Racescort666

I assume that this is SES-11? Edit: never mind, the article says it's SES-11 and that Koreasat 5A still doesn't have an official pad assignment. Also, it sounds like they haven't completed their damage assessment from the hurricane.

I was hoping that they would name something after H.P. Lovecraft but I guess there's still time since they said that more names are yet to be approved.

It's entirely possible that they increased the size to handle the heat as well (just spit balling here). More mass = more heat capacity = less degradation from heating. I'm sure the increased temperature limit of the titanium doesn't hurt either.

The NOAA gets asked about nuking hurricanes frequently enough to warrant an official response: http://www.aoml.noaa.gov/hrd/tcfaq/C5c.html Substitute "nuke" with "sonic boom" and you have your response. (Aside the radiation... unless you're using a nuclear powered aircraft... then it will be the same)

Live with 11 minutes on the countdown clock. Weather is go according to the broadcast.

It's more a cost and regulatory issue. Plenty of people are willing to pass the reigns to the computer. People love their autopilot but it's pretty limited in its capability compared to something like Waymo. There are already a few things that are becoming more common that are similar to autopilot: lane departure correction (and warning system) as well as adaptive cruise control/collision mitigation. With collision mitigation on track to becoming mandatory and being the basis for adaptive cruise control. As these systems become more common and reliable, both from a manufacturers standpoint and the consumer, they will slowly start to be added to the autonomous repertoire. As manufacturers increase their production volume of the systems, the costs will come down and we will see incremental increases in autonomy. However, this is still pretty basic and the implementation plan is 5 years out for passenger cars. I would say that the "autonomous only" lanes are more than 10 years away at the earliest. As for someone building an autonomous vehicle with no steering wheel or pedals, there is no regulation for that currently. Typically in the US, the federal government has regulated cars while the state governments have regulated drivers. Once you mix the two, things get tricky of which entity should make the rules since it's already a bit dicey on which states allow fully autonomous vehicles. The manufacturers have also been very cautious about just throwing something out there because it would be really easy to spook the regulators and risk an outright ban. I would say that this level of automation is also around 10 years out since the hardware is far too expensive for the average person to afford and I highly doubt the manufacturers would be willing to let it out into the uncontrolled public until thoroughly vetted. I suspect that the first scenario of autonomy slowly creeping into the market will pave the way for something fully autonomous. This will probably happen so subtly that no one would think twice about leaving it up to the computer.

I've been keeping an eye on this and I'm calling it now: FH is delayed until 2018. Even if OTV-5 launches on time, they're going to be behind on 39A upgrades and FH won't be launching in November. Sorry for the pessimism, I'm super excited about this launch but lets be realistic.

RE: FRP being called "plastic" In the auto industry, you have essentially 2 entities describing composites: marketing, and engineering. Engineering will definitely joke about stuff being made out of plastic when it's a composite (carbon/graphite or not). There is definitely a distinction made between carbon fiber and fiberglass though. Also, manufacturing technique like SMC will sometimes be used to describe them. Regardless, marketing will try to make it sound way fancier than it actually is, hence, the tongue-in-cheek description of "plastic". Since the catch all term "composite" is a bit too broad and includes things like concrete, FRP is the preferred term for the pedantic. But since FRP stands for fiber reinforced plastic, I'd say that shortening it to "plastic" is acceptable when said in a sarcastic tone. Back to your regularly scheduled programming...

*sadface* I suspect that this will push back Falcon Heavy as well if they are planning EchoStar 105/SES-11 from 39A.

Hey look almost all the work already done for me. Without having an enormous rocket, there is a practical limit to how much dV something with an ISP of 325 can get you. Unfortunately, as pointed out, NTRs are considerably heavier than their chemical counterparts. In fact, they pretty much always will be because there is a limit to how small they can be made. So even if TWR had no bearing on the decision to use one, the smallest an NTR can be made and still function is 1770 kg per the study I linked. So, where is the advantage? Storable propellants. While an RL-10 makes a far better upper stage engine than an NTR does, it's usefulness ends during a long duration mission. That is, >5 years even though ULA has proposed using the RL-10 in missions lasting as long as a week. Currently, it's impractical to store LH2 longer than the current time frames. Ammonia, on the other hand, would be relatively easy to store. Yes, you take a performance hit due to the weight of the engine, but having a long duration storage with a high ISP engine could hypothetically make up for it. Fuel storage seems to be the problem with an Ice Giant mission. After all, the JPL proposal was going to use a hypergolic bipropellant braking stage and their dV budget was in the neighborhood of 2.5-3 km/s. Several of the proposals were to use a solar electric propulsion stage during the inner solar system gravity assists but looking at the report, it seems to have just complicated the entire mission. They briefly mention radioisotope electric propulsion and it seems like an attractive option as it considerably cuts down on flight time. Anyway, my goal wasn't to compare directly to DCSS or Centaur, I was just considering structural requirements and tankage weights since they see similar tankage pressures to what you would need in order to keep ammonia liquid at a reasonable temperature. Also, they are in line with what can be reasonably fit within existing payload fairings. But now, on to my numbers: Orbiter Mass: 2500 kg NTR Mass: 1770 kg Tankage mass: 1170 kg (this is taking into account the higher density of NH3 vs LH2 thus the lower dry mass than Centaur) Fuel mass: 48790 kg (again, NH3 is around 9 times as dense as LH2 so you don't need nearly the tank volume) Launch vehicle payload (reduced to 85%): 54230 kg (this is Falcon Heavy payload and it has been reduced for margin) Exhaust velocity: 5101 m/s Delta V once in LEO: 11.7 km/s It's also worth noting that this would likely fit within the Falcon Heavy payload fairing. The Critically Limited NTR proposed by GRC has a length of 4.9 m and I calculate my tankage to be around 4.7 m in length (4.5 m in dia) leaving around 1.8 m for the probe. Although it would probably have to be mounted upside down. Things to criticize: I averaged tankage densities of Centaur (minus engine) and the space shuttle ET and came up with 15 kg/m3 for an empty tank. Maybe this wasn't entirely realistic, I probably should have gone by surface area but this was the easiest way I felt to do it. Falcon Heavy has yet to fly and there has been some discussion as to whether it can actually lift the advertised 63,800 kg into LEO. I will note that the JPL proposal also considers SLS to be a viable launch vehicle for an Ice Giant mission. Regardless, I needed someplace to start for an LEO mass. Falcon Heavy sounded like a great option. Actual ISP/Exhaust velocity for an ammonia NTR. I think it will probably be good, better than any hypergolic available. The ability for an NTR to have multiple starts. This is really unknown. The GRC report considered the critically limited engine as a single use demonstrator so who knows what can be built as a multi start capable engine. C3 dV of the launch vehice. I'm going to be honest, this is way beyond my back of napkin calculations. It seems that due to the engine mass minimum of NTRs, it makes some amount of sense to use 1 engine to leave earth orbit and arrive at an Ice Giant. Earth orbit fueling. (not something I was originally proposing, but...) This would be an easy one to criticize but hypothetically you could fuel an ammonia NTR in orbit with 2 or more launches. Putting the dry payload up would be well within most rockets' capabilities and something like Falcon 9 could send up fuel trucks to top off the probe before it leaves. You could even leave the upper stage attached as a kick stage. All of this was done while trying to think of ways to reduce transit time to Uranus and Neptune. Per the JPL report, basically anything done to try and decrease transit time increases the injection dV so they put a limit on how much injection dV they would allow for mission proposals and the entire report is considering that. I thought, why not keep the probes the same but use a different propulsion method to cut transit time? My first thought was using ClF3 as an oxidizer but you know... running shoes. Then I realized that NTRs can use basically anything for a reaction mass and ammonia seemed like the best candidate. This is probably way more involved on something entirely hypothetical but I'm glad I did it.

NTRs have some serious advantages. GRC took a serious look at them not too long ago: https://ntrs.nasa.gov/search.jsp?R=20150023036 I've been thinking about (procrastinating) running the numbers to see what a hypothetical NTR powered Ice Giant mission would need. Between GRC and JPL, most of the pertinent information is there. I was thinking something of an A to B comparison of a DCSS or Centaur to a hypothetical ammonia fueled NTR transit/injection stage.

The whole aircraft is mostly carbon fiber right? Maybe they wanted the fuselages to be as similar as possible to save money on tooling? You have to build tools for CFRP parts and it was probably cheaper to build the tools smaller and double up on the number of parts. It could be that the aerodynamics work for separate horizontal stabilizers and for one large one but manufacturing would drive to a design with more common parts. If the aerodynamics are negligible in the face of manufacturing costs, it's an easy decision.

Yeah, I knew the RL10 was a pretty low thrust engine but I was surprised to find it to be that low relative to Centaur. I suspect that Atlas V is booster thrust limited though and they can compensate for the low thrust upper stage with a steeper ascent. This would be evidenced by ULA adding more boosters to increase payload. Although, Starliner is supposed to be flying on a 2 engine Centaur. I'm not sure if this improves payload or just allows them to fly a different ascent profile.

I just ran the numbers for Atlas V and the Centaur has an initial TWR of 0.33:1 for a GTO payload. Data: http://spaceflight101.com/spacerockets/atlas-v-551/

I love this forum.

Anyone else have any information/speculation on the readiness of SLC-40? OTV-5 is listed as launching from LC-39A on SpaceflightNow and this appears to be the last Florida launch from that pad until Falcon Heavy. Also, is it too early to start the OTV-5 hypetrain?

They're taking their sweet time about starting the broadcast though.

@tater In the continuous landing footage video around 6:15 there's some glowing toward the bottom of the booster, is that entry heating on the engines? It definitely looks like it happens between the entry burn and the landing burn. Also, the vapor cone at 6:43, awesome.

I seem to remember something about a refrigerated payload...

If I could find a hard copy for less than $200, I'd probably buy it. I'm not much of a rare book person but I'd love to have a copy.

Also in the link that @shynung shared: http://www.projectrho.com/public_html/rocket/enginelist.php#ntrsolidcore

Ever since the proposal for Neptune/Uranus missions was shared, I have been thinking about hypothetical ways to improve the mission, specifically: time of flight. One of the things that irked me about the proposal was the injection burn dV limit: 4.5 km/s. We've all played KSP enough to know that this is a sizable feat to accomplish when your ISP is limited to <=325s so the report makes a good case for the 4.5 km/s limit for good reason. But it also assumes storable bi-propellant propulsion, read: A50 and NTO. If NTR using water as a propellant were on the table and the ISP of NTR+H2O is 410, the injection could be increased by over 1 km/s. I'm not really sure what this means in regard to time of flight and their flight was pretty complex for getting there with multiple Earth flybys. You could even get really creative with an Earth orbit rendezvous to load the water in the upper stage (which is hypothetically much easier to do than with transferring cryogenic fuel) to reduce launch mass.

I just assumed that their "g" key was a bit sticky.

Just divide by 3.6 nbd. I was going to make a joke about metric being easy to use but decided against it.

What stream are you watching because SpaceX's hasn't started showing anything yet?