Author Topic: Falcon 9R and Dragon Mk II Suborbital Tourism?  (Read 11445 times)

Offline aero

  • Senior Member
  • *****
  • Posts: 3050
  • 92129
  • Liked: 827
  • Likes Given: 294
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #20 on: 05/17/2014 01:54 am »
can a sealevel-seconed-stage (basically Falcon1) lift the capsule without the first stage?
How high?
I have not done the math, but IIRC, Blue Origins suborbital launch vehicle will have their capsule on top and it will later serve as the second stage for the orbital vehicle. So while it might not work with the F9 second stage in particular, it is not completely outrageous.

How do you want to deal with the second stage engine nozzle? It is designed for vacuum so it might not have a lot of thrust at sea level, flow separation being the concern.
Retired, working interesting problems

Online guckyfan

  • Senior Member
  • *****
  • Posts: 6939
  • Germany
  • Liked: 1906
  • Likes Given: 1966
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #21 on: 05/17/2014 03:45 am »

How do you want to deal with the second stage engine nozzle? It is designed for vacuum so it might not have a lot of thrust at sea level, flow separation being the concern.

The engines are basically the same. It should be possible to swap it for a first stage Merlin. Also they would need the reuse kit for a second stage. Likely a reusable first stage will be cheaper than an expendable second stage. Not that I believe they will actually do it.

Offline go4mars

  • Senior Member
  • *****
  • Posts: 3757
  • Earth
  • Liked: 153
  • Likes Given: 3252
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #22 on: 05/17/2014 05:47 am »
So... forget the Dragon, and bolt SpaceShipTwo on top of the F9R and release it at altitude.
I'd rather go in the electric supersonic jet, but I'd ride a dragon preferentially over SS2.  Not loin-cloth and spear, dragon riding; makes for an awkward brown pants landing you see.
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline aero

  • Senior Member
  • *****
  • Posts: 3050
  • 92129
  • Liked: 827
  • Likes Given: 294
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #23 on: 05/17/2014 06:21 am »

How do you want to deal with the second stage engine nozzle? It is designed for vacuum so it might not have a lot of thrust at sea level, flow separation being the concern.

The engines are basically the same. It should be possible to swap it for a first stage Merlin. Also they would need the reuse kit for a second stage. Likely a reusable first stage will be cheaper than an expendable second stage. Not that I believe they will actually do it.

Ok - just looking at some basics. Nine of those first stage engines gives a lift-off thrust of 5885 kN, so one engine would give a lift-off thrust of 654 kN, or 66,689 kg-f. The prop load of the second stage is 200,000 lb, or 90,900 kg, adding dry mass of 5.2 tonnes gives a lift-off T/W of about 0.7, a problem. Ten to 15 % more throttle won't be enough. At 115% throttle, the lift off T/W would be about 0.8 ... Lift off T/W has got to be greater than 1 in order to get off the ground, just for that one new reader.

So... forget the Dragon, and bolt SpaceShipTwo on top of the F9R and release it at altitude.
I'd rather go in the electric supersonic jet, but I'd ride a dragon preferentially over SS2.  Not loin-cloth and spear, dragon riding; makes for an awkward brown pants landing you see.

Well, the F9R should get a reasonable load off the ground.
« Last Edit: 05/17/2014 06:26 am by aero »
Retired, working interesting problems

Online guckyfan

  • Senior Member
  • *****
  • Posts: 6939
  • Germany
  • Liked: 1906
  • Likes Given: 1966
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #24 on: 05/17/2014 07:23 am »

The engines are basically the same. It should be possible to swap it for a first stage Merlin. Also they would need the reuse kit for a second stage. Likely a reusable first stage will be cheaper than an expendable second stage. Not that I believe they will actually do it.

Ok - just looking at some basics. Nine of those first stage engines gives a lift-off thrust of 5885 kN, so one engine would give a lift-off thrust of 654 kN, or 66,689 kg-f. The prop load of the second stage is 200,000 lb, or 90,900 kg, adding dry mass of 5.2 tonnes gives a lift-off T/W of about 0.7, a problem. Ten to 15 % more throttle won't be enough. At 115% throttle, the lift off T/W would be about 0.8 ... Lift off T/W has got to be greater than 1 in order to get off the ground, just for that one new reader.

You are right, of course. But you surely are aware that there is no law of physics requiring to fully fuel a stage. With a reduced fuel load it can take off and still provide very decent delta-v.

I repeat that I don't believe it will ever happen but it is possible.




Offline R7

  • Propulsophile
  • Senior Member
  • *****
  • Posts: 2738
    • Don't worry.. we can still be fans of OSC and SNC
  • Liked: 957
  • Likes Given: 662
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #25 on: 05/17/2014 08:11 am »
With them SuperDracos what you need the booster for? Just add a little trunklet for some extra prop.
AD·ASTRA·ASTRORVM·GRATIA

Offline aero

  • Senior Member
  • *****
  • Posts: 3050
  • 92129
  • Liked: 827
  • Likes Given: 294
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #26 on: 05/17/2014 08:53 am »

The engines are basically the same. It should be possible to swap it for a first stage Merlin. Also they would need the reuse kit for a second stage. Likely a reusable first stage will be cheaper than an expendable second stage. Not that I believe they will actually do it.

Ok - just looking at some basics. Nine of those first stage engines gives a lift-off thrust of 5885 kN, so one engine would give a lift-off thrust of 654 kN, or 66,689 kg-f. The prop load of the second stage is 200,000 lb, or 90,900 kg, adding dry mass of 5.2 tonnes gives a lift-off T/W of about 0.7, a problem. Ten to 15 % more throttle won't be enough. At 115% throttle, the lift off T/W would be about 0.8 ... Lift off T/W has got to be greater than 1 in order to get off the ground, just for that one new reader.

You are right, of course. But you surely are aware that there is no law of physics requiring to fully fuel a stage. With a reduced fuel load it can take off and still provide very decent delta-v.

I repeat that I don't believe it will ever happen but it is possible.

Depends on what you call a decent delta-v, but I can't disagree with what you think is decent. For myself, I don't think its very good. You have to cut the prop load nearly in half to lift off the ground with a 5 tonne spacecraft as payload. (Dragon?)  Once the prop is cut that much the delta-v is down to 3.5 to 5 km/s depending on what you estimate for aero and gravity drag. I would speculate drag at 1 km/s for that mostly vertical burn deep in the gravity well, giving 4 km/s achievable delta-v.

I do agree that I don't believe it will ever happen.
Retired, working interesting problems

Offline ncb1397

  • Full Member
  • ****
  • Posts: 1487
  • Liked: 656
  • Likes Given: 7
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #27 on: 05/17/2014 11:38 am »

The engines are basically the same. It should be possible to swap it for a first stage Merlin. Also they would need the reuse kit for a second stage. Likely a reusable first stage will be cheaper than an expendable second stage. Not that I believe they will actually do it.

Ok - just looking at some basics. Nine of those first stage engines gives a lift-off thrust of 5885 kN, so one engine would give a lift-off thrust of 654 kN, or 66,689 kg-f. The prop load of the second stage is 200,000 lb, or 90,900 kg, adding dry mass of 5.2 tonnes gives a lift-off T/W of about 0.7, a problem. Ten to 15 % more throttle won't be enough. At 115% throttle, the lift off T/W would be about 0.8 ... Lift off T/W has got to be greater than 1 in order to get off the ground, just for that one new reader.

You are right, of course. But you surely are aware that there is no law of physics requiring to fully fuel a stage. With a reduced fuel load it can take off and still provide very decent delta-v.

I repeat that I don't believe it will ever happen but it is possible.

Depends on what you call a decent delta-v, but I can't disagree with what you think is decent. For myself, I don't think its very good. You have to cut the prop load nearly in half to lift off the ground with a 5 tonne spacecraft as payload. (Dragon?)  Once the prop is cut that much the delta-v is down to 3.5 to 5 km/s depending on what you estimate for aero and gravity drag. I would speculate drag at 1 km/s for that mostly vertical burn deep in the gravity well, giving 4 km/s achievable delta-v.

I do agree that I don't believe it will ever happen.

The following suggests this would be more than enough to do sub-orbital space flight:

Quote
If one's goal is simply to "reach space", for example in competing for the Ansari X Prize, horizontal motion is not needed. In this case the lowest required delta-v is about 1.4 km/s, for a sub-orbital flight with a maximum speed of about 1 km/s.
http://en.wikipedia.org/wiki/Sub-orbital_spaceflight

The Dragon potentially has expendable delta-v as well assuming water landing.
« Last Edit: 05/17/2014 11:42 am by ncb1397 »

Offline metaphor

  • Member
  • Posts: 56
  • Liked: 13
  • Likes Given: 7
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #28 on: 05/19/2014 11:19 pm »
One big problem with suborbital landings is the very high g-forces encountered, much higher than re-entries from orbit.  Something like 10 g's or so.  Virgin Galactic counters that by having the shuttlecock wings.  But Dragon can't really do anything about it.

If a Falcon 9 first stage does launch a Dragon and stays with it, it might have enough propellant left over to do a braking burn halfway through the fall in order to lower the g's on the last part of re-entry.

Offline adrianwyard

  • Full Member
  • ****
  • Posts: 981
  • Liked: 201
  • Likes Given: 243
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #29 on: 05/19/2014 11:46 pm »
With a theoretical straight-up-and-down flight you're at ~0g on the return journey until you got to zero altitude. (And at that point there would be plenty of gs  :-[)

I bet the terminal velocity of a F9R in free-fall is quite high, so decelerating from that to zero will not be trivial, but this fantasy involves an F9R so I think you can start a gentle deceleration quite high (even though this is wasteful performance-wise) and give your tourists a pleasant ride. We can also infer that the g-loading of a first stage landing is not that great because it's already been done on the CRS-3 flight.
« Last Edit: 05/24/2014 08:59 pm by adrianwyard »

Offline Joffan

  • NSF Irregular
  • Full Member
  • ****
  • Posts: 1490
  • Liked: 505
  • Likes Given: 1432
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #30 on: 05/25/2014 03:27 am »
With a theoretical straight-up-and-down flight you're at ~0g on the return journey until you got to zero altitude. (And at that point there would be plenty of gs  :-[)

No - at terminal velocity you experience about 1g. Because air pressure is increasing as you descend, terminal velocity decreases and you should actually experience slightly more than 1g.
Max Q for humanity becoming spacefaring

Offline RyanC

  • Full Member
  • ****
  • Posts: 403
  • SA-506 Launch
  • Liked: 52
  • Likes Given: 9
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #31 on: 06/01/2014 01:33 am »
Since it appears that Dragon Mk II with the Super Dracos may have as high as 100> klbf thrust through the SuperDracos; I'm left wondering....is Falcon 9R even necessary for suborbital tourism? You could have an expendable Dragon II Trunk containing the propellants necessary for a Redstone style trajecotry -- though I would imagine that for suborbital tourism like this; the SuperDracos might need to be re-rated for using 'green' propellants, as the current toxic fuels used for it wouldn't enable routine and speedy launches -- plus there's a big difference between loading the amount of propellants needed for Draco orbital RCS manouvering and the amount needed to replicate Shepard/Grissom's flight profile.

Offline RanulfC

  • Senior Member
  • *****
  • Posts: 4446
  • Heus tu Omnis! Vigilate Hoc!
  • Liked: 814
  • Likes Given: 32
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #32 on: 06/02/2014 01:34 pm »
Since it appears that Dragon Mk II with the Super Dracos may have as high as 100> klbf thrust through the SuperDracos; I'm left wondering....is Falcon 9R even necessary for suborbital tourism? You could have an expendable Dragon II Trunk containing the propellants necessary for a Redstone style trajecotry -- though I would imagine that for suborbital tourism like this; the SuperDracos might need to be re-rated for using 'green' propellants, as the current toxic fuels used for it wouldn't enable routine and speedy launches -- plus there's a big difference between loading the amount of propellants needed for Draco orbital RCS manouvering and the amount needed to replicate Shepard/Grissom's flight profile.

Some discussion in the "DragonFly" thread starting here:
http://forum.nasaspaceflight.com/index.php?topic=34800.msg1207017#msg1207017

and goes about a dozen posts.

Main points:

- SD's are fed from high pressure tanks
-- Issues with transfering HP propellant between trunk and D-V2 as any "connection-point" that is designed to seperate at some point (emergency or normal operations) is going to be your "weak-point" in the design

- Major changes to D-V2 vehicle for operations
-- New "feed" system since all propellant for D-V2 is currently carried on-board. This may not be possible or feasible given the D-V2 design and may be possible only with "old" retired orbital D-V2 vehicles.

- Whole new "Trunk" design required either for propellant or propellant and propulsion if xfer to D-V2 is not possible.
-- Might be "simpler" to just design and build a whole new "VTVL" suborbital carrier vehicle.

-- Current propellants being "inadequate" was brought up, I never got any comments back though. My personal opinion is that HTP/Kero is a given if SpaceX plans on continuing to not have cryo's in this spot as its about the best for "simple" gas-and-go operations.

What I'm "seeing" is a squat, trunicated "cone" shaped VTVL stage with a D-V2 situated on top.

Are there any "details" on the specs for the D-V2 outside of L2 yet?

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline adrianwyard

  • Full Member
  • ****
  • Posts: 981
  • Liked: 201
  • Likes Given: 243
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #33 on: 06/02/2014 03:13 pm »
I see a Dragon V2 model has already been added to Kerbal Space Program. If anyone is adept in KSP it would be interesting to see how high it could hop on its own (my guess is not far) and how high a falcon 9R 1st stage could could take it if going straight up before returning separately (my guess is very high indeed).

In terms of imagining tourism scenarios it is noteworthy that Dragon V2 now has five quite large windows and so becomes the most suitable tourist spacecraft out there.
« Last Edit: 06/02/2014 03:17 pm by adrianwyard »

Offline cartman

  • Full Member
  • ****
  • Posts: 508
  • Greece
  • Liked: 490
  • Likes Given: 3097
Re: Falcon 9R and Dragon Mk II Suborbital Tourism?
« Reply #34 on: 06/02/2014 04:26 pm »
If they do not change too much until certification, I believe that Dragon has the advantage of much simpler controls, thus needing less training time, especially vs Soyuz or (my guess) Dream Chaser. For many wealthy individuals, the (at least) six months it takes to train for a ride on a Soyuz is maybe a bigger cost than the price of the ride itself.

Tags: