#11
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Great job SpaceX
On 6/2/2020 7:50 AM, Jeff Findley wrote:
An in-line design is more likely to transmit vibrations straight from the engine to the capsule with the propellant acting to dampen a bit of that out. Remember the horrible time NASA had trying to dampen the vibrations of Ares I? That's about as bad as it gets. Giant SRB in- line with a smallish upper stage. Jeff OMG yes. You have a bad tooth filling or a kidney stone? Take a sub-orbital ride in the Ares I. Will substitute the 2nd stage with a mass simulator of solid steel. :::---OOO Dave |
#12
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Great job SpaceX
On Tuesday, June 2, 2020 at 7:34:35 AM UTC-4, Jeff Findley wrote:
In article , says... Saturn 1B was huge and it dwarfed the Titan 3C, which was a large rocket in its own right. Here's a picture I found on Reddit showing various crewed launch vehicles to scale: https://www.reddit.com/r/nasa/commen...asa_human_spac eflight/ Falcon 9 really is a beast. It doesn't look like much compared to the Saturn IB, but to quote Han Solo: "She may not look like much, but she's got it where it counts, kid." But when you compare Saturn V to SLS 1A and SLS 1B (remains to be seen if the EUS for 1B will ever be built), SLS falls short in the performance department. NASA keeps boasting that SLS is "more powerful" than Saturn V, but that's only liftoff thrust. The fact is those SRBs do have high thrust, but their casings are *heavy* and their ISP is terrible, leading to worse performance compared to something like the Saturn V's first stage (LOX/kerosene like Falcon 9). FWIW, Wikipedia has these figures, whereby payload to LEO is slightly higher for SLS Block 2. The Space Launch System (SLS) is a US super heavy-lift expendable launch vehicle. Payload to LEO. Block 1: 95 t (93 long tons; 105 short tons); Block 2: 130 t (130 long tons; 140 short tons) Fully fueled, the Saturn V weighed 6.5 million pounds (2,950,000 kg) and had a low Earth orbit payload capacity originally estimated at 261,000 pounds (118,000 kg), but was designed to send at least 90,000 pounds (41,000 kg) to the Moon. |
#14
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Great job SpaceX
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#15
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Great job SpaceX
On 2020-06-03 8:44, JF Mezei wrote:
Smoothness of ride: Wouldn't the "complaint" be due to the Merlin engine for stage 2 being an awfull lot closer to the crew than the OMS or SSME engines on Shuttle were? Naively I would expect that in a three-engine system like the Shuttle, where each engine provides 1/3 of the thrust, combustion irregularities occur independently in each of the three engines, which means that they are reduced by a factor of 3 compared to irregularities in the single engine in the Falcon-9 second stage. That is, except for Pogo, but AIUI this "roughness" of the second-stage Crew Dragon ride is not Pogo. -- Niklas Holsti niklas holsti tidorum fi . @ . |
#16
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Great job SpaceX
On 2020-06-03 8:29 AM, Jeff Findley wrote:
In article , says... Smoothness of ride: [snip] Or is the "complaint" really due to engine characteristics? I'm not sure it's a complaint so much as an observation. Things that are different, just aren't the same. Jeff I agree with Jeff on this. I would not characterize what Doug said as a "complaint", but an observation. The reasons for that have already been discussed. I suspect if/when Starship flies, you'll see possibly even a smoother ride on it, mainly due to it's mass. Hopefully it flies soon enough with crew that we can get folks who have flown on both it and the F9 to compare. Dave |
#17
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Great job SpaceX
On 2020-06-02 7:50 AM, Jeff Findley wrote:
In article , says... .... I'd guess the Saturn IB and Saturn V would be a smoother ride (same upper stage really), simply because LOX/LH2 likely makes complete mixing easier resulting in more complete combustion. But, it certainly would be more apples to apples than the shuttle due to the in-line stage design and the single engine. The shuttle had that giant, heavy, ET structure hanging off the side that likely dampened some of the vibrations (it certainly did when the SRBs were firing!). I am going to disagree here a bit with you Jeff. As I understand it there was still some POGO with the Saturn 5 Stage 1. I would expect the higher it got and the less the fuel mass the worse it might have become. Contrary facts always welcome. Contrary opinions always greeted with skepticism. :-) Also understand from what I've read MECO and stage separation of the first stage was also a bit of a jolt. After that, I believe things smoothed considerably as they went to LH2/LOX engines. The Saturn 5 second stage was a marvel and largely ignored (unfortunately). Off the top of my head I count 5 crewed Apollo flights using the Saturn IB: Apollo 7, the 3 Skylab missions and Apollo/Soyuz. The last flight of a Saturn 5 was to launch the Skylab space station. Dave |
#18
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Great job SpaceX
On Wednesday, June 3, 2020 at 8:24:24 AM UTC-4, Jeff Findley wrote:
And if you looked at Saturn V upgrades (seems fair if you're comparing to Block 2 which is a *long* ways off), I'm sure an uprated Saturn V using upgraded engines (which were in the works) and some solid or liquid rocket boosters would beat an SLS Block 2 in LEO payload. Here's a cite to a study: http://www.astronautix.com/data/satvint.pdf From above (page 43, chart on page 44): SAT-V-25(S) two stage payload capability to 100 nautical mile orbit is almost 494,000 pounds Four solid rocket boosters added around the first stage. 100 seconds of burn time and total of 4.45 million pounds of thrust. Yeah, that would seriously increase the lifting capacity of the Saturn V! Probably should have gotten its own name, like Saturn X. So, a similarly upgraded Saturn V would have had nearly twice the payload to LEO as SLS Block 2. I don't think this comparison is unfair. If SLS Block 2 can get "advanced solid rocket boosters" that are only notional at this time, why can't Saturn V get similar upgrades as well? Given all the questions about using solid rockets for manned space flight back then, probably zero chance of getting it man-rated by the 1970s. May have had serious design issues even for unmanned flights. |
#19
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Great job SpaceX
On 2020-06-03 11:02 AM, Scott Kozel wrote:
On Wednesday, June 3, 2020 at 8:24:24 AM UTC-4, Jeff Findley wrote: And if you looked at Saturn V upgrades (seems fair if you're comparing to Block 2 which is a *long* ways off), I'm sure an uprated Saturn V using upgraded engines (which were in the works) and some solid or liquid rocket boosters would beat an SLS Block 2 in LEO payload. Here's a cite to a study: http://www.astronautix.com/data/satvint.pdf From above (page 43, chart on page 44): SAT-V-25(S) two stage payload capability to 100 nautical mile orbit is almost 494,000 pounds Four solid rocket boosters added around the first stage. 100 seconds of burn time and total of 4.45 million pounds of thrust. Yeah, that would seriously increase the lifting capacity of the Saturn V! Probably should have gotten its own name, like Saturn X. So, a similarly upgraded Saturn V would have had nearly twice the payload to LEO as SLS Block 2. I don't think this comparison is unfair. If SLS Block 2 can get "advanced solid rocket boosters" that are only notional at this time, why can't Saturn V get similar upgrades as well? Given all the questions about using solid rockets for manned space flight back then, probably zero chance of getting it man-rated by the 1970s. May have had serious design issues even for unmanned flights. I took a cursory look at this document. There were also liquid fueled strap-on options studied as well. The Saturn V 23L and Saturn V 24L. The 23L variant used pairs of "standard" F1s in each of four strap-on liquid "pods" and the 24L used pairs of "uprated" F1s in four strap-ons and an "advanced" engine for the upper stages. The document mentions aerospike engines and maybe so, but there were also ideas kicking around at the time for a higher performance J2 as well. The 24L didn't make it past phase 1 study but, the 23L got a rating in this document of 579,000 lbs (289.5 short tons) to orbit (2 stage configuration) and 220,000 lbs (110 short tons) I presume to the moon (3 stage configuration). Presumably the 24L variant with the higher thrust F1s could have done even better.* Let's be conservative and estimate first launch by 1975 (this document was written in 1966 and predicted a 1973 ready date). My date includes assuming mobile launch platform (known as MLs in the Apollo era) modifications and other pad modifications also needed. But at the time Wikipedia says NASA had three MLs, so NASA should have been able to dedicate one to support this configuration. Compare this to the also non-extant SLS Block 2 at 280,000 lbs (140 short tons) to LEO. What a monster this could have been. You're gonna need to move further back... What other country in the world (besides us) would have so thoroughly blown this advantage in rocketry? We're talking nineteen seventy freaking five! Dave *There's a tantalizing paragraph on page 9 that ends: "The liquid pod strap-on concept, with uprated F-1s and advanced engines in the second stage (SAT-V-24(L)), achieved payloads to 960,000 lbs. [480 short tons] to 100 nautical mile Earth orbit when stage and total vehicle length restrictions were relaxed." |
#20
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Great job SpaceX
In article ,
says... On Wednesday, June 3, 2020 at 8:24:24 AM UTC-4, Jeff Findley wrote: And if you looked at Saturn V upgrades (seems fair if you're comparing to Block 2 which is a *long* ways off), I'm sure an uprated Saturn V using upgraded engines (which were in the works) and some solid or liquid rocket boosters would beat an SLS Block 2 in LEO payload. Here's a cite to a study: http://www.astronautix.com/data/satvint.pdf From above (page 43, chart on page 44): SAT-V-25(S) two stage payload capability to 100 nautical mile orbit is almost 494,000 pounds Four solid rocket boosters added around the first stage. 100 seconds of burn time and total of 4.45 million pounds of thrust. Yeah, that would seriously increase the lifting capacity of the Saturn V! Probably should have gotten its own name, like Saturn X. So, a similarly upgraded Saturn V would have had nearly twice the payload to LEO as SLS Block 2. I don't think this comparison is unfair. If SLS Block 2 can get "advanced solid rocket boosters" that are only notional at this time, why can't Saturn V get similar upgrades as well? Given all the questions about using solid rockets for manned space flight back then, probably zero chance of getting it man-rated by the 1970s. May have had serious design issues even for unmanned flights. True, but if we're fantasizing about a time line where Saturn wasn't canceled, you could use a Saturn 1B (stock or upgraded) for crewed launches of Apollo capsules. Actually, I rarely entertain such fantasies these days and prefer to focus on emerging launch vehicles (we live in exciting times in that regard). My bigger point is that I believe that SLS Block 2 is as fantastical as an upgraded Saturn V would have been. In the mid 1960s, NASA s budget was already being cut. Apollo/Saturn was seen as extremely expensive, so it was being funded only to continue the lunar program. Development funding (of things like evolved Saturn V) was simply never approved even though you can find dozens upon dozens of NASA studies on the subject. Today, we're finally getting to the point where it's becoming obvious that at $3 billion a flight ($2 billion for an expendable SLS and $1 billion for a supposedly reusable Orion) that Artemis is simply not going to be at all economically sustainable (when compared to private/NASA partnerships like commercial cargo and commercial crew). Furthermore, talk of Artemis creating a lunar base is an absolute fantasy if you can't launch enough crew to them (on SLS/Orion) to keep them staffed. At best, Artemis could launch a crew of four every nine months. And my guess is that since NASA only allows six month stays on ISS, a nine month stay on a lunar base would be "pushing it", especially when you consider radiation exposure. So, I don't see SLS/Orion being able to "permanently" staff a lunar base. It just doesn't have the flight rate necessary to realistically do so. Jeff -- All opinions posted by me on Usenet News are mine, and mine alone. These posts do not reflect the opinions of my family, friends, employer, or any organization that I am a member of. |
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