Author Topic: NASA Considering Flying EM-1 With Commercial Launchers  (Read 29546 times)

Offline ncb1397

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #200 on: 03/14/2019 08:01 pm »
Wikipedia says the SpaceX PUG says MVac can currently throttle down to 39% (~360kN/81klbf).

The MVac throttle range listed in the latest F9 User Guide is 220,500  lbf to 140,679 lbf FWIW.

That does not match up with the 6 g maximum axial acceleration for a sub 4 klb payload shown in the same guide. Burnout acceleration with that minimum throttle would be 8.7 g assuming a 5.5 t stage mass. And I'm pretty sure either Musk or SpaceX confirmed the 35% throttle, though I can't find it right now.

The <4000 lb box is the red line - i.e. 8.5 g max.

Offline jongoff

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #201 on: 03/14/2019 08:01 pm »
Wikipedia says the SpaceX PUG says MVac can currently throttle down to 39% (~360kN/81klbf).

The MVac throttle range listed in the latest F9 User Guide is 220,500  lbf to 140,679 lbf FWIW.

That does not match up with the 6 g maximum axial acceleration for a sub 4 klb payload shown in the same guide. Burnout acceleration with that minimum throttle would be 8.7 g assuming a 5.5 t stage mass. And I'm pretty sure either Musk or SpaceX confirmed the 35% throttle, though I can't find it right now.

I found a reference stating that the solar arrays on the Orion ESM are designed to cant forward or backward by ~60 degrees, and can take a sustained 1G loading to handle TLI and other maneuvers. So it seems like MVac is pretty close to having enough throttleability as-is. If they could get it down a hair lower (from the 35-39% numbers that I've seen references for to ~32.5%), then it should clearly be within limits for both the arrays and docking adapter.

So, close enough they can probably make it work, either by qualifying MVac a little deeper, or by getting comfortable with cutting into the margins on the docking adapter and solar arrays, or tweaking them to increase what they can handle by a hair.

~Jon
« Last Edit: 03/14/2019 08:04 pm by jongoff »

Offline spacenut

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #202 on: 03/14/2019 08:10 pm »
I have some questions. 

Does Orion have to be vertically integrated?
Can a Delta IV heavy upper stage with Orion replace a FH upper stage?  I know it is rocket lego, but NASA did it with Centaur upper stage on different Atlas rockets.  They did something like this with Saturn I. 

Would it be faster to stretch or widen FH upper stage?  Or build a 5m Raptor upper stage?  In the next year? 

Just wondering how they are going to handle this.  Loop the moon and come back, or go into moon orbit, stay awhile, then come back. 
 

Offline Rocket Science

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #203 on: 03/14/2019 08:25 pm »

"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator, Vintage auto racer

Offline woods170

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #204 on: 03/14/2019 08:40 pm »
It may be possible to either rate the MVac for lower thrust operations, or add in some sort of reinforcement structure so that all of the thrust loads from the MVac aren't taken just through the docking adapter.

What about G loads on the unfurled solar arrays? At the current MVac throttleability levels, at burnout the entire stack would experience around 2G acceleration, are the arrays sturdy enough to cope with that?

Here's four pieces of information I recently gleaned from a lecture given by a dude from Airbus Defence & Space.

The first figure is that the entire set of 4 solar arrays weighs just 255 kg. Or roughly 64 kg per solar array wing.

The second set of figures is in the image below. It's a table with maximum allowable force on the solar arrays during propulsion phases of the mission.

The third set is an image showing exact dimensions of a solar array wing in millimeters.

The fourth piece of information is that the maximum allowable bending moment, at the point where a solar array wing attaches to the ESM structure is 1250 NM.

Maybe folks here can do the math to figure out an answer to ugordan's question.
« Last Edit: 03/14/2019 08:44 pm by woods170 »

Offline Patchouli

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #205 on: 03/14/2019 09:29 pm »
I have some questions. 

Does Orion have to be vertically integrated?
Can a Delta IV heavy upper stage with Orion replace a FH upper stage?  I know it is rocket lego, but NASA did it with Centaur upper stage on different Atlas rockets.  They did something like this with Saturn I. 

Would it be faster to stretch or widen FH upper stage?  Or build a 5m Raptor upper stage?  In the next year? 

Just wondering how they are going to handle this.  Loop the moon and come back, or go into moon orbit, stay awhile, then come back. 
 

Putting a DCSS on Falcon Heavy would be a no go as it's normal upper stage is much heavier and supplies a proportionally larger part of the delta V.

As for putting a stage as a payload it has to be integrated and the pad and tower has to be equipped to handle to propellants.
Does 39a even still have hydrogen plumbing?

I really don't see how they could do the full EM-1 mission with a single commercial rocket.

The simplest solution I can think of is launch Orion on the Delta IV-H or FH and get it into as high an orbit as possible then have Atlas 551 place a Centaur with docking hardware in a matching orbit dock to it and use that for TLI.
« Last Edit: 03/14/2019 09:46 pm by Patchouli »

Offline Proponent

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #206 on: 03/14/2019 09:48 pm »
I agree and I really would like to know if anyone within NSF or the NSF reporter team can answer this question:
Can ULA even produce two DIVH vehicles between the time this might be approved and a 2020 NET date ?

I suspect the bigger problem would be launching two DIVH's so close together:  Could LC-37B at CCAFS be turned around in time?  Maybe ULA could manage closely spaced launches if one went from VAFB, but I wouldn't guess it feasible to launch to the same orbit.
« Last Edit: 03/14/2019 09:49 pm by Proponent »

Offline Patchouli

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #207 on: 03/14/2019 09:59 pm »
I agree and I really would like to know if anyone within NSF or the NSF reporter team can answer this question:
Can ULA even produce two DIVH vehicles between the time this might be approved and a 2020 NET date ?

I suspect the bigger problem would be launching two DIVH's so close together:  Could LC-37B at CCAFS be turned around in time?  Maybe ULA could manage closely spaced launches if one went from VAFB, but I wouldn't guess it feasible to launch to the same orbit.

Both sites can do a 51 degree orbit but it's sub optimal for lunar missions.

They may need to use both DIVH and FH to pull this off.

Offline Proponent

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #208 on: 03/14/2019 10:05 pm »
Lots of great posts!  Thanks, everybody!!  Brindenstine's announcement is the most exciting thing that's happened in space policy for a long time.  My wife and I just closed the deal on our dream home yesterday, but I'm actually more excited about a commercially launched EM-1!

Offline mlindner

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #209 on: 03/14/2019 10:23 pm »
I'm tired of people repeating the idea that a craft that's meant to withstand launch and reentry and heavy vibrational side loading in both cases can't withstand some static loading while horizontal. It just doesn't make sense from a physics perspective.

Well too bad, because it is true. Spacecraft designed for vertical integration can only support their weight when fully fueled in the velocity direction, not any other way. Just because you don’t want to hear that doesn’t make it true. Any rocket lifting Orion must integrate it vertically, no getting around it.

I don't care what it was _designed_ for I care about what the physics says about the issue. That's the only truth that matters here, not the paperwork. No one has come out and stated why this doesn't work. "Wasn't designed for it." is a non-answer.
« Last Edit: 03/14/2019 10:35 pm by mlindner »
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Offline FinalFrontier

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #210 on: 03/14/2019 10:40 pm »
Lots of great posts!  Thanks, everybody!!  Brindenstine's announcement is the most exciting thing that's happened in space policy for a long time.  My wife and I just closed the deal on our dream home yesterday, but I'm actually more excited about a commercially launched EM-1!
Same here but I am still doubting it happens.
Congratulations by the way.
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"Live Long and Prosper"

Offline jongoff

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #211 on: 03/14/2019 11:03 pm »
Lots of great posts!  Thanks, everybody!!  Brindenstine's announcement is the most exciting thing that's happened in space policy for a long time.  My wife and I just closed the deal on our dream home yesterday, but I'm actually more excited about a commercially launched EM-1!

Congrats man! And yes, I agree this is probably the most exciting announcement we've had in a while.

~Jon

Offline jongoff

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #212 on: 03/14/2019 11:25 pm »
Just to provide some documentation backing up my earlier statements about the solar arrays. I did some google searching and found these references:

https://space.stackexchange.com/questions/23182/do-orions-solar-panels-have-adjustable-sweep (contains a lot of links that I'll include below)

https://www.edn.com/Pdf/ViewPdf?contentItemId=4434268 (Figure 5 on page 8 shows the +55/-60 degree sweep the arrays can do).

This ESA page (https://directory.eoportal.org/web/eoportal/satellite-missions/o/orion-em-1) has more info, and mentioned that in either of these configurations the arrays can resist a 1 g acceleration load. Now they don't say if 1 g is the maximum, or how much margin they have over that. RUAG makes the Solar Array Drive Mechanism, so I could possibly quote them to see what they have to say.

Anyhow, here's the relevant section from that ESA page:

Quote
SADM of the ESM has a unique design incorporating a two axis gimbal. An inner axis provides rotation of the SAW about an axis perpendicular to the ESM longitudinal axis, and an outer axis which rotates the SAW about its own longitudinal axis. The two-axis capability is necessary for two reasons:

1) allow maximum sun tracking to meet the power requirements for particular vehicle attitudes of certain mission phases. Insufficient power is generated by the SAW with a single (roll) axis SADM not providing the avoidance capability of the shadowing effect of both the Orion vehicle on the SAW and the SAWs on each other

2) insure the structural integrity of the SAWs under injection maneuvers. For the trans-lunar injection performed with the upper stage of the Space Launch System rocket, actually the iCPS (interim Cryogenic Propulsion Stage), the arrays are canted backwards to sustain in deployed configuration the 1 g acceleration load. For the trans-earth injection performed with the ESM main engine, the acceleration is less severe and the arrays have to be canted forwards to prevent damages from the OMS-E engine plume while minimizing the load on the SAWs.


So, long-story short, from a structural standpoint, an Orion on FH is pretty close to working as-is, with the MVac throttling down to keep the G-loads within reason. With the lowest number I've seen for MVac (360kN), a 30mT stack would be at a bit over 1.2G, and a 35mT stack would just be a hair over 1.0G.

~Jon

Online butters

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #213 on: 03/14/2019 11:25 pm »
The double-DIVH option doesn't appear feasible due to LV inventory and pad turnaround.
The DIVH + Atlas option is very marginal on performance.
The Orion on DIVH option seems doubtful because TLI stage on FH seems doubtful.

The FH/Orion + DIVH option appears to be most likely. Vertical integration may be a thing. Risk assessment may be a thing. Political optics may be a thing. But I think these things are more easily solved than the issues raised by the LV options above.

Offline TrevorMonty



I have some questions. 

Does Orion have to be vertically integrated?
Can a Delta IV heavy upper stage with Orion replace a FH upper stage?  I know it is rocket lego, but NASA did it with Centaur upper stage on different Atlas rockets.  They did something like this with Saturn I. 

Would it be faster to stretch or widen FH upper stage?  Or build a 5m Raptor upper stage?  In the next year? 

Just wondering how they are going to handle this.  Loop the moon and come back, or go into moon orbit, stay awhile, then come back. 
 

As for putting a stage as a payload it has to be integrated and the pad and tower has to be equipped to handle to propellants.
Does 39a even still have hydrogen plumbing?

Given liquid Methane was in their future plans, SpaceX may have plumbed pad for liquid methane. Whether it could handle LH I don't know.

As others have said, I doubt Bridenstine would've done this annoucement if preliminary investigations hadn't addressed most of technical issues we can think of. At this stage costs and schedules are probably big unknowns, something report in few weeks time will answer.

The process won't be total waste of time, even if idea is shelved as it gives a backup plan to SLS. Very useful to have when building gateway HW and eventually human lander.






Offline mclumber1

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #215 on: 03/15/2019 12:36 am »
Is FH upper stage engine too powerful and would put too many g's on Orion to work unless it can be throttled down?

Can FH launch a Centaur upper stage with docking adapter to dock with Orion to push it to lunar location?  Would boil off be a problem waiting to dock?

Centaur upper stage might be a pain to integrate.  SpaceX does have a very simple, low thrust rocket engine they could use - the Kestrel.  Not nearly as efficient as the RL-10, or even the as Merlin Vac, but it's dead simple, and uses the same fuel as the Falcon stack.

Offline TrueBlueWitt

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #216 on: 03/15/2019 12:50 am »
Is FH upper stage engine too powerful and would put too many g's on Orion to work unless it can be throttled down?

Can FH launch a Centaur upper stage with docking adapter to dock with Orion to push it to lunar location?  Would boil off be a problem waiting to dock?

Centaur upper stage might be a pain to integrate.  SpaceX does have a very simple, low thrust rocket engine they could use - the Kestrel.  Not nearly as efficient as the RL-10, or even the as Merlin Vac, but it's dead simple, and uses the same fuel as the Falcon stack.

Draco has slightly worse ISP at 300 vs 317 for Kestrel, but seems much easier and a lot lighter.
You don't need high thrust for a kick-stage do you?
Could gang together as many as you needed.
No worries about boil-off or long duration loiter.

Offline Proponent

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #217 on: 03/15/2019 01:10 am »
Both sites can do a 51 degree orbit but it's sub optimal for lunar missions.

Since you mention 51 degrees, does that mean ISS has been reached from VAFB?  If so, that seems like something any self-respecting space cadet ought to know:  which mission(s) was it?

Offline mclumber1

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #218 on: 03/15/2019 01:17 am »
Draco has slightly worse ISP at 300 vs 317 for Kestrel, but seems much easier and a lot lighter.
You don't need high thrust for a kick-stage do you?
Could gang together as many as you needed.
No worries about boil-off or long duration loiter.

That is a great point.  A super draco based kick stage would have the benefits you mentioned.  An entire kick stage and maneuvering bus could be based on dracos and a super draco.

Offline Proponent

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Re: NASA Considering Flying EM-1 With Commercial Launchers
« Reply #219 on: 03/15/2019 01:37 am »
SpaceX does have a very simple, low thrust rocket engine they could use - the Kestrel.  Not nearly as efficient as the RL-10, or even the as Merlin Vac, but it's dead simple, and uses the same fuel as the Falcon stack.

Kestrel is pressure fed.  The resulting lack of a turbopump means it is light, but a stage based on it would be heavy, because of the need for high-pressure tankage and a powerful pressurization system.  And, unless the plan is to restart production of Falcon 1 upper stages and gang them together, that stage would probably need to be developed from scratch.

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