Author Topic: Cargo BFS with Dragon crew.  (Read 6179 times)

Online 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.

Offline AbuSimbel

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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 »
Failure is not only an option, it's the only way to learn.

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.

Offline AbuSimbel

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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 »
Failure is not only an option, it's the only way to learn.

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?

Online 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 »

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