than two boosters without a complete redesign of the core. The "AJAX" concept by Downix would have used existing Atlas V CCB's and attached them around a shorter core than SLS, designed to take between 2 and 8 of them, whatever the mission requried.I think one problem you have with multiple cryo boosters, is on the pad you need to get to them all, as well as the cryo core. tri-core configurations are the easiest multi-core system, as the three are inline, and you can easily access them all from one side of the LV. A tower arm or strongback on the one side can get to all three. If you have a 4 booster system, then you'll have one booster on the opposite side. So you need some way to tank and detank the propellants over there, and vent cryo gases, which I think complicate things on the pad. The Soviets managed to do it with Energia, but they needed to towers, one on each side. The RUssians will manage it with Angara, and that will use a type of dual tower gantry too. So it's not a deal breaker, but it complicates things on the pad vs. multiple solids like Delta II or Atlas or Delta IV which don't need any service access on the pad.I'm not sure how AJAX would have worked using the LC-39 hardware. (Note, I'm a big fan of AJAX). It might have needed a dual tower gantry built onto the pad that could access all of the boosters as well as the core. And the LV itself could have rolled out to the pad without a tower like STS. However, even AJAX would have needed the design and development of a new core stage, not unlike SLS. It just would use existing production boosters rather than 1-off big SRB's or new Advanced boosters.This is where I think the -best- way for NASA to build a new rocket (if NASA -must- build their own rocket...which they probably shouldn't) then go with a narrower core, that can launch by itself, or as a tri-core heavy with identical cores. A scaled up version of Atlas V-Heavy, Delta IV-Heavy, or Falcon Heavy.That would allow a simgle tower on the MLP to access all three booster plus the upper stage, and probably be easier to use with the heritage hardware at KSC.
RS-68 isn't air-startable either.
Lobo - All this talk of 6.5 meter common cores reminds me of one of my favorite "Saturn-Derived" ideas the the Eyes Turned Skyward thread @ Alternate History Wiki. Its a 6.6 meter core with 1 F-1a and SIV-B upper stage. Granted, your idea of using in production engines makes more sense, but the J-2x is ready to go and Dynetics / AJR is hard at work on the F-1B...http://wiki.alternatehistory.com/doku.php/timelines/spacecraft_and_launch_vehicle_technical_data
Quote from: Lars_J on 01/09/2014 06:35 amRS-68 isn't air-startable either.Yes, I am aware of that, however modifications to make it air started have been discussed a lot here. The same is true of RS-25, but if I remember correctly Downix' primary design for AJAX used RS-68. I know you could ground start the core. I was thinking of ways to maximize booster thrust then take advantage of all core propellant after staging. Since the thread title involves alternative concepts, I took the liberty to be mildly speculative.
If I recall correctly, it would have been possible (though not trivial) to modify the RS-25 for air start. The real showstopper was in-flight restart, which is what disqualified it from use on the Ares V EDS and started the chain reaction.I don't know about the RS-68.
Quote from: 93143 on 01/09/2014 08:41 pmIf I recall correctly, it would have been possible (though not trivial) to modify the RS-25 for air start. The real showstopper was in-flight restart, which is what disqualified it from use on the Ares V EDS and started the chain reaction.I don't know about the RS-68.That was my understanding too. The Ares V would need at least one air restart (after EOR with Orion), and I think that was going to be pretty much impossible for RS-25, so while it would have potentially worked for Ares 1, they wanted a common engine. Thus the J2X was born, and I think that's when they looked at dumping the RS-25 altogether and going with RS-68 on Ares V....until they figured out the base heating problem. Then they went back to RS-25. Then it was cancelled.But my understanding of it all might not quite be accurate.
I think about how ridiculously expensive and dangerous and time consuming it was building the ISS with so many launches, when, with a SHLV, it could be done with maybe four or five launches with Skylab sized modules, and with the goals of going to the moon, Mars and the asteroid belt, I can see the need for large payloads.
Quote from: davamanra on 01/09/2014 12:34 pmI think about how ridiculously expensive and dangerous and time consuming it was building the ISS with so many launches, when, with a SHLV, it could be done with maybe four or five launches with Skylab sized modules, and with the goals of going to the moon, Mars and the asteroid belt, I can see the need for large payloads. It was only expensive and dangerous because it was done with the shuttle. Done with a Falcon Heavy, it would be cheap and safe -- much cheaper than with SLS or an SLS derivative.
FH will get 53-55 mt (55 if no fairing) to LEO
Quote from: ChrisWilson68 on 01/11/2014 07:02 amQuote from: davamanra on 01/09/2014 12:34 pmI think about how ridiculously expensive and dangerous and time consuming it was building the ISS with so many launches, when, with a SHLV, it could be done with maybe four or five launches with Skylab sized modules, and with the goals of going to the moon, Mars and the asteroid belt, I can see the need for large payloads. It was only expensive and dangerous because it was done with the shuttle. Done with a Falcon Heavy, it would be cheap and safe -- much cheaper than with SLS or an SLS derivative.Dave, at one time I completely agreed with you. As time has passed, I have changed my mind and believe that Chris is right. The two reasons are 1.) realistic expectations of future funding levels and 2.) production line efficiencies. At one launch per every 12-24 months, the SLS production line is exceptionally inefficient, and then there's no funding left to build hardware. Wishful thinking is not going to engender new money. All the components for FH exist and its about to fly. Production lines are humming and efficiencies of scale are present. FH will get 53-55 mt (55 if no fairing) to LEO, twice the payload of DIVH @ 1/3 the cost, an astounding 6x better cost per mass unit. My guess is that FH cost/mass to LEO will be at least an order of magnitude better than SLS. When I look at this most recent F9 v1.1 launch (on time, no delays, first attempt, no anomalies, and all on the second launch of this vehicle iteration) it is obvious that these people know what they are doing and they are getting better and better at it. If NASA used F9 and FH, there actually would be money left over for payloads. As far as modules, 53-55 mt is nothing to sneeze at. Think of it this way: FH can put almost 3 times as much into orbit as Saturn I and well more than twice as much as the shuttle. Saturn V is the only successful LV to carry more mass, and it was too expensive to sustain. FH really is an HLV and authentic existing commerce is going to cause its components to remain available on an ongoing basis. For EDS, Raptor is under development and I think if NASA were buying the hardware, any obstacles could be overcome that might otherwise prohibit ACES from being developed and integrated with FH. After all the Apollo program integrated components from many unrelated corporations.Orion is too heavy for any purpose. Even Dragon is actually bigger than needed for a lunar mission. A Gemini sized capsule could do (though you need LAS and beefier TPS). A reusable lander could be docked with a new crasher stage on each mission and the crasher stage would provide 99+% of the descent impulse.FH could allow an economical two launch architecture for a lunar program. For Mars, 53-55mt multiple LEOR assembly is certainly doable. With an LV production line that already has a robust reason to exist, NASA could devote its attention (as well as actual funding) to developing the payloads it needs to actually go somewhere.There comes a point at which size is not your friend. Here are some examples. A couple of times male students of mine have had been reading books about submarines. They see that Soviet subs were much larger than ours and assume those subs were far superior. I give the students the reasons for the Soviet sub size. Inefficient warheads must be bigger to work. This requires bigger missiles. This requires a bigger sub. Other components of the sub cannot be miniaturized, also requiring a bigger sub. Now add these facts. The big sub is not built as well and it makes more noise. Now the most important fact of all: the bigger the sub, the slower it goes, the harder to turn, and the bigger the target at which you are shooting! Example 2: my wife and I built the biggest dream house we could afford. What happened? There was more cleaning to do; the insurance was more; the utility bills were more; rather than the expected appreciation, the market crashed. Example 3: think about NBA player. Sure you may be great at dunking baskets, but by existing as a statistical outlier, you also have to spend your entire life ducking door headers, cramming yourself into undersized seats, and having your bed, clothing, and shoes custom made for many thousands of dollars. You literally just don't fit where everyone else fits. I know these are not direct analogical comparisons to rockets, but the point remains, size is not always your friend. It is important to find the size that is most optimal, and finding that point requires examining every pertinent factor.Unfortunately, the main obstacle that prevents NASA from going somewhere is the same entity that allows it to exist. Despite their rhetoric calling for accountable spending, the same people use the Manned Space Program as a way to continue funneling cash to former shuttle component manufacturers.My own prediction is that humanity will reach Mars by 2060 and that SpaceX vehicles will do the heavy lifting. NASA may do it in cooperation with SpaceX, but if not I think Elon Musk will find a way to do it alone.
But, my vehicle concept would look very much like this. But each core would have four RD-180's rather than one F-1A. And probably be taller (although the SC kerolox means less propellant is needed for the same thrust. But four RD-180's is about twice the power as one F-1A, so the stage probably need to be about twice as tall. That's still not all that tall though.)The upper stage would be similar to the S-IVB, but taller like the stretched S-IVB the tri-core heavies have. And with options of two or four RL/MB-60's, instead of the single J2S like the S-IVB in these graphics.The RD-180's with their superior ISP can burn longer and do more ascent than the F-1A, so the upper stage doesnt' need to be as large as with the lower ISP GG engines. Especially with a crossfed tri-core. But where the tri-cores in this graphic are less powerful with less performance than the Saturn V, my concept would be more powerful and have better performance.
^I guess the 4xF1B Block 1 version of yours is hard to beat. Not so sure about Block 2.Problem is, SLS will be canceled anyway, would you rather end up with a bunch of RS-25E or F1B?
Quote from: Oli on 10/19/2013 08:15 pmQuote from: M129KF1B. I'd rather be stuck with a powerful engine that could be useful both for EELV-class vehicles and SHLVs, than with a niche sustainer engine. It's just too expensive to be mass-produced.Why? I could see it for a first stage of an ELV, for a reusable TSTO with one engine type, and for SSTO.It could. But it's an expensive, low thrust engine. It could be useful for Ariane 5-like vehicles, but I don't know if it would be a very good alternative to a more standard EELV design that could much more easily evolved into a SHLV than an Ariane-ish design could.
Quote from: M129KF1B. I'd rather be stuck with a powerful engine that could be useful both for EELV-class vehicles and SHLVs, than with a niche sustainer engine. It's just too expensive to be mass-produced.Why? I could see it for a first stage of an ELV, for a reusable TSTO with one engine type, and for SSTO.
F1B. I'd rather be stuck with a powerful engine that could be useful both for EELV-class vehicles and SHLVs, than with a niche sustainer engine. It's just too expensive to be mass-produced.
You're chasin' rabbits again. But the ones you're chasin' can fly and kill medieval English knights with a fierce bite to the neck. IOW, what you're chasing only exists in stories created by great comedians.
And finally here is an F-1B based core option. Again I've optimized these for Escape missions and made them with only two stages, EELV style. A two-stage core can roughly do the SLS Block 1 mission. Switching to an RP core solves the VAB height constraint. Adding F-1B boosters gets the machine to Block 2 capability. As far as I'm concerned, the Block 1 rocket could run any space program. - Ed Kyle