Quote from: guckyfan on 09/03/2015 09:25 pmInteresting calculations. I keep wondering how much FH non cf with disposable central core could send to Mars. That might be something SpaceX wants to do and I would like to know if a Red Dragon can be sent to Mars expending only the central core. Red Dragon might be 10t.From their website 13,200kg
Interesting calculations. I keep wondering how much FH non cf with disposable central core could send to Mars. That might be something SpaceX wants to do and I would like to know if a Red Dragon can be sent to Mars expending only the central core. Red Dragon might be 10t.
Quote from: Bargemanos on 09/03/2015 10:58 amQuote from: MP99 on 09/03/2015 06:27 amQuote from: Lars-J on 09/02/2015 11:56 pmSpaceX has updated the renderings on their F9/FH pages with the "v1.2" renderings, which are more detailed, and presumably accurate. It does seem to indicate a ~6ft stretch as well in the upper stage.Here is the old (left) FH rendering compared to the new one (right), but it is difficult to match them exactly:Changes: - stretched upper stage - more detail on booster attachment - grid finsAnd a larger interstage. Cheers, MartinIt indeed does looks a bit longer. Also, the leg's seem shorter and the center engine alignment is different. This could be just the rendering ofcourse.it looks to me like the previous render was displayed in parallel projection, while the new one is displayed in perspective from a long viewing distance. i think thats whats making the center engine look different.
Quote from: MP99 on 09/03/2015 06:27 amQuote from: Lars-J on 09/02/2015 11:56 pmSpaceX has updated the renderings on their F9/FH pages with the "v1.2" renderings, which are more detailed, and presumably accurate. It does seem to indicate a ~6ft stretch as well in the upper stage.Here is the old (left) FH rendering compared to the new one (right), but it is difficult to match them exactly:Changes: - stretched upper stage - more detail on booster attachment - grid finsAnd a larger interstage. Cheers, MartinIt indeed does looks a bit longer. Also, the leg's seem shorter and the center engine alignment is different. This could be just the rendering ofcourse.
Quote from: Lars-J on 09/02/2015 11:56 pmSpaceX has updated the renderings on their F9/FH pages with the "v1.2" renderings, which are more detailed, and presumably accurate. It does seem to indicate a ~6ft stretch as well in the upper stage.Here is the old (left) FH rendering compared to the new one (right), but it is difficult to match them exactly:Changes: - stretched upper stage - more detail on booster attachment - grid finsAnd a larger interstage. Cheers, Martin
SpaceX has updated the renderings on their F9/FH pages with the "v1.2" renderings, which are more detailed, and presumably accurate. It does seem to indicate a ~6ft stretch as well in the upper stage.Here is the old (left) FH rendering compared to the new one (right), but it is difficult to match them exactly:Changes: - stretched upper stage - more detail on booster attachment - grid fins
Quote from: meekGee on 09/03/2015 10:28 pmQuote from: francesco nicoli on 09/03/2015 10:09 pmthe logic is that if you don't recover the cetral core you get more payload to GEO; in fact 50% more, so 50% payload more to GEO is well worthy 20M.For that to be true, you need to show that recovering the center core downrange costs 33% of the payload.I thought that was the number when considering RTLS, and even that was deemed acceptable.You need to look at cost, since that's the ultimate driver.If the other two cores are reused, an expendable center core becomes the most expensive component in the stack, and so you're highly motivated to reuse it too - it's much more than "one core out of three". Luckily, they have down-range recovery capabilities, which has a lower payload penalty than RTLS, so I can't see why they'd refrain from using it.No it costs more like 50% of the payload beyond GTO, it costs much less against the LEO payload figures. If people have time to wait, I will put up a break down of based on the assumptions I was using to calculate from either tomorrow or sometime over the weekend.
Quote from: francesco nicoli on 09/03/2015 10:09 pmthe logic is that if you don't recover the cetral core you get more payload to GEO; in fact 50% more, so 50% payload more to GEO is well worthy 20M.For that to be true, you need to show that recovering the center core downrange costs 33% of the payload.I thought that was the number when considering RTLS, and even that was deemed acceptable.You need to look at cost, since that's the ultimate driver.If the other two cores are reused, an expendable center core becomes the most expensive component in the stack, and so you're highly motivated to reuse it too - it's much more than "one core out of three". Luckily, they have down-range recovery capabilities, which has a lower payload penalty than RTLS, so I can't see why they'd refrain from using it.
the logic is that if you don't recover the cetral core you get more payload to GEO; in fact 50% more, so 50% payload more to GEO is well worthy 20M.
i just thought about this again and perhaps they cut and pasted the engines from one render onto a different render. the stages are too perfectly straight to be perspective. if it was parallel at an angle the horizontal lines between stages would be curved.
So if we presume that we are presuming a 200 KM LEO orbit and that GTO is a 2450m/s impulse past that then here are the following capabilities of an FH either with side boosters RTLS and centre core recovered down range:25t to LEO with centre core landing down range and side cores RTLS40t to LEO with centre core expended and side cores landing down range8t to GTO with centre core landing down range and side cores RTLS17t to GTO with centre core expended and side cores landing down range
Quote from: nadreck on 09/04/2015 11:01 pmSo if we presume that we are presuming a 200 KM LEO orbit and that GTO is a 2450m/s impulse past that then here are the following capabilities of an FH either with side boosters RTLS and centre core recovered down range:25t to LEO with centre core landing down range and side cores RTLS40t to LEO with centre core expended and side cores landing down range8t to GTO with centre core landing down range and side cores RTLS17t to GTO with centre core expended and side cores landing down rangeSo first, you're double presuming up there, and I don't know if that's legal.Less importantly, this is not an apples to apples comparison. You're evaluating the two center core options (expend it or recover downrange) under two different scenarios (side core RTLS and side core down-range recovery)The question was, suppose we RTLS the side cores, what is the payload hit for recovering the center core deep downrange as opposed to expending it.You will need to make some assumptions on the amount of slow-down necessary before re-entry, and we don't quite know what that is.My understanding is that they were able to get by with a rather minimal braking burn on a regular F9 launch, and so I would guestimate that they need to slow down from center-core speed (which we don't quite know either) to just under single-core speed. (which we should have a better guess at)
For Guckyfan's question on TMI presuming that TMI is accomplished with an impulse of 1.3km/s more than GTO:3t to TMI with centre core landing down range and side cores RTLS9t to TMI with centre core expended and side cores landing down range
Quote from: nadreck on 09/04/2015 11:01 pmFor Guckyfan's question on TMI presuming that TMI is accomplished with an impulse of 1.3km/s more than GTO:3t to TMI with centre core landing down range and side cores RTLS9t to TMI with centre core expended and side cores landing down rangeThanks a lot. Sadly this seems to indicate that Red Dragon needs a fully expended FH which is still quite reasonable for a NASA mission but expensive for a mission self funded by SpaceX.Note: side cores downrange, is that even an option? It would need two ASDS or possibly a new landing site in Florida assuming launch from Texas.
Quote from: guckyfan on 09/05/2015 06:05 amQuote from: nadreck on 09/04/2015 11:01 pmFor Guckyfan's question on TMI presuming that TMI is accomplished with an impulse of 1.3km/s more than GTO:3t to TMI with centre core landing down range and side cores RTLS9t to TMI with centre core expended and side cores landing down rangeThanks a lot. Sadly this seems to indicate that Red Dragon needs a fully expended FH which is still quite reasonable for a NASA mission but expensive for a mission self funded by SpaceX.Note: side cores downrange, is that even an option? It would need two ASDS or possibly a new landing site in Florida assuming launch from Texas.Side cores won't have gone all that far, and given that there seem to be more than 2 ASDS's in the Atlanatic (at least as far as I recall from the very long winded ASDS thread) I think they could be recovered handily. Also expending the side cores would add between 400 and 500m/s which doesn't sound like much but would push the TMI number up past 11, however Full Thrust and densification might do as much, put the two together maybe you get 13. Remember I used vanilla V1.1 stats to build these tables yet after Jason-3 there will be no more vanilla V1.1.
The question was, suppose we RTLS the side cores, what is the payload hit for recovering the center core deep downrange as opposed to expending it.
Quote from: meekGee on 09/05/2015 04:49 amQuote from: nadreck on 09/04/2015 11:01 pmSo if we presume that we are presuming a 200 KM LEO orbit and that GTO is a 2450m/s impulse past that then here are the following capabilities of an FH either with side boosters RTLS and centre core recovered down range:25t to LEO with centre core landing down range and side cores RTLS40t to LEO with centre core expended and side cores landing down range8t to GTO with centre core landing down range and side cores RTLS17t to GTO with centre core expended and side cores landing down rangeSo first, you're double presuming up there, and I don't know if that's legal.Less importantly, this is not an apples to apples comparison. You're evaluating the two center core options (expend it or recover downrange) under two different scenarios (side core RTLS and side core down-range recovery)The question was, suppose we RTLS the side cores, what is the payload hit for recovering the center core deep downrange as opposed to expending it.You will need to make some assumptions on the amount of slow-down necessary before re-entry, and we don't quite know what that is.My understanding is that they were able to get by with a rather minimal braking burn on a regular F9 launch, and so I would guestimate that they need to slow down from center-core speed (which we don't quite know either) to just under single-core speed. (which we should have a better guess at)I assumed slowing down to 900m/s and using 400m/s of delta V to land that is all in my spread sheets, if you don't read my spreadsheets and assumptions then you are simply left with taking my conclusions with out any reasoning behind it and can't criticize it.
You're supposed to compare expend/recover of center core under identical assumptions.Instead, you compared:- recover-center-core with side-core-RTLS, to- expend-center-core with side-core-downrange Which inflates the difference in payload to orbit (any orbit) - the "expend" version benefits from not having to RTLS the side cores.
So here is the updated spreadsheet.I added a 2nd column on the tables in the {Centre core performance} worksheet for 100% remaining propellant for the cross feed case, and I added another table allowing for 20% propellant reserve for recovering the centre core in that case. I also added another worksheet for the 3 booster boost phase in the cross feed scenario.So with the cross feed and side boosters RTLS'ing and centre core recovery down range The payload to GTO would be 12twith cross feed and side boosters RTLS'ing and centre core expending the payload to GTO is 20tGTO performance with side cores recovered down range and centre core expended is 25tTMI under those same 3 cases is, respectively, 5t, 12t and 14tREMEMBER this is V1.1 legacy specs not the new full thrust.ALSO note that my spreadsheet does not calculated several factors, that while some cancel others, it is still only an approximation and a better indication of relative performance rather than absolute. On the underestimating side it presumes sea level ISP for the 3 core boost phase, also when coming up with my delta V budgets for the scenarios I ignored the benefit of launching east from the cape. On the other side of the ledger I didn't allow for air resistance and while I accounted for gravity loss in the 3 core boost phase I ignored it after that and while it is minimal after that it is not zero.
Aviation Week has a new item on Falcon Heavy. Lists launch customers. First launch is SpaceX funded test.http://aviationweek.com/space/spacex-introduce-falcon-heavy-early-2016-0?NL=AW-19&Issue=AW-19_20150909_AW-19_329&sfvc4enews=42&cl=article_4&utm_rid=CPEN1000000903672&utm_campaign=3734&utm_medium=email&elq2=0bc134d29fc64b68921dade1f49f5f80
Peter B. de Selding @pbdesViaSat: Our ViaSat-2 sat to launch on Falcon Heavy in Q4 2016, after 1st Falcon Heavy ~ May. Plan B, an Ariane 5, would cost time & money.https://twitter.com/pbdes/status/641654264918634496