# Tag Info

21

What's the reason that they don't use the Delta Heavy for crewed flights to the Moon and beyond? The Delta IV Heavy isn't powerful enough to send Orion beyond low Earth orbit. Orion masses about 26.5 tons in its lunar-mission configuration, which is just within Delta Heavy's LEO launch capability. SLS is much more powerful, and can launch both Orion and a ...

18

In the late 70's and early 80's I worked for a company named Unidynamics Defense Systems. We provided this subassembly. We were not the design originators, this design I am quite sure came from NASA. My guess as to who the upstream contractor was would land on either Martin Marietta or Thiokol. On this particular design my drawings did not indicate who the ...

18

The 53 metric tonne number comes from the use of propellant cross feed. And only when using propellant cross feed. When not using it, payload to LEO is lower, but I cannot find a reference to that number. Cross feed means that the center core has connections to the side cores, sending fuel and oxidizer over from each side to the engines of the center core. ...

15

Your assumption that rotating the rocket removes asymmetry is incorrect. The total thrust of the rocket can be visualized as a vector. This vector should point at the center of gravity of the rocket. If it doesn't, the thrust will change the direction of the rocket. It's easy to see that a rocket with 1 booster will not have its thrust vector pointing at its ...

12

They do use sparklers: the Radially Outward Firing Initiators (ROFI), derived from the Shuttle system, are started at T-15 seconds. Note that a hydrogen fire is the expected result of this system; they just didn't expect it to be this extensive. On the NasaSpaceflight forum, someone suggested that the scorching of the insulation is caused by the hydrogen not ...

11

The answer is more political than technical. (Will be some opinion here, alas) SLS exists as a booster without much of a mission. Well it has Orion, since SLS is the only booster (except maybe Falcon Heavy once man-rated) that can launch Orion. In Constellation there were several projects. Ares-1 - SRB based manned booster for original Orion design. ...

10

Consider the amount of thrust the various cited side boosters provide: Falcon 9 Heavy: 9 Merlin 1Ds at 155Klbs each = 1.4 Mlbs thrust Delta 4 Heavy: 1 RS-68 ~ 600Klbs thrust Araine 5: P230 solid 1.45 Mlbs thrust Angara: RD-191 on a URM ~432 KLbs thrust These are not minor numbers (conceding my point is less valid on Angara and D4-H) If you generate a ...

10

From perusing online, it seems there's a consensus that the insulating foam is just that color. They painted the Delta II, but stopped painting due to the added weight. As to why they painted the Delta II (and Saturns), I believe it is for protection against UV. They probably solved the UV issue, and thus opted for the lower weight for the Delta IV.

9

There is some information in this paper although it does not directly address your question. It does mention that the first Venus flyby is at a relatively high altitude (about 2500 km) which may make it less sensitive. I also observe that, since all of the gravity assists are with Venus, once the first Venus flyby is completed, the absolute time doesn't ...

9

You haven't defined "optimal" here. The commercial launch business is more concerned with cost optimization than mass optimization. Atlas V offers two variants of Centaur, with one or two RL10 engines on it, although the two-engine version hasn't yet been flown on an Atlas V; adding solid rocket boosters seems to be incrementally more cost-effective than ...

9

Here are the projected Delta Heavy upgrades from United Launch Alliance (ULA) in different configurations. You can see that the payload value at the name of the rocket version is not the same as the LEO payload value. I guess the name of the rocket version shows the payload for a low earth orbit, 200 km at 28.5 degrees (probably 28.7), that’s why is ...

7

All rockets need to keep the center of thrust (Ct) beneath the Center of Mass (Cm). Let's assume for the moment a 2-booster rocket stack; the rocket and the boosters all produce thrust of 500 Tons-thrust. the left booster is 3m from centerline, and the right also 3m from centerline. The center of thrust can be figured multiplying the thrust by the distance ...

7

There are a number of differences between the two systems. One of them is the cross-feed system of the Falcon Heavy. The cross-feed is only expected to be used on the Falcon Heavy with the heaviest loads, over 45 tons. The Delta IV has a LEO capability of about 28 tons. Falcon Heavy's max capacity is 54 tons. Wikipedia states that a Delta Heavy with cross-...

7

At 9 hours after launch, the Parker Space Probe's current speed is about 12.4 km/s with respect to the center of the Earth. This is smaller than it was a bit over 8 hours ago when the third stage burn had completed. I calculate the vehicle's velocity was about 14.7 km/s just after third stage cutoff. The vehicle's current velocity (9 hours after launch) ...

6

Technically this answer doesn't specify what slows it down, but it does explain how it does. I've never done anything with orbital mechanics before today, but I got bored and read a few articles, linked below and made a scale model of the Parker solar probe's final orbit in my program I wrote from scratch! Click Here for Animation What you see here is the ...

6

Partial answer (covering By what mechanism do RS-68s light?): The RS-68 uses electrically fired solid-propellant igniters in the gas generator and main combustion chamber. It also uses a helium spin line (purple arrow) to start the turbopumps rotating. Sources: PACSCI EMC PROPULSION for the 21st Century—RS-68

5

Problems Starting Space Shuttle Engines Prior to the first flight of the Space Shuttle we were test firing the Main Propulsion System Engines at the test site in Mississippi when we experienced a VERY LARGE explosion at the time we attempted to start the engines. Had this explosion occurred on an actual Space Shuttle during launch, it would have destroyed ...

5

https://en.wikipedia.org/wiki/Falcon_9 Falcon 9 payload to LEO: 22.8tons to GTO: 8.3tons https://en.wikipedia.org/wiki/Falcon_Heavy Falcon Heavy payload to LEO: 63.8tons to GTO: 26.7tons FH performance is just 180% more for LEO, but 220% more for GTO So, no, its NOT 4x more to LEO, that was using cross feed, which has been abandoned because its ...

5

I added this to a special page to Where is Roadster, you can find the Parker Solar Probe info here. The current location is 7,338,815 miles (11,810,682 km, 0.079 AU) from Earth, moving away from Earth at a speed of 27,043 mi/h (43,522 km/h, 12.09 km/s). By the way, that is CRAZY fast. For comparison, to get that far Elon's Tesla Roadster took about 2 ...

5

You are correct in your assumption that larger launch windows require higher fuel margins on the rocket. Therefore, the main reason for such a large launch window is not because they just want to, but because it allows for some flexibility in the actual launch point. Should they have to abort the countdown and need to recycle, they need some time (usually ...

5

The short answer is that the Isp of the Falcon's RP-1/LOX upper stage engines is much less than the Atlas V's LH/LOX. The primary metric of interest is $\Delta v$, which depends on $I_{sp}$ and mass fraction. If you need more $\Delta v$ for a particular mission, but your $I_{sp}$ is lower than another rocket's, that means you'll need a better mass fraction, ...

5

The answers on the reddit thread you linked are essentially correct. The camera angle is the only difference between the two images, making the flare appear further away. As you mention, Delta IV and Heavy use cryogenic hydrogen and oxygen as propellants at approximately -255°C and -185°C respectively. As these are loaded into the tanks in the lead up to ...

5

New launch schedule: Rescheduled to lift off at 3:31 a.m. EDT on Aug. 12, 2018. Scrub Announcement Video: "Parker Solar Probe Launch Postponed". There will be live coverage on the NASA Kenedy YouTube Channel. Current live stream: "NASA Live: Official Stream of NASA TV's Media Channel". To me, this makes it sound like the margins for the ...

5

The engines on the Delta IV Heavy, like most large liquid-fueled engines, can gimbal, vectoring up to 6º in any direction, so any mass imbalance can be corrected for almost instantly. That said, it would also be possible to just start with a couple hundred kg of propellant more in the tanks on the booster that lights first; propellant tanks are generally ...

4

The goals of Assured Access to Space are (PDF of a hearing by the House Committee on Armed Services, page 14): The existing policy, codified in federal law, requires that assured access policy and spending, at a minimum, achieve the following two objectives: the availability of at least two space launch vehicles (or families of space launch ...

4

According to NASASpaceflight.com article from December 4, 2013, yes: Another element that will heading uphill on EFT-1 will be an inert Launch Abort System (LAS). Most of the LAS won’t be active for the flight – not least because there will be no humans on board the Orion. However, the jettison motor will be active, allowing for a separation ...

3

No, it does not seem that the 3 different CBC's are interchangeable. The Common Booster Core employs separate spherical bulkheads on the LH2 and LOX tanks. The tanks employ internal stringers for additional stability and the LOX tanks use anti-slosh baffles. An external wiring tunnel runs down the length of the entire booster whereas some of these components ...

3

According to descriptions in the KSC's Mission Preparation and Prelaunch Operations and the Launch Pad/Mobile Launcher Platform Interfaces pages, the hydrogen burn-off system for the Shuttle was located on the tail service masts on the launch pad, suggesting that the system was built by the Kennedy Space Center. While the site doesn't go into further detail ...

3

According to John Schilling's calculator, Delta IV Heavy should be able do about 9.8 tons to TLI (defined as a 185km perigee, 400000km apogee Earth orbit). Because of the nonlinearity of the rocket equation and wide range of launcher performance characteristics, there's not a general rule for estimating TLI capacity from LEO or GEO capacity, unfortunately.

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