Author Topic: Deep Space Gateway Power/Propulsion RFI  (Read 8694 times)

Online theinternetftw

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Deep Space Gateway Power/Propulsion RFI
« on: 07/20/2017 09:00 PM »
I searched and didn't find any discussion of this, on NSF or anywhere else.  As Chris put his DSG article from June in here, I'm (tentatively) putting this here as well.

https://www.nasa.gov/feature/nasa-power-propulsion-rfi

NASA has issued an RFI on the first DSG module, the PPE (Power Propulsion Element).  Despite the press release being quite threadbare, the RFI itself has a good bit of information in it.

* 24kW of providable power
* 50kW-class SEP engine
* 2000kg-class Xenon tank
* On-orbit refueling of xenon and hydrazine (requests info on green hydrazine drop-in replacements)
* No heavier than 7,500kg (including payload adapter)
* Currently planned to be co-manifested on EM-2

Edit: added a bullet point, attached RFI itself to save a step or two
« Last Edit: 07/20/2017 09:09 PM by theinternetftw »


Offline brickmack

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #2 on: 07/20/2017 10:05 PM »
I wonder why they went with hydrazine RCS instead of xenon. SEP RCS+CMGs is now a well-proven combination. Not enough torque for a station this size? Or not enough for control during docking?
« Last Edit: 07/20/2017 10:05 PM by brickmack »

Offline redliox

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #3 on: 07/20/2017 10:09 PM »
I wonder why they went with hydrazine RCS instead of xenon. SEP RCS+CMGs is now a well-proven combination. Not enough torque for a station this size? Or not enough for control during docking?

Hydrazine is frequently used and, while toxic, is stable and predictable for thrusters.  SEP/xenon will have its moment to shine, but in short hydrazine is fast while xenon is slow.  Xenon would still be used to put the module around the moon, probably some station keeping, whereas hydrazine would be used for crew visit dockings.
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Online theinternetftw

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #4 on: 07/20/2017 10:30 PM »
Thanks Chris.  Check my registration date to marvel at my previous steadfast commitment to lurkerdom :D

Offline yg1968

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Offline Propylox

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #6 on: 07/21/2017 03:09 AM »
"Near rectilinear halo orbit" is a non-starter. If you'd like to know more about the impossibility of station keeping, manned habitation and severe constraints on every mission plan it creates, NASA has plenty of papers - oddly pointing this out and concluding we should do it anyways. Much like the terrible idea of "Lagrange Gateways" that's been floated for years, now NASA pushes an even worse idea.

Cislunar Near Rectilinear Halo Orbit for Human Space Exploration - Sept 2016
https://ntrs.nasa.gov/search.jsp?R=20160003078


Is there anything about that image that makes you think it's a good idea or in any way useful? It's a hot mess in the middle of nowhere. Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.
« Last Edit: 07/21/2017 03:11 AM by Propylox »

Offline A_M_Swallow

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #7 on: 07/21/2017 04:18 AM »
{snip}
Is there anything about that image that makes you think it's a good idea or in any way useful? It's a hot mess in the middle of nowhere. Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.

1. Pretty picture.

2. I thought low lunar orbits (LLO) were unstable, requiring between 0-400 m/s of station keeping.

Putting the DSG in LLO would make lunar landing much easier.

I suspect NASA wants to put the DSG in a high lunar orbit to reduce the delta-v needed by the large mass transfer vehicle to go to Mars. However if the DSG only has a 15 year life expectancy then the Mars Transfer Vehicle (MTV) will still be under construction at the end of the Gateway's life. DSG #2 may be the return point for the MTV.

Online theinternetftw

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #8 on: 07/21/2017 04:26 AM »
"Near rectilinear halo orbit" is a non-starter. [...] Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.

Is part of it about wanting a big SEP project in a post-ARM world?  Back-solving from the tech they want to fund?

Offline TrevorMonty

Re: Deep Space Gateway Power/Propulsion RFI
« Reply #9 on: 07/21/2017 05:48 AM »
"Near rectilinear halo orbit" is a non-starter. If you'd like to know more about the impossibility of station keeping, manned habitation and severe constraints on every mission plan it creates, NASA has plenty of papers - oddly pointing this out and concluding we should do it anyways. Much like the terrible idea of "Lagrange Gateways" that's been floated for years, now NASA pushes an even worse idea.

Cislunar Near Rectilinear Halo Orbit for Human Space Exploration - Sept 2016
https://ntrs.nasa.gov/search.jsp?R=20160003078


Is there anything about that image that makes you think it's a good idea or in any way useful? It's a hot mess in the middle of nowhere. Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.
What use is DSG at LLO when no one can visit it. Orion could make it to LLO but it would be oneway trip.

Offline Jim

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #10 on: 07/21/2017 12:53 PM »
{snip}
Is there anything about that image that makes you think it's a good idea or in any way useful? It's a hot mess in the middle of nowhere. Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.

1. Pretty picture.

2. I thought low lunar orbits (LLO) were unstable, requiring between 0-400 m/s of station keeping.

Putting the DSG in LLO would make lunar landing much easier.

I suspect NASA wants to put the DSG in a high lunar orbit to reduce the delta-v needed by the large mass transfer vehicle to go to Mars. However if the DSG only has a 15 year life expectancy then the Mars Transfer Vehicle (MTV) will still be under construction at the end of the Gateway's life. DSG #2 may be the return point for the MTV.

Has nothing to do with MTV

Online envy887

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #11 on: 07/21/2017 01:43 PM »
{snip}
Is there anything about that image that makes you think it's a good idea or in any way useful? It's a hot mess in the middle of nowhere. Dump the circus act for a useful LLO and the electric power and propulsion requirements evaporate, as does funding requirements.

1. Pretty picture.

2. I thought low lunar orbits (LLO) were unstable, requiring between 0-400 m/s of station keeping.

Putting the DSG in LLO would make lunar landing much easier.

I suspect NASA wants to put the DSG in a high lunar orbit to reduce the delta-v needed by the large mass transfer vehicle to go to Mars. However if the DSG only has a 15 year life expectancy then the Mars Transfer Vehicle (MTV) will still be under construction at the end of the Gateway's life. DSG #2 may be the return point for the MTV.

Has nothing to do with MTV

Specifically, the Deep Space Transport (the Mars transfer vehicle) can easily enter and exit LLO.

The problem is Orion cannot enter and then exit LLO, so no infrastructure using Orion will be built or moved there.

Offline oldAtlas_Eguy

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #12 on: 07/21/2017 04:57 PM »
The other item I noticed was max weight for this co-manifested payload showing there is likely going to this orbit with Orion on a SLS-1B only 7.5mt of excess capability. Which also means that the DSG itself will have to weigh no more than 7.5mt. This orbit was probably picked because for other orbits there just was not enough excess capability to have a useful co-manifested payload.

Offline GWH

Re: Deep Space Gateway Power/Propulsion RFI
« Reply #13 on: 07/21/2017 05:13 PM »
The other item I noticed was max weight for this co-manifested payload showing there is likely going to this orbit with Orion on a SLS-1B only 7.5mt of excess capability. Which also means that the DSG itself will have to weigh no more than 7.5mt. This orbit was probably picked because for other orbits there just was not enough excess capability to have a useful co-manifested payload.
Yes mass restrictions seem to be popping up and causing development problems, see links below:
http://russianspaceweb.com/imp-ppb.html#2017

http://russianspaceweb.com/imp-lcub.html

Offline Khadgars

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #14 on: 07/21/2017 05:47 PM »
The other item I noticed was max weight for this co-manifested payload showing there is likely going to this orbit with Orion on a SLS-1B only 7.5mt of excess capability. Which also means that the DSG itself will have to weigh no more than 7.5mt. This orbit was probably picked because for other orbits there just was not enough excess capability to have a useful co-manifested payload.

No, that means each "delivery" is constrained by 7.5mt, not the entire DSG.

NASA is pushing quite an aggressive schedule, delivery in 2021 for launch in 2022 for propulsion module.  Habitation module to follow the following year. 

Offline A_M_Swallow

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #15 on: 07/21/2017 06:04 PM »
The other item I noticed was max weight for this co-manifested payload showing there is likely going to this orbit with Orion on a SLS-1B only 7.5mt of excess capability. Which also means that the DSG itself will have to weigh no more than 7.5mt. This orbit was probably picked because for other orbits there just was not enough excess capability to have a useful co-manifested payload.

7.5 mT is the weight of each module. The current plan is for 4 modules.
https://www.nasaspaceflight.com/2017/04/nasa-goals-missions-sls-eyes-multi-step-mars

IMHO A small spacestation containing 4 tiny modules to be lifted by 4 SLS and assembled by 4 Orions appears excessive.

Offline okan170

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #16 on: 07/21/2017 06:41 PM »
The other item I noticed was max weight for this co-manifested payload showing there is likely going to this orbit with Orion on a SLS-1B only 7.5mt of excess capability. Which also means that the DSG itself will have to weigh no more than 7.5mt. This orbit was probably picked because for other orbits there just was not enough excess capability to have a useful co-manifested payload.
Yes mass restrictions seem to be popping up and causing development problems, see links below:
http://russianspaceweb.com/imp-ppb.html#2017

http://russianspaceweb.com/imp-lcub.html

Should probably be noted that some of these are due to a less-optimal but safer launch trajectory being used for EM-2, since its the first crew launch.

Offline jgoldader

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #17 on: 07/21/2017 08:40 PM »
NASA is pushing quite an aggressive schedule, delivery in 2021 for launch in 2022 for propulsion module.  Habitation module to follow the following year. 

Can this really be done by 2021?  This looks like the "hard" part of the Gateway, with the most powerful SEP system ever, no?  Four years to delivery, and no contracts yet?  I could believe a docking node or hab module in 4 years, if there was a lot of money, but the propulsion module seems a lot more ambitious technologically.
Recovering astronomer

Offline okan170

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #18 on: 07/21/2017 09:56 PM »
NASA is pushing quite an aggressive schedule, delivery in 2021 for launch in 2022 for propulsion module.  Habitation module to follow the following year. 

Can this really be done by 2021?  This looks like the "hard" part of the Gateway, with the most powerful SEP system ever, no?  Four years to delivery, and no contracts yet?  I could believe a docking node or hab module in 4 years, if there was a lot of money, but the propulsion module seems a lot more ambitious technologically.

Probably helps that its almost literally the latest design of ARM without any of the grabbing equipment and an extra docking port.

Offline ncb1397

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Re: Deep Space Gateway Power/Propulsion RFI
« Reply #19 on: 07/21/2017 10:03 PM »
NASA is pushing quite an aggressive schedule, delivery in 2021 for launch in 2022 for propulsion module.  Habitation module to follow the following year. 

Can this really be done by 2021?  This looks like the "hard" part of the Gateway, with the most powerful SEP system ever, no?  Four years to delivery, and no contracts yet?  I could believe a docking node or hab module in 4 years, if there was a lot of money, but the propulsion module seems a lot more ambitious technologically.

Probably helps that its almost literally the latest design of ARM without any of the grabbing equipment and an extra docking port.

ARM had a docking port for Orion. PPE would just need the one. Right?


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