Talk-Polywell.org

Could anyone take an educated guess as to how long the turn-around for a reusable first stage would be?

What will they have to do? Like, make sure there's no "loose bolts", do X-Ray scanning? Will they have to fire it up between flights? How many times do you think a an F9-R can be used?

An interesting bit on reusability:

The X-15 Rocket Plane: Implications for Reusable Booster Schedule & Cost (1966)

http://www.wired.com/wiredscience/2013/ ... ters-1966/

Station supporters envisioned that reusable spacecraft for logistics resupply and crew rotation would make operating the station affordable. In November 1966, James Love and William Young, engineers at the NASA Flight Research Center at Edwards Air Force Base, completed a brief report in which they noted that the reusable suborbital booster for a reusable orbital spacecraft would undergo pressures, heating rates, and accelerations very similar to those the X-15 experienced. <snip>

“Love and Young wrote that some space station planners expected that a reusable booster could be launched, recovered, refurbished, and launched again in from three to seven days. The X-15, they argued, had shown that such estimates were wildly optimistic. The average X-15 refurbishment time was 30 days, a period which had, they noted, hardly changed in four years. Even with identifiable improvements, they doubted that an X-15 could be refurbished in fewer than 20 days.

“At the same time, Love and Young argued that the X-15 program had demonstrated the benefits of reusability. The cost of refurbishing an X-15 in 1964 had, they estimated, come to about $270,000 per mission. In 1964, NASA and the Air Force had accomplished 27 successful X-15 flights. The total cost of refurbishing the three X-15s for those flights had thus totaled $7.3 million.

“Love and Young cited North American Aviation estimates which placed the cost of a new X-15 at about $9 million, then calculated the cost of 27 X-15 missions if the rocket plane had not been made reusable. They found that the all-expendable X-15 program would have cost the United States $243 million in 1964. This meant, they wrote, that the cost of refurbishing the three X-15s amounted to only 3% of the cost of building 27 X-15s and throwing each one away after a single flight.”

polyill wrote:Could anyone take an educated guess as to how long the turn-around for a reusable first stage would be?

Best case airliner style operation:

- every flight
-- verify that no problem flags were raised by on board diagnostics last flight.
-- flush the plumbing. Mixing of certain fluids in the wrong place might cause a problem.
-- refill propellant and other expendable supply tanks.
-- recharge battery.
-- Load and secure payload (upper stage). For a proper reusable system I'd favor electrical servo release over explosive bolts.
-- verify servo response to flight controls.
Maybe a few hours.

- Every N flights, or when problem flags are raised
-- additional checks which may include an ultrasound check for developing cracks.
-- swap out limited lifetime components, which should be few.

Until you get a flight history you'll want to do the extra checks more often.

rjaypeters wrote:“Love and Young wrote that some space station planners expected that a reusable booster could be launched, recovered, refurbished, and launched again in from three to seven days. The X-15, they argued, had shown that such estimates were wildly optimistic. The average X-15 refurbishment time was 30 days, a period which had, they noted, hardly changed in four years. Even with identifiable improvements, they doubted that an X-15 could be refurbished in fewer than 20 days.

The X15 was hardly what one would call a commercial aircraft.

Those gentlemen wrote their report from their experience:

"Station supporters envisioned that reusable spacecraft for logistics resupply and crew rotation would make operating the station affordable. In November 1966, James Love and William Young, engineers at the NASA Flight Research Center at Edwards Air Force Base, completed a brief report in which they noted that the reusable suborbital booster for a reusable orbital spacecraft would undergo pressures, heating rates, and accelerations very similar to those the X-15 experienced."

rjaypeters wrote: reusable suborbital booster for a reusable orbital spacecraft would undergo pressures, heating rates, and accelerations very similar to those the X-15 experienced."

But with totally different market forces.

Yes. And let us hope fifty plus years of technology development make a difference.

Well, somehow I doubt the 1964 data for a Government-Mil project is still valid in 2013 for a commercial company employing an IT-like standards in management, development and testing, led mostly by a single person's will, which person is not much less than an Engineering/Management prodigy with a proven success record (as opposed to the gov-mil bureaucracy of the X-15 project, IMBW here, apologies if I am).

At least I'd like to think things have changed. You can argue that a rocket is a rocket, but, to my understanding, the technology itself has made some progress since 1964 in manufacturing as well as in design and modeling and in sensors and data acquisition (computers, etc.), has it not?

I'd like to hope a week long turn-over is a realistic goal. I don't think a real Space Industry is possible with anything less than 365 launches annually for a given launchpad. And I suspect this to be a conservative estimate. So about ten F9-R boosters on-site will allow you to launch once-a day.

Obviously, there's got to be a market for 365/y launch capability, but then again, coming form IT, Musk knows that if there's no market, you create one and are the first-to-it. At which Musk is OK

Edit for spelling

hanelyp wrote:

polyill wrote:Could anyone take an educated guess as to how long the turn-around for a reusable first stage would be?

Best case airliner style operation:

- every flight
-- verify that no problem flags were raised by on board diagnostics last flight.
-- flush the plumbing. Mixing of certain fluids in the wrong place might cause a problem.
-- refill propellant and other expendable supply tanks.
-- recharge battery.
-- Load and secure payload (upper stage). For a proper reusable system I'd favor electrical servo release over explosive bolts.
-- verify servo response to flight controls.
Maybe a few hours.

- Every N flights, or when problem flags are raised
-- additional checks which may include an ultrasound check for developing cracks.
-- swap out limited lifetime components, which should be few.

Until you get a flight history you'll want to do the extra checks more often.

You are an optimist and I like it. I don't think a few hours is a realistic turn-over time. There are payloads, which means there are insurance contracts, which in turn means you have to make them SURE you are able to deliver the payload...

An STS-300 mission according to nasa could be launched in 40 days and no longer than 49 days. IG take a shuttle that just landed and have it up in the air on rescue mission. So any turn around time faster than that makes them very good at what they do.

rjaypeters wrote:Yes. And let us hope fifty plus years of technology development make a difference.

That's not how it works in the US.

The way it works in the US is;
R&D a game-changing concept to astounding new heights, then let the Harvard/Wall Street elite kill it, replacing it with an unsustainable, but more near-term profitable, alternative.

As a side benefit, the "cancelled" R&D can go "dark", for use only by the elite, as with Polywell.

You mean, like polywell, it turns into a slow burn, career making science project with low bureaucratic risk, intended to be "good" science.

polyill wrote:

hanelyp wrote:

polyill wrote:Could anyone take an educated guess as to how long the turn-around for a reusable first stage would be?

Best case airliner style operation:
...
Maybe a few hours.
...
Until you get a flight history you'll want to do the extra checks more often.

You are an optimist and I like it. I don't think a few hours is a realistic turn-over time. There are payloads, which means there are insurance contracts, which in turn means you have to make them SURE you are able to deliver the payload...

As I said, best case. It's not going to happen that fast until the ground crew has practice and vehicle wear is well characterized. And it depends on system failure being some combination of predictable and tolerated. Airliners have engine out incidents routinely without loss of vehicle, payload, or mission.

@mvanwink5:
I view that as the "twilight" phase of the "darkening".

polyill wrote:Well, somehow I doubt the 1964 data for a Government-Mil project is still valid in 2013 for a commercial company employing an IT-like standards in management, development and testing, led mostly by a single person's will, which person is not much less than an Engineering/Management prodigy with a proven success record (as opposed to the gov-mil bureaucracy of the X-15 project, IMBW here, apologies if I am).

You're probably off base here. Government aerospace in the '60s was like commercial is today, but better funded. As for the "gov-mil bureaucracy" not having a proven success record... you're joking, right? WWII, Manhattan project, breaking the sound barrier, guided missiles, nuclear submarines, ICBMs, artificial satellites... the B-52 itself had seen just four years of service when it was first used to carry an X-15 to operational altitude...

On the other hand, the X-15 program was a research program. Fast, cheap turnaround for commercially viable operation was pretty low on their list of priorities...

The DC-X program was also research, but in this case the objective was specifically fast, cheap turnaround. The vehicle wasn't orbital or even particularly high-speed, but it was still a VTOL rocket of significant size and delta-V, and despite the deep-cryo fuel it once managed a 26-hour turnaround.

Reaction Engines Ltd. estimates a two-day turnaround for Skylon, dominated by heat shield inspection. This is admittedly not historical data...

At least I'd like to think things have changed. You can argue that a rocket is a rocket, but, to my understanding, the technology itself has made some progress since 1964 in manufacturing as well as in design and modeling and in sensors and data acquisition (computers, etc.), has it not?

Definitely. For example, the SSME underwent continuous development over its lifetime. The early models ran a noticeable risk of catastrophic turbopump failure and had to be disassembled, inspected, and refurbished piecemeal after every flight. Later models were easier to maintain and didn't need disassembly every time; the Block II was much more robust, with a final version apparently estimated to be four times safer than the original engine. The Block III (never completed and flown, probably due to the fallout from STS-107, but a lot of the work is applicable to the RS-25E) would have been several times safer and much easier to manufacture than the Block II, and the improved robustness combined with advanced health monitoring (which the Block II eventually got) would have allowed it to stay in the orbiter for perhaps ten flights without significant maintenance.

The RS-83 (hydrolox GG, 750 klbf, 446 s, cancelled 2005) was supposed to last 100 flights, with probably a much better chance of actually achieving its original goal due to lessons learned from the SSME (combustion chamber failure modes, for example).

In any case, SpaceX is not using SSMEs or even hydrolox. Merlins should be much less highly stressed than RS-25s, though coking could be an issue over the long term (IIRC they've gotten one engine past 20 full-duration test firings), and while they don't have the flight experience yet, they use ten of the things on each flight and recover nine of them, so it should build up pretty fast...