NASA SLS/Orion/Payloads

[_Augustus_]

https://arstechnica.com/science/2018/03/nasa-chief-explains-why-agency-wont-buy-a-bunch-of-falcon-heavy-rockets/

Gerst says DSG will be using "large monolithic pieces" that require SLS. What large monolithic pieces? The DSG modules would all fit on FH or New Glenn. 

Someone in the comments section said this:

Quote

The SLS is required in order to build the Lunar Orbiting Platform-Gateway, because the Lunar Orbiting Platform-Gateway was designed to require SLS. Also it hasn't been designed yet, but when it is it will require SLS. Funding for designing it hasn't been allocated yet, but if and when it is, it will be on the basis that it require SLS. As you can see, SLS is clearly required by SLS requirements and Falcon Heavy is not SLS and so therefore does not meet the requirements of being SLS.

Sad but true.

[Ultimate Steve]

https://www.nasa.gov/press-release/nasa-s-webb-observatory-requires-more-time-for-testing-and-evaluation-new-launch

 

 

JWST is now NET May 2020. At this point SLS may beat it to space.

[PB666]

13 minutes ago, _Augustus_ said:

https://arstechnica.com/science/2018/03/nasa-chief-explains-why-agency-wont-buy-a-bunch-of-falcon-heavy-rockets/

Gerst says DSG will be using "large monolithic pieces" that require SLS. What large monolithic pieces? The DSG modules would all fit on FH or New Glenn. 

Someone in the comments section said this:

Sad but true.

ROFLMAO. Somewhere in the background stands a smiling Joseph Stalin.

But the problem is the dV required for DSG is a little bit on the high side of what FH can accomplish, I also looked what FH could do if the upperstage was Methane instead of Kerolox, about 600 dV more. You get about 2/3rds of the way to orbit, provided your cryogenic engine has enough ummph to push to orbit, theres a big pay-off beyond. As for NG, SLS, and BFR . . .vaporware. I will say one thing, pouring over the chemistry of metholox and seeing how both hyrdrolox and kerolox have really been pushed in the last few years, I think they can get at least 20 more sec of ISP out of their Raptor engines if the push it.

[Canopus]

The DSG pieces might fit Falcon Heavy but what good would it do just shoot them past the moon?

FH may be phenomenal for low earth orbit, but it‘s performance drops fast the higher and faster your payloads needs to go. It‘s a very heavy launcher but for a different regime. It‘s not a drop in replacement for the SLS.

[kerbiloid]

Or they should build DSG in LEO and raise the orbit with a single low-thrust nuke tug.

Edited March 28, 2018 by kerbiloid

[sevenperforce]

5 hours ago, kerbiloid said:

Or they should build DSG in LEO and raise the orbit with a single low-thrust nuke tug.

Or the DSG's own engines.

[kerbiloid]

35 minutes ago, sevenperforce said:

Or the DSG's own engines.

Then it will be DSS.

[sh1pman]

51 minutes ago, sevenperforce said:

Or the DSG's own engines.

I don't think its own engines are powerful enough for the insertion burn.

[Bill Phil]

Just now, sh1pman said:

I don't think its own engines are powerful enough for the insertion burn.

Even if they were, they run on solar power. And night happens about half the time in LEO.

Although a chemical/nuclear tug could do the job.

[sevenperforce]

1 hour ago, Bill Phil said:

Even if they were, they run on solar power. And night happens about half the time in LEO.

Although a chemical/nuclear tug could do the job.

Or a bloody Falcon Heavy upper stage.

[wumpus]

14 hours ago, _Augustus_ said:

https://arstechnica.com/science/2018/03/nasa-chief-explains-why-agency-wont-buy-a-bunch-of-falcon-heavy-rockets/

Gerst says DSG will be using "large monolithic pieces" that require SLS. What large monolithic pieces? The DSG modules would all fit on FH or New Glenn. 

Someone in the comments section said this:

Sad but true.

I'm sure half the specification of the DSG (now LOP-G) is to be more than ~30tons per launch to make sure that the Falcon-Heavy can't be used.  I've seen claims that it would be 60 tons and that an SLS block B could throw it all the way to LTI, but that depends on SLS block A either launching or being canceled followed by block B launching.  Proton is listed as a possible launch vehicle, and I doubt that it can send anything to LTI that Falcon Heavy can't (FH's main limitation is that it is unlikely be able to lift anything that F9 (expendable) can't lift to orbit thanks to structural issues - no idea if block 5 changes that).

I'm sure that Congress will carefully stick their fingers in their ears and chant "not listening" to any suggestion to spend money anywhere but SLS.  Space requires funding, and only SLS gets funding.  Therefore DSG/LOP-G requires SLS.

[Canopus]

Habitat modules will be around 10 tons, lower than the suspected Falcon heavy TLI payload. But remember that it carries the Orion on the same launch or else the modules would just fly past the moon. Weirdly enough i constantly read people talking about how the modules could be launched by current launch vehicles, yet forgetting that having the parts just do lunar flybys wouldn't accomplish much. 

@wumpus SLS is older than FH so they couldn't plan for it. This isn't some conspiracy against Musk you know.

Edited March 28, 2018 by Canopus

[Canopus]

2 hours ago, sevenperforce said:

Or a bloody Falcon Heavy upper stage.

Falcon heavy stage is dead before it arrives in lunar orbit

[sevenperforce]

41 minutes ago, Canopus said:

Habitat modules will be around 10 tons, lower than the suspected Falcon heavy TLI payload. But remember that it carries the Orion on the same launch or else the modules would just fly past the moon. Weirdly enough i constantly read people talking about how the modules could be launched by current launch vehicles, yet forgetting that having the parts just do lunar flybys wouldn't accomplish much.

3 hours ago, sevenperforce said:

Or a bloody Falcon Heavy upper stage.

Falcon heavy stage is dead before it arrives in lunar orbit

Which is why I suggested, above, that the DSG be assembled in LEO, boosted onto TLI by current launch vehicles (for example, Falcon Heavy upper stage launched empty), and then use its own engines for orbital insertion at its destination. Its engines are not powerful enough for trans-lunar injection but they can handle insertion.

[Canopus]

8 minutes ago, sevenperforce said:

Which is why I suggested, above, that the DSG be assembled in LEO, boosted onto TLI by current launch vehicles (for example, Falcon Heavy upper stage launched empty), and then use its own engines for orbital insertion at its destination. Its engines are not powerful enough for trans-lunar injection but they can handle insertion.

The final station including Propulsion unit would have to be less than 29 tons then. 

I'm not saying you are wrong, there are sensible alternatives to SLS, it's just that Falcon heavy isn't one of them and the others haven't flown yet.

Edited March 28, 2018 by Canopus

[sevenperforce]

11 minutes ago, Canopus said:

The final station including Propulsion unit would have to be less than 29 tons then. 

I'm not saying you are wrong, there are sensible alternatives to SLS, it's just that Falcon heavy isn't one of them and the others haven't flown yet.

By my math, a naked Falcon Heavy upper stage can launch upwards of 65 tonnes to TLI.

Edited March 28, 2018 by sevenperforce

[Canopus]

Just now, sevenperforce said:

By my math, an empty Falcon Heavy upper stage can launch upwards of 65 tonnes to TLI.

By empty you mean one flown without payload? 

[sevenperforce]

4 minutes ago, Canopus said:

By empty you mean one flown without payload? 

Right. Assemble the DSG however you want in LEO, fully refuel it, and then launch a Falcon Heavy on an instantaneous intercept launch window with nothing but an international docking adapter on top. Load the upper stage with extra helium bottles, like the first FH launch. The Falcon family upper stage can provide pointing via cold gas thrusters even though it has no meaningful RCS to speak of, which is enough for the DSG to rendezvous and dock with the IDA. A couple of orbits later, the extra helium bottles repressurize the stage and the MVac does the TLI burn.

[Canopus]

2 minutes ago, sevenperforce said:

Right. Assemble the DSG however you want in LEO, fully refuel it, and then launch a Falcon Heavy on an instantaneous intercept launch window with nothing but an international docking adapter on top. Load the upper stage with extra helium bottles, like the first FH launch. The Falcon family upper stage can provide pointing via cold gas thrusters even though it has no meaningful RCS to speak of, which is enough for the DSG to rendezvous and dock with the IDA. A couple of orbits later, the extra helium bottles repressurize the stage and the MVac does the TLI burn.

Still, the payload mass can't be that high. A fully fueled ACES would "only" do 30 tons to TLI. I can't believe the Falcon upper stage could do twice that.

[ment18]

20 minutes ago, Canopus said:

Still, the payload mass can't be that high. A fully fueled ACES would "only" do 30 tons to TLI. I can't believe the Falcon upper stage could do twice that.

350*9.8*ln((115+4.5 + 60/4.5+60) = 3768m/s.  You need to refuel the stage in orbit, which is pretty difficult.  You can only get about 70t of propellant into orbit with an empty falcon heavy launch.

[Canopus]

24 minutes ago, ment18 said:

You need to refuel the stage in orbit, which is pretty difficult. 

So it's not gonna happen.

[sevenperforce]

39 minutes ago, Canopus said:

Still, the payload mass can't be that high. A fully fueled ACES would "only" do 30 tons to TLI. I can't believe the Falcon upper stage could do twice that.

Falcon Heavy has a really ridiculously good mass fraction.

15 minutes ago, ment18 said:

You need to refuel the stage in orbit, which is pretty difficult.  You can only get about 70t of propellant into orbit with an empty falcon heavy launch.

My math is saying much more than 70 tonnes of propellant to LEO.

TLI requires 2,730 m/s, which with an Isp of 345 seconds requires a propellant fraction of 55%. Stage mass, plus mating equipment, is about 4.5 tonnes. So, depending on the amount of propellant you have (which may depend on whether you use an expendable Falcon Heavy, a two-core-recovery Falcon Heavy, or an all-core-recovery Falcon Heavy), you can send varying payloads to TLI:

• 20 tonnes propellant: 11.8 tonnes payload
• 30 tonnes propellant: 20 tonnes payload
• 40 tonnes propellant: 28.2 tonnes payload
• 50 tonnes propellant: 36.4 tonnes payload
• 60 tonnes propellant: 44.6 tonnes payload
• 65 tonnes propellant: 48.7 tonnes payload
• 70 tonnes propellant: 52.8 tonnes payload
• 75 tonnes propellant: 56.9 tonnes payload
• 80 tonnes propellant: 61 tonnes payload
• 85 tonnes propellant: 65 tonnes payload
• 90 tonnes propellant: 69.1 tonnes payload
• 95 tonnes propellant: 73.2 tonnes payload

(yes, I could have done that with a chart; so sue me)

4 minutes ago, Canopus said:

30 minutes ago, ment18 said:

You need to refuel the stage in orbit, which is pretty difficult.

So it's not gonna happen.

I think he was talking about ACES? No one needs to refuel FH.

[DDE]

3 hours ago, Canopus said:

Habitat modules will be around 10 tons, lower than the suspected Falcon heavy TLI payload. But remember that it carries the Orion on the same launch or else the modules would just fly past the moon.

Uhm, citation needed? If Orion can only barely make it out of NRHO under its own Service Module power, it's not an awfully effective lunar injection stage - so long as you're not into suicide missions.

[Canopus]

25 minutes ago, DDE said:

Uhm, citation needed? If Orion can only barely make it out of NRHO under its own Service Module power, it's not an awfully effective lunar injection stage - so long as you're not into suicide missions.

EUS is not performing LOI

https://www.nasaspaceflight.com/2017/09/sls-em-1-em-3-notional-mission-outline/

"Following this initial orbit insertion, which will allow Orion to reenter Earth’s atmosphere safely in the event that the Exploration Upper Stage (EUS) suffers a failure after this point, the nominal mission timeline would call for the EUS to perform an ascent burn to circularize the Orion and Hab module into an 100 nmi (115 miles; 185 km).

After post-launch vehicle checkouts are complete, the EUS will fire its engines again for the Trans-Lunar Injection burn, which will send Orion, the EUS, and the Hab module into a transfer orbit to the Moon. 

Once safely en route to the Moon, Orion will separate from the top of the remaining SLS stack and will likely turn around to mate to the Hab module. 

The exact details of this are not yet known as the design process for the DSG continues. 

Regardless, over the course of the 3-10 day outward trip from Earth to the Moon, Orion’s auxiliary engines will perform at least four Outbound Trajectory Correction (OTC) maneuvers to refine the craft’s approach to the Moon.

These OTCs will allow Orion/Hab to target a precise point to enter a NRHO around the Moon while the EUS performs a disposal into a heliocentric orbit."

Edited March 28, 2018 by Canopus

[sevenperforce]

1 hour ago, DDE said:

Uhm, citation needed? If Orion can only barely make it out of NRHO under its own Service Module power, it's not an awfully effective lunar injection stage - so long as you're not into suicide missions.

NRHO isn't too hard to hit.

EM-2 is free-return; EUS places both Orion and the DSG propulsion module on a lunar free-return and then separates. The DSG (excuse me, LOP-G) propulsion module separates from Orion shortly after EUS jettison. I believe Orion will simply do the free-return while the DSG prop module does its own LOI at NRHO.

It's EM-3 when you'll start to see Orion performing LOI to deliver modules to the LOP-G. Supposedly.

FH can do EVERYTHING that SLS can do, up until the point that BFS is flying.