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They may also have avoided using separation motors.
Don't need separation motors when you have cold gas thrusters already.
They landed on the moon on my 16th birthday.  I didn't care about the "cold war".  I wanted to explore space.  So did most of the space enthusiasts I knew back then.

I grew up in a military town, and spent as much time as possible climbing over "my toys", which happened to be weapons of war.  There can be a difference between reality and perception.

To us it didn't have anything to do with the "cold war".

Yet it did.  Just because you weren't aware of the politics of the day doesn't make it any different.

During the 50's Von Braun had stories of going to Mars on Disney, etc.  Growing up to be an astronaut was one of the things kids wanted to do besides being a policeman or fireman.

And many kids grow up wanting to operate weapons of destruction.  That doesn't mean Congress is funding our military just to satisfy the wishes of children.

However, when he gets to space, he is going to want to go, and go at he lowest cost, and the quickest way.  Probably won't be NASA designed stuff, but privately designed.  NASA may coordinate the efforts, but probably not design them, because of costs savings.

Not sure you remember how our government works, but Presidents can't decide what taxpayer money is spent on, only Congress can do that.  So Trump can be enthusiastic about whatever he wants, but if he wants taxpayer money then he has to articulate a clear and convincing argument for how taxpayers are going to benefit.

I find it interesting that people can assign so much intent from this rather brief encounter.  What in Trump's past would indicate that he has a true desire to expand humanity out into space - other than an opportunity to attach his name to something "BIG!"?
Blue Origin / Re: Blue Origin's BE-4 Engine
« Last post by sanman on Today at 08:23 PM »
It is merely a charade to appease influential people and organizations that they are "keeping an open mind" about the AR-1, IMO. Once BE-4 has been tested, they can drop that pretense.

I have that sense that ULAS and BO feel some urgency for getting BE-4 tested. I guess ULA are under pressure to use AR-1 and that pressure will increase when test dates for BE-4 slip. I personally don't doubt BO will get there and even worst case they will probably be ahead of AR-1.

I know the thread's about BE-4, but what will happen to AR-1 if/when ULA selects BE-4?

Are there any other customers waiting in the wings for it? Orbital ATK, or somebody?
So are there going to be Grasshopper-style test flights for ITS? Will they likely start at McGregor?
... and contract line item 001 for SpaceX by $91 million for a hardware requirement change and the addition of cargo during an ISS test flight.
So it seems SpaceX DM1 will have a cargo manifest paid outside either CRS contract.
For high value metals like gold and platinum, they could be returned to earth in reusable 2nd stage. Assuming moon or asteriod water extraction is already in place, the metals can be delivered to LEO on water/fuel tanker as secondary payload. A 1t gold would take up very little space in 2nd stage but could add a few $M to mission profit for normally unprofitable return leg.

Even if water isn't being return to LEO a OTV still needs to return so a extra few $M on this leg from   1t gold would help profit margin.

Missions To Mars (HSF) / Re: Scaling Agriculture on Mars
« Last post by sanman on Today at 07:58 PM »
Some people here have said that hydroponics is the more economical way to grow plants on Mars - can something similar be used if agriculture extends to livestock cultivation?

Wow, that was unsettling - visions of Alduous Huxley - the Spaarti cylinders come later.  :o

But the idea of decoupling reproduction/gestation from the rest of an organism's life cycle might allow greater efficiencies in livestock breeding. It also might allow fetuses to be carried to longer terms for higher birth-weights, which are correlated to better survival rates beyond the womb.

Also, if Mars is to serve as a "backup for Earth", then could it mean even supporting a backup ecosystem, including animals? (a la Noah's Ark)
It's one thing to hatch insects from frozen eggs, but to revive animal species from scratch, an artificial womb might be useful.

Furthermore, while your mature livestock were busy grazing inside the greenhouse domes on the surface, the livestock fetuses could be gestating inside the biobag wombs in a safer environment underground.
Payload to LEO with expendable Falcon Heavy boosters is just a "what-if" measuring stick since most rockets are compared by LEO payload.

More interested in just the TMI number for the expendable FH scenario, as if one were trying to land volume+mass on Mars as soon as possible it would probably be the fastest path forward.
The scenario where expendable booster 3-cores of Falcon Heavy might launch this mini-ITS direct to Mars would be where: in space prop transfer isn't developed yet, but one really wants to get a test of the system to land on Mars with at least some meaningful payload, so you expend some used FH cores.
Right, makes perfect sense.

Here's the table showing payloads. Everything is listed in tonnes.

Falcon 9 FT (RTLS)18.3|5.7|2.7
Falcon 9 FT (droneship)19.2|6.6|3.3
Falcon 9 FT (expended)22.3|8.1|4.4
Falcon H (recovered)31.6|11.7|6.7
Falcon H (core expended)39.3|15.4|9.3
Falcon H (expended)51.5|20.6|12.9
Falcon 9M (RTLS)19.9|7.4|4.0
Falcon 9M (droneship)21.9|8.4|4.7
Falcon 9M (expended)25.5|10.2|6.1
Falcon HM (recovered)37.3|14.5|8.9
Falcon HM (core expended)46.4|19.0|12.1
Falcon HM (expended)59.51|25.1|16.3
Falcon 9M+ (RTLS)22.0|7.8|1.4
Falcon 9M+ (droneship)23.8|8.8|2.1
Falcon 9M+ (expended)27.0|10.4|3.3
Falcon HM+ (recovered)42.4|16.9|7.7
Falcon HM+ (core expended)50.2|20.8|10.6
Falcon HM+ (expended)64.8|27.0|14.9

"Falcon 9 FT" and "Falcon H" represent the current incarnations with expendable kerolox upper stages. Standard recovery for Falcon Heavy is RTLS for the boosters and droneship for the core; "core expended" means droneship recovery for the boosters.

"Falcon 9M" and "Falcon HM" represent the current configuration with an expendable methalox upper stage powered by a single vacuum-optimized devRaptor. Upper stage material and dimensions are the same, with a shifted common bulkhead.

"Falcon 9M+" and "Falcon HM+" represent the replacement of the current upper stage with my two-engine reusable composite upper stage, including landing thrusters and recovery margins. LEO missions have enough margin for bringing the full payload back to Earth (e.g., crewed missions), GTO missions have enough margin for bringing the stage back empty, and TMI missions have enough margin to land the full payload on Mars.

Not shown in the table is the theoretical maximum performance to LEO (e.g., upper stage fully expended, with plan to refuel in LEO); this is 65.7 tonnes. However, these are all Falcon 9 FT numbers, with Falcon Heavy based on this. SpaceX is currently projecting Falcon Heavy (based on Block 5 cores) at an expendable payload of 63.8 tonnes to LEO, while my table has it at 51.5 tonnes to LEO. So the true theoretical maximum performance could be significantly higher, maybe as high as 75 tonnes.

Not sure how Block 5 FH can make 63.8 tonnes to orbit, though. That's a jump far larger than what thrust increases alone can manage. Maybe specific impulse is coming up too?

Mars is 6,000 m/s past LEO; if you bring the upper stage tanks and propulsion along all the way to the surface the payload drops to about what Red Dragon can do with a fully expendable FH - roughly 2,000 kg.

Cryo prop transfer is really, really important if we want to go to Mars or anywhere else. It's not that hard, compared to landing on Mars and making fuel there. It's something that could easily be flight-ready before the rest of a mini-ITS system.
Actually, I got 15 tonnes to the Martian surface with a direct ascent on fully-expendable Falcon Heavy. And this number, like the rest of the numbers, is based on the FT Heavy, not the Block 5 Heavy.

But you're right, orbital prop transfer is super important. A reusable methalox upper stage for Falcon 9 and Falcon Heavy would be a fantastic test bed for this.
It's closed on both sides, but it's split on the oxygen.
Forgive my ignorance, but split on the oxygen side means that the oxygen is heated by a heat exchanger and only LH2 is used as coolant?
I took that to be referring to what's discussed here:

Due to pressure loss from moving through the cooling channels, pump power is saved by diverting part of the propellant flow and sending it directly to the combustion chamber.

I also understand the fuel to be methane, not LH2. I'd guess that influences the decision to go to a dual expander.

This is essentially correct, except there are more losses than just the one through the cooling jacket, namely the turbine drop. For the oxygen, we have lots of mass flow available and simply do not need that much coolant. Better not to spend the energy pumping all of it up past injector pressure.

Yes, Broadsword is emphatically a LOX/Methane engine.

Benefits to dual expander are that you eliminate the interpropellant seal and keep the turbine inlet temperatures extremely low. The propellants also remain in a temperature range where they are more effective coolants, since the fluid properties affecting that drop off fairly rapidly past the critical temperature.

Lastly, one might note that the cycle is essentially identical to a full-flow staged combustion cycle, except that it is missing the requisite preburners.
Space Science Coverage / Re: Pluto Orbital Mission
« Last post by Bob Shaw on Today at 07:51 PM »
The interesting thing about any consideration of atmospheric deceleration is that, although very thin, the atmosphere of Pluto should (at times) extend a really long way from the planet - at altitude, it would be denser than our own atmosphere at similar altitudes. Unlike Mars, however, where aerocapture is an established technique, the atmospheric density at Pluto seems to be wildly variable. Perhaps my enquiry is a solution in search of a problem!
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