Author Topic: Cargo BFS with Dragon crew.  (Read 11201 times)

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 »

Offline 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.

Offline 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 »

Offline 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 doesn’t 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 FAA’s only concern is safety of the public.

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