New Mars Forums

Oldfart1939

Member

Registered: 2016-11-26

Posts: 2,452

Re: Apollo 8, redux

New acronym: BNNT. Please explain!

kbd512

Administrator

Registered: 2015-01-02

Posts: 7,856

Re: Apollo 8, redux

Oldfart1939,

BNNT = Boron-Nitride NanoTube

NASA is adding extra Hydrogen to BNNT's for GCR protection.  It's the lightest and best performing GCR blocker known to science, thus far.  It's good at stopping Solar Particle Events (SPE's), too.  Even so, the PE water tank at the base of Cygnus is where the crew must be during a SPE.  The BNNT panels are just dead weight.  Cygnus is a thin aluminum can, like an ISS module.  The GCR's produce secondary particle showers when they strike thin metal plates.  The BNNT panels are intended to stop the secondary showers and slow the GCR's.  There's no such thing as completely blocking heavy ions in an aerospace vehicle, but we can filter out the protons (90% of the radiation), slow the heavy ions to the extent practical, and capture secondary particles thrown off the aluminum plate when GCR's impact the aluminum pressure vessel.

Oldfart1939

Member

Registered: 2016-11-26

Posts: 2,452

Re: Apollo 8, redux

Then these BNNT should be encapsulated in a polyethylene matrix, which also is a decent cosmic ray shield. Polyethylene-type polymers are very effective against H+ (protons).

Last edited by Oldfart1939 (2017-05-19 20:19:36)

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Apollo 8, redux

Space x announcements have painted a picture of using the BFR to get men to the moon and back with a man with money stepping up to the plate to pay his own money to make the journey.

I watched the SpaceX presentation live last night, and Musk was at his usual best. The Japanese art collector-billionaire made a short speech in English wherein he explained why he was doing this.

Here's the SpaceNews.com story:https://spacenews.com/spacex-signs-up-japanese-billionaire-for-circumlunar-bfr-flight/

Here's the link to the entire presentation:https://youtu.be/DV2TLnMfoYo

And another link:https://youtu.be/PPMvvUEenUU

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Apollo 8, redux

Repost:

Falcon Heavy can lift 16,800kg to trans-Mars trajectory or 26,700kg to GTO. So let's assume Falcon Heavy can lift the same mass to TLI as it can to TMI.

Falcon Heavy upper stage is capable of multiple engine restarts. If you want to use Dragon v2 as is, without modification, can it do an Apollo 8 mission? That would require the Falcon Heavy upper stage not only do the TLI burn, but also LOI, and TEI. Let's see...

Dragon v2 has a dry mass of 6,350kg. Cargo capacity 3,307kg or 7 astronauts. Cargo capacity includes astronaut body mass and spacesuit. For the Moon you would reduce crew to 4, remove the 3 lower seats and use that space for food and life support supplies (spare lithium hydroxide canisters). Apollo CM could install 2 seats in that lower (aft) space for the Skylab rescue ship, but for the Moon they used that space for food, life support supplies, and lunar samples. Dragon v2 is designed for 1 week free flight, or 2 years docked to ISS. That means it has enough life support (oxygen) for 1 week. Trip to the Moon takes 3 days each way, so that only gives you 1 day in Lunar orbit. You may want to reduce that to hours to provide a contingency. But even 8 hours in orbit staring at the Moon would be a lot. What do you do if you can't land? I don't have propellant mass for Dragon v2, but Dragon v1 carries 1,290kg propellant. However Dragon v2 has abort engines that Dragon v1 does not; I don't know how much propellant is needed for those. If we assume 360kg abort propellant, that works out to an even 8,000kg plus cargo and astronauts. Abort propellant is probably higher. This article from spaceflight now says the Dragon v2 abort test "consumed their nearly two-ton load of hydrazine and nitrogen tetroxide propellant in less than six seconds". It says "ton" not the metric term "tonne", so assuming that's US short tons, that's "nearly" 907.18474kg. For the same of simplicity, let's assume 900kg. That makes Dragon v2 8,540kg plus astronauts, spacesuits, and cargo including food and lithium hydroxide canisters.

Apollo era astronaut maximum body weight was 180 pounds (82kg). I don't have mass figures for the SpaceX spacesuit. I would like to use the orange ACES suit used on Space Shuttle from 1995 on, but don't have mass of that either. Shuttle LES suit was used on Space Shuttle after the Challenger disaster of January 1986 until the ACES suit was used in 1995. Total mass of the Shuttle LES suit was 11kg. So 4 astronauts with spacesuits would mass (82+11)*4=372kg.

Dragon doesn't use hydrogen fuel cells for power, so won't have a supply of water. It won't have a recycling life support like ISS either, just bottled O2 and lithium hydroxide like Apollo. That means whole food, not dehydrated. A military MRE masses 18 to 26 oz each, depending on menu. Let's use 22oz as an average. With one MRE per person per day, 4 astronauts over 7 days, that's 17.4633kg; round off to 17.5kg.

Apollo CM LiOH canisters massed 4kg, two used at a time, replaced alternately every 12 hours. That means one set of two canisters lasted 24 hours. They supplied 3 astronauts, so a Dragon with 4 astronauts would require 5.3kg canisters. Assuming LiOH and activated charcoal are the same. Frame could be plastic instead of aluminum alloy, but that won't save much mass. So a mission lasting 7 days would require 14 canisters. Apollo CM carried 30. So 14*5.3=74.2kg.

Total launch weight is now 8,540kg + 372kg + 17.5kg + 74.2kg = 9,161.2kg
Falcon Heavy can lift 16,800kg to TMI so it will have a lot of propellant left over after throwing this mass to TLI.

TEI requires that plus the Falcon Heavy upper stage plus propellant. Return from lunar orbit to trans-Earth trajectory requires 4,800 m/s delta-V. Lunar Orbit Insertion requires 700 m/s delta-V.

So let's assume the FH upper stage has 16,800kg - 9,161.2kg = 7,638.8kg of propellant remaining after TLI burn. The upper stage would have to be attached until end of TLI burn, so in this case just leave it attached. FH upper stage has a dry mass of 4,000kg, it's single Merlin-D vacuum engine has an Isp=348s. Total mass approaching the Moon will be 9,161.2kg + 4,000kg + 7,638.8kg = 20,800kg. Delta-V calculator says after LOI burn, total mass will be 16,940kg. You can do the math to see how much of that is propellant. Now we need the TEI burn. Total mass after TEI burn would have to be 4,150kg. However, Dragon mass is 9,161.2kg + FH upper stage dry mass is 4,000kg = 13,161.2kg. That means you just don't have enough propellant.

This is what staging is for. You need to eject the Falcon Heavy upper stage after LOI burn, use something smaller for TEI burn. That's why I said to convert the Dragon trunk into a service module with enough propellant for TEI. In fact my idea was to add one more stage, with 3 jobs: LOI, propellant transfer to LM, and crasher stage to de-orbit LM.

This indicates how far we can push the current block 5 falcon heavy for getting beyond earth orbit

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Apollo 8, redux

This Christmas season marks the 50th anniversary of one of humankind's most memorable spaceflights: the Apollo 8 moon mission.
The Apollo 8 astronauts circled the moon in December 1968, marking the first time human ever saw the lunar surface from up close with their own eyes.

'Apollo's Daring Mission': NASA's Epic Apollo 8 Moonshot Stars in PBS Documentary

So the count down begins for Nasa can you do it again or was it just a hoak as many still believe....

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Apollo 8, redux

Missed being able to take 2 falcon heavies for this journey...I think this would have sparked a race for sure....

Mars_B4_Moon

Member

Registered: 2006-03-23

Posts: 9,776

Re: Apollo 8, redux

Frank Borman - Apollo Legend
https://www.thenakedscientists.com/podc … llo-legend
His Apollo 8 mission was the first manned mission to the Moon..