Yes, I think the FH needs a heavier upper stage, because the payload capability with 3-core reuse is too low, probably only 8 tons to GTO. Which is less than Ariane V at 10t, and Delt 4H at 13t.
Quote from: Nathan2go on 07/01/2017 08:48 pmYes, I think the FH needs a heavier upper stage, because the payload capability with 3-core reuse is too low, probably only 8 tons to GTO. Which is less than Ariane V at 10t, and Delt 4H at 13t.Of course 3-core reuse is ideal, but what is the payload with full expendable? That is the valid comparison.
If they just stretched the upper stage propellant tanks a bit more and upgraded the Merlin vacuum engine again - most of the same benefits could be achieved. In fully expendable mode; FH could then get almost 70 metric tons into low Earth orbit, nearly 20 tons on Trans-Mars Injection and nearly 30 tons to GTO. Pretty darn good.
Quote from: MATTBLAK on 07/02/2017 10:17 pmIf they just stretched the upper stage propellant tanks a bit more and upgraded the Merlin vacuum engine again - most of the same benefits could be achieved. In fully expendable mode; FH could then get almost 70 metric tons into low Earth orbit, nearly 20 tons on Trans-Mars Injection and nearly 30 tons to GTO. Pretty darn good.And a dual launch architecture of that could make a very robust and economic manned lunar program.
Quote from: punder on 07/02/2017 08:15 pmQuote from: Nathan2go on 07/01/2017 08:48 pmYes, I think the FH needs a heavier upper stage, because the payload capability with 3-core reuse is too low, probably only 8 tons to GTO. Which is less than Ariane V at 10t, and Delt 4H at 13t.Of course 3-core reuse is ideal, but what is the payload with full expendable? That is the valid comparison.26.7 tonnes per SpaceX site, or a bit over 3x F9 expendable (8.3t) which makes sense. F9 reusable with ASDS landing is around 5.5-6.0t, so FH should get 16-18t with boosters RTLS and core downrange recovery. Definitely will outperform Ariane 5 and Delta Heavy.
Additionally, there's a good chance they think block 5 can do 8t, so that gives them the flexibility of two different configurations for launch.
Quote from: Robotbeat on 07/03/2017 10:16 pmAdditionally, there's a good chance they think block 5 can do 8t, so that gives them the flexibility of two different configurations for launch.that exactly opposite of what Spacex does
Quote from: Robotbeat on 07/03/2017 10:16 pm...market segmentation.Been thinking about this. One thing you could do as a novel market segment might be effectively an ACES like concept as an unmanned high C3 missions "tug".
...market segmentation.
I had an idea of how SpaceX can increase the wt of a payload a Falcon rocket can launch, or save fuel for second stage recovery. My idea is to put springs on the second stage, that would launch the payload, like the shuttle use to do when launching satellites. The spring could give the payload extra delta-v, while acting to slow the second stage at the same time, thereby saving fuel for recovery. I don't know if this is practical because of the extra wt of the springs or other considerations.
Quote from: R.Simko on 07/25/2017 02:58 pmI had an idea of how SpaceX can increase the wt of a payload a Falcon rocket can launch, or save fuel for second stage recovery. My idea is to put springs on the second stage, that would launch the payload, like the shuttle use to do when launching satellites. The spring could give the payload extra delta-v, while acting to slow the second stage at the same time, thereby saving fuel for recovery. I don't know if this is practical because of the extra wt of the springs or other considerations.The energy density of a spring is very low compared to the fuel it would replace. So as you suspect, its not practical.
Quote from: hkultala on 06/28/2017 08:04 amQuote from: BobHk on 06/28/2017 03:41 am"Despite describing the Block 5 as the final version of the Falcon 9, Shotwell hinted at the possibility of a future version of the rocket that could use the Raptor engines designed for transportation to Mars. Shotwell said Raptor, a liquid methane and oxygen engine for SpaceX’s interplanetary spaceship, has undergone “many dozens of tests” and is progressing well.“The original idea for those engines were to serve as a propulsion system for the big Mars system, but we are looking at the utility of it on the Falcon program,” she said."I think of of the reasons why they are changing their mind about using raptor in falcon rocket is that originally they thought they cannot land raptor-based falcon first stage because of too high minimum T/W, but now they are getting confident that they can do it, and they already proved the minimum T/W is not too high by landing the bulgariasat booster with 3 merlin 1d engines.We have not had any evidence to show they are chaining their mind about a Raptor US. We have one off the cuff comment that they might take a look at it. That's all. Their investigation may be as simple as "We reckon this is a stupid idea, just go and confirm it is"I've with Jim on this one, it just doesn't seem to have any real reason for existence. Test bed for Raptor? Nah. Not needed. Makes the stage reusable? Nah, too expensive to implement and would never make the cash back. Need for bigger payloads? Nah, not enough payloads to make it pay. The only thing I can think of that might make a Raptor engined stage on top of an F9 even vaguely useful would be a custom combined stage/satellite dispenser for the constellation. That might be cost effective if they are able to make it reusable.
Quote from: BobHk on 06/28/2017 03:41 am"Despite describing the Block 5 as the final version of the Falcon 9, Shotwell hinted at the possibility of a future version of the rocket that could use the Raptor engines designed for transportation to Mars. Shotwell said Raptor, a liquid methane and oxygen engine for SpaceX’s interplanetary spaceship, has undergone “many dozens of tests” and is progressing well.“The original idea for those engines were to serve as a propulsion system for the big Mars system, but we are looking at the utility of it on the Falcon program,” she said."I think of of the reasons why they are changing their mind about using raptor in falcon rocket is that originally they thought they cannot land raptor-based falcon first stage because of too high minimum T/W, but now they are getting confident that they can do it, and they already proved the minimum T/W is not too high by landing the bulgariasat booster with 3 merlin 1d engines.
"Despite describing the Block 5 as the final version of the Falcon 9, Shotwell hinted at the possibility of a future version of the rocket that could use the Raptor engines designed for transportation to Mars. Shotwell said Raptor, a liquid methane and oxygen engine for SpaceX’s interplanetary spaceship, has undergone “many dozens of tests” and is progressing well.“The original idea for those engines were to serve as a propulsion system for the big Mars system, but we are looking at the utility of it on the Falcon program,” she said."
What a Raptor US +B5 would allow, is launching the average sized GEO satellite to GTO and having the booster RTLS. It's not hard, with a faster launch cadence, to see the slow-moving ASDS ship as a potential bottleneck. Raptor US may be unlikely, but this fact with the fact that they have been testing MiniRaptor probably makes this less unlikely than some think.
There are perhaps good reasons for Raptor US + B5 but launch cadence for GEO sats is not one of them.
Quote from: ZachF on 09/11/2017 12:31 pmWhat a Raptor US +B5 would allow, is launching the average sized GEO satellite to GTO and having the booster RTLS. It's not hard, with a faster launch cadence, to see the slow-moving ASDS ship as a potential bottleneck. Raptor US may be unlikely, but this fact with the fact that they have been testing MiniRaptor probably makes this less unlikely than some think.There are only about 20 GEO satellites a year maximum that SpaceX could launch, that is not enough for launch cadence with ASDS return to be a limiting factor.There are perhaps good reasons for Raptor US + B5 but launch cadence for GEO sats is not one of them.
Based on IAC 2017 info on BFR, Raptor now seems down-sized from 3000kN class to 1700kN class.That's closer to Merline1D(Vac)'s 900kN class.Maybe that make the Falcon9 with Raptor upper more likely to happen?Titus