The rocket will fly 11 satellites to orbit for Orbcomm, and will be followed soon after by launch of another Falcon-9 to Geostationary Transfer Orbit (GTO) with another satellite, SES-9, by the end of the year.
“As we prepare for return to flight, SpaceX together with its customers SES and Orbcomm have evaluated opportunities to optimize the readiness of the upcoming Falcon 9 return-to-flight mission,” says SpaceX in a statement released this afternoon. “All parties have mutually agreed that SpaceX will now fly the Orbcomm-2 mission on the return-to-flight Falcon 9.”
Launch of the SES-9 communications satellite, on behalf of the Luxembourg-headquartered SES, had been speculated for some time as SpaceX’s Return to Flight mission, but the company “switched” in order to conduct on-orbit testing of their now modified Falcon-9 upper stage.
“The Orbcomm-2 mission does not require a relight of the second stage engine following orbital insertion. Flying the Orbcomm-2 mission first will therefore allow SpaceX to conduct an on-orbit test of the second stage relight system after the Orbcomm-2 satellites have been safely deployed. This on-orbit test, combined with the current qualification program to be completed prior to launch, will further validate the second stage relight system and allow for optimization of the upcoming SES-9 mission and following missions to geosynchronous transfer orbit.”
Built by Sierra Nevada Corp., the original plan was to launch 18 OG-2 satellites, the first of which flew ‘piggyback’ on SpaceX’s first dedicated Dragon mission in October 2012. However, an upper-stage engine shortfall of the Falcon-9 v1.0 rocket caused the satellite to be injected into a low orbit of just 125 x 200 miles (200 x 320 km), instead of the intended 220 x 470 miles (350 x 750 km). As a result, the satellite re-entered Earth’s atmosphere and was destroyed.
SpaceX’s third Falcon-9 launch of 2014 flew the first six Orbcomm OG-2 satellites (OG-2 Mission-1), successfully delivering the 380 pound satellites into a circular 460 x 460 mile high orbit. Each satellite measures 42.7 feet (13 meters) x 3.3 feet (1 meter) x 1.6 feet (0.5 meters) when fully deployed, and each can generate about 400 watts of electrical power. Designed with Automatic Identification System (AIS), it is expected that the OG-2 network will be marketed by Orbcomm to U.S. and international coast guards and government agencies, as well as private security and logistics companies.
“We are excited to launch our eleven OG2 satellites aboard SpaceX’s newly upgraded Falcon 9 rocket and have full confidence in SpaceX and their dedication to this launch,” said Marc Eisenberg, ORBCOMM’s Chief Executive Officer. “We look forward to completing the deployment of our next generation constellation and delivering a higher level of performance, coverage and reliability through our modernized and upgraded OG2 network to our customers around the world.”
The rocket itself has been upgraded in many ways. SpaceX refers to it as the “Falcon 9 v1.1 Full Thrust”, which is an internal code name for calculating the Merlin 1D engine output at 100 percent, and many of the modifications are outlined in a recent Falcon-9 update by AmericaSpace Senior Writer Ben Evans. Upgraded Merlin 1D+ engines, increased thrust performance, structural enhancements to the vehicle’s airframe, increases in propellant tank volumes, a lengthened second stage, upgraded landing legs and grid fins and an improved “Octaweb” support structure for the first-stage engine suite all compliment the “new” Falcon-9.
The Orbcomm OG Mission-2 flight will also give SpaceX another try at landing their rocket’s first stage on an offshore barge known as the Autonomous Spaceport Drone Ship (ASDS), part of the company’s efforts to turn the Falcon-9 into a truly reusable launch system. A series of “controlled oceanic touchdowns” in April, July, and September 2014 were followed with mixed fortune earlier this year, when two attempts were made to land on the ASDS. The first reached the deck, but impacted hard at a 45-degree angle and exploded, whilst the second landed with excessive lateral velocity and toppled over upon impact.
Stabilizing the 150-foot-tall rocket stage in flight, traveling at a velocity of 2,900 mph at separation, has been likened to someone balancing a rubber broomstick on their hand in the middle of a fierce wind storm.
SpaceX CEO Elon Musk expects that the new improvements will allow Falcon-9 to soft-land even during high-energy launches to the 22,300-mile (35,900-km) altitude of GTO, where SES-9 will launch to. Previously, only comparatively low-energy launches to Low-Earth Orbit (LEO) had seen soft-landing attempts, although SpaceX originally intended to bring the first stage from NASA’s L1-bound Deep Space Climate Observatory (DSCOVR) back to the ASDS in February 2015, but was ultimately thwarted by rough seas.
When they do finally land a rocket successfully, it will be a history-making feat, a game-changer that many expect the company to accomplish sooner rather than later, including their main competitor United Launch Alliance (ULA). Never has a rocket made a controlled landing after a launch, and the expectation is that once the Falcon-9 is truly reusable it will drive down dramatically both the costs of access to space and turnaround time between launches.
In the meantime, SpaceX is building the actual landing site for their rockets, at the old Launch Complex-13 on Cape Canaveral Air Force Station, under a five-year lease agreement with the U.S. Air Force. Although instead of being called “Launch Complex-13,” it is now designated as “Landing Complex-1.” A primary concrete landing pad will be developed, surrounded by four smaller contingency landing pads for use in case a landing rocket is not quite on the bull’s eye.
The company is also planning similar operations at their west coast launch site at Vandenberg AFB, Calif. Another ASDS will serve as the company’s Vandenberg barge while SpaceX continues on the reusability development path to landing their rockets back on solid ground.
Will be glad to hear of the Falcons return to flight, and cant wait. Also will be waiting for the Falcon to make history with its first successful barge landing. Goooooo SpaceX!!!!!!!
“Now the Hawthorne, CA-based company stands ready to resume launches of its heavily modified Falcon-9 rocket in as soon as “6-8 weeks”, and will do so for the Orbcomm OG-2 Mission-2.
The rocket will fly 11 satellites to orbit for Orbcomm, and will be followed soon after by launch of another Falcon-9 to Geostationary Transfer Orbit (GTO) with another satellite, SES-9, by the end of the year.”
This is 10/16/2015 if SpaceX were to make the inside of that “as soon as “6-8 weeks”” time frame that would leave them a maximum of five weeks to produce the second launch “by the end of the year”.
Don’t forget that SpaceX has demonstrated turn around times of 13 days and 14 days. So it is possible to quickly turn around the pad and launch again.
They have demonstrated that, but not on purpose. They were also in full production swing back then.
The 14 day turnaround (AsiaSat 6 and CRS-4) was due to AsiaSat’s initial launch attempt in late August being scrubbed after the F9R Dev-1 failure, so that they could make sure the test rocket failure didn’t point to a problem in the launch vehicle.
The 13 day turnaround was the result of CRS-6 being bumped from February to April. But delays in cargo supply missions is fairly routine, since the schedule for CRS launches has to be juggled amongst four (formerly five) providers. This time the delays just happened to land CRS-6 very close to TurkmenSat’s launch, which itself was delayed from late March to investigate potential helium bottle issues.
So I think all they’ve demonstrated is that they can turn around the launch site quickly if their fortunes just happen to present them with two vehicles and their payloads being there at or near the same time. That’s great, but it still remains to be seen how well they can coordinate things so that it happens as scheduled, rather than a lucky combination of delays.
Don’t forget that with the full-thrust upgrades they are chilling the LOX (and I believe RP-1 as well) to lower temperatures to increase its density. That means changes to ground service equipment and fueling/launch procedures.
They did manage a couple of quick turn-arounds in the past, but not while introducing major changes like that.
I’m definitely looking forward to their return to flight, but I’m not holding my breath for two launches this year.
Not sure about the RP-1 either, but they are definitely claiming they will use what they are describing as “densified” LOX.
That has previously been called “slush” LOX and has been discussed numerous times (usually in connection with some kind of SSTO).
(1) Has this “densified” LOX has ever been produced in the quantities required before? (2) Does it have flow characteristics different from “standard” LOX?
I saw mention this last week of the RP-1 being chilled to gain a small amount of density, but not much since it will gel up if too cold – but that was discussion on Reddit, with no links confirming it, so I took it with a large grain of salt.
A few weeks ago, there were reports of SpaceX having done a test fire of the full thrust first stage at McGregor (there are community announcements of the test fires). Even if the duration wasn’t as long as a first stage burn on launch, the ability to produce enough deep cryo LOX to pull that off would be on comparable scale to what they’ll need at CCAFS.
Still though, updating the GSE at the cape, implementing new tanking procedures as a part of the launch procedure, analyzing everything after the first launch to look for problems… It took them several launches to get to reasonable turn-around times, I just can’t expect a record-breaking turn around time when that’s all going down.
Yeah, the RP-1 thing is interesting. I have not researched the subject, but there is a lot of water in kerosene (what RP-1 basically is) and water gets less dense as it cools (at least at some point – ice floats in water).
The “slush” LOX thing is easier to discuss. They say they have performed a test stand run using it, but the work at the launch site would be extensive.
(1) What is the base temperature of this new version of LOX (as compared to “standard” LOX?
(2) Where is it being produced and stored?
(3) What changes had to be made to the pumps/flow lines of the Merlin engines to allow for the different flow characteristics?
Just three question of many and add the fact that the Merlin Engines are also being “evolved” (presumably meaning increased pump speed and chamber pressures – increased performance certainly means that for everybody else’s engines).
Minor nitpick. Pumps develop a pressure head that is similar in feet for all propellants at a given rpm. If they have denser fluid, it will
Have higher pressure at the same rpm. 10 percent more density will have 10’percent higher pressure and 10 percent more
Mass flow at similar rpms. The question is if the pumps can handle the increased stress without problems if they don’t drop the rpm.
However, SpaceX is claiming higher thrust (and presumably thrust to weight performance ratio – though it is hard to tell from their statements)for the new Merlin Engines in addition to the denser propellant. That by itself would require higher RPM’s on the pumps.
Also the original term for the colder LOX is slush LOX which would mean a difference in the flows through the lines (regardless of pump speed) as there would be almost ice like components of the LOX. The questions there are:
(1) What does SpaceX mean by “densified”?
(2) Is it the same as “slush”?
(3) What is the temperature of the “densified” LOX?
SpaceX, of course, does not say.
Oxygen is liquid below -183 C (boiling point)
Oxygen is solid below -218 C (freezing point)
You can see there’s not a huge difference between the two temperatures (it’s like the difference between long pants and sweater weather and shorts and t-shirt weather). My understanding is they are going to push it down to just barely above its freezing point.
The LOX is being produced and stored in the same places as before. SpaceX has installed chillers near its launch pads, so it will be cooled just before being pumped into the rocket.
I would guess that the programming in the computers controlling the pump flow rates in the rocket had to be modified, but few physical changes needed to be made. This is ITAR controlled territory so the best we can do here is guess.
If you consider 95 F to be the “the difference between long pants and sweater weather and shorts and t-shirt weather”, I admire your perseverance.
The issues for processing and operations are numerous and include (but are not limited to the following:
(1) How and when are they going to “push it down to just barely above its freezing point”?
(2) How is the storage and transfer to the vehicle tanks without loosing the chill to be accomplished (how much additional insulation)?
(3) How much shorter must the time to launch be after fueling to not lose “extra chill” (alternatively how much extra insulation – and thus extra mass – must be added to the vehicle to maintain the “chill”)?
(4) How much extra gross payload capability do they achieve (assuming they can make this work)?
(5) What are the extra cost and operational impacts for supplying the “densified” LOX (and potentially turning the F9 into a “hangar queen”)?
I assume you mean Fahrenheit, so it’s not 95 degrees difference, it’s 63 degrees difference. 35 C = 95 F is definitely shorts and t-shirt weather. 0 C = 32 F is definitely long pants and sweater weather. I’ve lived in both Southern California and in Illinois, I have experienced long periods of time at both temperatures. Anyway, that was only meant to give you an idea of how much of a temperature difference we’re talking about.
I already told you. They have installed chillers near the launch pad. The chilling will take place right before they pump it into the rocket.
I don’t think it will gain much heat in the transfer, it’s not going that far, and if it was a concern, adding extra insulation to the pipes on the ground is easy.
LOX loading begins about 2 1/2 hours before launch, and is completed about 1 1/2 hours before launch (source, multiple SpaceX press kits). This gives enough leeway prior to launch to complete loading if there’s any issues with the process. Because of that, I doubt the start of LOX loading time will change much, though they might start a bit later in the pre-launch countdown. Also, it will probably take longer to load the LOX since there will also have to be some additional time for it to be chilled. We’ll have to see what the next press kit looks like. I doubt the rocket will require any additional insulation, as we’re not talking about hugely decreasing the temperature of the LOX and it was already well insulated to begin with.
About 10% more payload, though the extra capability is really so they can launch satellites to GTO and still return the core to the launch site.
Installation and maintenance of the chillers at the launch site. Your parenthetical about the Falcon 9 becoming a hangar queen is ridiculous.
Just FYI, this isn’t exactly the first time in the history of rocketry that fuel / oxidizer has been densified. SpaceX has lots of records related to densification to draw on.
“I assume you mean Fahrenheit”
Yes that is what the F after the 95 means.
“95 F is definitely shorts and t-shirt weather. 0 C = 32 F is definitely long pants and sweater weather.”
Which has nothing to do with maintaining LOX at cryogenic temperatures surrounded by much higher ambient temperatures.
Will skip the rest of the tirade and jump to your conclusion.
“Just FYI, this isn’t exactly the first time in the history of rocketry that fuel / oxidizer has been densified. SpaceX has lots of records related to densification to draw on.”
Do you have any links to this history? Would make for fascinating reading.
Way to entirely miss the point about temperature.
It wasn’t a tirade, I responded to each of your questions point by point. For some reason the site formatting removed the numbers I had at the beginning of each point.
Do a damn google search if you’re going to just ignore every thing I’m saying anyway.
Do not have to do a “damn google search” (to use your colorful terminology).
Here is a link to a compilation of research into densified (actually triple point is a more descriptive term)propellants/oxidizers and it dates back to March 2000 (little if anything has been done since then):
It is interesting reading and includes references to (among other things):
(1) Flight tests of jet engines using Cryogenic Hydrogen (not triple point and not Oxygen) in the 1950’s.
(2) Production of triple point hydrogen (not oxygen)to a maximum of 800 gallons during research on the NASP program in the 1980’s.
(3) Theoretical and laboratory work on manufacture of triple point Oxygen during the X-33 Program in the 1990’s.
You will not find:
(1) Demonstration of manufacture, storage, transfer of triple point Oxygen on the industrial scale required to support Falcon 9 launches.
(2) Test stand evaluations of any rocket engines using triple point Oxygen.
(3) Flight tests of any rocket engines using triple point Oxygen.
If SpaceX is actually doing all this more power to them and I hope they succeed.
But the original subject of this discussion was whether or not they were likely to be able to (coming off their last launch exploding) fly two missions in two months by the end of the year.
I said the goal was ambitious (and was not even thinking at the time about the fact that the Falcon 9 was about to morph – once again – into an entirely new vehicle).
Densified LOX was used in several Soviet era rockets. It was also used in the X-15 program.
Operational launchers that employ sub-cooled LOX are Antares (in its original version, using LOX at –196°C) and Soyuz 2-1v (-192°C LOX).
The Antares Launcher (now defunct because it blew up) did indeed use LOX, but I find no reference to densified, slush, triple point, or your new term sub-cooled.
There is a reference to sub-cooled on the Soyuz 2-1v, but this is also stated:
“Because of that, the LOX temperature for Soyuz 2-1v is -187 degrees Celsius.”
That is a whopping 4 degrees below the boiling point of -183 C (as you noted above). So it starts to get into whether densified and sub-cooled mean the same thing (nice try at confusing things though).
It should also be noted that of the two rockets you named:
(1) One is defunct because it blew up.
(2) The other has flown once since its maiden (and only) flight in 28 December 2013 and that maiden flight was delayed three years due to hardware problems.
Maybe you should repeat your assertion that my “parenthetical about the Falcon 9 becoming a hangar queen is ridiculous.”
Now, I have expended enough time on you and the double talk.
Have a nice day.
Without even getting into the terminology games about the definitions of sub-cooled vs. densified/triple point (nice try though) your selection of boosters is interesting:
(1) The Antares is defunct because it blew up.
(2) The Soyuz 2-1v has flown once since its maiden (and only) flight in 28 December 2013 and that maiden flight was delayed three years due to hardware problems.
Maybe you should repeat your assertion that my “parenthetical about the Falcon 9 becoming a hangar queen is ridiculous.”
Have a nice day
Since we don’t know exactly what temperature SpaceX wants to cool its LOX to, you’re right, there’s no point arguing about it, however, it is a fact that any cooling would produce denser LOX, therefore these temperatures both produce “densified” LOX.
Oxygen at -184 C = 4.37 kg/m3 (just below boiling point)
Oxygen at -192 C = 4.80 kg/m3
Oxygen at -196 C = 5.05 kg/m3
Oxygen at -217 C = 6.93 kg/m3 (just above freezing point)
Yes, that comment was and is ridiculous.
Like I said have a nice day.
A truly excellent question that gets to (what I believe to be) the crux of the matter.
Unfortunately due to the secretiveness of SpaceX it is not possible to give a definitive answer.
(1) They say (without giving specifics) that they are “upgrading” the Merlin engines. To anyone else that would mean greater pump speeds and chamber pressures and a higher propellant/oxidizer flow rate.
(2) That higher propellant/oxidizer flow rate would require more propellant/oxidizer. If the tankage size is fixed then both the propellant and oxidizer would have to be denser.
(3) Theoretically the oxidizer (LOX) can be “densified” by reducing it’s temperature too closer to its triple point, but that would require additional changes to the hardware to handle the flows of the “slush” oxygen (think about a slerpy as opposed to a glass of water). Reverences to sub-cooled LOX (only a few degrees below the LOX boiling point) does not address the issue
(4) The RP-1 would also have to be “densified”. Not an expert in this area, so I am only going to say that chilling the kerosene (which is what RP-1 essentially is) to “densify” it is counter intuitive. Kerosene has a large component of water which is non-compressible and actually becomes less dense when it freezes.
So none of this makes any sense based on the publicly available information.
Perhaps with greater insight as to what SpaceX is planning it would become more credible, but such information is not currently available.
You’ve been asking for information, I supply it. You’re welcome.
Joe, Jester et al….,
Please help the layman here…
1)Does the densified LOX increase energy output to provide for retrograde landing back at launch pad without cargo weight loss?
2)Or does this allow F9R fuel ability to provide for one orbit before landing of the booster at launch pad?
(1) SpaceX CAN’T give specifics, due to ITAR restrictions. It is very likely correct that the things you mention are part of the changes being rolled into the Falcon 9.
(2) SpaceX is indeed increasing the tank sizes for both LOX and RP-1 on both stages. This is publicly available information.
(3) It’s not theoretical, as I showed you a few posts up.
(4) RP-1 is very highly refined Kerosene. It is a hydrocarbon, it doesn’t actually have water in it, and it does get denser as it gets colder. Its freezing point is -36 F / -37 C. Again, the Russians have been doing densification of it for decades. Since you have a history of not listening to me, I suggest you do a basic google search and find these things out for yourself.
(1) The Russians sub-cooled the LOX in the N-1’s engines not to densify it sufficiently to increase the vehicles performance but to assist in cooling the engine pumps. This can be seen by comparing N-1 performance to LEO to that of the Saturn V (which also used Kerosene/LOX but did not sub-cool it).
(a) Saturn V – Gross Mass 6,478,000 pounds, LEO payload, 310,000 pounds, Payload Fraction 4.7%
(b) N1 – Gross Mass 6,060,000 pounds, LEO payload 209,000 pounds, Payload Fraction 3.5%
So the N1 was actually less efficient than the Saturn V.
(2) The ITAR reference is interesting. For anyone else reading this who may not know ITAR stands for International Traffic in Arms Regulations. It is a set of United States Government regulations on the export and import of defense related articles and services.
So first you claim that SpaceX is using well known technology that the Russians were using 50 years ago (and have subsequently sold to Orbital Sciences), and then you claim that that SpaceX can’t talk about it because of ITAR restrictions.
You can claim one or the other, but you cannot credibly claim both.
Your problem is not that I don’t listen to you; your problem is that I do. My problem is that it would easier to take you seriously it you would pick a side and stay on it.
(3) Since you play by the internet rule “he who posts last wins”, have fun. But realize that you are playing by yourself.
This will be my last response to you on this subject.
(1) Cooling the LOX makes it denser, so what if it’s a side-effect of keeping the engine cooler, it’s still densified LOX.
(2) It is both known in the industry and it is covered under ITAR. Yes, it is both, and if you think that’s incredible, then look up what ITAR covers; it is exactly the case that SpaceX can’t divulge detailed information on the operation of its rocket engines due to ITAR restrictions. There is no contradiction here.
I’m not on a side, I’m simply correcting your misunderstandings.
(3) Your loss, my gain. You are the one who chose to be an ass.
“SpaceX CEO Elon Musk expects that the new improvements will allow Falcon-9 to soft-land even during high-energy launches to the 22,300-mile (35,900-km) altitude of GTO”
Is this to say that now with every launch SpaceX will be able to land the first stage?
Might want to wait until SpaceX successfully lands a first stage at all, before betting on that.
Another question, is this supposed to be a barge landing or a launch site landing? There ia a big difference in the amount of Delta V required.
SpaceX will be able to ATTEMPT a landing on the ASDS for each launch if they want, yes Tracy.
For Joe, from my report:
“The Orbcomm OG Mission-2 flight will also give SpaceX another try at landing their rocket’s first stage on an offshore barge known as the Autonomous Spaceport Drone Ship (ASDS)”
No update available on development of LC-1, it’s SpaceX so they will tell the world in a Tweet when they feel like saying anything, rather than acknowledging media inquiries.
Thanks for the clarification.
The reason I keep asking about any fly back to the launch site attempts is because of the impact to payload. Everyone I have talked to about such a maneuver says that (if it can be done at all)it would cost somewhere between 35%/40% gross payload. SpaceX’s Shotwell acknowledged a 30% penalty.
Even granting the 30% figure leads to some interesting questions.
SpaceX (on their web page) says that Falcon 9 (presumably the old unimproved Falcon 9)can launch 28,991 lbs. to LEO and the Dragon can deliver 13,228 lbs. up-mass to the ISS; but the largest amount they have delivered to date is only 5,108 lbs. (on CRS-5).
Since all the reduction in Falcon 9 gross payload would have to come from the up-mass, that would be an up-mass reduction of 8,697 pounds. If the current Falcon 9/Dragon’s actual up-mass is less than that 8,697 lbs. the Falcon 9 would not even be able to put an empty Dragon into orbit with the reserves needed to attempt the fly back maneuver.
So, how much up-mass can the Falcon 9/Dragon actually deliver and how much would the new improved Falcon 9 supposedly increase that amount?
Good questions, I’ve been waiting all summer for answers. One thing I’m working on too regards USAF concerns with SpaceX constantly “upgrading” the F9 booster. They want to be competitive with ULA for those contracts but F9 keeps evolving. USAF doesn’t want or need evolution, they want assured access.
Responding to your questions above,
The cooling the LOX increases its density (hence “densification”) by reducing the amount of space between the individual atoms. This means they can fit more of it in the set volume of the LOX tank. It also effectively allows the rocket to run oxygen-rich, since it is delivering more oxygen to the engine.
This does increase the energy output of the engine a bit, but more importantly, the rocket is carrying more oxygen, so it can burn its engines a little longer.
Not enough to orbit the Earth (in fact, nowhere near enough, as the first stage cuts its engines at about 60 miles up and 60 miles downrange), but enough to launch a payload and be able to return to the launch site to land.
“Not enough to orbit the Earth (in fact, nowhere near enough, as the first stage cuts its engines at about 60 miles up and 60 miles downrange), but enough to launch a payload and be able to return to the launch site to land.”
Thanks for the clarification… Is this “densification” something that SpaceX designed themselves or is this a known technology throughout the industry? Was this SpaceX’s “Ace in Hole” as a means to complete the retrograde burn to return the booster to the launch pad? It seems that such a requirement would have been known from the very beginning of concept design… No?
It’s not a common rocket launch industry practice in the US, but it had been done by the Soviets for years on their Proton rocket upper stages. The X-15 rocket plane also used densified LOX. The NK-33 engine was developed for the N-1 (the Soviet moon rocket) and it used densified LOX. Since the engines on the first stage of Orbital’s Antares rockets used refurbished NK-33 engines, the Antares rocket used densified LOX, so there was some recent use of densified LOX in the US for that.
It is a part of SpaceX’s plan to return nearly all Falcon 9 first stages to the launch site, yes, along with slightly increasing the size of the fuel and oxidizer tanks on both stages and running the Merlin 1D rocket engines at 20% higher thrust.
SpaceX has been incrementally improving its designs since Day 1, and it would not surprise me if they have been working towards the use of densified LOX for a long time now. It is possible they have designed the Merlin 1D engine to handle using it from the beginning, or they may have improved it. My guess is it is slightly improved, but not enough to give it a different version name. At minimum the turbopump would need to spin at a different rate and the thrust chamber would need to be strengthened to handle the higher combustion pressures. If the thrust chamber were already designed for the higher thrust, it could be as simple as slightly altering the computer code that runs the turbopump.
Soviets used a special kerosene type and super-cooled it along with oxygen.