Author Topic: SpaceX Dragon XL  (Read 245677 times)

Offline John Alan

  • Full Member
  • ****
  • Posts: 958
  • Central IL - USA - Earth
    • Home of the ThreadRipper Cadillac
  • Liked: 721
  • Likes Given: 2735
Re: SpaceX Dragon XL
« Reply #200 on: 03/29/2020 09:43 am »

My guess is that the S2 and DXL will be inserted in a somewhat eccentric orbit, simply because it doesn't need to be circular.  The S2 will then coast to perigee and provide all of the delta-v to TLI.  The DXL will then separate, and the Dracos will provide the delta-v necessary to insert into NRHO via a lunar flyby, as well as whatever is needed for rendezvous and docking.  It comes out to about 450 m/s.

If we assume a 6 t DXL with 3 t of MMH/NTO for the Dracos, I get the following max payloads to TLI, using the remaining prop from the S2:

FHE:  9.2 t
FH2R: 6.5 t
FH3R: 1.0 t

I think you may be heavy on your empty DXL weight...
I'm currently assuming ~4 t DXL with ~5 t of MMH/NTO and spec 5 t payload...
FH Boosters to ASDS's (try anyway) and Core will be expended (no choice)... Fairing catch attempted also...
S2 burns twice... Once to initial and once Oberth... releases DXL on 2nd outbound leg...
S2 saves enough to burp once more at top of arc and then burns up on next earth inbound pass...
DXL first burn is just enough to get away from S2 and lengthen it's outbound arc just a bit...
Swings around and does several Oberth thruster passes to lengthen the arc till it reaches moon capture.
Does its job... has enough prop still left to, with careful planning, end up burning up in earths atmosphere...

See... I'm figuring up to 2 weeks to get there and maybe a month getting back...
There is no real hurry... no souls aboard... Just stuff and latter trash...
This is not Apollo 2.0... this is an unmanned space truck doing a job 50 years later.

JMHO... JA

On edit...
I hope like heck SpaceX puts some good cameras on DXL and runs a near 24/7 YouTube feed while this thing does its job...
That would be epic, and great PR for them AND for space in general...  8)
« Last Edit: 03/29/2020 10:56 am by John Alan »

Offline Jimmy Murdok

  • Full Member
  • **
  • Posts: 213
  • Lausanne - Barcelona
  • Liked: 185
  • Likes Given: 197
Re: SpaceX Dragon XL
« Reply #201 on: 03/29/2020 01:22 pm »
Updated the vehicle with solar panels, same size as original Dragon.
- 6x900 liter tanks: 3600 5600 liters of hydrazine
- 4000kg dry weight (Bit lower than 4200kg from Dragon1 as: no parachutes, no heatshield but bigger size and deep space hardened).   
- Super Draco with 300isp
- ∆v to be updated with 5600liters of propellent
- ∆v:990m/s: 5mt payload
- ∆v:1220m/s: 3mt payload
- ∆v:1600m/s: 1mt payload


CAD Design
https://cad.onshape.com/documents/d32435cb16f1fe696165b0f7/w/e324511fb848d24897bf37cf/e/b9d1809c586d174ba6e8f9b8
DV calculator:
http://www.strout.net/info/science/delta-v/
Disclamer: all the data is speculative based on IDA docking port and the 3.7m diameter F9 tanks.
edit:∆v notation
« Last Edit: 03/30/2020 07:43 am by Jimmy Murdok »

Offline indaco1

  • Full Member
  • **
  • Posts: 283
  • Liked: 64
  • Likes Given: 37
Re: SpaceX Dragon XL
« Reply #202 on: 03/29/2020 02:22 pm »
If it is supposed to transfer both pressurized and unpressurized cargo, how could it have docking at both ends?
It would need a different variant. But I think putting a docking tunnel through the propulsion section is the harder part, which is already done as part of the basic design.

Naive question:  why not laterally?

This could solve propulsion/unpressurized issue, and enable much more configurations, expecially with double lateral docking ports.

I'm vaguely aware it will require reinforced structure and a lot of complex stuff.

Non-native English speaker and non-expert, be patient.

Offline Cherokee43v6

  • Full Member
  • ****
  • Posts: 1165
  • Garner, NC
  • Liked: 920
  • Likes Given: 232
Re: SpaceX Dragon XL
« Reply #203 on: 03/29/2020 02:33 pm »
This brings up a question I've wondered about a bit.

This is cargo.  It's not necessarily 'speed sensitive' on delivery.  Therefore, would it not be a reasonable consideration to increase cargo mass by going with a different proven thruster technology. Say an Ion Thruster something like DS-1 used?  Trading fuel mass for cargo mass?  So it takes weeks instead of days to arrive.  Again, it's not necessarily time critical on the delivery.

Back when NASA still had the HLS option analysis up (I saved a copy of it here, p. 27), they addressed the topic of why they had ruled out SEP for 15 t payloads:
Quote
A SEP Tug comparable to Gateway PPE would have a minimum Time-of-Flight (ToF)
greater than 420 days to deliver a 15 t HLS element from GTO to NRHO
(300+ days of spiral time GTO-TLI; 120 day ballistic transfer TLI-NRHO).

This transfer time is more than 20% of the remaining schedule for HLS and it was judged
to be an impractical approach for achieving the 2024 mission timeline.

As always, to use SEP effectively, you either need tiny payloads or you have to be really, really sure of your schedule.

Thank you.  I was aware SEP was slower, but not THAT much slower!
"I didn't open the can of worms...
        ...I just pointed at it and laughed a little too loudly."

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 38675
  • Minnesota
  • Liked: 24347
  • Likes Given: 11919
Re: SpaceX Dragon XL
« Reply #204 on: 03/29/2020 02:54 pm »
If it is supposed to transfer both pressurized and unpressurized cargo, how could it have docking at both ends?
It would need a different variant. But I think putting a docking tunnel through the propulsion section is the harder part, which is already done as part of the basic design.

Naive question:  why not laterally?

This could solve propulsion/unpressurized issue, and enable much more configurations, expecially with double lateral docking ports.

I'm vaguely aware it will require reinforced structure and a lot of complex stuff.
Can be done laterally, but axial ports are better from a forces and stresses perspective, particularly if your vehicle is going to be under any kind of significant thrust.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Online gongora

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 9803
  • US
  • Liked: 12985
  • Likes Given: 5625
Re: SpaceX Dragon XL
« Reply #205 on: 03/29/2020 03:10 pm »
This brings up a question I've wondered about a bit.

This is cargo.  It's not necessarily 'speed sensitive' on delivery.  Therefore, would it not be a reasonable consideration to increase cargo mass by going with a different proven thruster technology. Say an Ion Thruster something like DS-1 used?  Trading fuel mass for cargo mass?  So it takes weeks instead of days to arrive.  Again, it's not necessarily time critical on the delivery.

Back when NASA still had the HLS option analysis up (I saved a copy of it here, p. 27), they addressed the topic of why they had ruled out SEP for 15 t payloads:
Quote
A SEP Tug comparable to Gateway PPE would have a minimum Time-of-Flight (ToF)
greater than 420 days to deliver a 15 t HLS element from GTO to NRHO
(300+ days of spiral time GTO-TLI; 120 day ballistic transfer TLI-NRHO).

This transfer time is more than 20% of the remaining schedule for HLS and it was judged
to be an impractical approach for achieving the 2024 mission timeline.

As always, to use SEP effectively, you either need tiny payloads or you have to be really, really sure of your schedule.

Thank you.  I was aware SEP was slower, but not THAT much slower!

PPE is more powerful than shown in that slide, which would cut off a good portion of a year from the time estimate.  Also those numbers are for a much larger payload than what Dragon XL will be carrying.  The slide is for a SEP tug plus a 15t payload.

Online edkyle99

  • Expert
  • Senior Member
  • *****
  • Posts: 15134
  • Liked: 8021
  • Likes Given: 1268
Re: SpaceX Dragon XL
« Reply #206 on: 03/29/2020 03:20 pm »
Does anyone have a good estimate for Falcon Heavy near-escape capability for core-expendable and booster down-range recovery mode?  Such a mode does not yet exist, of course, because SpaceX hasn't demonstrated dual downrange recovery.  I know about Elon's 10% payload reduction estimate, but he never said if that was for LEO or GTO, etc.  My guess is 10% for LEO, but a bigger reduction for higher energy orbits. 

My estimate for 5 tonnes cargo to Near Rectilinear Halo (lunar) Orbit (NRHO) is that 12 to 16 tonnes (payload, spacecraft, propellant) would need to separate into TLI, providing 10.5 to 13.8 tonnes to NRHO (13.5% of mass used for the burns to NRHO).  The three-core recovery mode for Falcon Heavy only provides 8 tonnes to GTO, while fully expendable Falcon Heavy is listed at 26.7 tonnes GTO or 16.8 tonnes trans-Mars.

 - Ed Kyle
« Last Edit: 03/29/2020 03:23 pm by edkyle99 »

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 38675
  • Minnesota
  • Liked: 24347
  • Likes Given: 11919
Re: SpaceX Dragon XL
« Reply #207 on: 03/29/2020 03:40 pm »
Does anyone have a good estimate for Falcon Heavy near-escape capability for core-expendable and booster down-range recovery mode?  Such a mode does not yet exist, of course, because SpaceX hasn't demonstrated dual downrange recovery.  I know about Elon's 10% payload reduction estimate, but he never said if that was for LEO or GTO, etc.  My guess is 10% for LEO, but a bigger reduction for higher energy orbits. 

My estimate for 5 tonnes cargo to Near Rectilinear Halo (lunar) Orbit (NRHO) is that 12 to 16 tonnes (payload, spacecraft, propellant) would need to separate into TLI, providing 10.5 to 13.8 tonnes to NRHO (13.5% of mass used for the burns to NRHO).  The three-core recovery mode for Falcon Heavy only provides 8 tonnes to GTO, while fully expendable Falcon Heavy is listed at 26.7 tonnes GTO or 16.8 tonnes trans-Mars.

 - Ed Kyle
Citation needed for just 8 tons GTO with 3 booster recovery. I think the assumptions for that are much more conservative (sandbagged) than those for the 16.8tonnes TMI estimate.

Also, center core expended and 2 cores RTLS is a thing.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline soltasto

  • Full Member
  • ****
  • Posts: 636
  • Italy, Earth
  • Liked: 1116
  • Likes Given: 40
Re: SpaceX Dragon XL
« Reply #208 on: 03/29/2020 06:28 pm »
Does anyone have a good estimate for Falcon Heavy near-escape capability for core-expendable and booster down-range recovery mode?  Such a mode does not yet exist, of course, because SpaceX hasn't demonstrated dual downrange recovery.  I know about Elon's 10% payload reduction estimate, but he never said if that was for LEO or GTO, etc.  My guess is 10% for LEO, but a bigger reduction for higher energy orbits. 

My estimate for 5 tonnes cargo to Near Rectilinear Halo (lunar) Orbit (NRHO) is that 12 to 16 tonnes (payload, spacecraft, propellant) would need to separate into TLI, providing 10.5 to 13.8 tonnes to NRHO (13.5% of mass used for the burns to NRHO).  The three-core recovery mode for Falcon Heavy only provides 8 tonnes to GTO, while fully expendable Falcon Heavy is listed at 26.7 tonnes GTO or 16.8 tonnes trans-Mars.

 - Ed Kyle
Citation needed for just 8 tons GTO with 3 booster recovery. I think the assumptions for that are much more conservative (sandbagged) than those for the 16.8tonnes TMI estimate.

Also, center core expended and 2 cores RTLS is a thing.

I think that comes directly from SpaceX:

https://www.spacex.com/about/capabilities

Offline Karloss12

  • Full Member
  • ***
  • Posts: 300
  • Liked: 173
  • Likes Given: 7
Re: SpaceX Dragon XL
« Reply #209 on: 03/29/2020 07:15 pm »
Even though the hardware is largely derived from legacy equipment, the Earth-Lunar transfer and docking technology will be an important boost for SpaceX experience.
And SpaceX will be making an absolute packet in profit margins for each mission as they know that they are only competing with the astronomically priced Delta IV Heavy.
This is going to be a much celebrated mission for SpaceX.  They will pocket a lot of cash and also develop themselves a new technology.

My bolding
Can you site evidence of anyone making a killing on a NASA contract?
Even Boeing isn't "cleaning up" on SLS.  They are just getting fixed or award fees for the last decade, and that's good enough.
The company I work for has done a many instruments and missions for NASA.  It's a good business.  Higher margin than the commodity stuff.  But it doesn't bloat the bottom line.
A big issue for SpaceX is that this is seems to be a fixed price contract, IDIQ, for a system involved with astronauts, and at any time NASA can increase the requirements.  SpaceX has experience with this, and probably didn't underbid the competition by $1.6B again. 
But it remains a risk, not a bonanza.
I site the laws of capitalism.  In particular, competition.
The FH costs about $120mil.  The Delta IV is $400mil.
SpaceX will have bid around $350mil and be making a packet.  Good on them.  They need the cash to fund R&D.

Offline ZChris13

Re: SpaceX Dragon XL
« Reply #210 on: 03/29/2020 07:24 pm »
Even though the hardware is largely derived from legacy equipment, the Earth-Lunar transfer and docking technology will be an important boost for SpaceX experience.
And SpaceX will be making an absolute packet in profit margins for each mission as they know that they are only competing with the astronomically priced Delta IV Heavy.
This is going to be a much celebrated mission for SpaceX.  They will pocket a lot of cash and also develop themselves a new technology.

My bolding
Can you site evidence of anyone making a killing on a NASA contract?
Even Boeing isn't "cleaning up" on SLS.  They are just getting fixed or award fees for the last decade, and that's good enough.
The company I work for has done a many instruments and missions for NASA.  It's a good business.  Higher margin than the commodity stuff.  But it doesn't bloat the bottom line.
A big issue for SpaceX is that this is seems to be a fixed price contract, IDIQ, for a system involved with astronauts, and at any time NASA can increase the requirements.  SpaceX has experience with this, and probably didn't underbid the competition by $1.6B again. 
But it remains a risk, not a bonanza.
I site the laws of capitalism.  In particular, competition.
The FH costs about $120mil.  The Delta IV is $400mil.
SpaceX will have bid around $350mil and be making a packet.  Good on them.  They need the cash to fund R&D.
ULA wouldn't have bid Delta IV Heavy. They would have bid Vulcan. Delta IV Heavy is retired

Offline laszlo

  • Full Member
  • ****
  • Posts: 802
  • Liked: 1067
  • Likes Given: 431
Re: SpaceX Dragon XL
« Reply #211 on: 03/29/2020 07:27 pm »

I site(sp) the laws of capitalism.  In particular, competition.
The FH costs about $120mil.  The Delta IV is $400mil.
SpaceX will have bid around $350mil and be making a packet.  Good on them.  They need the cash to fund R&D.

Is that like the Ferengi Rules of Acquisition?

Offline Coastal Ron

  • Senior Member
  • *****
  • Posts: 8563
  • I live... along the coast
  • Liked: 9930
  • Likes Given: 11636
Re: SpaceX Dragon XL
« Reply #212 on: 03/29/2020 07:57 pm »
I site the laws of capitalism.  In particular, competition.
The FH costs about $120mil.  The Delta IV is $400mil.

Elon Musk said a fully expendable Falcon Heavy would be $150M.
https://twitter.com/elonmusk/status/963076231921938432?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed&ref_url=https%3A%2F%2Fwww.cnbc.com%2F2018%2F02%2F12%2Felon-musk-spacex-falcon-heavy-costs-150-million-at-most.html

Quote
SpaceX will have bid around $350mil and be making a packet.  Good on them.  They need the cash to fund R&D.

Government procurement guidelines don't allow for predatory pricing, and SpaceX is not known for predatory pricing, so if NASA required the fully capabilities of a Falcon Heavy they would pay $150M for the basic launch service. And if they needed more than the basic launch service, which they normally do, then that would be an added cost, but the basic launch service cost does not change.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline TheRadicalModerate

  • Senior Member
  • *****
  • Posts: 3926
  • Tampa, FL
  • Liked: 2958
  • Likes Given: 576
Re: SpaceX Dragon XL
« Reply #213 on: 03/29/2020 08:14 pm »
I think you may be heavy on your empty DXL weight...
I'm currently assuming ~4 t DXL with ~5 t of MMH/NTO and spec 5 t payload...
FH Boosters to ASDS's (try anyway) and Core will be expended (no choice)... Fairing catch attempted also...
S2 burns twice... Once to initial and once Oberth... releases DXL on 2nd outbound leg...
S2 saves enough to burp once more at top of arc and then burns up on next earth inbound pass...
DXL first burn is just enough to get away from S2 and lengthen it's outbound arc just a bit...
Swings around and does several Oberth thruster passes to lengthen the arc till it reaches moon capture.
Does its job... has enough prop still left to, with careful planning, end up burning up in earths atmosphere...

See... I'm figuring up to 2 weeks to get there and maybe a month getting back...
There is no real hurry... no souls aboard... Just stuff and latter trash...
This is not Apollo 2.0... this is an unmanned space truck doing a job 50 years later.

JMHO... JA

On edit...
I hope like heck SpaceX puts some good cameras on DXL and runs a near 24/7 YouTube feed while this thing does its job...
That would be epic, and great PR for them AND for space in general...  8)

I think you're right that I may be a little conservative on both dry mass and needed prop (which of course increases dry mass by a bit).  However, my model doesn't have any margins built into it, so my numbers are probably pretty close.

I'd be very surprised if there were two perigee burns as you've described.  To do so, you'd be reducing the mass of kerolox available in the S2 in favor of lower-Isp MMH/NTO in the DXL, to say nothing of adding dry mass to the DXL to handle the increased tankage.

I can't even pretend to be able to compute the optimal launch trajectory for an FH to do a TLI mission.  I'd guess that, because it'll be handling a very light payload, that putting some extra loft in the trajectory will be doable, which may easily mean that the initial LEO insertion will be more eccentric.  (200x1000?  200x2000?  Probably not much more than that.)  However, that's at the first S2 burnout.  Once the second S2 burn occurs near perigee, the DXL will be in the lunar transfer orbit.

From there, you really do need the storables, due to stage life considerations.  There are basically two transfer options from here:

1) The so-called "direct transfer", which involves a powered lunar flyby that sends the DXL on a second transfer to NRHO, where it does a second burn to insert into the halo orbit itself, and can begin rendezvous ops.  Flyby burn is about 180 m/s and NRHO insertion burn is about 250 m/s.
(This is a good paper for all things NRHO.)  Total transfer time is about 5 days.

2) A "ballistic lunar transfer", which takes 3-6 months, but reduces the total delta-v to insert into NRHO to 50-150 m/s.  (Here's a preso on these.)

Offline TheRadicalModerate

  • Senior Member
  • *****
  • Posts: 3926
  • Tampa, FL
  • Liked: 2958
  • Likes Given: 576
Re: SpaceX Dragon XL
« Reply #214 on: 03/29/2020 08:27 pm »
PPE is more powerful than shown in that slide, which would cut off a good portion of a year from the time estimate.  Also those numbers are for a much larger payload than what Dragon XL will be carrying.  The slide is for a SEP tug plus a 15t payload.

PPE is what they used as a baseline for that slide.  The current PPE award is for a 50 kW version, which is listed in the chart.

The big difference between the slide and what we've been talking about here is the payload mass.  The HLS studies assumed 15 t payloads, and here we're only talking about 5 t payload, albeit pressurized payloads.  A good apples-to-apples comparison is probably 15 t vs. about 10 t.

Offline clongton

  • Expert
  • Senior Member
  • *****
  • Posts: 11963
  • Connecticut
    • Direct Launcher
  • Liked: 7082
  • Likes Given: 3641
Re: SpaceX Dragon XL
« Reply #215 on: 03/29/2020 08:44 pm »
Government procurement guidelines don't allow for predatory pricing, and SpaceX is not known for predatory pricing, so if NASA required the fully capabilities of a Falcon Heavy they would pay $150M for the basic launch service. And if they needed more than the basic launch service, which they normally do, then that would be an added cost, but the basic launch service cost does not change.

Agree with the basic launch cost figure, but I would assume that SpaceX would add some appropriate premium - agreed to by NASA - based on a 5-launch demonstrated capability for the vehicles they will now no longer be able to reuse.
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline Cherokee43v6

  • Full Member
  • ****
  • Posts: 1165
  • Garner, NC
  • Liked: 920
  • Likes Given: 232
Re: SpaceX Dragon XL
« Reply #216 on: 03/29/2020 09:29 pm »
I site the laws of capitalism.  In particular, competition.
The FH costs about $120mil.  The Delta IV is $400mil.

Elon Musk said a fully expendable Falcon Heavy would be $150M.
https://twitter.com/elonmusk/status/963076231921938432?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed&ref_url=https%3A%2F%2Fwww.cnbc.com%2F2018%2F02%2F12%2Felon-musk-spacex-falcon-heavy-costs-150-million-at-most.html

Quote
SpaceX will have bid around $350mil and be making a packet.  Good on them.  They need the cash to fund R&D.

Government procurement guidelines don't allow for predatory pricing, and SpaceX is not known for predatory pricing, so if NASA required the fully capabilities of a Falcon Heavy they would pay $150M for the basic launch service. And if they needed more than the basic launch service, which they normally do, then that would be an added cost, but the basic launch service cost does not change.

True, but there is a surcharge on top of the $150M for the additional insight, documentation and processing controls that NASA insists on for missions of this type (see price differential between F9 launches for commercial vs F9 launches for NASA and USAF (soon to be USSF) missions).
"I didn't open the can of worms...
        ...I just pointed at it and laughed a little too loudly."

Online wannamoonbase

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 5162
  • Denver, CO
    • U.S. Metric Association
  • Liked: 2905
  • Likes Given: 3578
Re: SpaceX Dragon XL
« Reply #217 on: 03/29/2020 09:59 pm »
Government procurement guidelines don't allow for predatory pricing, and SpaceX is not known for predatory pricing, so if NASA required the fully capabilities of a Falcon Heavy they would pay $150M for the basic launch service. And if they needed more than the basic launch service, which they normally do, then that would be an added cost, but the basic launch service cost does not change.

Agree with the basic launch cost figure, but I would assume that SpaceX would add some appropriate premium - agreed to by NASA - based on a 5-launch demonstrated capability for the vehicles they will now no longer be able to reuse.

Certainly it will cost more, but likely be the cheapest $/KG to the Gateway.

When other cargo providers are selected it will be interesting to see which launch vehicles they select.  Maybe F9/FH will get more flights than Dragon XL.
Superheavy + Starship the final push to launch commit!

Offline Coastal Ron

  • Senior Member
  • *****
  • Posts: 8563
  • I live... along the coast
  • Liked: 9930
  • Likes Given: 11636
Re: SpaceX Dragon XL
« Reply #218 on: 03/29/2020 10:30 pm »
Government procurement guidelines don't allow for predatory pricing, and SpaceX is not known for predatory pricing, so if NASA required the fully capabilities of a Falcon Heavy they would pay $150M for the basic launch service. And if they needed more than the basic launch service, which they normally do, then that would be an added cost, but the basic launch service cost does not change.

True, but there is a surcharge on top of the $150M for the additional insight, documentation and processing controls that NASA insists on for missions of this type (see price differential between F9 launches for commercial vs F9 launches for NASA and USAF (soon to be USSF) missions).

I wouldn't call it a "surcharge". NASA buys additional services for their missions, just like you may buy additional features for the car you buy. That doesn't change the base cost of the product or service.

So in order to make apples-to-apples comparisons the norm is to ignore additional services, and stick with the cost for a basic launch. Especially since what NASA asks for on each mission launch is different, so there is no way to estimate what amount of additional services they will want, or how much the provider the charge. So that just confuses things.

So for purposes of comparison, an expendable Falcon Heavy is $150M.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 38675
  • Minnesota
  • Liked: 24347
  • Likes Given: 11919
Re: SpaceX Dragon XL
« Reply #219 on: 03/29/2020 10:51 pm »
Does anyone have a good estimate for Falcon Heavy near-escape capability for core-expendable and booster down-range recovery mode?  Such a mode does not yet exist, of course, because SpaceX hasn't demonstrated dual downrange recovery.  I know about Elon's 10% payload reduction estimate, but he never said if that was for LEO or GTO, etc.  My guess is 10% for LEO, but a bigger reduction for higher energy orbits. 

My estimate for 5 tonnes cargo to Near Rectilinear Halo (lunar) Orbit (NRHO) is that 12 to 16 tonnes (payload, spacecraft, propellant) would need to separate into TLI, providing 10.5 to 13.8 tonnes to NRHO (13.5% of mass used for the burns to NRHO).  The three-core recovery mode for Falcon Heavy only provides 8 tonnes to GTO, while fully expendable Falcon Heavy is listed at 26.7 tonnes GTO or 16.8 tonnes trans-Mars.

 - Ed Kyle
Citation needed for just 8 tons GTO with 3 booster recovery. I think the assumptions for that are much more conservative (sandbagged) than those for the 16.8tonnes TMI estimate.

Also, center core expended and 2 cores RTLS is a thing.

I think that comes directly from SpaceX:

https://www.spacex.com/about/capabilities
Nope!

Read again! That’s just the performance you get for $90m; it says nothing about what the mode of launch would be at that price.

Secondaries? RTLS for all 3 cores? Extra margin for a softer recovery? Cheaper/lighter payload adapter? Who knows! It isn’t specified!

We do know from that page it can do 26.7t GTO in fully expendable mode.
« Last Edit: 03/29/2020 10:54 pm by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1