Your calculations for STS are wrong as you count the weight for the engines and supporting hardware to the LEO payload capability.
it's just in how it's added up.With the STS total masses the orbiter is both the fairing and an upper stage.With SLS the mass of the fairing and the SSMEs on the core are not included in the payload.I'm not sure on SLS but with the J-130 it was possible for the core stage to reach orbit.
SLS Block1: 2 five-segment boosters, 8.5m core tank + 4 RS-25 engines, 1 RL-10 engine upper stage = 70t to LEOSLS Block1a: 2 "more advanced" boosters, 8.5m core tank + 4 or 5 RS-25 engines, unknown "more capable" upper stage = 100t to LEOSLS Block2: 2 "more advanced" boosters, 8.5m core tank + 5 RS-25 engines, 3 J-2X engines upper stage = 130t to LEO
Did you factor in the weight of the SSME's on the orbiter, which would not be counted as payload on SLS?
Quote from: bulkmail on 01/16/2012 07:14 pmSLS Block1: 2 five-segment boosters, 8.5m core tank + 4 RS-25 engines, 1 RL-10 engine upper stage = 70t to LEOSLS Block1a: 2 "more advanced" boosters, 8.5m core tank + 4 or 5 RS-25 engines, unknown "more capable" upper stage = 100t to LEOSLS Block2: 2 "more advanced" boosters, 8.5m core tank + 5 RS-25 engines, 3 J-2X engines upper stage = 130t to LEOI haven't seen all of these details given, or even decided upon, for the SLS configurations. Here's my understanding.Block 1 uses five segment boosters and at least 3 RS-25 engines. It can lift at least 70 tonnes to a suborbital ascent trajectory. All of the SLS LEO numbers are for a suborbital insertion, as I understand things. In practice Block 1 will probably fly with ICPS (likely a Delta IV Heavy type upper stage) and will boost 24+ tonnes beyond LEO with that stage.Block 1A is Block 1 with new boosters. It should lift more than Block 1, but we won't know how much until we know about the new boosters, which won't be for years yet.Block 2 is Block 1A with the full-up Cryogenic Propulsion Stage, which has yet to be defined. It may have one J-2X. It may have two. It might use RS-25E. It might use none of these engines since it won't be developed for a decade or more. NASA and its contractors haven't even decided how big it should be or how much propellant it should carry. Since it doesn't have a specific mission, no one knows its specifications. Depending on the boosters and upper stage, Block 2 might lift 145 tonnes to "LEO" or 60+ tonnes to escape velocity.Orbiter dry mass, or much of it, cannot be counted as payload. If so, then you must also count the mass of any orbited SLS stage, etc. - Ed Kyle
Quote from: SpaceRock on 01/16/2012 07:44 pmDid you factor in the weight of the SSME's on the orbiter, which would not be counted as payload on SLS?What do you mean? For STS we have the following equipment reaching orbit: orbiter + engines + payload = 105tFor SLS-Block1 we have the following equipment reaching orbit: payload = 70tWhy does a more capable vehicle with more powerful boosters, engines and upper stage deliver 35t less?
Quote from: bulkmail on 01/16/2012 08:03 pmQuote from: SpaceRock on 01/16/2012 07:44 pmDid you factor in the weight of the SSME's on the orbiter, which would not be counted as payload on SLS?What do you mean? For STS we have the following equipment reaching orbit: orbiter + engines + payload = 105tFor SLS-Block1 we have the following equipment reaching orbit: payload = 70tWhy does a more capable vehicle with more powerful boosters, engines and upper stage deliver 35t less?It doesn't. You're not counting the empty mass of the SLS core. Just like the Orbiter, the core includes engines and plumbing and thrust structure and whatever they use for APUs. That's heavy. Think of it like it's half an orbiter.
Quote from: Robotbeat on 01/16/2012 08:14 pmQuote from: bulkmail on 01/16/2012 08:03 pmQuote from: SpaceRock on 01/16/2012 07:44 pmDid you factor in the weight of the SSME's on the orbiter, which would not be counted as payload on SLS?What do you mean? For STS we have the following equipment reaching orbit: orbiter + engines + payload = 105tFor SLS-Block1 we have the following equipment reaching orbit: payload = 70tWhy does a more capable vehicle with more powerful boosters, engines and upper stage deliver 35t less?It doesn't. You're not counting the empty mass of the SLS core. Just like the Orbiter, the core includes engines and plumbing and thrust structure and whatever they use for APUs. That's heavy. Think of it like it's half an orbiter.So, you're saying that the SLS core tank reaches LEO? Are you sure? Ed Kyle above says it's only suborbital.
OK, but still, if the STS manages to put 105t in LEO what is preventing the SLS to do the same - it's even using a more powerful configuration? Discarding the main engines & fairing should only help/increase LEO payload - not reduce it. And on top - SLS has more booster segments and more engines...
If SLS core is really reaching LEO - this offers many possibilities (after some rework/redesign of course) - empty tanks to be used as fuel depot or deep space habitat and it even has engines (RS-25 are already multiple-times re-startable in vacuum)...
The SLS core is a lot more than just a few SSMEs and an ET. It's essentially the whole back end of the Shuttle, minus OMS pods and TPS. There's a bunch of expensive thrust structure, Auxillary Power Units (or whatever equivalent), avionics, plumbing, hydraulics for gimballing the engines, the gimbal mounts, etc.Also, the SLS core is designed to fit 5 SSMEs, so is significantly heavier than if it was made for just 3 like the Shuttle (or some sidemount proposals).
OK, all this equipment maybe explains the weight difference. And if adding that "small" dv thrust is so easy/cheap - then why does nobody propose using the core+engines+all auxillary equipment? Depot, habitat, etc.?Such usage should be envisioned from the start so that all design decisions are taken accordingly...
Quote from: Robotbeat on 01/16/2012 08:35 pmThe SLS core is a lot more than just a few SSMEs and an ET. It's essentially the whole back end of the Shuttle, minus OMS pods and TPS. There's a bunch of expensive thrust structure, Auxillary Power Units (or whatever equivalent), avionics, plumbing, hydraulics for gimballing the engines, the gimbal mounts, etc.Also, the SLS core is designed to fit 5 SSMEs, so is significantly heavier than if it was made for just 3 like the Shuttle (or some sidemount proposals).OK, all this equipment maybe explains the weight difference. And if adding that "small" dv thrust is so easy/cheap - then why does nobody propose using the core+engines+all auxillary equipment? Depot, habitat, etc.?Such usage should be envisioned from the start so that all design decisions are taken accordingly...
The SLS core is a lot more than just a few SSMEs and an ET. It's essentially the whole back end of the Shuttle, minus OMS pods and TPS. There's a bunch of expensive thrust structure, Auxillary Power Units (or whatever equivalent), avionics, plumbing, hydraulics for gimballing the engines, the gimbal mounts, etc.
Quote from: Robotbeat on 01/16/2012 08:35 pmThe SLS core is a lot more than just a few SSMEs and an ET. It's essentially the whole back end of the Shuttle, minus OMS pods and TPS. There's a bunch of expensive thrust structure, Auxillary Power Units (or whatever equivalent), avionics, plumbing, hydraulics for gimballing the engines, the gimbal mounts, etc.Why does the SLS core need Auxillary Power Units? It doesn't need to operate when the engines are off, so why not just put generators on the engines?
BTW, SLS Block I (70mt) is 5 seg SRB with 3 RS-25E
Block I uses a Core Stage Propulsion of LO2/LH2 with Four SSMEs (RS-25Ds) now sported by the configuration, an advance on the three RS-25Ds, as previously noted.
Quote from: bulkmail on 01/16/2012 09:03 pmOK, all this equipment maybe explains the weight difference. And if adding that "small" dv thrust is so easy/cheap - then why does nobody propose using the core+engines+all auxillary equipment? Depot, habitat, etc.?Such usage should be envisioned from the start so that all design decisions are taken accordingly...It was never done with Shuttle and when they started to do it for Skylab, they found it wasn't worth it and just launched the habitat completely dry on a Saturn V. It's been thought of before and found to be impractical and just simply not worth it. That doesn't keep every single space cadet on the internet proposing the same idea at one point or another.
Quote from: Robotbeat on 01/16/2012 09:21 pmQuote from: bulkmail on 01/16/2012 09:03 pmOK, all this equipment maybe explains the weight difference. And if adding that "small" dv thrust is so easy/cheap - then why does nobody propose using the core+engines+all auxillary equipment? Depot, habitat, etc.?Such usage should be envisioned from the start so that all design decisions are taken accordingly...It was never done with Shuttle and when they started to do it for Skylab, they found it wasn't worth it and just launched the habitat completely dry on a Saturn V. It's been thought of before and found to be impractical and just simply not worth it. That doesn't keep every single space cadet on the internet proposing the same idea at one point or another.Indeed - there have been hundreds (if not thousands) of proposals to use the Shuttle external tanks as on-orbit habitats or dry/wet storage. None of them practical. A simple google search would illustrate that this futile idea is far from new.
If SLS core is really reaching LEO - this offers many possibilities (after some rework/redesign of course) - empty tanks to be used as fuel depot or deep space habitat and it even has engines (RS-25 are already multiple-times re-startable in vacuum)...But let's check the numbers if SLS core tank is reaching LEO - STS core tank is ~26,5t and 4 RS-25 engines are ~13,5. So, it's about ~40t. So, a mere 5t advantage from 2 more SRB segments, 1 more RS-25 engine and an upper stage... still doesn't fit.
The core of SLS Block I (70mt to LEO) is around 200klbs. So that and payload is around 340klbs (170t). This is the number to compare with the shuttle. Orbit is 30 x 130 nmi, so subtract a little for a circularization burn.SLS also has a fairing that weighs 25klbs that reduces performanceBTW, SLS Block I (70mt) is 5 seg SRB with 3 RS-25E
Once the depot is empty, there is no practical way to refuel the depot. You'd need a super-shuttle to act as a tanker for that concept to work.
Quote from: Jim on 01/16/2012 08:56 pmThe core of SLS Block I (70mt to LEO) is around 200klbs. So that and payload is around 340klbs (170t). This is the number to compare with the shuttle. Orbit is 30 x 130 nmi, so subtract a little for a circularization burn.SLS also has a fairing that weighs 25klbs that reduces performanceBTW, SLS Block I (70mt) is 5 seg SRB with 3 RS-25E Out of curiosity, Jim, for STS and its derivatives do you instinctively *think* (not convert) in tonnes or klbs, or equally well in both? Do you find one more helpful? Did that change at some point? I would guess that klbs was universal in the 80s and much of the 90s, since the system is thoroughly designed in FPS-R, and its only relatively recently (Phase I? ISS? ESAS?) that STS is commonly spoken of in metric for ease of comparison. Any truth to that? Did anything similar happen during the Atlas III/V program? (Oddly, metric for the most part, I think only in klbs-thrust, not kN.) -Alex
Quote from: TomH on 01/17/2012 03:10 am Once the depot is empty, there is no practical way to refuel the depot. You'd need a super-shuttle to act as a tanker for that concept to work.No, there are resupply vehicles that refill the depot. That is the key to it.
Quote from: Jim on 01/16/2012 08:56 pmBTW, SLS Block I (70mt) is 5 seg SRB with 3 RS-25EMinor correction, SLS block I has 4 SSME's:QuoteBlock I uses a Core Stage Propulsion of LO2/LH2 with Four SSMEs (RS-25Ds) now sported by the configuration, an advance on the three RS-25Ds, as previously noted.http://www.nasaspaceflight.com/2011/10/sls-trades-opening-four-rs-25s-core-stage/
Why does a more capable vehicle with more powerful boosters, engines and upper stage deliver 35t less?
Quote from: bulkmail on 01/16/2012 09:03 pmOK, all this equipment maybe explains the weight difference. And if adding that "small" dv thrust is so easy/cheap - then why does nobody propose using the core+engines+all auxillary equipment? Depot, habitat, etc.?Such usage should be envisioned from the start so that all design decisions are taken accordingly...No, because it is not worth the effort, see above post. Nor is there a need.
Quote from: Robotbeat on 01/16/2012 09:21 pmQuote from: bulkmail on 01/16/2012 09:03 pm(1) OK, all this equipment maybe explains the weight difference. And if adding that "small" dv thrust is so easy/cheap - then why does nobody propose using the core+engines+all auxillary equipment? Depot, habitat, etc.?Such usage should be envisioned from the start so that all design decisions are taken accordingly...(2) It was never done with Shuttle ... Skylab ... Saturn V. It's been thought of before and found to be impractical and just simply not worth it. That doesn't keep every single space cadet on the internet proposing the same idea at one point or another.(3) Indeed - there have been hundreds ... of proposals to use the Shuttle external tanks as on-orbit habitats or dry/wet storage. None of them practical. (4) A simple google search would illustrate that this futile idea is far from new.
Quote from: bulkmail on 01/16/2012 09:03 pm(1) OK, all this equipment maybe explains the weight difference. And if adding that "small" dv thrust is so easy/cheap - then why does nobody propose using the core+engines+all auxillary equipment? Depot, habitat, etc.?Such usage should be envisioned from the start so that all design decisions are taken accordingly...(2) It was never done with Shuttle ... Skylab ... Saturn V. It's been thought of before and found to be impractical and just simply not worth it. That doesn't keep every single space cadet on the internet proposing the same idea at one point or another.
(1) OK, all this equipment maybe explains the weight difference. And if adding that "small" dv thrust is so easy/cheap - then why does nobody propose using the core+engines+all auxillary equipment? Depot, habitat, etc.?Such usage should be envisioned from the start so that all design decisions are taken accordingly...
The cost to convert it to a habitat in space by astronauts is considerably more than constructing a habitat on earth and sending it up on another vehicle. ...It is not of use as a depot because you would send up yet another vehicle with the propellant in that vehicle's tanks. Why transfer the liquids from vehicle b to vehicle a?
English units are still prevalent in the business.
Nothing is set in stone yet ...
This is Jim's perennial "need" argument, which explains only the current state of affairs and not the desired state of affairs. The current state of affairs is disposable rocketry, with its inevitable unsustainability as a result of expense.
Quote from: JohnFornaro on 01/18/2012 01:39 pmThis is Jim's perennial "need" argument, which explains only the current state of affairs and not the desired state of affairs. The current state of affairs is disposable rocketry, with its inevitable unsustainability as a result of expense. No, the current state of affairs is perfectly sustainable and has persisted for 55 years. If nothing changes it can and will continue. Of course this has nothing to do with what you (or I) might desire. The current launch market is too small to warrant the development of RLV's commercially.
The "specialized" definitions of "payload" all avoid the commonsense suggestion that STS was a 105 mt rocket. The orbiter was "mass going into orbit". I know that it's not a good idea to leave junk in orbit, but still SLS doesn't seem as capable as STS.
Earlier, an objection to launching ET's to orbit concerned the popcorning of foam, but I ask if the expedient solution of the 60's is the only way for cryo propellants to be launched for all time? If any disposable stage gets launched, it will be in the future, and not necessarily an old design.
LV-MLI should have 34% the mass of the SOFI insulation, while providing about 85 times better thermal insulation.
QuoteLV-MLI should have 34% the mass of the SOFI insulation, while providing about 85 times better thermal insulation.
Is there a good reason it couldn't be used on a core? Or the Shuttle ET, if STS were still running? I suppose it'd be more expensive, but it would have solved the foam shedding issue (and the popcorning issue) completely...
You aren't listening. A lot of the back end of the orbiter was engines and plumbing and APUs and thrust structure. You're counting it as payload to orbit. You are not counting the ET, even though it basically makes orbit (the circularization burn is trivial). Why not?
A ruggedized [layer ?] of Integrated MLI, high performance lightweight thermal insulation, could be bonded to the sidewalls of LOX/LH2 cryotanks in the Atlas V and Delta IV and might be able to withstand aerodynamic loading during launch ascent.
The desirable state of affairs would be an intelligent reuse of valuable assets. That would require an intentional sustainability.