Author Topic: Cargo BFS with Dragon crew.  (Read 10305 times)

Offline KelvinZero

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Cargo BFS with Dragon crew.
« on: 09/30/2017 09:29 AM »
I have twice been tempted to post this throwaway idea, on two different threads.
It could solve two popular issues:

LAS is a popular topic, though it has been established it is not part of the crewed BFS. (and was fairly clear long before the recent presentation)

I really like the idea of five 20-person escapable capsules, one on each tanker flight.

Will NASA let that monster near the ISS anyway? One solution is to dock with a Dragon 2 that is already certified.

While the bit with the ISS isn't exactly Mars-centric, it now leads me to wonder how they'll handle airlocks and docking.

They don't need airlocks. But docking the BFR with the ISS is going to put a lot of mechanical stress on the IDS.

The bigger issue is getting NASA to certify BFR for ISS operations, and SpaceX implementing any changes, before ISS is retired. I don't see that ever happening.

Im thinking along the lines of a special option for the cargo variant, just as the legs were optional on F9R, that lets you include a Dragon 2. The Dragon 2 should be both a LAS and also be able to leave and redock with the Cargo BFS.

I like the absurd levels of redundant safety this allows. You would have a choice of two heat shields. You have two landing rockets on the BFS, plus the SuperDracos&parachute, or if a fault is discovered in orbit, the option of landing via Dragon alone, Parachute with backup of SuperDracos.

This would make the Cargo BFS everything the Shuttle was meant to be and more. 7 crew is plenty for most missions.

Im unsure of a convenient configuration though. I think probably the Dragon would be entirely within the fairing, which opens like jaws. For LAS you would perhaps need some explosive way of removing the fairing? Anyone got better ideas?

Offline su27k

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Re: Cargo BFS with Dragon crew.
« Reply #1 on: 09/30/2017 11:55 AM »
I don't see a way to do this, is there ever a LAS design that involves blowing away the fairing?

Offline Nibb31

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Re: Cargo BFS with Dragon crew.
« Reply #2 on: 09/30/2017 12:02 PM »
I don't see a way to do this, is there ever a LAS design that involves blowing away the fairing?

Soyuz. Also Apollo and Orion.

Online nacnud

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Re: Cargo BFS with Dragon crew.
« Reply #3 on: 09/30/2017 12:05 PM »
I think Vostok and Gemini used ejection seats that blew away a cover which you might refer to as a fairing.

Offline tonya

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Re: Cargo BFS with Dragon crew.
« Reply #4 on: 09/30/2017 12:15 PM »
For a time, the first shuttle test flights were planned to carry an Apollo capsule in the payload bay. Not for launch abort, but for return in the event the vehicle had to be abandoned in orbit.

I think the Dragon will still be with us for sometime. NASA may approve BFS for use at the ISS, but I think it will be SpaceX who object when they ask them to leave it there for six months at a time! I can't see risk averse NASA relaxing its lifeboat provision.

Online douglas100

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Re: Cargo BFS with Dragon crew.
« Reply #5 on: 09/30/2017 12:35 PM »
I think Vostok and Gemini used ejection seats that blew away a cover which you might refer to as a fairing.

On Gemini there was no fairing of course. The hatches were opened/jettisoned (can't remember which) and the crew ejected. On Vostok there was an actual fairing which wasn't jettisoned. There was a cut out on the side of the fairing which allowed the capsule hatch to be jettisoned followed by ejection.
Douglas Clark

Online guckyfan

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Re: Cargo BFS with Dragon crew.
« Reply #6 on: 09/30/2017 01:17 PM »
If they do it I see them putting Dragon on the nose of a cargo or tanker BFS. So outside the cargo pod and free to use its abort engines.

Online douglas100

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Re: Cargo BFS with Dragon crew.
« Reply #7 on: 09/30/2017 01:22 PM »
Yeah, makes more sense. Whether such a thing would be tried depends on lots of unknowns, the main ones being how long ISS will be maintained and how long it will take to get BFS operational.
Douglas Clark

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #8 on: 09/30/2017 10:40 PM »
If they do it I see them putting Dragon on the nose of a cargo or tanker BFS. So outside the cargo pod and free to use its abort engines.
You mean on top, outside the frame of the BFS, just like it sits on top of the F9 ? I think this is the simplest to implement but then I think you would HAVE to separate the dragon 2 to land. So you wouldn't get the double redundancy. (Double redundancy is cool because it changes LOC from hopefully much better than 1:100 to something hopefully better than 1:10,000)

How about we extensively modify just the door of the Cargo BFS? The goal being that the Dragon 2 is still outside of the BFS, but usually returns to earth protected by the BFS heat shield. (Of course the door cannot support the mass of the Dragon, there must be some unspecified way to distribute the weight of the Dragon on the door to the rest of the vehicle, not just the door hinges)

This isn't purely for ISS. In the short term Cargo probably has the most uses. Then there are a subset of cases where some crew are useful, ie shuttle-like missions.

The Crew BFS I think only becomes useful a fair bit later when you have more confidence: Moon, where your small crew need more room, LEO Tourism and Mars, where the goal is 50-100 people crammed in like sardines. This approach lets you delay the Crew version while also providing huge safety while the BFS is young.

Offline Ludus

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Re: Cargo BFS with Dragon crew.
« Reply #9 on: 10/01/2017 02:35 AM »
So far, it seems to me like the Tanker is the same as the Cargo version and thereís very little practical reason for a long time for SpaceX to build anything but this single type of simpler ship. For Mars or the Moon human transport put a hab in the cargo hold. This has the major advantage that it lets you leave the hab where itís more useful while returning the ship. Your idea of finding a way to carry a Dragon2 for passenger launches fits with this. Iím assuming just the Dragon2 not the Trunk.

If you reoriented the couches? you could mount the Dragon2 in the hold sideways, pointed out the hatch. In an abort the hatch blows off and the D2 fires itís super Dracoís. In an approach to the ISS the hatch opens normally and itís slowly pushed out and uses its Dracoís to dock. Thereís no exterior mod to the BFR, just D2 mounting hardware wherever most appropriate in the hold. D2 can operate like an emergency abort pod or do normal docking with ISS. It just canít operate in orbit on its own for long without the trunk.
« Last Edit: 10/01/2017 02:43 AM by Ludus »

Offline envy887

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Re: Cargo BFS with Dragon crew.
« Reply #10 on: 10/01/2017 02:47 AM »
So far, it seems to me like the Tanker is the same as the Cargo version and thereís very little practical reason for a long time for SpaceX to build anything but this single type of simpler ship. For Mars or the Moon human transport put a hab in the cargo hold. This has the major advantage that it lets you leave the hab where itís more useful while returning the ship. Your idea of finding a way to carry a Dragon2 for passenger launches fits with this. Iím assuming just the Dragon2 not the Trunk.

If you reoriented the couches? you could mount the Dragon2 in the hold sideways, pointed out the hatch. In an abort the hatch blows off and the D2 fires itís super Dracoís. In an approach to the ISS the hatch opens normally and itís slowly pushed out and uses its Dracoís to dock. Thereís no exterior mod to the BFR, just D2 mounting hardware wherever most appropriate in the hold. D2 can operate like an emergency abort pod or do normal docking with ISS. It just canít operate in orbit on its own for long without the trunk.

Dragon 2 can't do an atmospheric abort without the trunk, it needs it for stabilization. I don't know about flying D2 in the cargo bay... It just seems really likely to hit something during an abort.

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #11 on: 10/01/2017 03:09 AM »
I was wondering about the trunk, (including the possible relevance to abort).

If the dragon is not exposed on lift off and only reenters by itself in emergencies then there are some options to move things around a bit that we could speculate on.

Another thing I wanted to add. Many people advocate that a problem with space is that we do not accept enough risk. There may be some truth here, but I also think that "absurd safety" can be transformative. With enough flights, the BFR may become the 747 of space, but we don't have markets or destinations for 100s of people yet. The dragon-variant might leapfrog us to 747-safety while being sufficient for current numbers almost immediately. It could give the population a whole decade more time to get used to space being just as safe as an overseas holiday.


Offline John Alan

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Re: Cargo BFS with Dragon crew.
« Reply #12 on: 10/01/2017 03:39 AM »
Early on (2022 - 2030)
The safest solution would be construct a crew transfer space station in orbit...
Once built and in use...
A crew type yet unmanned BFcrew launches first to the transfer station... side docks via the hatch...
A Dragon 2 with it's F9 S2 still attached (but vented and inert ed) brings up 7 crew safely and in a proven system.
It docks via nose hatch... crew goes aboard station...
A station robot arm grapples the D2/S2 assy and swings it over into an empty BFpacman cargo equipped to secure and haul it back down in one piece...
It then returns the D2/S2 set cleanly and nearly ready to be put on a used F9 S1 and relaunched...
Repeat till BFCrew is manned to required staffing...

I think a pair of D2/S2's will fit side by side in a BFpacman cargo...  not 100% sure on that...

Just saying... NASA or anyone would have a hard time saying no to this idea for early crew missions...  ;)
Once BFR system has demonstrated it to be safe and reliable... repurpose the transfer station
« Last Edit: 10/01/2017 04:01 AM by John Alan »

Online Norm38

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Re: Cargo BFS with Dragon crew.
« Reply #13 on: 10/01/2017 03:47 AM »
If they do it I see them putting Dragon on the nose of a cargo or tanker BFS. So outside the cargo pod and free to use its abort engines.

If Dragon goes in the nose, how does the BFS renter?  There's a lot of heating and pressure on the nose. Can that structure coexist with Dragon?

Offline biosehnsucht

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Re: Cargo BFS with Dragon crew.
« Reply #14 on: 10/01/2017 05:17 AM »
If you want a crew transfer station, why not the BFS itself? It's pretty much the volume of ISS, in a much more convenient layout. Just fly the Dragon to the BFS and dock directly to it.

I don't think this is likely to happen though, I think Elon is going to push for just launching on BFS (after some unmanned testing of course).
« Last Edit: 10/01/2017 05:18 AM by biosehnsucht »

Offline John Alan

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Re: Cargo BFS with Dragon crew.
« Reply #15 on: 10/01/2017 05:35 AM »
Early on (2022 - 2030)
The safest solution would be construct a crew transfer space station in orbit...
Once built and in use...
A crew type yet unmanned BFcrew launches first to the transfer station... side docks via the hatch...
A Dragon 2 with it's F9 S2 still attached (but vented and inert ed) brings up 7 crew safely and in a proven system.
It docks via nose hatch... crew goes aboard station...
A station robot arm grapples the D2/S2 assy and swings it over into an empty BFpacman cargo equipped to secure and haul it back down in one piece...
It then returns the D2/S2 set cleanly and nearly ready to be put on a used F9 S1 and relaunched...
Repeat till BFCrew is manned to required staffing...

I think a pair of D2/S2's will fit side by side in a BFpacman cargo...  not 100% sure on that...

Just saying... NASA or anyone would have a hard time saying no to this idea for early crew missions...  ;)
Once BFR system has demonstrated it to be safe and reliable... repurpose the transfer station
If you want a crew transfer station, why not the BFS itself? It's pretty much the volume of ISS, in a much more convenient layout. Just fly the Dragon to the BFS and dock directly to it.

I don't think this is likely to happen though, I think Elon is going to push for just launching on BFS (after some unmanned testing of course).

I agree that Elon will push to launch Crew on BFR with no Launch abort system as shown...
And yes they could send a Dragon 2 straight to a BFcrew and offload...

But that will cost you a F9 stage 2... a trunk... (both burned up in the atmosphere)
...and you get a toasted and salt water dipped Dragon 2 back...

With what I outlined above...
You turn Dragon Crew as approved into a fully reusable system with quick turn around times...
And you only use it until everyone gets happy with BFS flying with no Launch abort system...

It was just an idea...  ;)
« Last Edit: 10/01/2017 05:38 AM by John Alan »

Offline su27k

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Re: Cargo BFS with Dragon crew.
« Reply #16 on: 10/01/2017 05:48 AM »
If they do it I see them putting Dragon on the nose of a cargo or tanker BFS. So outside the cargo pod and free to use its abort engines.

If Dragon goes in the nose, how does the BFS renter?  There's a lot of heating and pressure on the nose. Can that structure coexist with Dragon?

Dragon will need to leave BFS and re-enter by itself, the structure (adapter) will probably need to be jettisoned before BFS re-enter. So this idea is basically just using BFR as replacement for F9, the downside is they'll need to build a super high crew access tower for this, and they'll still need to refurbish Dragon.

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #17 on: 10/01/2017 06:10 AM »
Just a reminder, What I really wanted to talk about in the OP was a Cargo BFS + Dragon 2 where

*The Dragon serves as a LAS at every point, up, down and in LEO (hopefully making 1:100~1:1000 odds of LOC into 1:10,000~1:1000,000) - so it has to be able to return inside (or at least protected by) the Cargo BFS.

*The dragon can leave the Cargo BFR and return to it while in LEO, removing any ISS issues but possibly having a bunch of other uses also.
« Last Edit: 10/01/2017 06:13 AM by KelvinZero »

Offline Nibb31

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Re: Cargo BFS with Dragon crew.
« Reply #18 on: 10/01/2017 06:17 AM »
Just a reminder, What I really wanted to talk about in the OP was a Cargo BFS + Dragon 2 where

*The Dragon serves as a LAS at every point, up, down and in LEO (hopefully making 1:100~1:1000 odds of LOC into 1:10,000~1:1000,000) - so it has to be able to return inside (or at least protected by) the Cargo BFS.

*The dragon can leave the Cargo BFR and return to it while in LEO, removing any ISS issues but possibly having a bunch of other uses also.

Your solution doesn't solve any problems.
* BFS is supposed to be reliable enough to not need a LAS.
* If BFS is carrying NASA astronauts and cargo, then NASA will want to certify it.
* There will be very little overlap, if any, between ISS and BFS, so there is no point in engineering an expensive solution for one or two flights.

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #19 on: 10/01/2017 06:48 AM »
* It gives you a 100x safety improvement while you are working up the confidence in your vehicle.. and NASA may point blank refuse a vehicle without a LAS for a good long time.
* Surely NASA is not so bureaucratic that they cannot separate launching and docking risks.
* Probably true, but the same issue may apply to the next station we have not seen yet.

Another advantage of this is that you can start with just one variant, the Cargo variant. This also happens to be the most immediately useful and a lot cheaper than the Crew variant.

Offline Nibb31

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Re: Cargo BFS with Dragon crew.
« Reply #20 on: 10/01/2017 06:59 AM »
* NASA doesn't need BFR at the ISS. SpaceX doesn't cannot use BFR for the ISS contracts.
* NASA payloads or crew will not fly on non-certified launchers.
* There is no new station except DSG, and if you have something like BFR, with more space than the ISS and an ECLSS that can support 100 people for 6 months, you don't need a DSG.

Offline su27k

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Re: Cargo BFS with Dragon crew.
« Reply #21 on: 10/01/2017 07:29 AM »
* NASA doesn't need BFR at the ISS. SpaceX doesn't cannot use BFR for the ISS contracts.
* NASA payloads or crew will not fly on non-certified launchers.
* There is no new station except DSG, and if you have something like BFR, with more space than the ISS and an ECLSS that can support 100 people for 6 months, you don't need a DSG.

There're commercial stations being planned, could be potential customers.
« Last Edit: 10/01/2017 07:30 AM by su27k »

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #22 on: 10/01/2017 07:52 AM »
(1) * NASA doesn't need BFR at the ISS. SpaceX doesn't cannot use BFR for the ISS contracts.
(2) * NASA payloads or crew will not fly on non-certified launchers.
(3) * There is no new station except DSG, and if you have something like BFR, with more space than the ISS and an ECLSS that can support 100 people for 6 months, you don't need a DSG.
One more go, but im beginning to suspect this will not be profitable for either of us. It might be better for you to accept that sometimes forum threads do not represent goals you consider worthwhile, at which point you focus on other threads or you treat it as an academic exercise to come up with constructive solutions.

Here goes.

(1) The claim of BFS to ISS was introduced by Elon Musk so that makes it a topic.
(2) This doesn't answer my response: surely there can be a situation where NASA is happy with launch but unhappy with docking. You appeared to just double down that "certified" was a single checkbox.
(3) NASA may choose not to pay you for this. Also this requires a future, significantly more expensive BFS variant.

Offline biosehnsucht

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Re: Cargo BFS with Dragon crew.
« Reply #23 on: 10/01/2017 09:09 AM »
Dragon on BFS doesn't get you 100x safety without throwing away the BFS design and building a totally new design to support Dragon being integral, which is obviously not where Elon is headed with the BFS.

Putting aside everything else, the engineering problems of putting a Dragon on or in a BFS make this a non-starter. The BFS cargo/satellite deployer configuration depicted could hold a Dragon, but would not support any kind of LAS and at best could be used to re-enter separately from BFS if there's time to open the "mouth" and slowly and safely extract the Dragon. There are no ways to non-destructively exit the BFS with Dragon in any short time frame during ascent or descent, and the aerodynamic situation would be very difficult to simulate and test, not to mention the massive structural changes needed to allow for this which would compromise the BFS' mass fraction and so forth.

I understand wanting a LAS, and the feeling that "it would be easy to just put A and B together", but it isn't easy, and drags things further away from the goal for little benefit and likely a lot of downsides. Without essentially ruining BFS' mass fraction to enable such a scenario, you're just going to make things more dangerous.

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #24 on: 10/01/2017 10:36 AM »
biosehnsucht, there is a lot of assertion there that I can't really do anything with. I totally accept you are probably right and it can't be done. That is generally a safe bet where space is concerned.

It is not about Dragon being integral, and there is no mass fraction problem. If it takes 100t of sawdust to protect the Dragon while you disintegrate the entire fairing around you, you would still have a perfectly good option for certain missions.. merely double the performance of the shuttle, with at least 100x it's safety, in a 100% reusable vehicle, at a tiny fraction of the cost. Sometimes that is good enough.

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #25 on: 10/01/2017 12:08 PM »
If they do it I see them putting Dragon on the nose of a cargo or tanker BFS. So outside the cargo pod and free to use its abort engines.
Hey, just had a random thought where possibly you could do this AND get my wish-list also.

During ascent, The dragon is on the nose. This seems pretty conventional and thus safe. No ejecting sideways into a huge supersonic gale with a fragile shuttlecock-like trunk.

In space you do several things, including offloading your cargo.

Before returning to earth, the Dragon docks INSIDE the BFS. It is pointing directly out of the cargo area. During descent this is probably much safer than during ascent. If there is an abort during the most energetic part of descent it would emerge with exactly the right alignment to the airstream. for this sort of abort you would leave the trunk inside the BFS. By the time the BFS has reoriented to land speeds are slow enough not to matter so much.

There might still be a bad moment during supersonic retropropulsion. Im not sure how much of that there was for the BFS. There was mention of dumping 99% of speed passively.

Offline Ludus

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Re: Cargo BFS with Dragon crew.
« Reply #26 on: 10/02/2017 04:22 PM »
* It gives you a 100x safety improvement while you are working up the confidence in your vehicle.. and NASA may point blank refuse a vehicle without a LAS for a good long time.
* Surely NASA is not so bureaucratic that they cannot separate launching and docking risks.
* Probably true, but the same issue may apply to the next station we have not seen yet.

Another advantage of this is that you can start with just one variant, the Cargo variant. This also happens to be the most immediately useful and a lot cheaper than the Crew variant.

I think just cheaply adding crew to the Cargo/Tanker is the strongest feature. LAS or docking with ISS is just a bonus. Making a huge pressure vessel and life support for BFS is a bigger task than the rest of the system and not required for most of the functionality at least up front. Just adding a mount for a Dragon 2 is a cheap mod that achieves capacity for crew.

Offline ranger84

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Re: Cargo BFS with Dragon crew.
« Reply #27 on: 10/04/2017 02:16 AM »
What it seems like to me is that SpaceX is giving up on NASA crew contracts after their current contract is up, and going it alone with private space that is surely  to follow. I canít see NASA being ok with no LAS and propulsive landing any time soon, not to mention no crew lifeboat on the ISS. I believe this is the biggest mistake with their current plans.
« Last Edit: 10/04/2017 02:18 AM by ranger84 »

Offline Robotbeat

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Re: Cargo BFS with Dragon crew.
« Reply #28 on: 10/04/2017 02:33 AM »
LAS gives you about a factor of 10 improvement in safety, at best. It can also introduce new failure mechanisms, and is only useful in a fraction of the total mission time. And can easily cost a billion or two to design, build, verify, and operate. Might be cheaper to just fly BFR 1000 times.
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Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #29 on: 10/04/2017 02:40 AM »
LAS gives you about a factor of 10 improvement in safety, at best. It can also introduce new failure mechanisms, and is only useful in a fraction of the total mission time. And can easily cost a billion or two to design, build, verify, and operate. Might be cheaper to just fly BFR 1000 times.
Anyone care to estimate how much it would cost to launch with the Dragon on top?

The ability to launch with a payload outside of the main airframe could be a useful feature anyway. I was thinking you could use this to launch an almost engineless variant of the ITS, part of a scheme to eventually reduce colonist costs.

Offline drzerg

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Re: Cargo BFS with Dragon crew.
« Reply #30 on: 10/06/2017 10:35 PM »
if you look on the cargo BFS it has half fairing that opens in space. so just put inside dragon with trunk vertically on the side just behind the fairing. and any other structures that you will need for holding cargo, pople in other space inside. in case of abort BFS will jettison fairing and dragon will fly on its own.

in space fairing will open and dragon will do what is need to do and then returns back

before landing dragon will be secured with additional clamps to withstand lateral loads from aerobraking

Offline octavo

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Re: Cargo BFS with Dragon crew.
« Reply #31 on: 10/07/2017 07:13 AM »
I just can't get behind this idea. If a les was needed for the bfs, the very capable engineers at SpaceX would no doubt have found some clever way to design one. They didn't. There's a reason they didn't and I just can't see them ever flying this configuration - it would be tantamount to admitting they aren't confident in their launch vehicle. If they want to be cautious, launch Dragon on F9 and meet on orbit.

Re: Cargo BFS with Dragon crew.
« Reply #32 on: 10/07/2017 08:30 AM »
IMO, SX's decision to broaden the applications of BFR doesn't only have an economical reason. It's a way to leverage reusability to actually acquire real life data and improve reliability in an unprecedented way, at least in this industry. BFR is being designed to transition rockets from cutting edge technology, relatively unreliable for the lack of data points, to airline like, routine operations tech. You don't need an abort capsule on an airplane because you don't fear it will blow up with no apparent reason. Not an engineer and happy to be corrected, but I think SpaceX wants to achieve safety through high data/fast engineering turnaround: for the first time, reusability, low operational costs and SpaceX's corporate culture allows to tackle fear with hard data, instead of designing contingency (and unpractical) countermeasures like LAS.
« Last Edit: 10/07/2017 08:35 AM by AbuSimbel »
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Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #33 on: 10/07/2017 08:33 AM »
I just can't get behind this idea. If a les was needed for the bfs, the very capable engineers at SpaceX would no doubt have found some clever way to design one. They didn't. There's a reason they didn't and I just can't see them ever flying this configuration - it would be tantamount to admitting they aren't confident in their launch vehicle. If they want to be cautious, launch Dragon on F9 and meet on orbit.
This wasn't intended as a long term idea.

* It assumes there may be a fair period with just a cargo version, learning how to ramp up to significant flight rates launching com sats. possibly an iteration or two before the passenger version is attempted.
* NASA will probably take a long time to accept a crew launcher without a LAS. And they may simply refuse anything that size docking with whatever station they have at the time.
* And the passenger version will probably be quite a bit of work, another reason it's arrival could be delayed.

..but they could begin using the Cargo version for NASA crew after only a few successful flights by putting a fully qualified Dragon 2 design on top, which by then hopefully has a good flight history. This means F9 can be retired faster and more effort directed to BFR.

As you say though, if putting a dragon 2 on top is a significant diversion from maturing BFS, they could just keep using F9R until the BFS has proven itself. Depending how fast they can get the flight rate up, that might not take too long.

This does suggest that getting the flight rate up right from the start would be very valuable.

Re: Cargo BFS with Dragon crew.
« Reply #34 on: 10/07/2017 09:03 AM »
I just can't get behind this idea. If a les was needed for the bfs, the very capable engineers at SpaceX would no doubt have found some clever way to design one. They didn't. There's a reason they didn't and I just can't see them ever flying this configuration - it would be tantamount to admitting they aren't confident in their launch vehicle. If they want to be cautious, launch Dragon on F9 and meet on orbit.
This wasn't intended as a long term idea.

* It assumes there may be a fair period with just a cargo version, learning how to ramp up to significant flight rates launching com sats. possibly an iteration or two before the passenger version is attempted.
* NASA will probably take a long time to accept a crew launcher without a LAS. And they may simply refuse anything that size docking with whatever station they have at the time.
* And the passenger version will probably be quite a bit of work, another reason it's arrival could be delayed.
SpaceX is designing this system in such a way that real life data on reliability will be acquired with an unprecedented pace. We are talking about vehicles intended to be flown hundreds of times each, multiple times per day. No doubt they won't achieve this from the beginning, but remember where we are now. Outside of SX, no vehicle can be flown more than once, every launcher gets at most 10-15 launches per year, and that's the absolute best case. Outside of SX nobody can even acquire real data about the effects of orbital flight on their vehicles. On the other hand, SX is close to demonstrating a launch cadence of 30-40 flights/yr, of which more and more will be reflights. And that's with F9, partially reusable. With BFR they are applying all their experience with first stage reuse and Dragon reuse. With that said I fully expect them to achieve, relatively from the beginning, an unprecedented flight rate. A giant leap from current expendable rockets, a major improvement at least from F9. That's just the beginning of BFR, and the the rates will grow fast, if you account for the agility in development that SX has demonstrated and the low costs afforded by reusability.
Why then bother developing a LAS, if you'll be able in just 2/3 years of unmanned flight to acquire more data on your spacecraft (keep in  mind that the manned ship and the unmanned one share the same basic design, and that's genius) than literally anyone in history, and by far?
PS. By writing this I'm starting to see the genius of developing a hybrid second stage/spaceship: they updated the 2016 plan to address how to fund a system that's not only reusable, but both reliable and reusable. The financial genius of SX with F9's 1st stage was developing reusability with real data while delivering paying payloads to orbit. BFS allows them to do exactly the same but with the second stage. But in this case, aside from reusability, they'll actually improve safety for their manned ship. They can test BFS unmanned hundreds of times, while delivering payloads on orbit and recovering it to further improve the design. That's an unprecedented capability that will result in unprecedented reliability.
I'm never been so excited for the future of aerospace.
« Last Edit: 10/07/2017 09:26 AM by AbuSimbel »
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Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #35 on: 10/07/2017 09:42 AM »
Hi AbuSimbel,
I get it. If it is sufficiently hard to stick a dragon on top of a cargo BFS, and sufficiently easy to get a high flight rate for the BFS right from the beginning, the window of the justification can easily shrink to zero.

I disagree with RobotBeat that it would at most give a 10x improvement on safety. He has used that figure in other threads also when just talking about LAS. So I think he is missing that it also had the potential to save you in situations after launch and all the way till after landing. You get some suspect readings while in space, or your rockets entirely fail to ignite for the deorbit burn? just use the dragon. The vehicle lands but suddenly a leg fails or a fire starts? Just use the dragon.

Offline Jcc

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Re: Cargo BFS with Dragon crew.
« Reply #36 on: 10/07/2017 02:14 PM »
Besides all the above issues, you are left with the fact that crew to ISS will be max 2 flights per year, and given certification requirements it will be more feasible and probably cheaper to just fly D2 on F9.

SpaceX can propose BFS when that becomes a reality, but I would not expect NASA to pay development costs, so it would have to be already proven.

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #37 on: 10/09/2017 10:31 PM »
Although putting on top is the easiest option, I have decided I am less interested in that because we are only talking about a cludge before developing confidence in a final version, and you already have the option of just using F9R.

I still really like the idea of a large cargo, small crew version which has this huge additional safety margin, and also extra utility. Im thinking not a cludge now, but a variation that may come after the cargo version and the sardine-packed passenger version. It is the shuttle on steroids variant. It could also be an asteroid explorer, where a modified Dragon could be your 'excursion module'. They have living/working area outside the Dragon so I suppose this is now a variant of the passenger version rather than the cargo version.

Anyway, thinking about how a Dragon could be properly integrated, allowing aborts during launch and landing, I realised it is not obvious how to orient it when g forces come from one direction during lift off and another during landing.

How did the shuttle deal with this? Was one seat orientation good enough for both?

Offline Bynaus

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Re: Cargo BFS with Dragon crew.
« Reply #38 on: 10/10/2017 06:27 AM »
Every real (BF) spaceship needs a (Dragon) shuttle-craft!

But in all seriousness, I can only see SpaceX considering this in case NASA does not let them dock the BFS with the ISS (whatever the reason might be). Then they could use a Dragon in the payload bay to shuttle the supplies over to ISS. Otherwise, Dragon would also seem to be quite over-engineered for an "excursion module", with the heavy heatshield, parachutes, detachable trunk, deployable solar, etc. At best, in the long term SpaceX might think about a including a potentially human-tended, Dragon-based "space drone" for all kinds of in-space operations in proximity of the BFS (e.g., overseeing and supplying repair operations, shuttling crew and goods between BFSs and/or space stations where direct docking is not possible, for heatshield inspections, servicing satellites or safing them before capture by a BFS, excursions to asteroid surfaces, etc.).

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #39 on: 10/10/2017 07:07 AM »
Every real (BF) spaceship needs a (Dragon) shuttle-craft!

But in all seriousness, I can only see SpaceX considering this in case NASA does not let them dock the BFS with the ISS (whatever the reason might be). Then they could use a Dragon in the payload bay to shuttle the supplies over to ISS. Otherwise, Dragon would also seem to be quite over-engineered for an "excursion module", with the heavy heatshield, parachutes, detachable trunk, deployable solar, etc. At best, in the long term SpaceX might think about a including a potentially human-tended, Dragon-based "space drone" for all kinds of in-space operations in proximity of the BFS (e.g., overseeing and supplying repair operations, shuttling crew and goods between BFSs and/or space stations where direct docking is not possible, for heatshield inspections, servicing satellites or safing them before capture by a BFS, excursions to asteroid surfaces, etc.).

There is a whole thread here just on whether to have a LAS or not:
https://forum.nasaspaceflight.com/index.php?topic=43438.0

This is a Launch escape system, a landing escape system, an assured crew return vehicle, back up lifesupport (shades of apollo 13) .. and it could also be an excursion module, or perhaps for that particular version you decide to throw away the other 4 purposes and have something specialised, but it could still fit into the same bay. The dragon is well suited for specialised trunks also. you could have one with enough deltaV to abort from lunar orbit if you wanted.

Im more interested in technical problems and solutions. For example that question about how space shuttle crew deal with g forces from different directions.
« Last Edit: 10/10/2017 07:15 AM by KelvinZero »

Offline alexterrell

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Re: Cargo BFS with Dragon crew.
« Reply #40 on: 10/10/2017 07:33 AM »
..... I'm never been so excited for the future of aerospace.

Let's hope that is the case, but bear in mind most of what you wrote could have have been written about the Space Shuttle.

Offline kkattula

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Re: Cargo BFS with Dragon crew.
« Reply #41 on: 10/10/2017 09:03 AM »
If you desperately want an escape pod on BFS, it would make more sense to build the crew stations into it, and make it part of the OML, F-111 or B-1 style. Something like embedding a Dream Chaser in the nose.

On the other hand, a small in-space crew/cargo shuttle could well be handy for docking in tight spaces, and general work.

Offline octavo

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Re: Cargo BFS with Dragon crew.
« Reply #42 on: 10/10/2017 10:54 AM »
Let's hope that is the case, but bear in mind most of what you wrote could have have been written about the Space Shuttle.

Note of caution noted... BUT: Imagine if the Space Shuttle program had Wernher von Braun leading it and no meddling congress!

:)

I'm also very excited for the next few years and hope to be able to travel to the US one day to watch a launch in person. I'm afraid I'm not that much of an optimist that I can picture a BFR P2P launch site off the coast of South Africa any time soon...  :D
« Last Edit: 10/10/2017 10:54 AM by octavo »

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #43 on: 10/10/2017 11:14 AM »
If you desperately want an escape pod on BFS, it would make more sense to build the crew stations into it, and make it part of the OML, F-111 or B-1 style. Something like embedding a Dream Chaser in the nose.

On the other hand, a small in-space crew/cargo shuttle could well be handy for docking in tight spaces, and general work.
I was imagining this acting as the primary cockpit, though functions could be accessible elsewhere. After all the crew have to be there during launch and landing, and it already is exactly that.
I was also thinking it might be the solar storm shelter and the sleeping area.

Just having it on the nose outside the hull was discussed as the simplest option, and also that it could dock inside the cargo area for landing, but now Im thinking of the more difficult, more long term goal of having the Dragon entirely internal, available for escape during every phase of launch and landing, and also able to repeatedly dock and undock for excursions, and to have a customisable trunk.

I have moved on from the quick addition to a cargo variant. We could do that but there is not much to say. It would probably go on top because anything else is a major change, not a quick hack.

I still like the idea but I think of it not so much as a quickfix, as a difficult but worthwhile problem for another variant.
* Cargo variant
* Crew variant (actually, passengers as cargo)
* A Shuttle on steroids variant. 6-ish crew, some workspace, lots of cargo.

This is a variant for actually doing work in. Also exploration missions where there is not backup and support at the other end, such as an asteroid mission. (Asteroids have the real risk of debris that could damage heatshields as well so there are multiple safety advantages. Additionally the Dragon could be an exploration module)
« Last Edit: 10/10/2017 11:16 AM by KelvinZero »

Online guckyfan

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Re: Cargo BFS with Dragon crew.
« Reply #44 on: 10/10/2017 12:04 PM »
In the medium term a Dragon has no place in a BFS architecture. It means carrying a vehicle with plenty of hypergolic propellant. If they want a mobile pod for local actions they would build one based on the BFS RCS-thrusters, maybe a smaller version. It runs on methalox and can be refueled from the BFS main tanks. A Dragon would not be a good match. Such a vehicle needs an airlock. Dragon is designed around the ability to reenter. It has a quite small internal volume due to the cone shape.

Online guckyfan

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Re: Cargo BFS with Dragon crew.
« Reply #45 on: 10/10/2017 02:12 PM »
In the medium term a Dragon has no place in a BFS architecture. It means carrying a vehicle with plenty of hypergolic propellant.
Please have that conversation here instead: https://forum.nasaspaceflight.com/index.php?topic=43438.0

...in fact I will quote it there and reply to it there now.

Why there? I am in no way talking about a LES-system but my understanding was that Dragon could become a utility vehicle around BFS. I argued that Dragon is not good for that purpose.

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #46 on: 10/10/2017 10:23 PM »
Why there? I am in no way talking about a LES-system but my understanding was that Dragon could become a utility vehicle around BFS. I argued that Dragon is not good for that purpose.

You havent responded to my earlier reply there. (edit: from timestamps, I guess I posted this after?)

...
« Last Edit: 10/10/2017 10:49 PM by KelvinZero »

Offline Nilof

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Re: Cargo BFS with Dragon crew.
« Reply #47 on: 10/11/2017 01:15 AM »
Just design the cargo version first and launch it at least few dozen times (Ideally a few hundred if the launch rate is as good as advertized) before you ever attempt a manned launch. Once cargo BFR is in operation, you can drop the Falcon 9 for anything that isn't a dragon launch so your stock of F9 rockets will last for a while. The cargo BFR could also be used for in-space breadboard testing of the manned BFS systems since it has downmass capability.
« Last Edit: 10/11/2017 01:15 AM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Razvan

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Re: Cargo BFS with Dragon crew.
« Reply #48 on: 10/11/2017 01:34 AM »
Just design the cargo version first and launch it at least few dozen times (Ideally a few hundred if the launch rate is as good as advertized) before you ever attempt a manned launch. Once cargo BFR is in operation, you can drop the Falcon 9 for anything that isn't a dragon launch so your stock of F9 rockets will last for a while. The cargo BFR could also be used for in-space breadboard testing of the manned BFS systems since it has downmass capability.
Why should waste time and money limiting BFS lift capacity to reduced size of the dragon?!
SpaceX will be able to continue using Dragon along with F9 or even with FH for higher orbit or deep space.
I think, focusing on BFS as presented at IAC 2017 is the best option. And. beside, we should wait a little longer to see how the new Raptor will perform.

Offline RDoc

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Re: Cargo BFS with Dragon crew.
« Reply #49 on: 10/11/2017 07:34 PM »
Just design the cargo version first and launch it at least few dozen times (Ideally a few hundred if the launch rate is as good as advertized) before you ever attempt a manned launch. Once cargo BFR is in operation, you can drop the Falcon 9 for anything that isn't a dragon launch so your stock of F9 rockets will last for a while. The cargo BFR could also be used for in-space breadboard testing of the manned BFS systems since it has downmass capability.
Agreed. That seems like the most reasonable course of action that both gets SpaceX experience and, hopefully, profits from the BFR, yet keeps them in the NASA human space flight world.
« Last Edit: 10/11/2017 07:45 PM by RDoc »

Online guckyfan

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Re: Cargo BFS with Dragon crew.
« Reply #50 on: 10/11/2017 09:09 PM »
Just design the cargo version first and launch it at least few dozen times (Ideally a few hundred if the launch rate is as good as advertized) before you ever attempt a manned launch. Once cargo BFR is in operation, you can drop the Falcon 9 for anything that isn't a dragon launch so your stock of F9 rockets will last for a while. The cargo BFR could also be used for in-space breadboard testing of the manned BFS systems since it has downmass capability.
Agreed. That seems like the most reasonable course of action that both gets SpaceX experience and, hopefully, profits from the BFR, yet keeps them in the NASA human space flight world.

Do you assume a stock of unused first stages for crew or do you assume that NASA will be OK with reuse for manned flight?

Offline RDoc

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Re: Cargo BFS with Dragon crew.
« Reply #51 on: 10/11/2017 10:27 PM »
Do you assume a stock of unused first stages for crew or do you assume that NASA will be OK with reuse for manned flight?
That is a MOST excellent question IMHO!

I had assumed a stock of unused stages, but who knows? They've accepted used Dragons, and I suspect that will be the deal with most Dragon II launches, so it's probably not at all out of the question. However, I also suspect NASA will be putting together quite a few multi-dimensional hoops for SpaceX to jump through to get that OK.
« Last Edit: 10/11/2017 10:28 PM by RDoc »

Offline pathfinder_01

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Re: Cargo BFS with Dragon crew.
« Reply #52 on: 10/12/2017 07:13 AM »
One thought occurred to me. Is it possible to use the ITS in a more conventional manner? Musk wants direct landing of the ITS on the moon. I can think of two big concerns over it. One landing something that large tall on unprepared ground and the height from which the crew would have to ingress/egress from.  I also think that NASA would have some trouble agreeing to propulsive landing of crew on earth as well as lack of LAS. Not to mention wait time and risk for tanking flights and refueling. Is it possible to fit say a 20-30MT(wet mass)single stage lunar lander in the Cargo version with a small capsule like dragon?


The idea is that cargo BFR launches with a lander (and perhaps a very small habitation module).  Once tanked off a small capsule docks carrying a crew say of 4. The capsule is stowed and BFR leaves earth orbit(LEO or the high elliptical orbit) and heads to LLO. Lander lands for a short mission returns to BFR with tanks nearly empty say 8MT dry. BFR departs moon for direct entry to earth. Capsule departs BFR a day or two before landing with crew. BFR returns lander to earth where it could be inspected and reused.

Offline biosehnsucht

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Re: Cargo BFS with Dragon crew.
« Reply #53 on: 10/12/2017 07:29 AM »
Getting up and down from that height isn't particularly unsafe with a vehicle the size of BFS, if it has a large hatch and crane as depicted. You just use the crane to lower and raise a large basket (no need for rappelling down the side of the vehicle)

Offline pathfinder_01

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Re: Cargo BFS with Dragon crew.
« Reply #54 on: 10/12/2017 07:42 AM »
Getting up and down from that height isn't particularly unsafe with a vehicle the size of BFS, if it has a large hatch and crane as depicted. You just use the crane to lower and raise a large basket (no need for rappelling down the side of the vehicle)

On a vehicle that could be landing on a lean? I think a smaller vehicle and a ladder would be a better idea at first. Once a landing pad is developed then perhaps a crane would work.

Offline octavo

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Re: Cargo BFS with Dragon crew.
« Reply #55 on: 10/12/2017 11:44 AM »
Getting up and down from that height isn't particularly unsafe with a vehicle the size of BFS, if it has a large hatch and crane as depicted. You just use the crane to lower and raise a large basket (no need for rappelling down the side of the vehicle)

On a vehicle that could be landing on a lean? I think a smaller vehicle and a ladder would be a better idea at first. Once a landing pad is developed then perhaps a crane would work.

Don't we have enough hi-res imagery of the moon (LRO among others) that we can identify a nearly flat, boulder-free, plane to land on?

Offline envy887

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Re: Cargo BFS with Dragon crew.
« Reply #56 on: 10/12/2017 01:18 PM »
Getting up and down from that height isn't particularly unsafe with a vehicle the size of BFS, if it has a large hatch and crane as depicted. You just use the crane to lower and raise a large basket (no need for rappelling down the side of the vehicle)

On a vehicle that could be landing on a lean? I think a smaller vehicle and a ladder would be a better idea at first. Once a landing pad is developed then perhaps a crane would work.

Don't we have enough hi-res imagery of the moon (LRO among others) that we can identify a nearly flat, boulder-free, plane to land on?

BFR will have a lot of fuel in the tanks and little payload in the nose when landing the moon. It will be very bottom-heavy.

Offline RDoc

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Re: Cargo BFS with Dragon crew.
« Reply #57 on: 10/12/2017 03:59 PM »
I'm not sure landing the BFS itself on the Moon is a good idea since it will have a lot of mass that won't do any good on the moon, e.g. airframe, heat shield, Earth return fuel, tanks, second stage engines. Why waste the fuel needed to get all that mass to a soft landing on the Moon, and then lift it back off?

A separate lander with enough structure, engines, and fuel to go up and down and support the crew on the surface sounds more sensible to me. Perhaps a two part lander with living quarters that could remain on the Moon for later incorporation into a larger lunar habitat, and a much lighter launcher just to get the people back to the orbiting BFS. Maybe that could be left in lunar orbit for the next flight to be refueled and reused.

Back on topic for a moment: I remain doubtful NASA is going to accept the BFR without an escape system for a very long time, however, there are so few crewed flights, why should SpaceX bother?

A related question though is if there will be enough (or any) non-NASA crewed flights that would justify designing and building a crewed version of the BFS. My personal guess is that for a long time the answer will be no.
« Last Edit: 10/12/2017 04:08 PM by RDoc »

Offline envy887

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Re: Cargo BFS with Dragon crew.
« Reply #58 on: 10/12/2017 04:11 PM »
I'm not sure landing the BFS itself on the Moon is a good idea since it will have a lot of mass that won't do any good on the moon, e.g. airframe, heat shield, Earth return fuel, tanks, second stage engines. Why waste the fuel needed to get all that mass to a soft landing on the Moon, and then lift it back off?...
Fuel is cheap. Vehicles are expensive. Human rated in-space vehicles are really expensive.
« Last Edit: 10/12/2017 04:22 PM by envy887 »

Online cppetrie

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Re: Cargo BFS with Dragon crew.
« Reply #59 on: 10/12/2017 04:31 PM »
AIUI NASA only has to man-rate it to put their own people on it. If SpaceX want to put there own people on it, it doesnít matter one lick what NASA thinks about having or not having LAS. FAA will only become interested if it hosts paying customers. If internal employees only, the FAAís only concern is safety of the public.

Offline Negan

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Re: Cargo BFS with Dragon crew.
« Reply #60 on: 10/12/2017 06:45 PM »
I'm not sure landing the BFS itself on the Moon is a good idea since it will have a lot of mass that won't do any good on the moon, e.g. airframe, heat shield, Earth return fuel, tanks, second stage engines. Why waste the fuel needed to get all that mass to a soft landing on the Moon, and then lift it back off?

A separate lander with enough structure, engines, and fuel to go up and down and support the crew on the surface sounds more sensible to me. Perhaps a two part lander with living quarters that could remain on the Moon for later incorporation into a larger lunar habitat, and a much lighter launcher just to get the people back to the orbiting BFS. Maybe that could be left in lunar orbit for the next flight to be refueled and reused.

Back on topic for a moment: I remain doubtful NASA is going to accept the BFR without an escape system for a very long time, however, there are so few crewed flights, why should SpaceX bother?

A related question though is if there will be enough (or any) non-NASA crewed flights that would justify designing and building a crewed version of the BFS. My personal guess is that for a long time the answer will be no.

Also it would be interesting to know what the implications will be to landing and launching BFR off an unprepared surface.
« Last Edit: 10/12/2017 07:19 PM by Negan »

Offline RDoc

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Re: Cargo BFS with Dragon crew.
« Reply #61 on: 10/12/2017 07:21 PM »
Fuel is cheap. Vehicles are expensive. Human rated in-space vehicles are really expensive.
Actually, fuel on the surface of the Moon is extremely expensive. If the goal is to actually put hardware mass on the Moon and do something with it, carrying a hundred tons of useless stuff along for the ride doesn't sound like a good idea.
« Last Edit: 10/12/2017 07:41 PM by RDoc »

Offline CuddlyRocket

Re: Cargo BFS with Dragon crew.
« Reply #62 on: 10/12/2017 08:19 PM »
Fuel is cheap. Vehicles are expensive. Human rated in-space vehicles are really expensive.
Actually, fuel on the surface of the Moon is extremely expensive. If the goal is to actually put hardware mass on the Moon and do something with it, carrying a hundred tons of useless stuff along for the ride doesn't sound like a good idea.
I'm sure SpaceX will do the appropriate engineering trades. But it's important to remember that SpaceX optimises for cost. If it turns out cheaper to carry a hundred tons of useless stuff along for the ride then that's what they will do. People will other ideas are welcome to build their own rocket.

SpaceX's approach is designed to work through the cost of development and manufacture of the spacecraft being amortised over a much greater number of flights. Thus each flight becomes so relatively cheap that even if you need more flights to accomplish a given task (such as landing a particular tonnage of hardware on the Moon) it's still cheaper overall.

Online guckyfan

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Re: Cargo BFS with Dragon crew.
« Reply #63 on: 10/13/2017 07:24 AM »

I'm sure SpaceX will do the appropriate engineering trades. But it's important to remember that SpaceX optimises for cost. If it turns out cheaper to carry a hundred tons of useless stuff along for the ride then that's what they will do. People will other ideas are welcome to build their own rocket.

Or purchase cargo capacity to the moon and produce propellant to sell to SpaceX. SpaceX would buy it if cheaper than bringing their own propellant. But the propellant would have to be delivered to where SpaceX needs it.

Offline CuddlyRocket

Re: Cargo BFS with Dragon crew.
« Reply #64 on: 10/13/2017 08:40 PM »
Or purchase cargo capacity to the moon and produce propellant to sell to SpaceX. SpaceX would buy it if cheaper than bringing their own propellant. But the propellant would have to be delivered to where SpaceX needs it.

I doubt that lunar-produced propellant would be cheaper to SpaceX than propellant sourced on Earth. The advantage of such propellant is that it enables a greater payload mass to the Moon, so the comparison would be between the additional income to SpaceX from that greater payload against the additional propellant expense to SpaceX. And the former depends on demand - if no-one needs the additional payload capability, they won't pay for it!

Online guckyfan

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Re: Cargo BFS with Dragon crew.
« Reply #65 on: 10/13/2017 10:05 PM »
Or purchase cargo capacity to the moon and produce propellant to sell to SpaceX. SpaceX would buy it if cheaper than bringing their own propellant. But the propellant would have to be delivered to where SpaceX needs it.

I doubt that lunar-produced propellant would be cheaper to SpaceX than propellant sourced on Earth. The advantage of such propellant is that it enables a greater payload mass to the Moon, so the comparison would be between the additional income to SpaceX from that greater payload against the additional propellant expense to SpaceX. And the former depends on demand - if no-one needs the additional payload capability, they won't pay for it!

The mission profile proposed by Elon Musk was refuelling from a tanker in Earth Moon transfer. this would enable them to fly the full payload to the moon if not back. So anyone producing propellant on the moon would compete with the cost of that tanker. Or there is something on the moon valuable enough to justify large return payloads that need more propellant.

Offline CuddlyRocket

Re: Cargo BFS with Dragon crew.
« Reply #66 on: 10/15/2017 11:28 AM »
Or purchase cargo capacity to the moon and produce propellant to sell to SpaceX. SpaceX would buy it if cheaper than bringing their own propellant. But the propellant would have to be delivered to where SpaceX needs it.

I doubt that lunar-produced propellant would be cheaper to SpaceX than propellant sourced on Earth. The advantage of such propellant is that it enables a greater payload mass to the Moon, so the comparison would be between the additional income to SpaceX from that greater payload against the additional propellant expense to SpaceX. And the former depends on demand - if no-one needs the additional payload capability, they won't pay for it!

The mission profile proposed by Elon Musk was refuelling from a tanker in Earth Moon transfer. this would enable them to fly the full payload to the moon if not back. So anyone producing propellant on the moon would compete with the cost of that tanker. Or there is something on the moon valuable enough to justify large return payloads that need more propellant.

Propellant availability on the Moon enables you to send more payload to the Moon. Without such propellant availability, the BFS has to carry sufficient propellant to enable it to return. If propellant is available on the Moon, the BFS doesn't have to carry that amount of return propellant and additional payload can be carried instead.

Online guckyfan

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Re: Cargo BFS with Dragon crew.
« Reply #67 on: 10/15/2017 01:15 PM »
Propellant availability on the Moon enables you to send more payload to the Moon. Without such propellant availability, the BFS has to carry sufficient propellant to enable it to return. If propellant is available on the Moon, the BFS doesn't have to carry that amount of return propellant and additional payload can be carried instead.

My understanding was that the additional tanker enables BFS to land its full 150t LEO payload on the Moon. To land more it would require adding payload in orbit. I am not sure this would make sense.

Offline envy887

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Re: Cargo BFS with Dragon crew.
« Reply #68 on: 10/15/2017 10:35 PM »
The mission profile proposed by Elon Musk was refuelling from a tanker in Earth Moon transfer. this would enable them to fly the full payload to the moon if not back. So anyone producing propellant on the moon would compete with the cost of that tanker. Or there is something on the moon valuable enough to justify large return payloads that need more propellant.
Musk proposed refueling in elliptical Earth orbit before TLI. BFS needs to be about 500 m/s above LEO in order to land 150 tonnes on the Moon and return empty. It can return with cargo if it lands less.

Offline CuddlyRocket

Re: Cargo BFS with Dragon crew.
« Reply #69 on: 10/15/2017 11:15 PM »
Propellant availability on the Moon enables you to send more payload to the Moon. Without such propellant availability, the BFS has to carry sufficient propellant to enable it to return. If propellant is available on the Moon, the BFS doesn't have to carry that amount of return propellant and additional payload can be carried instead.

My understanding was that the additional tanker enables BFS to land its full 150t LEO payload on the Moon. To land more it would require adding payload in orbit. I am not sure this would make sense.

I suspect you're going to need more than one tanker flight! The BFS propellant load is more than 1,000t and a tanker can't get much more than 150t of spare propellant into LEO, let alone the high elliptical orbit it is proposed the BFS is in before TLI. You'll probably have to have multiple tanker flights to refuel the tankers that meet the BFS in its high elliptical orbit!

Elon was a bit vague on payload to the Moon. I was assuming that a fully refueled BFS wouldn't be able to carry its own return propellant and a full 150t cargo. It's possible I'm wrong about that!

Online guckyfan

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Re: Cargo BFS with Dragon crew.
« Reply #70 on: 10/16/2017 06:36 AM »

I suspect you're going to need more than one tanker flight! The BFS propellant load is more than 1,000t and a tanker can't get much more than 150t of spare propellant into LEO, let alone the high elliptical orbit it is proposed the BFS is in before TLI. You'll probably have to have multiple tanker flights to refuel the tankers that meet the BFS in its high elliptical orbit!

Elon was a bit vague on payload to the Moon. I was assuming that a fully refueled BFS wouldn't be able to carry its own return propellant and a full 150t cargo. It's possible I'm wrong about that!

I understand they send a fully refueled tanker from LEO to that highly elliptical orbit along with the ship. So one tanker leaving LEO but a number of tanker flights to refuel it. That's what I refered to and Elon mentioned.

Offline RDoc

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Re: Cargo BFS with Dragon crew.
« Reply #71 on: 10/24/2017 12:32 AM »
I must say that NASA might be better employed figuring out things like a lunar lander/ascender system and orbital fuel depot than messing around with the SLS. Private companies can come up with good business cases for heavy lift to LEO, but none, apart from NASA, for Lunar specific work.

Offline RDoc

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Re: Cargo BFS with Dragon crew.
« Reply #72 on: 10/24/2017 01:05 AM »
AIUI NASA only has to man-rate it to put their own people on it. If SpaceX want to put there own people on it, it doesnít matter one lick what NASA thinks about having or not having LAS. FAA will only become interested if it hosts paying customers. If internal employees only, the FAAís only concern is safety of the public.
That may well be true, but if NASA can't send its people, who's going to pay for the flights? SpaceX doesn't have either the money or the motivation I wouldn't think.

I could imagine some cludge involving launching the BFS unmanned, then a F9 with a Dragon to carry up the crew for an in orbit transfer, but not more than a few times. If this kind of thing were to be more than a flag waving stunt, it would seem a lot more efficient and safe to design and build an escape system for the BFS.

There may well be a good argument for the proposals with a Dragon in the BFS nose with a way to blow the nose apart to release it in an emergency. After ascent, the crew could access the rest of the BFS volume.

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #73 on: 10/24/2017 07:27 AM »
There may well be a good argument for the proposals with a Dragon in the BFS nose with a way to blow the nose apart to release it in an emergency. After ascent, the crew could access the rest of the BFS volume.
I tried to start a discussion about that earlier. What would a well designed, non-kludge solution look like.

The nose, with some sort of ejectable nose cone, is no doubt the least controversial for LAS. It is a pity though if you are going to carry a Dragon all that way and not be able to use it for escape during reentry. Reentry may very likely be more dangerous than launch. There are more variables that you will have no control over, such as weather and micrometeoroid damage from months in space.

(An ACRV would just be an easy bonus, pretty much for any configuration)

Offline RDoc

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Re: Cargo BFS with Dragon crew.
« Reply #74 on: 10/24/2017 06:58 PM »
There may well be a good argument for the proposals with a Dragon in the BFS nose with a way to blow the nose apart to release it in an emergency. After ascent, the crew could access the rest of the BFS volume.
I tried to start a discussion about that earlier. What would a well designed, non-kludge solution look like.

The nose, with some sort of ejectable nose cone, is no doubt the least controversial for LAS. It is a pity though if you are going to carry a Dragon all that way and not be able to use it for escape during reentry. Reentry may very likely be more dangerous than launch. There are more variables that you will have no control over, such as weather and micrometeoroid damage from months in space.

(An ACRV would just be an easy bonus, pretty much for any configuration)
Why wouldn't the Dragon in the nose be usable for an emergency reentry lifeboat?

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #75 on: 10/24/2017 11:35 PM »
Why wouldn't the Dragon in the nose be usable for an emergency reentry lifeboat?
The problem of being sideways to the plasma is fairly obvious. There are lots of solutions of course, right up to designing a whole new Dragon 3.0 that is fully integrated with the nose cone and halfway to a Dream Chaser... though that is cheating a bit.

Im open to a Dragon on the nose that can be used during launch and reentry. Outline it for me. If people get enthusiastic maybe they will start playing around with models to show how the BFS, BFS nose cone and Dragon all fit together.

Online Lars-J

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Re: Cargo BFS with Dragon crew.
« Reply #76 on: 10/25/2017 12:20 AM »
Im open to a Dragon on the nose that can be used during launch and reentry. Outline it for me. If people get enthusiastic maybe they will start playing around with models to show how the BFS, BFS nose cone and Dragon all fit together.

Who is 'they'?

Offline Patchouli

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Re: Cargo BFS with Dragon crew.
« Reply #77 on: 10/25/2017 12:54 AM »

The problem of being sideways to the plasma is fairly obvious. There are lots of solutions of course, right up to designing a whole new Dragon 3.0 that is fully integrated with the nose cone and halfway to a Dream Chaser... though that is cheating a bit.

Im open to a Dragon on the nose that can be used during launch and reentry. Outline it for me. If people get enthusiastic maybe they will start playing around with models to show how the BFS, BFS nose cone and Dragon all fit together.

They'd have to pretty much go to something along the lines of Winged Gemini if they were to keep any of the original internal structure and systems.

I guess a side benefit Musk won't have to eat his words when he called Boeing's landing mode crude after power landings were taken off the board.
« Last Edit: 10/25/2017 01:01 AM by Patchouli »

Offline RDoc

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Re: Cargo BFS with Dragon crew.
« Reply #78 on: 10/25/2017 01:11 AM »
Why wouldn't the Dragon in the nose be usable for an emergency reentry lifeboat?
The problem of being sideways to the plasma is fairly obvious. There are lots of solutions of course, right up to designing a whole new Dragon 3.0 that is fully integrated with the nose cone and halfway to a Dream Chaser... though that is cheating a bit.

Im open to a Dragon on the nose that can be used during launch and reentry. Outline it for me. If people get enthusiastic maybe they will start playing around with models to show how the BFS, BFS nose cone and Dragon all fit together.
I'm assuming the lifeboat would be used if something disastrous happened in orbit, not while actually reentering! I'm pretty doubtful that would be possible with anything like current technology.

Realistically, I suspect that literally putting a Dragon inside the BFS is unlikely, an integrated design likely makes a lot more sense, but the development time and cost sounds pretty serious.

Offline KelvinZero

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Re: Cargo BFS with Dragon crew.
« Reply #79 on: 10/25/2017 08:50 AM »
I'm assuming the lifeboat would be used if something disastrous happened in orbit, not while actually reentering! I'm pretty doubtful that would be possible with anything like current technology.
It is almost certainly doable. Just very likely so expensive and such a radical redesign that it never happens, for sure.

My position is that first you brainstorm what it might look like. There is not much cost in that. Just thinking about it will not will force Elon Musk into a pointless multibillion dollar dead end.

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