Nutrition and Temperature Regulation

ASEN 5016 Lecture 5: Nutrition and Temperature Regulation

OBJECTIVES

1. Identify Basic Nutritional Needs

2. Describe Unique Aspects of Space Flight

3. Describe Options for Water Supply in Space

4. Explain Mechanisms for Temperature Regulation

1. Basic Nutritional Needs

Average male astronaut over 30 – daily energy requirement is 2875 cal

USDA guidelines met for balanced meals (and there’s a lot of current debate about these guidelines), but space travel factors related to changes in body composition (mass reduction, fluid/electrolyte redistribution, mineral loss) and the necessary energy expenditures in 0-g, 1/6 g or 1/3 g may need to be assessed.

Current criteria:

· Minimal in-flight preparation

· Minimal waste

· Ambient stowage

· Good taste

Psychological vs. Physiological Drivers

Physiological "need" (hunger)
vs.
Psychological "desire" (learned response)

Palatability

· Taste & Smell – obvious and strongly related

· Vision – aesthetically pleasing = more readily consumed

· Hearing

· Touch / Texture

2. Unique Aspects of Space Flight

Protein – muscle maintenance, but excessive protein increases potential for kidney stones

Carbohydrates (complex sugars) – major energy source

Lipids (Fats) = taste! No changes noted in ability to metabolize or in HDL and LDL levels

Minerals – Ca loss during Skylab: 50mg/day at day 10 and 300 mg/day at day 84…
Fe - RBC mass loss?

Electrolytes - Na and K à necessary for muscle contraction and nerve conduction

Vitamins – e.g. Vitamin D and bone mass loss relationship, no evidence of more = better

Bland Taste!

· Stuffy head due to cephalic fluid shift

· SMS

· Loss of free convective aromas

· Overall build up of odor à Olfactory adaptation

· Preference towards hot and spicy foods

Early concerns of swallowing in 0g led to "food in a tube"

Peristaltic action works even against 1g…

US and Soviet dietary and nutrition programs developed in a parallel fashion

Early - Rehydratable, thermostabilized, ready to eat natural, pre-cooked / frozen and irradiated

Shuttle - Commercially available fresh and dehydrated items, individual menus

Frozen, refrigerated and microwaveable foods planned for ISS

Future – bioregenerative systems – plant crops and animal products

Energy intake – ranged from 1910 – 3838 kcal/day per crewmember on first 24 shuttle missions

Increase caloric intake to offset mass loss?

Counteract a natural bio-tendency towards homeostasis or let nature run its course?
e.g. Is less bone mass required to live in space? Or on Mars?

Ca has a negative balance in space (osteoporosis-like condition) mobilized from skeleton via urine

· Simply taking more doesn’t help without deposition and may even be detrimental

· Means of inducing/maintaining deposition must be addressed (~osteoporosis treatment)

Body Water

Total body water composition = balance between intake (food, drink) and output (respiration, perspiration, urine, feces)

Weightlessness immediately modifies body water distribution followed by water reduction

Water and electrolyte modifications occur early and a new balance is achieved in days

Gastrointestinal (GI) Tract Functions

Cessation of GI sounds during SMS

Pharmacokinetics altered?

Microflora (including pathogens) and antibiotic sensitivity concerns?

Other Possible Interactions

Convective cooling reduction – heat dissipation – appetite suppression

Acute exercise – depression of food intake

Elevated CO2 – metabolic compensation

Bottom Line à Nutrition needs of crew must be satisfied for short and long term health maintenance in space

Diet and exercise relationship must be considered

Maintain vs. Regain philosophies…

Ideal diet for space travelers?

Bone loss

Radiation damage / cancer

Cardiovascular health

Dental issues

Operational factors

Social ritual / psychological effects

3. Water Supply in Space

Total Daily Consumables ~22.5 kg per person per day (including hygiene water)

Total estimated consumables per person per year ~8213 kg

· Food = 219 kg

· Oxygen = 292 kg

· Potable Water = 1132 kg

· Hygiene Water = 2008 kg

· Laundry Water = 4562 kg

Water = Greatest single mass consumable (~7702 kg/person/year for a ‘high end’ system, which is only ~5.5 gal/day)

Mercury / Gemini – water stored in bags

Apollo – FC generated and chlorinated

LM – stored and iodinated

Skylab – 10 x 600 lb (2722 kg) water tanks (including tank mass?) launched with the vehicle - (28+59+84) x 3 = 513 person-days (no generation or recycling)

@ $10k / lb launch cost (today) à $60M worth of water!

Mir –condensate (filtration) and urine recovery (electrolysis)

STS – FC and MCV iodinated at 1-2 ppm (removed prior to use at the galley)

ISS – delivered by Shuttle or Progress and partially recycled from atmosphere humidity (plans for urine recovery)

CEV and LSAM ?

Beyond – Regenerative (biological, physical and/or chemical) sources necessary for increased self-sufficiency and economic viability of long duration stays in space

Concerns with iodine treatment – other ways to sterilize water?

4. Temperature Regulation - local (human) and environment (spacecraft)

Physiological thermoregulatory responses include:

· Shivering / vasoconstriction in cold à hypothermia

· Sweating / vasodilation in heat à hyperthermia (heat stroke)

Performance impacts can occur much sooner on either end

Short-term effects of weightlessness stemming from cephalic fluid shift include decrease in total peripheral resistance (TPR) to prevent blood pressure increase

Alcohol is also a vasodilator

Individual heat balance à clothing, sleeping bag, directed airflow

Maintain spacecraft thermal equilibrium between heat generated/absorbed and heat radiated to space

Spacecraft attitude and structural / surface properties à thermal absorptivity / reflectivity / transmissivity effects

Overall cabin set point à heat load / forced cabin air or cold plate conduction / water / freon or ammonia / space

Also must account for humidity control à water separation / collection / stowage / dump or recycle

Orbiter Active Thermal Control System