Author Topic: The fate of SLS after Falcon Heavy debut  (Read 35363 times)

Offline A_M_Swallow

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Re: The fate of SLS after Falcon Heavy debut
« Reply #80 on: 02/09/2018 07:43 pm »
Musk has stated many times now that he wants to retire the Falcons and Dragons as soon as possible. Does it make sense for NASA to start a BEO exploration program when the vendor wants to retire their product in 5 or so years? At this point the first question any proposed exploration program needs to ask is will the BRF happen? If the answer is no then the Falcon Heavy and maybe SLS likely do have an important role to play.

Lets imagine that BFR is successful and everything that SpaceX is promising with it. It would be better for NASA to wait for that to come online and buy it off the shelf. While a payload meant for the Falcon Heavy could launch on the BFR it would be underutilizing the capability of the BFR.

Imagine if NASA contracted to have a Moon lander launched on the Falcon Heavy. I doubt a lander could be made and ready to launch before the BFR, if it shows up when Musk is proposing. It would be a funny situation for the BFR to be launching a moon lander while itself being capable of landing on the moon because NASA contacted another company to build the lander.

Go with what you have. You may be able to return with something better.

NASA should build its lunar mission around the Falcon Heavy because that is what it has got.

A clause in the contract can say that as a part of the on ramping process a variant of the BFR should be able to lift payloads designed for the Falcon Heavy. (Basically a backward compatible payload adaptor.) Also the Falcon Heavy shall be kept in production until the BFR flies.

As they on ramp Vulcan/ACES and Blue could apply for lunar project payloads. The SLS can then carry extra heavy payloads and Orion.

A LEO to lunar orbit tug would also be useful.

Offline envy887

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Re: The fate of SLS after Falcon Heavy debut
« Reply #81 on: 02/09/2018 07:56 pm »
How can one discuss the relative merits of two rocket systems without acknowledging that one is throwaway and the other is reusable? The first SLS is going to go up in 4-5 years and then... it will be vaporized. Then you get to build another one.

Any Falcon Heavy lifting a heavy payload is also throwaway. And that'll be most of them, given that F9 can loft most commercial satellites.

Not necessarily. F9 will be reserved for lighter payloads. And FH can lift around 30 to 40 tonnes to LEO with reuse. With EOR and possibly refueling a mission of many hundreds of tonnes of IMLEO is possible. FH with reuse can support the cadence to launch much more mass faster than SLS.

Offline envy887

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Re: The fate of SLS after Falcon Heavy debut
« Reply #82 on: 02/09/2018 08:05 pm »
You're relying on figures from the KSC ELV performance page, which has figures that are years out of date. For instance, FH can do about 16 tons through trans Mars insertion, which is about c3= 7km^2/s^2 on an *exceptionally* good opportunity. According to KSC's page, FH can only do 10t. So for high energy trajectories, FH can do about 60% better than the KSC page suggests.
No, I didn't use the KSC page.  I have expendable Falcon Heavy at 16.8 tonnes TMI.  SLS Block 1 would be 19+ tonnes, but of course it is only going to fly one trans-lunar mission. For TLI, I show expendable Falcon Heavy at 20+ tonnes and SLS Block 1 at 24.5 tonnes.

The real comparison is with SLS Block 1B, which is expected to be 32 and 39 tonnes to TMI/TLI, respectfully.

 - Ed Kyle

Your FHR payloads for TLI/TMI are probably a bit underestimated. Musk said they could possibly recover all three boosters after sending Red Dragon (which between Dragon itself and the landing propellants would be at least 10 tonnes) to TMI. That is equivalent to nearly triple the 5500 kg you have for TLI.

https://twitter.com/elonmusk/status/726820238361120768

Offline envy887

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Re: The fate of SLS after Falcon Heavy debut
« Reply #83 on: 02/09/2018 08:25 pm »
... so multiple expended Falcon Heavies would be needed.  These expendable versions are going to cost substantially more than the numbers everyone sees on the SpaceX web site.

How much more, though?

And what are they launching that in more than 30 tonnes to LEO and couldn't fit on FH or later on New Glenn with reuse?

Offline AncientU

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Re: The fate of SLS after Falcon Heavy debut
« Reply #84 on: 02/09/2018 08:48 pm »
...

It doesn't matter what the throw-weight is of the SLS or any other launch system, it only matters how they are used. For instance, there are really two approaches to doing human space exploration:

A. Single-launch architectures, which is what Apollo used and what the SLS is.
B. Multi-launch architectures, which allows many launch systems to be used.

For single-launch architectures the limitation is that you get diminishing returns the farther out you go, so in reality our Moon is the furthest NASA could go with humans. That was how far Apollo went, and the SLS is about the same as the Saturn V.

This is what SLS will be in 2028-2030, if the program stays on track -- which is unlikely -- probably $30-40B down the road from here.

Quote
...
The best way forward is to allow many launch vehicles to participate in expanding humanity out into space, and use a launch architecture that embraces that.

My $0.02

Well-spent $0.02.  The impact of FH will be to start a discussion (maybe a short one) on this new way forward.  Chances of success probably less than 50/50, but maybe the seed will be planted.

Most likely outcome is that FH will be glossed over by the incumbency, maybe be given a couple token supply missions or something.  NG and Vulcan/ACES... more of the same, except that the big defense contractors will then have something to gain by allowing change. 

BFR will not be so easy brush aside.  Before SLS Block 1B flies, SLS will be head to head with a vastly more capable rocket and an approach to exploration that actually can accomplish some exploring.  We'll see how that goes.

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Offline TomH

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Re: The fate of SLS after Falcon Heavy debut
« Reply #85 on: 02/10/2018 03:44 am »
The Orion Spacecraft would launch on the second Falcon Heavy after the Lander was in Lunar orbit. The Orion would make a rendezvous with the Lander, dock, transfer crew.

Orion SM has enough ΔV only for TEI, not enough for both LOI and TEI. FH-US cannot remain in standby mode for three days waiting to perform a LOI burn. How would you get the Orion into Lunar orbit and still have enough prop for TEI? You need aux tanks on SM or a small kick stage for LOI. Alternately, you use a lighter D2, but then you need a far more robust SM that can provide ΔV for both burns and ECLSS for 3 weeks.

Offline Robotbeat

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Re: The fate of SLS after Falcon Heavy debut
« Reply #86 on: 02/10/2018 03:52 am »
Don't go into *Low* lunar orbit but instead an elliptical orbit. Way less delta-V to enter and leave. Solves a whole bunch of problems and makes logistics by a whole range of rockets easier.
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Offline A_M_Swallow

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Re: The fate of SLS after Falcon Heavy debut
« Reply #87 on: 02/10/2018 05:54 am »
Don't go into *Low* lunar orbit but instead an elliptical orbit. Way less delta-V to enter and leave. Solves a whole bunch of problems and makes logistics by a whole range of rockets easier.

Does an elliptical orbit result in spacecraft having to use instantaneous launches due to tiny windows?

Offline Steven Pietrobon

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Re: The fate of SLS after Falcon Heavy debut
« Reply #88 on: 02/10/2018 06:17 am »
Orion SM has enough ΔV only for TEI, not enough for both LOI and TEI. FH-US cannot remain in standby mode for three days waiting to perform a LOI burn. How would you get the Orion into Lunar orbit and still have enough prop for TEI? You need aux tanks on SM or a small kick stage for LOI. Alternately, you use a lighter D2, but then you need a far more robust SM that can provide ΔV for both burns and ECLSS for 3 weeks.

The Falcon Heavy upper stage does LOI. Orion does TEI. However, an expendable FH can only put 16.7 t into LLO, while Orion is 20 t, so the scheme won't work anyway.

https://forum.nasaspaceflight.com/index.php?topic=42363.msg1782831#msg1782831

Don't go into *Low* lunar orbit but instead an elliptical orbit. Way less delta-V to enter and leave. Solves a whole bunch of problems and makes logistics by a whole range of rockets easier.

This increases the delta-V for the lander, which makes the problem worse since the delta-V increases from 4 km/s to 5 km/s. This means you need a much heavier lander.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline MATTBLAK

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Re: The fate of SLS after Falcon Heavy debut
« Reply #89 on: 02/10/2018 06:25 am »
Dr Steve; in a 2x launch scenario where an expendable Falcon 9 launches a 23 ton, hypergolically fueled Lander into LEO, then a Falcon Heavy places an upper stage with a docking collar and plenty of propellants nearby, they dock and go TLI... Would that Lander have enough delta-v to insert itself into low lunar orbit, or would the Falcon upper stage have to do it? I've been wondering if the Falcon stage would need extensive modifications to last a three day coast to the Moon, or would the Lander have to use 6-to-8 tons of it's propellant load for lunar orbit insertion?

That would leave a fueled mass of about 16 tons - about the same as the Apollo LM. Then I guess we'd have to ask ourselves if the Lander would be a single or double stage design. I imagine a single-stage would lend itself more easily to future reuse and refueling.
« Last Edit: 02/10/2018 06:33 am by MATTBLAK »
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Offline Steven Pietrobon

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Re: The fate of SLS after Falcon Heavy debut
« Reply #90 on: 02/10/2018 07:07 am »
Dr Steve; in a 2x launch scenario where an expendable Falcon 9 launches a 23 ton, hypergolically fueled Lander into LEO, then a Falcon Heavy places an upper stage with a docking collar and plenty of propellants nearby, they dock and go TLI... Would that Lander have enough delta-v to insert itself into low lunar orbit, or would the Falcon upper stage have to do it?

2x22.8 t is 45.6 t, while expendable FH is 63.8 t. Expendable FH can put 16.7 t into LLO, so I don't think dual expendable F9 will work.

Quote
I've been wondering if the Falcon stage would need extensive modifications to last a three day coast to the Moon, or would the Lander have to use 6-to-8 tons of it's propellant load for lunar orbit insertion?

The N-1/L-3 plan required kerolox Blok-D stage to do LOI and staged descent. So it should be possible to modify the Falcon upper stage to also last three days.

Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline MATTBLAK

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Re: The fate of SLS after Falcon Heavy debut
« Reply #91 on: 02/10/2018 08:13 am »
On this occasion, as I have suggested recently, this would be 1x Falcon 9 and 1x Falcon Heavy used to transport a 20+plus ton spacecraft to lunar orbit. Sort of like the '1.5 launch' Constellation architecture. I was also recently curious about whether 2x Falcon 9s could accomplish the circumlunar tourist flight - I wondered if the expendable F9 block 5 would place enough propellants into LEO for a Dragon 2 to come long, dock with it and be on its way.
« Last Edit: 02/10/2018 10:04 am by MATTBLAK »
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Offline Proponent

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Re: The fate of SLS after Falcon Heavy debut
« Reply #92 on: 02/10/2018 02:15 pm »
Don't go into *Low* lunar orbit but instead an elliptical orbit. Way less delta-V to enter and leave. Solves a whole bunch of problems and makes logistics by a whole range of rockets easier.

Does an elliptical orbit result in spacecraft having to use instantaneous launches due to tiny windows?

I don't think the windows are excessively short.  The problem I see is that an efficient TEI burn must take place at perilune and on the far side of the moon.  So it seems to me that an elliptical orbit leaves you with departure windows only once a month.  You could move perilune, but that takes delta-V.  Am I missing something?

Online ncb1397

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Re: The fate of SLS after Falcon Heavy debut
« Reply #93 on: 02/10/2018 06:24 pm »
You're relying on figures from the KSC ELV performance page, which has figures that are years out of date. For instance, FH can do about 16 tons through trans Mars insertion, which is about c3= 7km^2/s^2 on an *exceptionally* good opportunity. According to KSC's page, FH can only do 10t. So for high energy trajectories, FH can do about 60% better than the KSC page suggests.
No, I didn't use the KSC page.  I have expendable Falcon Heavy at 16.8 tonnes TMI.  SLS Block 1 would be 19+ tonnes, but of course it is only going to fly one trans-lunar mission. For TLI, I show expendable Falcon Heavy at 20+ tonnes and SLS Block 1 at 24.5 tonnes.

The real comparison is with SLS Block 1B, which is expected to be 32 and 39 tonnes to TMI/TLI, respectfully.

 - Ed Kyle

Your FHR payloads for TLI/TMI are probably a bit underestimated. Musk said they could possibly recover all three boosters after sending Red Dragon (which between Dragon itself and the landing propellants would be at least 10 tonnes) to TMI. That is equivalent to nearly triple the 5500 kg you have for TLI.

https://twitter.com/elonmusk/status/726820238361120768

With Reuse, FH is listed as 8 mT to GTO. How does it send 10 mT to Mars?

see:
http://www.spacex.com/about/capabilities

Falcon 9 price is listed as 5.5 mT which lines up with stage re-use. The line for FH right next to it is likely the same.

Offline TomH

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Re: The fate of SLS after Falcon Heavy debut
« Reply #94 on: 02/10/2018 09:15 pm »
On this occasion, as I have suggested recently, this would be 1x Falcon 9 and 1x Falcon Heavy used to transport a 20+plus ton spacecraft to lunar orbit. Sort of like the '1.5 launch' Constellation architecture. I was also recently curious about whether 2x Falcon 9s could accomplish the circumlunar tourist flight - I wondered if the expendable F9 block 5 would place enough propellants into LEO for a Dragon 2 to come long, dock with it and be on its way.

I have thought about this as well. Another scenario I have wondered about is a single SLS Block I and a FH or SLS Block IB with an F9 as sort of like the "1.5 launch" Constellation architecture. The first scenario could be ready sooner, but requires man-rating either iCPS or FH. The second scenario requires a longer wait, but requires no extra man-rating.

Offline alexterrell

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Re: The fate of SLS after Falcon Heavy debut
« Reply #95 on: 02/10/2018 10:03 pm »
Don't go into *Low* lunar orbit but instead an elliptical orbit. Way less delta-V to enter and leave. Solves a whole bunch of problems and makes logistics by a whole range of rockets easier.

Does an elliptical orbit result in spacecraft having to use instantaneous launches due to tiny windows?

I don't think the windows are excessively short.  The problem I see is that an efficient TEI burn must take place at perilune and on the far side of the moon.  So it seems to me that an elliptical orbit leaves you with departure windows only once a month.  You could move perilune, but that takes delta-V.  Am I missing something?

Isn't it one launch window (from Low Earth Orbit) per lunar orbit of the lunar gateway/orbiter. That doesn;t impose a constraint on launch from Earth, assuming the upper stage can orbit for between 0 and a few days. 

Offline envy887

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Re: The fate of SLS after Falcon Heavy debut
« Reply #96 on: 02/11/2018 02:31 am »
You're relying on figures from the KSC ELV performance page, which has figures that are years out of date. For instance, FH can do about 16 tons through trans Mars insertion, which is about c3= 7km^2/s^2 on an *exceptionally* good opportunity. According to KSC's page, FH can only do 10t. So for high energy trajectories, FH can do about 60% better than the KSC page suggests.
No, I didn't use the KSC page.  I have expendable Falcon Heavy at 16.8 tonnes TMI.  SLS Block 1 would be 19+ tonnes, but of course it is only going to fly one trans-lunar mission. For TLI, I show expendable Falcon Heavy at 20+ tonnes and SLS Block 1 at 24.5 tonnes.

The real comparison is with SLS Block 1B, which is expected to be 32 and 39 tonnes to TMI/TLI, respectfully.

 - Ed Kyle

Your FHR payloads for TLI/TMI are probably a bit underestimated. Musk said they could possibly recover all three boosters after sending Red Dragon (which between Dragon itself and the landing propellants would be at least 10 tonnes) to TMI. That is equivalent to nearly triple the 5500 kg you have for TLI.

https://twitter.com/elonmusk/status/726820238361120768

With Reuse, FH is listed as 8 mT to GTO. How does it send 10 mT to Mars?

see:
http://www.spacex.com/about/capabilities

Falcon 9 price is listed as 5.5 mT which lines up with stage re-use. The line for FH right next to it is likely the same.

Triple ASDS landing with block 5. The $90M/8 t is for at most 1 ASDS landing and IMO is actually triple RTLS.

Offline Robotbeat

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Re: The fate of SLS after Falcon Heavy debut
« Reply #97 on: 02/11/2018 03:46 am »
You're relying on figures from the KSC ELV performance page, which has figures that are years out of date. For instance, FH can do about 16 tons through trans Mars insertion, which is about c3= 7km^2/s^2 on an *exceptionally* good opportunity. According to KSC's page, FH can only do 10t. So for high energy trajectories, FH can do about 60% better than the KSC page suggests.
No, I didn't use the KSC page.  I have expendable Falcon Heavy at 16.8 tonnes TMI.  SLS Block 1 would be 19+ tonnes, but of course it is only going to fly one trans-lunar mission. For TLI, I show expendable Falcon Heavy at 20+ tonnes and SLS Block 1 at 24.5 tonnes.

The real comparison is with SLS Block 1B, which is expected to be 32 and 39 tonnes to TMI/TLI, respectfully.

 - Ed Kyle

Your FHR payloads for TLI/TMI are probably a bit underestimated. Musk said they could possibly recover all three boosters after sending Red Dragon (which between Dragon itself and the landing propellants would be at least 10 tonnes) to TMI. That is equivalent to nearly triple the 5500 kg you have for TLI.

https://twitter.com/elonmusk/status/726820238361120768

With Reuse, FH is listed as 8 mT to GTO. How does it send 10 mT to Mars?

see:
http://www.spacex.com/about/capabilities

Falcon 9 price is listed as 5.5 mT which lines up with stage re-use. The line for FH right next to it is likely the same.
It doesn't say that the 8t to GTO is for reuse, that's just something you've surmised. I think that's more market segmentation than it is a strict delineation of rocket performance. SpaceX could use the extra capacity for secondaries, reuse, margin, or all three.
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Offline alexterrell

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Re: The fate of SLS after Falcon Heavy debut
« Reply #98 on: 02/11/2018 07:40 am »
It would be useful to see a price table:
- Falcon 9, Falcon Heavy
- Reusable Mode with new boosters, with used once boosters, with used twice boosters
- Expendable Mode with new boosters, with used boosters, with used twice boosters

Anyway that is beside the point of article. NASA has spent $10 billion on their Heavy Lift Rocket (and another $6 billion on Orion).

I'm not sure what the latest cost estimates are but this says a target is $500 million per launch, yo make one flight per year: http://www.nbcnews.com/id/49019843/ns/technology_and_science-space/#.UFIyOxii5i4
That is probably a gross under-estimate - can NASA really maintain the systems and capability for one launch per year at less than $1 billion per year?

And what does SLS do that can't be done with 2 or 3 Falcon Heavy launches? No single module for space exploration needs to mass more than 60 tons.

The only reputed benefit over Falcon Heavy was the wider payload fairing, which might be useful for Mars entry heat shields. (Or I could see it being an advantage for large solar arrays which can't be packed so tightly). New Glenn might over come that issue.

So with hindsight, SLS should have been cancelled years ago, and the $10 billion spent on an upper stage rocket, or a space tug, or electric space tug. Orion could still be useful - and maybe a tender put out for a commercial heavy lift vehicle to carry it. Then there might be a choice of SpaceX or Boeing or New Glenn for heavy lift packages, and NASA could get completely out of the launch business and focus on space exploration.

Moving forward, can the politicians who have wasted the SLS money pay for it out their pockets?

SLS will now be completed, and have a test flight and a ceremonial flight. But then what? Every time NASA has a mission, manned or unmanned, they say it'll cost $1 billion to launch on SLS, or $180 million on Falcon Heavy. How does it work in NASA - does the top mandate the launch vehicle for every mission?

Perhaps they will be able to come up with a compromise. Falcon Heavy launches the fuel, and SLS launches the mission. But with that architecture, you don't need Block 2 in that case.

New Glenn might make it look worse for NASA. If there are two rockets able to lift >45 tons, at a fraction of the cost of SLS, who is going to be interested in using SLS?

Offline TomH

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Re: The fate of SLS after Falcon Heavy debut
« Reply #99 on: 02/11/2018 09:28 am »
How does it work in NASA - does the top mandate the launch vehicle for every mission?

I see you are from Germany. The US senate mandated the specifications for the rocket and required NASA to build it. And the senate did indeed specify that the Europa Clipper mission must fly on SLS and no other launch vehicle. SLS is simply a jobs program for companies who used to build parts for the space shuttle. Powerful senators who chair committees related to NASA and have space corporations in their own states make sure that money keeps getting spent on SLS in those states. It is what we in the US call Pork Barrel Politics. I'll let you look up the meaning of that idiom/metaphor. You can also find many threads on this site related to the US senate and SLS.

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